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Silicone PDMS layer - possible to replace PDMS without replacing whole resin tray?

Hi All+Formlabs

How many prints are people finding they can make before the silicone layer gets cloudy?The B9Creator wiki ( http://b9creator.pbworks.com/w/page/64029114/PDMS) suggests 3-7 prints before most find the silicone becomes cloudy. Of course the B9Creator folks only have to replace the PDMS layer, not the whole resin tank tray. If our silicone gets cloudy at a similar level of use, it’s going to get very expensive if we have to replace the resin tray every time.

So how many prints are people getting before the resin  tray becomes cloudy?

Has anyone thought of trying to just replace the PDMS layer like the B9Creator folks instead of replacing the whole tray?

I would say you can easily print 1-2 resin bottles worth of parts before you see any clouding. Even then, I would worry more about sticking, then the cloudiness.

The b9 people don’t have much choice when it comes to printing area. The form1 printing area is much larger, and you should move the prints around to maximize the life of the tray.

I would also like the option of re-coating the tray with PDMS, but we need to know how much PDMS to use and Form Labs is not releasing the info yet. I’m actually more interested if we can use the teflon film like the Muve 1 3d printer uses. It seems much more durable than PDMS and seems to last longer too.

Is it safe to assume that the PDMS layer is the same material that the B9 uses?  If so, why not weigh the tray new, use the tray until the layer need to be replaced, peal it off, then mix up a batch and pour until the weight matches the new tray weight.

Then just replace the tray if and when the tray gets scratched up or damaged.

1 Like

Nice one David. I’d be assuming that even if they’re not the exact same brand of PDMS that weight would be very similar - I guess we could go one step further though and measure the volume as well of the formone pdms layer by submerging it in water in a measuring cylinder.

Something I’ll be trying soon as my printer arrives and my silicone goes cloudy …

I’ve also been having a lot of trouble with parts sticking to the PDMS layer. This is most apparent in seeing rounded corners in the parts I’m printing. Clouding has yet to become an issue (just finishing my first bottle of resin).

If anyone has a chance to experiment with the teflon film, or something similar, I’d be interested in hearing about the results.

The teflon film available is actually thinner (2.54mm) than what’s inside the form1 resin tank (3.9mm), so it’s not possible to use that. But it should be pretty easy to re-coat with PDMS. Just need to figure out how much to use. The amount has to be exact, because you can’t recalibrate the form1s zero point, or starting point.

I’m going to buy an accurate-ish (to 0.1g)  set of scales (these seem affordable: http://www.ourweigh.co.uk/top-pan-precision-balances/on-balance-3000-digital-table-scale.html) and once my Form1 arrives (I’m told it’s in the next UK shipment) I’ll weigh my 3 resin tanks. If they all weigh the same I’ll also peel out the silicone from one of them and weigh it, then I’ll re-coat it with PDMS using my scales - and then report results here…

@Monger - by they way how did you arrive at the 3.9mm silicone layer thickness - vernier callipers?

Yes I used calipers. I just thought of something. It may be impossible to replace the PDMS in the form1 tank (like they do for the b9 creator tanks), because since the Form1’s peel process puts so much force on the PDMS, it may be glued/fused to the bottom of the tank, and you can’t just lift/peel it off like the b9.

Thats’ why they call it a consumable. Haven’t tried replacing it, so it’s just a theory.

guess I’ll find out in a week or two (assuming delivery isn’t delayed more than it is already) - unless someone from Formlabs wants to chip in at this juncture?

@Monger Designs

“The teflon film available is actually thinner (2.54mm) than what’s inside the form1 resin tank (3.9mm), so it’s not possible to use that. But it should be pretty easy to re-coat with PDMS. Just need to figure out how much to use. The amount has to be exact, because you can’t recalibrate the form1s zero point, or starting point.”

It is possible to remove 1.34 mm (3.9-2.54) from top of the plastic rails of the tank. Then stick two gaskets of the same 1.34 mm thickness on the metal rails. Thus effectively making tank 1.34 mm higher than its current zero point.

