Flexvats, Build Plates And New Store

I have been spending some of my free time designing a new larger flexvat and build plates to go with the new flexvat and LittleRP compatible vat. I was surprised at the demand for the LittleRP flexvat and felt there might be an interest in a larger and more generic flexvat.

These flexvats can be adapted to printers that can accommodate their size using adapter plates or custom platforms (information for doing this can be found here). Two of the new build plates have level adjustments so they can be adapted to printers that do not have build plate leveling.

I will also be opening a web store at flexvat.com on monday 6/20/16 to sell the new vats in addition to FEP film, replacement materials and printer adapters for the vats, you will also find a lot of technical information there.

80mm X 130mm build area flexvat

80mm X 130mm build area flexvat

80mm X 130mm flexvat kit

80mm X 130mm flexvat kit

64mm X 84mm LittleRP compatible flexvat and build plate

64mm X 84mm LittleRP compatible flexvat and build plate

64mm X 84mm LittleRp compatible flexvat kit

64mm X 84mm LittleRp compatible flexvat kit

64mm X 84mm build plate for LittleRP compatible flexvat

64mm X 84mm build plate for LittleRP compatible flexvat

80mm X 130mm build plate with built in leveling

80mm X 130mm build plate with built in leveling

64mm X 84mm build plate with built in leveling

64mm X 84mm build plate with built in leveling

 

 

 

 

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The General Purpose Thing

I haven’t posted for a while even though I’ve had a couple of projects going. Much of the reason for this has been a combination of my day job which is setting up and maintaining dental office computer systems and the somewhat surprising response to my offering the LittleRP flexvat for sale on the website (I have sold about 150 of them) and the equally surprising response to selling FEP for DIY flexvats ((I have sold over 1000 feet of 12″ wide FEP). The combination of these things ate a considerable amount of my free time.

I have for some time been wanting to upgrade the design of the LittleRP vat and also create a larger more generic vat. The original “masters” for the LittleRP vat were made on a Prusa I3 type of printer that I built specifically for creating the masters . Over time I came to see the limitations of that printer event though I was able to create the masters I needed for the original version of the vat. The two issues I ran into with the prusa printer were the limited build size and the generally rickety nature of the printer that led to all kinds of artifacts in the 3d prints.

When I decided to update the vats I also decided to update the printer that I used to make the masters. I wanted a printer that would produce a high quality surface finish which meant the printer needed to be very rigid to have zero wobble or ringing on any axis, have very high dimensional accuracy and have a large build area with a heated bed, I also wanted it to be a general purpose machine that would do both 3d printing and cnc routing. It was looking like it was time to do some reasearch and spend some quality time on ebay.

I lean towards the pile of parts method of building machines, I decide what I want to build how I want to build it and then I start ordering parts. Once the pile of parts is about equal to the machine I wanted to build I start assembling it. I did not want to construct the linear slides myself (been there done that) so I decided to look for some good used slides. I was able to score high quality heavy duty linear slides for the x (30″), Y (20″) and Z (8″) axis for a good price. I ordered a controller (Rumba), motors (low inductance 560 oz in NEMA 34’s) on the x and y axis, 240 oz in NEMA 24 for z, step motor drivers (7A microsteppers for the nema 34’s) and power supplies (2-60v @ 7A, 1-24v @30A) timing belt pulleys and belts, aluminum extrusions, hot ends, sensors, spindle kit etc., etc. After getting the pile of parts I move to the “boil, boil, toil and trouble” phase. Make misc. parts, bolt it all together wire it turn it on run it, find what the problems are repeat until it works as needed.

As a 3d printer the “Thing” works great, really nice 3d print quality (after some serious tuning). It’s not a speed demon, the nema 34 step motors are capable of driving the slides at very high speeds but I run it at 40mm/sec because there is a lot of mass moving around with the heavy duty slides, at high speeds the Thing stays nice and rigid but the table it sits on moves quite a bit (doesn’t affect the print, it’s just very unnerving to watch). I am using Marlin firmware on the Rumba controller and Craftware for my slicer together they make for very good 3d printing.

As I mentioned I built the Thing to be a general purpose machine capable of cnc routing so I constructed the 3d print head in such a way that I can remove it by unscrewing two bolts and unclipping some connectors. I can replace the 3d print head with a 400 watt ER11 collet spindle. All of the power and control circuitry is installed for the spindle I just have not had the time to machine the spindle mounting plate yet (pretty much just a 3/8” aluminum plate with 8 holes)

When I get some time I will get into more build detail until then meet the Thing:

general purpose thing

the general purpose thing

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At The Store: Drumhead Flexvat Kit For The LittleRP

Available At The Store 

Updated Flexvat for the LittleRP 3D printer. Uses tensioned FEP (transparent teflon) for the release layer.

LittleRP Flexvat V3

LittleRP Flexvat V3

 

 

 

 

 

 

 

 

 

LittleRP V3 Flexvat Kit Parts

LittleRP V3 Flexvat Kit Parts

 

 

 

 

 

 

Vat Assembly (Updated 8/2/15), Original Video

Mounting

 

I decided to delay the LittleRP vat to clear up some issues that I thought made it more complicated than it needed to be.  I had initially intended to “stack” clamp plates to increase the depth of the vat but this had the effect of not only needing to add clamp plates but also gaskets, different length bolts etc.  Adding gaskets also complicated adjusting clamp pressure and FEP tension. Adding clamp plates increased materials costs and added cutting time on the laser cutter so I decided to go back to using an add on vat wall.

The add on vat wall like the riser throat is made of cast polyurethane, the vat wall is bonded to the top acrylic clamp plate using a high grade silicone made for plastics. After finalizing the design I tested the polyurethane vat wall and silicone sealant to make sure they would hold up to commonly used printing resins and not deteriorate. I tested Makejuice and  Fun To Do resins and had no problems.  The resulting vat is easier to assemble, disassemble and adjust.

Notes:

The vats FEP vat floor sits approximately 21.5mm above the LittleRP vat mounting platform.

The absolute maximum available printing area is 78mm X 58mm.

The bolts needed to hold down the vat need to extend at least 30 mm above the vat mounting platform.  40mm long replacement bolts are included with the kit (M4-0.7 X 40mm), 60mm bolts can be provided if needed.

