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DIY And Technical Information:


Index:

LittleRP Compatible Vat Technical Information

Mid Sized Vat Technical Information

Tensioning Vat FEP Film

Build Plate Leveling And Zeroing

Build Plate Adhesion Test For The Drumhead Flexvat

Exposure Testing

DLPMaskGen Program

Tips And Tricks




LittleRP Compatible Vat Technical Information:

Assembling The LittleRP Compatible Vat (video soon)

This Drumhead Flexvat can be used with printers that can project and focus layer images 20mm above the surface the 3d printer vat sits on. The Drumhead Flexvat can be adapted to many 3d printers by creating an adapter or printer platform using the window and hole layouts found below.

 

LittleRP Compatible Vat, Window And Mounting Hole Pattern (dxf)

If you have access to a laser cutter/engraver you can cut your own replacement FEP windows and gaskets using the following information.

LittleRP/Small Vat FEP Pattern (dxf):

40w laser: 45mm/sec with air. A 9" x 12"  sheet of FEP will yield 4 Windows. 1 window is needed when assembling this vat.

4 FEP Windows

 

LittleRP/Small Vat Gasket Pattern (dxf):

40w laser: 45mm/sec with air. A 9" x 12" (1/2 sheet) of craft foam will yield 4 gaskets. 1 gasket is needed when assembling this vat.

4 Gaskets

 


Mid Sized Vat Technical Information:

Assembling The Mid Sized Vat (video soon)

This Drumhead Flexvat can be used with printers that can project and focus layer images 20mm above the surface the 3d printer vat sits on. The Drumhead Flexvat can be adapted to many 3d printers by creating an adapter or printer platform using the window and hole layouts found below.

Layout Information for Custom Adapters Or Platforms: Mid Sized Flexvat On 20mm Grid DXF

Layout Information for Custom Adapters Or Platforms: Mid Sized Flexvat On 20mm Grid PDF


 If you have access to a laser cutter/engraver you can cut your own replacement FEP windows and gaskets using the following information.

Mid Sized Vat FEP Pattern (dxf):

40w laser: 45mm/sec with air. A 9" x 12"  sheet of FEP will yield 2 Windows.

1 FEP Window

2 FEP Windows

 

Mid Sized Vat Gasket Pattern (dxf):

40w laser: 45mm/sec with air. A 9" x 12" (1/2 sheet) of 2mm thick craft foam will yield 2 gaskets. 2 gaskets are needed when assembling this vat.

1 Gasket

2 Gaskets

 


Tests And Adjustments

Tensioning Vat FEP Film

To work well flexvats have to have highly tensioned FEP film as a vat floor. Tensioned FEP is what makes this type of vat work. The flexvats on this website are able to highly tension the FEP vat floor film and allow re-tensioning when needed without altering the printers focal plane (the part size or focus will not change when re-tensioning the vat).

 Adjusting the vat tension on the LittleRP compatible Flexvat:

Use the supplied 2.5mm hex bit  and thickness gauge. For the initial adjustment (new FEP and gasket) place the supplied thickness gauge flat into the gap between the top and bottom plates at the bolt you are tightening and begin tightening the tension so that roughly even tension is being put on the FEP (do not tighten each bolt all the way down before going to the next). Tighten each tension bolt until the top and bottom plates lightly touch the thickness gauge at each tension bolt position. The "teeth" on the thickness gauge can be used for re-tensioning the vat if needed, the initial tension corresponds to the "dot" tooth on the gauge.

 

Adjusting the vat tension on the Midsized Flexvat:

Use the supplied 2.5mm hex bit  and "3mm" thickness gauge. For the initial adjustment (new FEP and gaskets) place the supplied thickness gauge flat into the gap between the top and bottom plates at the bolt you are tightening and begin tightening the tension so that roughly even tension is being put on the FEP (do not tighten each bolt all the way down before going to the next). Tighten each tension bolt until the top and bottom plates lightly touch the thickness gauge at each tension bolt position. If the vat needs to be re-tensioned use 1/2 or 1 turns at a time on each of the tensioning bolts until the desired tension is reached.

Build Plate Leveling And Zeroing

Leveling and zeroing the Adjustable Build plate:

If you are using the LittleRP vat and build plates you can adjust the build plate by lowering and adjusting the build plate leveling thumbnuts until the build plate is sitting flush on the lip of the vats riser (flat on the EFP film) using a light under the vat will help. It is best to level and zero the build plate with the vat dry. It is ok for the build plates zero position to be lightly touching the riser lip/FEP film.

