Mold for PDMS window


as promised, here is the mold for PDMS window. designed by Jannik Peters.

bottom and top mold. printed on Dimension machine. you can print on Eden or Objet, just make sure the support material won’t get in touch with the PDMS, it will make the PDMS not able to cure.

put the glass in the bottom mold. then carefully pour some PDMS around the edge so that it seal the glass. put the whole thing in the oven for 20 min (150F). no need to put the top mold on for now.

After that take the bottom mold out, put the top mold on. pour the PDMS in till the PDMS reach to the surface of the mold. you might wanna level your oven so that the PDMS is flat.

(I manually drilled the hole a bit bigger later. it’s updated in the file already). After another 20 min in the oven, the PDMS should be cured.

remove the top mold.

get the PDMS window

then screw it back on the tray

Mold_Bottom_1.stl (112.0 KB)
Mold_Top_1.stl (36.8 KB)

Pdms-friendly resins

Thank you so much for the Mold for the PDMS Window!




Very Cool I will be giving this a try!


what type of glass did you use?


take the glass from the old tray. clean it well


Is there anyway you can print the mold for me? This is bigger than Ember can hold and I don’t have another 3d printer. I will pay you some money for your trouble if you are willing to print this for me.

Thank you so much for your help!



If Jifei is busy, I would try Shapeways or Fictiv – they should be pretty economical.


@J_O Thank you for this. May I know how many grams or ml of part A and B you need to make one pdms window? Thank you!

UPDATE: I figured out that it takes about 20-25ml of PDMS to make one window. Do you use a vacuum chamber before putting it into the oven? Mine had bubbles and the pdms separates from the glass, too.


How do you prevent PDMS from getting separated from glass? Ember support told us that they use Wacker Primer G790, but it is not sold in US. Is there anything else anybody use? Thanks,



does anyone have a supplier
for PDMS (article number, manufacturer)
thank you for your help



I use this :


Thanks for your help


@patrickleephoto @J_O
So it’s time I give this a try. Can either one of you elaborate on how successful this has been for you guys over all?
Patrick - did you find a primer for the glass?
Jifei - do you even use a primer?
Oven time and Temp?
Vacuum out the air bubbles before?
Does this last as long as the purchased trays?


Waker Primer G790 sold by Perma Flex Mold. 1-800-736-6653. $65.88 plus shipping (Hazardous so cost extra). We couldn’t get the J_O’s mold working so we’ve spent nearly $1,000 and HUGE amount of time and made Aluminum/Stainless steel mold from local machine shop. Vacuum out the air bubbles. We use vacuum pressure oven ( to remove remaining micro air bubbles.

Success rate of 80% to 90%.

I would say it lasts about 70-80% life time of purchased trays.



Good information!
80% is fair - but to only last 70% of that… hmmm - is it really worth the effort? Do you think your saving that much per tray?

I have access to a ‘free’ machine shop so I was already headed down that path. I figured I would treat it like an injection mold and add a draft angle to all sides. I planned to use a gasket under the glass slide as opposed to the ‘pre seal’ step that J_O outlined to seal the glass in the mold first.

How thin is the PDMS fluid? (water vs maple syrup)

In regards to the vacuum oven, I suspect it’s because you already had one. Are you actually injecting the PDMS under vacuum or just using filling the mold and using the chamber to heat it under vacuum?


I use B9C Yellow which I can only print 4 times on the PDMS. That’s reason I have to make my own. If I use CPS Resins, then I would not even worry about it.

I used to use Sylgard, but I found that QSil is just about same, but only 1/3 the cost of Sylgard. So I switched to QSil 216 :

We mix the QSil Part 1 and Part 2 (Activator) and then pour it to the molding. And then put glass on top. Pressure cook after that. A LOT of trial and error. We literally spent about 6 months try to get it right.

We are jewelers and we have Vacuum Wax Injector. We just emptied wax injector and use it as pressure oven.


By the way, I still only get 4 prints with B9C Yellow even I tilt tray when I am not using it.


Thanks again.
I’m using a tough resin from 3Dresyns with a custom color mix. I’m getting about 12 prints (327 layers @ 100um), so I’m going through the trays in less than 3 days.

With the ‘upside down’ approach your using - is it the aluminum or steel that forms the top side of the PDMS window in the tray? I would image you have this polished to a mirror finish.

I can also see how this approach would give more consistent results for the final PDMS height in the tray when it’s assembled.


Yes, mirror finished stainless steel for the top side of the PDMS.