The kit will sell for $72.00 plus shipping with 4 laser cut FEP films and 4 gaskets . Replacement laser cut FEP film and gasket will be available for $3.50 a set plus shipping.

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Drumhead Flexvat Kit For The LittleRP

The Drumhead Flexvat for the LittleRP 3D printer kit is just about ready to to get added to the store. I’m working on assembly and adjustment instructions, usage notes etc. It looks like I will have it available next week.

Vat Kit For LittleRP 3D Printer

Vat Kit For LittleRP 3D Printer

Assembled Vat

Assembled Vat for LittleRP 3D Printer

 

 

 

 

 

 

 

 

 

BTW Check this out:

Mr. Big: 1080 x 1920 @ 100 microns

Mr. Big And LittleRP

 

 

 

 

 

 

 

stay tuned.

HTL

 

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Torque Wrench For Tightening Flexvat Vat Gaskets And Tensioning Bolts

If your vat has adjustable tension using a torque wrench when tightening the tension bolts allow you to keep your vats FEP film at an even and consistent tension for printing and between FEP replacements. If you use a gasket on your vat using a torque wrench when tightening your vats clamp bolts ensures an even clamp pressure on the gasket so that the FEP film will not slip under tension and that there is no possibility of resin leaking through a part of the gasket that is over or under tightened.

The torques needed for vat gaskets and tensioning can be surprisingly small, the clamp bolt torque for the bolts on http://projectsinterestsandetcetera.com/drumhead-flexvat-for-the-littlerp-3d-printer/ is only 16 ounce inches on each bolt, the tensioning bolts are also torqued to 16 ounce inches. On a larger vat (since upgraded to a foam gasket) http://projectsinterestsandetcetera.com/sla-3d-printer-drumhead-fep-flexvat/ the bolt torques are 40 ounce inches for the clamp bolts and 130 ounce inches for the tensioning bolts.

Tools for setting torques this low are both expensive and hard to find (I know, I bought both Sturtevant PM5 and Sturtevant PM15 torque screwdrivers for my vat). This torque wrench design which is specifically for flexvats is a reasonably priced alternative to the other available options.

The torque wrench has 2 carbon fiber strip “torsion bars” that can be changed to cover the range of torques commonly needed for flexvats. Uses standard 1/4″ (6.35mm) shank bits or socket adapters.

Torque Wrench 1

Torque Wrench 2

Torque Wrench 3

 

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Drumhead Flexvat for the LittleRP 3D printer.

Laser cut “drumhead” flexvat for the LittleRP 3D printer with adjustable FEP film tensioning.

 

LittleRP Vat Parts: top clamp, bottom clamp, vat wall extension, gasket, base plate, tensioning riser and FEP

LittleRP Vat Parts

Assembled top view.

LittleRP Vat Top

Assembled bottom view.

LittleRP Vat Bottom

 

Torque wrench for tightening vat bolts.

Torque Wrench Parts

Torque Wrench Bottom View Torque Wrench Top View

 

 

 
 

How Strong Is .005″/.127mm FEP?

fep-tough-1

25 pounds (about 11.3 kg)

fep-tough-2

fep-tough-3

Real Strong

HTL

 

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Diagram of flexvat

Diagram of my SLA 3D printers FEP based vat (sometimes called a flex vat or flexvat).

Updated drawing showing a better gasket design:

Updated Flexvat Diagram

Updated Flexvat Diagram

Old design:

flexvat diagram

flexvat diagram

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Flexvat tests: I think this is going to work out

I made 2 test prints, one yesterday and one today

First test print : As good as or better than pretty much anything I’ve printed up to now using sylgard/qsil coated glass for my vat floor. The printout had a flawless surface finish (much better than sylgard or qsil) and extremely sharp features. One thing I did notice was a very slight convex rounding of the center of the finished printout.  I believe this was caused by insufficient tension on the FEP film combined with the resin not having enough time to squeeze out to an even thickness between the build plate and the FEP after the vat tilted up and build plate dropped down between exposures (this proved to be the case).

Second test print: I’m just going to come right out and say it, silicone coated glass vat floors don’t hold a candle to tensioned FEP. Flawless surface finish, sharp features and only a slight bowing along the parts long dimension from resin shrinkage. This is what I changed in the second printout: I increased the FEP tension and made sure the 4 tensioning bolts had as even a torque as I could by feel (I think this cleared up the “convex” issue mentioned above). I lowered my exposure by a half second (I’m not exposing the resin through glass and silicone layers so I felt I could lower the exposure). I also adjusted the parts wall thickness to a uniform 1mm (I think I can use even thinner walls with the FEP vat floor)

As far as I can see using FEP under tension for my 3d printers vat floor seems to be better than using sylgard/qsil coated glass by a long shot. Only time will tell but getting such good prints on the first and second tries must mean something.

Notes:

The part is 112mm Long X 64mm Wide X 11.95mm High

Both prints were made with Fun To Do Industrial Blend resin (I will test Makerjuice resin later this week).

With the exception of the first 2 or three layer exposures (the full face of the build plate in near contact with the FEP plus long base exposures) the peel was only noticeable when large flat areas were being peeled and only barely when peeling those areas.

My vat tilt and build plate raise/lower were much larger than they needed to be for these prints (I was using a much deeper vat before). This allowed the part to lift out of the resin during printing trapping bubbles between the build plate and the FEP during exposures, amazingly, this did not cause any problems at all even in the large flat areas.

The gasket clamping the FEP worked like a charm, no slippage of the FEP at all which is good because for the second test I put the FEP under a decent amount of tension.

I will probably hack together some sort of tension gauge so that I can maintain and monitor the FEP’s tension. A torque wrench or driver would also be helpful if I can find one with low enough settings.

I think I will lengthen the tensioning bolts and add some stiff springs to them so that any stretching of the FEP during printing will get soaked up.

A note to anyone thinking about making a vat like this out of acrylic: use cast acrylic do not use extruded.  Extruded acrylic has locked in stresses that will cause you no end to problems. Also, cast acrylic can be cleaned with almost anything, a drop of alcohol on any machined edge of extruded acrylic will make it crack.