 If you are using the Midsized vat and build plate insert the included leveling plate onto the lip of the riser and level the build plate against that using the build plate leveling thumb nuts. After you have leveled the build plate you can set your zero position by lowering the build plate until you see the edges if the FEP film slightly sag the slightly raise the build plate until the sag disappears, this is where you will set your build plates zero position. It is best to level and zero the build plate with the vat dry. It is ok for the build plates zero position to be lightly touching the FEP film.

  

Build Plate Adhesion Test For The Drumhead Flexvat:

Test stl file: 10 dot by 6 dot (49mm wide, 29mm high, 0.3mm thick)

Test stl file: 10 dot by 6 dot (49mm wide, 29mm high, 0.6mm thick)

The FEP release layer on your vat can last through many print jobs (50 to 100 or more being typical) or it can be damaged on the first. The one thing that is most likely to damage your vats FEP release layer is heat. Very high temperatures can be generated when a thick layer of resin is exposed to uv light, this can cause even FEP to soften. If a part being printed does not stick to the build plate and falls into the vat it will allow a thick layer of resin to be exposed often many times until the failure is noticed, this will cause the exposed lump of hardened resin to get very hot and damage the FEP. The easy way to avoid this problem is to run a few tests before you start to print real parts this will help to insure you do not have build plate adhesion problems

 Build plate adhesion test 1: make sure your build plate is reasonably parallel to the build plate and zeroed (zero your build plate with the vat dry, you do not need to have a zero position that has any gap between the build plate and the fep, the build plate lightly touching the FEP film is fine) create a test part 4 - 6 layers thick or get one from the "DIY And Technical Info" page of flexvat.com. Print the test part with 3 base layers of 30 seconds (this will not damage the FEP, thin layers can be exposed for very long times and not damage the FEP) with the remaining layers of the test having your normal exposure time. After completing the test the print should be firmly attached to the build plate. If the part is firmly attached to the build plate you are done but please read the rest of this paragraph anyway. If the test print is not firmly attached to the build plate (the part didn't stick at all or easily wipes off of the build plate) and your build plate is properly aligned and zeroed you most probably have over pigmented resin (it is not an exposure time problem, the test had 3 layers exposed for 30 seconds each which is plenty of exposure). Pigment in resin does not only color the resin it is instrumental in controlling the cure depth of layer exposures. A resin with a high pigment concentration will only successfully print thin layers no matter how high the exposure time so if your prints layer thickness is larger than the depth that the resin will cure you are going to see constant print failures. The trick is to get the resin pigment concentration to a point where the depth of cure is slightly thicker than the layer thickness.

 

Build plate adhesion test 2, if needed:  Let your resin settle overnight, pour the clear settled resin into a separate container. Shake up the settled resin/pigment mix in the original bottle and pour half of it in to the clear resin, shake the resin to mix the pigment and resin then use this resin to print the 4-6 layer test part. The part will most likely stick to the build plate very well. If you see problems like thickening of  your prints in unexpected areas or lack of detail add more of the concentrated pigment/resin mix to your resin.

 

The build plate adhesion test is one you should perform with new resins or when you change resins.

 

Exposure Testing

Exposure time controls the "hardness" of your resins cure, pigment concentration helps to limit the thickness of the cure.

Exposure testing for resin based 3d printers is not a straight forward as it may seem at first glance. The reason for this is that you are not just dealing with a photosensitive material (the resin) but also the effects of any pigment added to the resin. Pigments in 3d printing resins control the maximum thickness of a cured layer of resin over a very wide range of exposure times. As a rough example, lets say you are making a single exposure into a puddle of a particular suppliers red resin (no build plate) with a 3 second exposure. After making the exposure you measure the thickness of the hardened resin and it turns out to be 0.25mm. If you repeat the test but increase the exposure to 15 seconds then measure the thickness you may find that the cured layer has only increased to 0.28mm, test again increasing the exposure to 50 seconds and the thickness may only increase to 0.3mm.  So a high pigment concentration in your resin can make it impossible for you to make a successful 3d print, the reason for this is simple, if the depth of cure is less than or even equal to the layer thickness you are printing at the part will never stick to the build plate and if by chance it does your going to have a print that is going to fail in any number of ways.  The resins cure thickness for a particular exposure time must always be thicker than the the layer thickness you are printing at. Resin pigment concentration also has a lot to do with the actual resolution of your printed part and artifacts that may appear on your prints (such as a flat bottomed horizontal hole - too little pigment)

 

Testing Your Resin

You are ultimately shooting for a resin cure thickness roughly 20% to 30% thicker than the layer thickness you are printing at this allows the layers to bind together

This is what you will need:

A cheap digital caliper (harbor freight, ebay etc. expensive ones will work also)

Office supply store/hobby store clear mylar or a scrap FEP, a sheet of glass (cheap photo frame).