You can technically get that to work, except I wouldn’t recommend messing with the Form1, unless your warranty has expired or something.

@Monger Design, thank you for taking care.

re ‘zero position’

  1. There should be either fixed zero position - with switch or some opto electric device which could be adjusted by screw, etc.

  2. Alternatively they could have implemented variable ‘zero postion’ by measuring current which flows through corresponding drive and switching it off when there is no way to move building platform downward anymore.

(1) is easy to check having printer at hand.

(2) if you find no microswitches for zero position, you may experiment with placing some firm piece of plastic (2-3 mm thickness) instead of tank and start printing - so you will see if there will be physical touch when positioning starts.

I just found a good sized cut in my PDMS layer, so I will be playing with it later this week. My plan it to use the density of Sylgard 184 (~1102 kg/m3) to determine the weight necessary. Before pulling off the PDMS, I’ll also try putting a thin layer of plastic in the tank to see if there is an automatic switch for determining the build platform’s zero position.

In the meantime, two new tanks have been ordered.

Hey guys, we’ve replaced our non-stick coating in our vat and it’s been working great! We have owned a B9 for a while now and have changed out their vats probably 30 times, so changing the PDMS on the Form1 wasn’t a big deal. I used 88mL of Sylgard 184 in a 10:1 ratio. Seeing as I figure a few people are probably wondering if this can be done, I wrote a blog posting about it.

http://blog.madesolid.com/2013/09/changing-pdms-coating-form1-printer-vat/

I think the Form1 auto levels every time the build platform dips into the vat. From leveling the B9 creator by hand so many times, I know that even a slight difference in the amount of PDMS you put in your vat  requires re-leveling. I don’t think FormLabs could guarantee that the PDMS in every vat they send out is at the same level, so the printer has to auto-level when you hit print.

I hope this helps. Let me know if you have any other questions.

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Excellent news Brian !! thankyou so much for the update, that’s exactly the result I was hoping for in this thread :slight_smile:

This right here is awesome! Thank you so much for clearing this up! I will be ordering a second vat with my order and some sylgard 184! :slight_smile:

You have no idea how many people you have saved! Now i cant wait to get my printer!!!

Anyone has do that? I have bad printouts with 80+8ml and 75+7,5ml from Sylgard184. The PDMS Layer is over the minimal resin filling marking = too high

The ground plate from the support is 0,75mm instead of 1,5mm.
My next try is 60+6ml.

@Carsten The PDMS Layer on every vat I’ve seen from FormLabs has had the PDMS layer higher than the minimal filling mark on the vat, so we didn’t take that as an indication that we had done the calculation wrong. The most recent vat that we received from FormLabs had less PDMS in the vat to start. It’s the first time that I have seen the PDMS so low from the manufacturer. It also lead me to believe that there is definitely some auto-leveling going on before the print initiates. How else would the printer know if you had a new or old vat installed?

We have a vat we need to replace the PDMS on right now. After seeing the new Form1 vat, we decided to give 60+6mL a try as well. We should compare notes after giving that amount a try.

My measurement tell me mine is just over 77ml (Volume = 77521.69 cubic millimeters)

160.75mm square by 3mm thick (Hard to measure the thickness as it has a little sponginess)Closer to 2.98mm thick but the extra should be about right for excess still in the mixing cup.

www.ellsworth.com Ellsworth Adhesives

| 1 | 184 SIL ELAST KIT 0.5KG | Dow Corning Sylgard 184 Silicone Encapsulant Clear 0.5 kg Kit |   |

Totals

| Product Total: | $59.48 |
| Sales Tax: | $5.28 |
| Shipping: | $15.97 |
| Grand Total: | $80.73 |
|   |   |

Package arrived today, the Base is 453G = just under 1 pound with a specific gravity of 1.03

Volume = 453/1.03 = 440 ml

440/70 = 6.3

should get 6 new PDMS layers per Base and Curing Agent