Test Print 2

Test Print 2

Test Print 2

Test Print 2

HTL

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SLA 3D Printer “Drumhead“ FEP Flexvat

Anyone who uses a SLA 3D printer has had to deal with vat floor release layers of one sort or another. Every since I built my printer I have been using Sylgard 184 or Qsil 216 2-component silicones. These materials have very good release characteristics but they have a big downside, the coatings do not last long. To renew my vats release layer I would mix the silicone, pour the silicone into the vat then I would put the vat in my vacuum rig and place it under vacuum until all of the bubbles had disappeared I would then place the vat in a leveled toaster oven for about 2 hours until the silicone had cured, total elapsed time at least 3 hours. I tend to print objects that use most of my printers 68mm x 120 mm build area (my current settings, the usable area on my printer is about 100mm X 150mm) with prints that have large flat areas and bed of nails type supports, both of which are murder on vat release layers, so I would have renew my vat floor quite often.

For a while now I have been looking at the FEP “flexvats” people have been building over at buildyourownsla.com and I finally found some time to build one. The first hurdle was finding the FEP film at a reasonable price so I started looking for it some time ago and was able to purchase a considerable quantity of .005” FEP at a decent price a couple of weeks ago. It became clear to me after messing around with some quick vat designs that a vat that had an adjustable tensioning system for the FEP vat floor was the only real solution for me (because of the type of printing I do). I also felt that the ability to quickly change the FEP would be a real plus. The design I came up with uses a silicone gasket to tightly clamp the FEP film so that it’s reasonably flat before tensioning and a tensioning “riser” that the clamped FEP is pulled down on to which allows me to tension the FEP film, the silicone gasket also serves to prevent the vat from leaking. My flexvat consists of 6 parts: the top and bottom FEP clamp frame, a silicone gasket (cast from RTV SILICONE), the vat wall, a base that mounts to the printer that also mounts the FEP tensioner riser and the tensioner riser (plus misc. nuts bolts and threaded inserts).

I am pretty confident that this design will work well as a vat for my printer, .005” FEP is a pretty tough material so I am not really concerned about the FEP being pierced or splitting also the silicone gasket is not going to allow the FEP to come loose (the gasket is made from a shore 60a silicone which is only slightly softer than an automobile tire) the FEP clamp assembly also puts the edges of the FEP under a decent amount of clamping force. Since the FEP will stretch over time from normal use and is also subject to being dented by failed prints the design allows me to swap out the FEP by unscrewing the FEP clamp frame removing the old sheet inserting a new sheet and screwing the assembly back together a 5 minute operation.

I should have some time to run some tests this weekend and I will update this post when I have some news.

Vat Parts

Vat Parts

FEP Clamp Parts

FEP Clamp Parts

Gasket Detail

Gasket Detail

Gasket Mold

Gasket Mold

Mount Plate And Tensioner Riser

Mount Plate And Tensioner Riser

Vat On Printer 1

Vat On Printer 1

Vat On Printer 2

Vat On Printer 2

HL

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Old school voltage regulation for my 3d printers dlp projector. To eliminate random lines in 3d printouts.

After printing a part last week I noticed a line about a millimeter or so high running through my part that had occurred about 2/3 rd’s of the way through the print run. I sometimes have to think about what causes printing issues but not this time, I immediately thought voltage drop (sag). Consumer DLP projectors have reasonably good voltage regulation but they were not built for 3d printing, outside of a particular input voltage range to the projector, I suspect, the bulb can dim or brighten enough to alter layer exposures. This is not a problem if you are watching a movie because you probably wouldn’t notice the projected images change in brightness but for 3d printing it can be an issue.  My neighborhood is not exactly known for rock steady line voltage (I monitor line voltage with a Kill A Watt meter/monitor. If the line voltage is consistently out of range I let the power company know, they can’t fix a problem they don’t know about). The power has been pretty good lately but in the past I have seen it drop lower than 105 volts and if the furnace or air conditioner comes on while the line voltage is on the low side all bets are off if you are printing.

I didn’t have to think of a solution to a low voltage problem I already knew of one, something I had used in the past when I needed stable voltage it’s called a constant voltage transformer. What a constant voltage transformer does is for a pretty wide range of input voltage the output voltage will remain stable within a few percent of the transformers specified output voltage. You may think a battery backup (UPS) serves the same purpose but they do not and they cannot be used as a source of constant voltage, most ups’s will let the voltage drop to 100 volts or lower before kicking in, they will maintain a minimum voltage (until the battery runs out) but do not provide a constant voltage. See updates below

I decided to hop online (ok, ebay) and see what was available (just looking, not going to buy anything). After searching on “constant voltage transformer” for about 5 minutes I ran across a Sola (check), 500va constant voltage transformer (check), 60hz (check), 120vac +-3% output for input voltages 10% above to 20% below 120vac, continuous, +20% to -35% surge/sag (check), legit vendor 99% plus rating for tens of thousands of sales (check), new (check), $125.00 (reflexively click buy now). Constant voltage transformers are expensive, very expensive and  I know a major score when I see it.  The transformer will be in this week and I will probably set it up this weekend.  I am going to use the transformer for the projector only, my projector uses about 300 watts running, 500 va will handle that just fine.

Some notes on constant voltage transformers. : They are power HOGS, a 500va cvt uses a considerable amount of power (70 – 90 watts) even if you don’t plug anything into it. They get HOT, one of the transformer spec’s is btu’s at the rated va’s (they don’t get hot enough to burn you but you wouldn’t want hug one after it’s been on for a while either). They take 60 hz hum to the next level (my phones sound level app showed 58db at roughly 1 meter but they do quiet down under load). For a dlp projector you need at least 500va, there are a lot of 250va units out there, they will not work, they do not have sufficient power output, more than 750va is probably too much, these transformers like to run at 60 to 100 percent of the va rating for the most efficient operation (my projector draws about 260 VA and about 250 watts , only a bit under the efficiency sweet spot).  The transformer should match your countries line frequency, in the US it’s 60hz in other counrties the line frequency is 50hz.  Sola, I’m sure there are other quality manufacturers of these transformers but I know Sola and I stick to what I know if I can. Many of this type of transformer are configured for hard wiring, that is, you have to wire a power cable and receptacles to them. Wiring a CVT is pretty simple but people who are not VERY comfortable wiring for line voltages are better off trying to find a cvt that has a plug and recepticals or an electrician.

This post is informational only and describes work I am doing on my own equipment.