A way to post cure the test image (a source of uv, in a pinch use daylight)

Some settled (clear) resin. You can pour a small amount of resin into a container and let it sit overnight.

Use DLPMaskGen software (how it works, what it does, windows only) or something that does the same thing. Note: this is software I wrote to make projector brightness masks and perform exposure tests, however the brightness mask generator tab is disabled at this time. Even though the brightness mask generator works very well (I use a generated mask on my printer) I still need to work on the user interface a bit to make it easier to use and I do not have the time right now to field support inquiries. Give me a month or so to clean up the code and I will enable the dlp projector mask creator tab.

Please note that windows or your antivirus program may complain when you download or try to run the DLPMaskGen installer or program because the program is new and it has few users. You can safely download and run this program.

Download and run the DLPMaskGen Installer. To run the program click the DLPMaskGen application icon in your programs folder (programs, all program, all apps depending on you version of windows). Play with the exposure test settings and projector blanking button to get a feel for how the test works (this test is definitely not rocket science).

To run the test:

You will want to click one of the "Blank Projector" buttons in the the DLPMaskGen program to make the projector show a black image. I usually also block the projector image so that there is no hardening of the resin by the black image. Enter the base exposure time and exposure step time.

You can use your vat for this but i suggest using the piece of glass for this test. Place the glass where your vat would normally sit. and use something to raise the glass to roughly the height that your vats floor would be at. You can use the glass directly but I suggest using a scrap of mylar or FEP (cut or bend a corner so that you know the orientation of the exposed "dots" after the test). Center the mylar or fep on the glass and carefully pour a puddle of resin on it large enough to cover the test area (I use an eyedropper, pouring directly from the bottle is not recommended). Click the "Make Exposure" button. The DLPMaskGen program will make 16 exposures in the form of an array of dots whose exposure times corresponds to the times shown on the programs "Exposure Times" table. After the test exposures are done pour the unexposed resin back into the resin containers (be careful to not pour underexposed "dots" into the container).  Take the exposed sheet and wash it off using your usual method (I use diluted Dawn dish washing liquid in a spray bottle with a water rinse then 92% alcohol) any dots that dissolve or easily wash off probably don't matter but note how solidly the dots have cured (poke then with something). Post cure the test. After curing you can either measure the thickness of the mylar then measure the thickness of the "dots" on the mylar and subtract the thickness of the mylar from that measurement to get the cured dots thickness or you may be able to pop individual dots off of the sheet and measure the cure thickness directly. You want a dot that is about 20% - 30% thicker than your desired layer thickness.

If no dot is thicker than your desired layer thickness you need to increase your layer exposure time or decrease your resins pigment concentration (see below) or you are going to have problems.

If all dots are thicker than twice your desired layer thickness you need to decrease your exposure time or increase the amount of pigment in you resin (do not just dump pigment into your resin, an amount that clings to the tip of a toothpick in a liter can go a long way). Thick layers decrease print resolution 

If one of the dots in the test is 20% to 30% thicker than your desired layer thickness look up the corresponding exposure time for that dot from the DLPMaskGen exposure table and use that exposure for printing.

 

 

Tips And Tricks

Base exposures

Using a Flexvat you can have extremely long base exposures so that you can firmly attach your part to the build plate, 3 or 4 30-60 second base exposures are not uncommon. Long base exposures do several things they increase the thickness of the cured layer, the "hardness" of the cured layer is also increased, in addition, long base exposures give the resin time to squeeze out from under the build plate into a thin layer since the base exposures are those most likely to present the full face of the build plate to the FEP film. You will not damage the FEP release layer if you expose the resin at your normal layer thickness, if you try to expose resin in a thick layer (with the build plate sitting above the FEP or with no build plate) you risk damaging the FEP because of the heat generated when exposing thick layers of resin.