Constant voltage transformer for 3d printer DLP projector

Constant voltage transformer for 3d printer DLP projector

Constant voltage transformer for 3d printer DLP projector wired

Constant voltage transformer for 3d printer DLP projector wired

Update:

I got the CVT set up and plugged my projector ( acer 6500) in to it and let it run for a couple of hours with a voltage monitor connected to the output of the transformer. The voltage stayed between 119. 6 and 120.1 volts consistently and only dropped to 119.3 volts for about a second when I plugged a shopvac into the same outlet and turned it on (looks like no more waiting for the 3d printer to finish before turning on the compressor, vacuum etc.). The projector was drawing about 260 VA and about 250 watts at the transformer output.  Also, the transformer “core” temperature was reading about 130F after a few hours.

3d printer with CVT

3d printer with CVT

Update:

Since writing this post I have become aware that certain AVR “Automatic Voltage Regulating” UPS’s may work in this application also certain line conditioners (google “tripp lite avr” for a overview of what you can expect from these type of devices). If you consider an AVR UPS or line conditioner pay careful attention to the regulation values while on ac, the range over which the regulation operates and the type of output sine wave if these specs are available, the higher the va/watt rating the better, and read reviews on the product if available. In my opinion an AVR line conditioner would probably be the best option for providing stable voltage to a dlp projector (the projector only), the ability to keep your projector on during a power failure for another few minutes isn’t going to help you that much.  However, if you find an avr ups at a good price with good specs clearly stated, good user reviews and made by a solid company, that automatically becomes the best option. Whatever the device the bottom line here is good regulation of the line voltage to your projector. For me, I will stick with the cvt because nothing I’ve seen has such bullet proof regulation specs.

HL

 

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3d printer vat refresh update: Tilting vat type sla dlp projector 3d printer

I decided to replace the pdms in my 3d printers vat not because it had begun to start sticking but because it was the same ratty pdms layer that prompted me to try the pressure vat refresh method in the first place. I made the new pdms layer thicker, about 3.5mm, my rationale being that you could diffuse more oxygen into the top layer of the pdms using pressure without diffusing the oxygen so far into the pdms that it will outgas out of the bottom and cause bubbles to form between the pdms and the glass vat floor window. So far everything seems to be working well, I have printed over 1000 layers so far in 2 print runs pressurizing the vat to 20 pounds of pressure for 5 minutes before each run (I am beginning to think that using a reletively low pressure and adusting the time the vat is under pressure is the best way to adjust the diffusion rate).

The type of 3d models I was printing insured that I would be printing flat layers that covered most of the live print area on my build plate (130mm X 73mm @ 67.7 microns X/Y, 75 microns Z, 1080 X 1920 projector) in addition to a “bed of nails” set of supports (which are notorious for fogging pdms).  Because of the design of my printer I can tell a lot about how well things are printing from the sounds it makes and how it moves. I was getting smooth “vacuum release” type vat tilts for layers that were large flats or presented large closed “suction cup” type profiles, other layer exposures like small flats or small open or closed profiles did not give any signs of being released at all, also, none of the layer exposures showed any signs of resin sticking to the pdms when the vat tilted and, at this point, there are no signs of the pdms fogging.  A note: I have started using Dawn dishwashing liquid (the Swiss army knife of dishwashing liquids) water and a microfiber “washcloth” to clean my vat and the pdms vat floor, it works a lot better than alcohol for Makerjuice SubG+ and you clean the vat like you would a dish.

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How I prevent failed printouts on my sla 3d printer

I have found that doing the following things have cut the number of failed prints I have when using my 3d printer to almost none.

I “paint” the build plate face with resin and harden it before each print run. The resin does not naturally want to stick to my un anodized aluminum build plate but what I have found is that coating the face of the build plate with resin seems to create a resin “suction cup” and during printing the first few base layers of a printout stick to that suction cup very well.  I have to build up the resin coat on the build plate in several very thin layers curing each layer before the next is applied to build up a decent thickness I have since found that a very thick initial layer works best, so if you are going to pre-coat your build plate slather the resin on especially for pigmented resin (I use a nail curing lamp to cure the build plate coating and to post cure parts). Since the resin does not really stick to the aluminum build plate very strongly after a part is finished printing removing it from the build plate is just a matter of getting a putty knife or spatula under an edge and “breaking” the vacuum, then the part peels right off with very little effort. I prep the build plate for the next print run by lightly sanding the build plate face to “feather” the edges of the resin left on the build plate before I re-coat it.

I have found that trying to print large solid parts are a no no, the combination of part shrinkage and heat buildup in the part during printing will make the part separate from the build plate every time.  I always hollow any part that is large enough to have 1-2mm thick walls and a hollow able interior (for example, a 6mm thick box could have a 2mm thick hollow inside with 2mm walls). I try to use 2mm walls when I can because I find that overhangs and unsupported flat areas hold up well with that wall thickness. Hollow parts also seem to shrink less.  I will have a post on how I prep, hollow and make resin drain holes with stl files soon.

I float the part I’m printing on supports. Supports do a few things, they provide a layer that does not want to separate from the build plate if the base (foot) of the supports are kept reasonably thin (I like my supports base layer to look like an array of slightly overlapping circles), the supports themselves “soak up” shrinkage from the part they are supporting (sometimes you can even see the supports bending slightly inward during a print run). I generally use a minimum support height of 5mm and I will often tilt the part I’m printing 3 or 4 degrees around both the x and y axis especially for parts with large flat areas.

When printing a part I keep enough resin in the vat to keep the part’s build face under the resin surface while the vat is tilting.  I have found that if I do not do this I may get gaps in the edges of the part being printed (an air bubble sitting in one place for a couple of layers seems to be one cause of this problem although a worn out vat floor release layer or lack of supports under certain profiles are also suspects).

I have also been doing this lately:  vat floor refresh

HL

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PDMS vat floor refresh method for DLP projector based 3d printer. Maybe, possibly, could be…

Note: see the updates at the end of this post.

I had a couple of ideas about methods of refreshing my 3d printers pdms vat floor knocking around in my head for a couple of weeks and I finally decided to try one. The root of this particular idea was a thread about the Solidator vat release patent over at buildyourownsla.com. Instead of going over what was discussed I will refer you to the thread: http://www.buildyourownsla.com/forum/viewtopic.php?f=16&t=44#p728 this thread was started by Anderson Ta who I met this weekend at the Midwest RepRap Festival along with Jordan Miller and other members of Jordan’s team at the AMRI institute at Rice University (I think my conversation with Jordan and Anderson spurred me to actually try the vat refresh method I had been thinking about). I also met Josh Ellis from Makerjuice at the RepRap Festival.

A PDMS (sylgard 184 etc) vat floor coating prevents an exposed layer from sticking to it by “inhibiting” the cure of any resin touching it (any resin touching the pdms stays liquid in a thin layer, resin above the layer solidifies during a layer exposure).  Oxygen diffused into the top layer of the pdms is what causes the inhibition. As the oxygen layer on top of the pdms is depleted the pdms vat floor becomes less and less effective as a release layer (this is why the B9 Creator uses a wiper to clear resin from the surface of the pdms between exposures, so the pdms can breathe and refresh the oxygen layer).

So what does all this have to do with refreshing my vat floor?  If maintaining an oxygen layer at the surface of the pdms is what is needed to maintain a good release when printing then why not “force” oxygen into the surface of the pdms before printing (pdms is oxygen permeable) and let it diffuse back out to the surface during a print run.

My printers vat floor was starting to get “sticky” (I can tell by how certain layers release during printing) so I was considering removing the pdms and recoating the vat but instead of doing that I decided to try the vat refresh idea I had been thinking about.

I took my printers vat and cleaned the pdms vat floor with a microfiber cloth and 92% alcohol and set it aside to dry for about a half an hour. After drying the vat I placed it in a vacuum chamber (see update 2 below) and put it under vacuum for about 5 minutes (my rationale for this was to boil off any remaining alcohol or moisture from the surface of the pdms).  After removing the vat from the vacuum chamber I then placed it in a pressure pot and pressurized the pot to 40 pounds and left it for 30 minutes. During the time the vat was in the pressure pot I setup a print run in creation workshop for a part that was a slight modification of the last part I had run. After 30 minutes I removed the vat from the pressure pot set it up on the 3d printer, filled it with resin and began the print run. Each layer was releasing so smoothly that for a time I thought the print had failed and had come off of the build plate. Even the first two long exposure base layers barely stuck at all. The printout was 442 layers using makerjuice subg+ yellow, the part printed out perfectly.

So, this is what I think is happening:

The non stick property of pdms, as it applies to 3d printing, is a surface effect caused by a thin layer of oxygen on the surface of the pdms that inhibits curing of the resin, ensuring that a layer of liquid resin is between the build plate and the vat floor at all times, sticking occurs when that layer of liquid resin is not maintained (the oxygen on the surface is depleted). PDMS is an oxygen permiable material, I believe by pressurizing the pdms oxygen in the air is diffused into the pdms to a depth determined by the amount of pressure it is exposed to and the length of time. When the pressure is released the oxygen diffused into the surface of the pdms “sees” normal atmospheric pressure as a slight vacuum and begins to slowly diffuse back out thus refreshing the oxygen layer at the surface of the pdms until the pressure is equalized.

Whether this holds up as a vat refresh method only time will tell.  I am going to use this method or some variation of it before making prints unless I find over time that it is not effective (if so I will let you know) but so far it seems to have worked well for me. Anyone out there that tries this let me know what your results are.

 

Update 1:

I found that vacuuming the vat then putting it under 20 pounds of pressure for 5 minutes rather than 40 pounds for 30 minutes seems to work just fine. I have used the vat several times since I originally wrote this post and it still releases very easily during printing and does not seem to be “wearing” very much. I did have a bubble appear between the pdms and the vat floor glass one time when I used 40 pounds of pressure for 30 minutes (which I was able to get rid of by placing the vat under vacuum for 30 minutes). I don’t know whether it was because I skipped the vacuum step while prepping the vat for the print run or too much air pressure but I will find out and let you know.

Update 2:

Skip the vacuum step it may cause bubbles to form under the pdms especially after the first pressurization. What I’m doing now is after a print run I clean the resin out of the vat with 91% alcohol then a water rinse then a spray of alcohol to displace the water from the surface of the pdms (to eliminate water spots) then I wipe down the pdms with a microfiber cloth while it’s still wet with alcohol  Dawn dishwashing liquid water and a microfiber “washcloth”.  I let the vat dry then pressurize it to 20  pounds for 5 minutes right before the next use.

I have found that the trick is to difffuse oxygen into the pdms but not all the way through it. If air makes it all the way through the pdms you will get bubbles forming between the pdms and your vat floor window glass/plastic. It appears that the pdms will outgas from it’s top and bottom surfaces if over pressurized so if you try this method start with conservative pressures and time and work up from there. I suggest 20 pounds of pressure for 5 minutes to start with for a 2-3 mm thick layer of pdms. It does not seem to take much time under pressure to “charge” the pdms.

So far so good.

HL

 

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DLP projector SLA 3d printer. 3d print timelapse

HL

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Setting up a new DLP projector for my 3d printer.

For a while I have wanted to be able to print higher resolution parts with my 3d printer and have more flexibility in adjusting the usable build area (XY build area size) so I decided to upgrade to a high def (1080 X 1920 pixel resolution, aka 1080p) projector from my unmodified Toshiba T95 (1024 X 768 pixel resolution) projector. I decided to go the used projector route to upgrade and found an Acer H6500 “with issues” at a very good price on ebay. The description of the projector on ebay led me to believe that the problems with the projector were mechanical rather than electronic so I took the risk and purchased it (electronic problems are a show stopper, mechanical problems you can often fix or work around). It turns out that the projectors main cooling fan had somehow broken two of the 4 “legs” that hold the fan centered in it’s assembly and the fan blades were hanging on the edge of the fan housing so the projector was not able to cool itself and would go into thermal shutdown soon after being turned on.  This problem apparently caused a cascade of problems within the projector. At some point in the past it appears that the projector lamps reflector cracked (probably from the fan issue) and the color wheel was broken possibly from thermal stress or a piece of glass from the lamps reflector. The lamp, however, worked fine even with a small piece of the reflector missing (I have ordered another lamp, why tempt fate).

This was all good with me. The first issue I went after was the fan, after some disassembly I removed the fan (a 4 inch “muffin” fan)  and repaired the damaged support legs with superglue (the breaks were clean and fit back together flush) the fan had also been attached to a metal housing where the metal had been stamped out to exactly match the support legs of the fan so I wire tied the broken legs to the housing as an added precaution. Next came the color wheel, I am not a fan of removing or modifying color wheels or any projector modifications for a 3d printer because it’s a good way to get yourself in trouble (and not being able to use the old one for the super bowl, summer evening movies on the patio etc.).  But since the previous owner of the projector was so kind as to pre-destroy the color wheel for me wheel I decided,  just this once, to do the deed. I grabbed a wire cutting tool that had a very small tip and began very carefully and gently nipping away at the remaining glass on the color wheel. The glass is extremely fragile and broke away with very little effort and I was able to remove the glass all the way down to the motor housing. You may ask why I didn’t just  remove the color wheel entirely, the answer is, if I had, the projector would not work. The projector requires a “sync” signal from a sensor on the motor to tell it the rotational position of the color wheel so it knows what image to show for a particular color wheel filter segment, without this signal you will have a very confused projector.  After re-assembling the projector there came the moment of truth, I plugged it in hit the power switch and…  It worked just fine. I plugged it into a hdmi video feed and it projected the video perfectly although in black and white.

I mounted the projector to my 3d printer then leveled and squared the projector, vat and build plate using a leveling block I made out of spirit level and a small block of corian. To level and square my 3d printer I set the leveling block in the vat floor first and noted the position of the bubbles (I mark the positions with a fine point sharpie) then I place the leveling block directly on the lens barrel of the projector in the same orientation as it was when I took the level in the vat. I adjusted the projector mount until the bubble positions matched the vat to make the vat and projectors projected image plane reasonably parallel (I parallel the build plate in a similar way).  I have found that I get near perfect parallel and alignment of my printer using this method, however, since the projectors optics project “up” some slight additional adjustment beyond leveling was needed for the projector, these adjustments were made while setting up the build area in Creation Workshop.

Connecting the projector to the  3d printers computer and setting the resolution: After mounting the projector to the 3d printer and adjusting the projector mount and tilt assembly to line up. It was time to connect it to the computer. In order to be able to use the full resolution of a high definition projector (1920X1080 resolution) it is best to connect through a digital video connection, DVI or HDMI.  If you use the vga connection on your computer you may not able to go higher than a resolution of around 1400 X 1050 or so. The video card on my computer had both DVI and HDMI so I connected the projector via HDMI. Note that there are DVI to HDMI adapters available so if your computer has DVI and VGA and the projector has HDMI and VGA you can use one of these: DVI-D Single Link Male to HDMI® Female adapter with a HDMI cable to connect your computer and projector using the computers DVI connector. After connecting the projector to the computer I turned on the projector then the computer and let the computer boot to the Windows desktop.  I have both a monitor and projector connected to the 3d printers computer that work in a “dual monitor extended desktop” configuration. To set the projector resolution I right clicked on the Windows desktop then clicked on “Properties” (Windows XP) then clicked the “Settings” tab and set the projectors resolution to 1920 X 1080 (for a 1080p projector). Monitor resolutions can be set in a similar way on the different versions of windows, there may also be dedicated utility programs for adjusting monitor resolutions.

Note: The projector will appear as a monitor, select the projector and set the resolution to 1920 X 1080 (for a 1080p projector), if the projector does not allow you to set this resolution these are the usual suspects: you are using a VGA connection to the projector that does not support the resolution of the projector, you are using a vga splitter of some sort (this may limit the resolution of the projector to the resolution of a lower resolution monitor). Your video cards driver software is not up to date or it is using the generic widows driver (rare).  If you only have one video output on your computer you should consider purchasing and installing an inexpensive video card with DVI/HDMI connectors, this will make your life much easier in the long run.  3d printing is not a video intensive operation any video card with the correct connectors from a reputable manufacturer will work, many will come with 2 output connectors.

Using eye protection (welding goggles, #5 filter) I used a digital caliper to set the projected image on the vat floor to roughly the build size X axis width (my build area is 144mm(X) X 81mm(Y) for a resolution of 0.75mm).  I measured the top and bottom width if the projected image and adjusted the projector mount until they were equal in size then the diagonals (if the diagonals are equal the image is square). After making sure the image was squared up I finished sizing the projected image to the width of the build area X axis(144mm), the Y axis measured 81mm as expected.

The Acer H6500 projector is waaay brighter than the Toshiba (and waaay waaay hotter. I think I am going to have to move the projector shutter higher to keep it from burning). Before removing the Toshiba I measured a patch of white projected on the vat floor with a photographic light meter and made a note of the reading. When I installed the Acer I Made the same measurement and the Acer was more than 2 “stops” brighter.  With the Toshiba my exposures were 14 seconds with the Acer that exposure time will go down to under 3 seconds. I may end up using the eco mode setting with the Acer not to extend the life of the bulb (for 3d printing it’s going to last forever anyway) but to lengthen the exposure time. I believe short exposure times may quicken the deterioration of the sylgard vat floor release layer by making the resin being exposed very hot very quickly, possibly hot enough to damage the sylgard (this is an opinion).

Layer exposure testing note: I test for exposure times using a 1 layer stl file printed using Creation Workshop. To use the test file I place some resin on a sheet of mylar and place that mylar on the vat floor. I then expose the resin for X amount of time and clean the resulting layer with a 92% alcohol spray. If there is no layer or the layer falls apart the exposure is too low. If the exposure is too low for the next test I will add 1 or more seconds to the exposure and repeat the test until I have a good layer. When I get a good layer I will uv cure it and measure it’s thickness with a caliper, in general I like a thickness of no less than about 0.02 thicker than my layer thickness and no more than about o.o6 thicker, I control the thickness with yellow pigment (after determining the exposure).

HL

 

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Setting up a DLP projector based 3d printers build size and resolution for Creation Workshop

I am able to move the projector on my DLP based 3d printer up and down in relation to the vat easily because the backbone of the printer is a MP4 heavy duty photographic copy stand. The projector is mounted on the copy stands movable carriage. This allows me, with some additional adjustments, to change the size of the build area if I need to. The Creation Workshop software that I use for slicing and control allows me to size the build area and let the print resolution match the build area or set a resolution and let the build size match that resolution without affecting the size of a printout (10mm cube will print as a 10mm cube at any resolution or build area size). What follows are instructions on how that’s done and some generic information on sizing and squaring the projected image on the vat floor.

Setting up the 3d print build area and letting the resolution match: I will use the X axis of the desired build area and a 1080p projector (1920 X 1080 resolution) as the basis for the following calculations. Let’s say I want a build area 144mm wide along the X axis (the Y axis will be calculated later). Divide 144 (the desired width) by 1920 (the projectors width resolution in pixels) this will equal 0.075. Use this number (0.075) to multiply the projectors height resolution in pixels by (1080 X 0.075=81) which gives you the height of the build area in millimeters. Incidentally 0.075 (75 microns) will also be the build areas XY resolution in millimeters. Make a note of these numbers as width, height, resolution.

these are the formulas without the talk.

DesiredBuildAreaWidth / ProjectorWidthResolutionInPixels = XYBuildResolution

ProjectorHeightResolutionInPixels * XYBuildResolution = DesiredBuildAreaHeight

 

Setting up a 3d print resolution and letting the build area match: Lets say you want to print at an XY resolution of  0.05mm (50 microns) multiply 1920 (the projectors width resolution in pixels) by 0.05 for a build area width of 96mm, multiply 1080 (the projectors height resolution in pixels) by 0.05 for a build area height of 54mm. Make a note of these numbers as width, height, resolution.

ProjectorWidthResolutionInPixels * DesiredResolution = BuildAreaWidth

ProjectorHeightResolutionInPixels *  DesiredResolution = BuildAreaHeight

 

Entering the build area information into Creation Workshop

Your projector should be on and operational.  Open Creation Workshop (beta 3), Click “Configuration” (gear icon) > click “Machine Config” tab, select the profile you want to use from the “Profile in Use” list (just use Default_SLA). Both your monitor and the projector should be in the “Select Print Display Device” list.  You may be able to determine which is the projector by clicking on the selections in the list, in general, the selection with the resolution of “Width” 1920 and “Height” 1080 will be the projector for a 1080p projector or “Width” 1024 and “Height” 768 for a low def projector (you can also use the “Machine Control” tabs “Show” button to determin which is the projector), in any case, figure out which is the projector and make sure it is selected. Note that the “Select Print Display Device” fields are automatically filled by Creation Workshop, you should not enter any settings in these fields. In the fields under “Axis Length”  enter the X and Y numbers you made note of earlier and enter a Z axis size appropriate to your printer. Enter any other settings in Machine config as needed then click the “Apply” button. Note that the Z axis resolution is separate from the XY axis resolution and is set in “Configuration” > “Slice Profile Config” > “Slice Thickness (mm)”.   “Slice Thickness” is your Z axis resolution and it can be set independently of the XY axis resolution, for example, you can have 0.1 mm Z axis resolution and 0.05mm XY axis resolution.

At this point you have to set up the projector to project the correct sized image on the vat floor.  You will need an inexpensive digital caliper and eye protection such as welding/brazing goggles (goggles with a #5 filter work very well and can be had for about $10.00). Your projector should be on and operational before starting the following operations.  Setting the projector to a lower brightness mode, if supported,  may make things a bit easier.  In Creation Workshop click “Configuration” (gear icon) then click the “Show Blank” button. The projector will project a blank image that clearly shows the “frame” of the projectors image area, what you need to do is to set your caliper for the build area width you made a note of earlier and lock it. Set the projectors zoom in the middle of it’s range then position your projector so that you get a focused image on the vat floor as close to the desired image size as possible, use closeup lenses if needed.  Measure the top and bottom width if the projected image and adjust the projector mount until they are equal in size (if they are not equal the projected image plane and the vat floor are not parallel) then measure the diagonals (if the diagonals are equal the image is square). Use the projectors zoom to fine tune the width of the projected image to the build area width. Don’t worry about the height it will be the calculated height (ok, go ahead and measure it if you want to).  Mark or tape the projector lens settings.

You can set up or change your 3d print area for any size or resolution you want, if you use the techniques explained above and your 3d prints will print the same size as you designed them regardless of resolution or build area size you select.

HL

 

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3d printing notes 2

Vat Stuff

The vat is where the rubber meets the road.

My 3d printers vat is made of .5″ (12.7mm) cast acrylic (not extruded).  Cast acrylic does not have locked in stresses, so when you clean it with a solvent (like alcohol) it does not crack. After you saw or drill extruded acrylic it will start cracking as soon as you expose it to solvents. Making a vat out of cast acrylic is a bit more expensive but being able to clean your vat without it falling apart makes up for that big time.

I make my vat so that the outside edges are 5″ X 7″ (This allows for a print area of 102.4 mm X 76.8 mm (for a 1024 X 768 pixel resolution projector at 0.1 mm print resolution or 51.2mm X 96.0 mm for a 1080 X 1960 projector at 0.05mm print resolution) or any variations up to about 4.5″ X 6.5″ (the resin uses the edges around the build plate as a reservoir). This size also allows me to use pre cut 5″ X 7″ photo frame glass (I’m not in to deep and exotic, if picture frame glass works for my vat floor that’s good enough for me).

Why are the vat walls so thick (.5″):  If you cut (have cut) the pieces of the vat with a reasonable amount of accuracy all you have to do to construct a vat is to run a line of (thick) acrylic adhesive on the edges and hold the parts temporarily together on a flat surface then clamp or strap the parts together until the adhesive sets, the edges are essentially self aligning. Try that with 0.125 or even 0.25 thick acrylic sheet. Also, after the adhesive sets a flat vat wall bottom allows you to attach the vat floor glass easily with just a thin bead of silicone sealant (I place a sheet of sand paper on a flat surface and sand the bottom of the vat smooth before attaching the vat floor glass).

The care and feeding of my Sylgard 184 vat floor coating.

I use Sylgard 184 as a vat floor release layer (I am going to try other release layers as time permits), and I have found several things affect the Sylgard 184 vat floor layer.

One of the most important issues is vat tilt/build plate lift timing. If you lift the build plate before or at the same time you tilt the vat after your layer exposure you might as well have not created a vat tilt mechanism at all.  I have found that if you tilt the vat to the point where the part releases then lift the build plate you are going to be a lot better off.  A slow tilt is best, if you are in a hurry you are going to find that you are going to have the sylgard wearing out quicker and parts peeling off of the build plate (resin shrinkage also has a part in this).  If you hear the build plate “snapping off” the vat floor then something is wrong, either the vat floor release layer is worn out or the build plate is lifting too soon (before the tilt releases the part from the vat floor), the vat floor release and build plate lift should be relatively smooth with only light sticking even when the entire build plate is releasing from the vat floor. I also think (my opinion only) that the thickness of the Sylgard release layer has an effect on the part releasing from the vat floor. I use a thickness of about 3mm, I have used thinner layers and have found that thinner layers do not work as well.  My belief is that the thicker layer “stretches” more as the part is peeling from the release layer making the release easier. When 3d printing resin is exposed it can get hot and if over exposed the resin can possibly get hot enough to damage the sylgard release layer, very short exposure times I think may also be problematic (this is admittedly speculation on my part). I run exposure tests to get the minimum exposure needed to get a good layer and to adjust layer thickness (more on this in another note).

I drain and clean my vat after every print unless I am making multiple prints one after the other without problems (failed prints etc).  This is what I do: drain the vat of resin back into the resins storage container through a re-usable coffee filter (cheap, fine metal mesh, cleanable with alcohol).  Then I rinse the vat with water and shake as much water out as I can then spray with alcohol (92%) from a spray bottle (avoid breathing the spray), rinse with water again, spray with alcohol again, then wipe off any “shadows” on the vat floor with a piece of microfiber cloth or “sham wow” dipped in alcohol then a last light alcohol spray on the vat floor to “wet” the vat floor (so that it dries without spots), then I set the vat on edge to dry.

Sorry about jumping between inch and metric measurements.  3d printing is mostly metric but a lot of easily available parts are inch.

vat

vat

HL

 

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3d prints done on the updated printer

The photos show a 3d print made on my updated dlp based 3d printer. The lines on the print represent well defined 0.1 mm layers.  The layers stand out because I printed the part at an angle to minimize large flat faces of the part having to separate from the vat floor. The photos also show the support structure I used which were created using Creation Workshops auto support generator. The part is 86mm X 70mm X 19mm without the supports. Printed with Makerjuice SubG+ yellow resin and Creation Workshop RC3 software.

3d print image 100_1776

3d print

3d print

HL

 

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3d printer rebuild

It started the way these things usually start, you decide to upgrade a part and then one thing leads to another which leads to another which leads to another…  In this case I wanted to have a vat that was easier to remove from the printer so that it was easier to clean the vat, drain the resin and replace the vat floor when needed. The only problem is if you change the vat design you have to change the tilt assemblies vat mounting hardware to accommodate  the new vat design. I decided that since I was going to change the tilt assemblies vat mounting hardware, which was a considerable change to the assembly anyway, I might as well go on and change the vat tilt assembly itself to an improved design I had been thinking about. Of course since I was going to change the vat and tilt assembly I figured I might as well change the build plate release and leveling hardware which I hadn’t been totally satisfied with and since I was going to go to all the trouble of upgrading the build plate release and leveling I might as well change the build plate to aluminum . However, by changing the vat tilt assembly I changed the relationship between the build plate and the vat so I needed to change the z axis carriage assembly. Oh yes, I also needed to change the projector mount because after the other changes the projector no longer lined up with the vat.  Since I was changing everything anyway I also changed the step motor drivers to better step/direction drivers (which of course forced me to rewrite my arduino software to work with the new motor drivers).

All in all I think it turned out pretty well.

 

3d printer rebuild

dlp projector 3d printer rebuild

I will be posting build details in a day or two.

HL

 

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3d printer rebuild, the z axis and build plate

One thing I have come to realize about this type of 3d printer is that what counts is that the build “face” (the layer that is being exposed), the vat floor and the projected layer image have a particular relationship to each other during the layer exposure.  Before each layer exposure the build face should be 1 layer thickness higher than it was for the previous exposure and the build face should not have moved in the X or Y direction or have rotated. The vat floor should return to the exact same position and be parallel to the build face for each exposure.  Between exposures the parts of the printer can twist and jiggle all they want as long as the build plate and vat are where they are supposed to be and settled down for the layer exposure.

If you look at my printer you see the vat/tilt and build plate assemblies are mounted on arms, not good for stiffness you might think but if repeatability rather than absolute stiffness is the goal having these assemblies on arms does the job just fine and makes the printer both easier to build and highly adjustable.

The z axis assembly consists of an adept linear slide scored on ebay for $60.00. The main reason it was so cheap is that it was an older unit that used a servo motor that required an absurdly expensive controller that you would be crazy to buy for an obsolete part. The solution, buy it and replace the servo motor with a stepper motor and get a matching timing belt cog wheel ($5.00 plus $15.00 shipping from sdp). the linear slide is attached to the “backbone” column (an old polaroid mp4 copystand, basically a large aluminum extrusion) with custom made polypropylene “clamps” that I fabricated on my cnc router. Attached to the linear slide carriage is another polypropylene part made on the cnc router that holds an aluminum extrusion horizontally that, in turn, another extrusion is attached to forming an elbow joint. The build plate assembly is attached to the end of the second extrusion. This configuration allows me to adjust the position of the build plate in relation to the vat considerably.

3d printer build plate carriage arm

3d printer build plate carriage arm

The build plate assembly is made to be relatively easy to adjust for parallel to the vat floor, it basically consists of a leveling foot being held in tension by three screws. Instead of trying to explain how it works I have a photo:

Build plate leveling assembly

Build plate leveling assembly

I adjust the parallelism between the vat floor and build plate using a level glued to a block of corian. Since the top and bottom faces of the corian are paralle adjusting the parallelism of the vat floor and build plate is just a matter of placing the  “level block” on the vat floor noting the location of the bubbles on the level then holding the level block on the face of the build plate and adjusting the build plate leveling screws until the level bubble positions match the positions measured when the leveling block is on the vat floor.

level block in vat

level block in vat

level block on build plate

level block on build plate

I also changed the build plate from corian to aluminum. Printed parts would attach to the corian so aggressively that after removing the parts from the build plate I would often need to refinish the build plate using a stationary belt sander. Parts adhere to the aluminum reasonably well but putting some time into planning part supports and wall thicknesses go a long way towards making successful prints with the aluminum plate. For larger parts I will also “paint” the build plate face with a thin coat resin and cure it prior to printing a part. This creates a surface that parts can better adhere to when being printed.

HL

 

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