PDMS curing

Hardware issues, problems and solutions
jasonspyke
Newbie
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Posts: 7

PDMS curing

Post#1 » Wed Jul 17, 2013 6:36 am

Hi guys,

Recently I wrecked my PDMS (and vat, which is another long story since rectified).
In trying to recoat the PDMS, both attempts to do it ended up unsatisfactory. Basically it took a long time to cure (>4 days), and even post cure, the build side was still tacky, and significantly thinner than the well. There was no noticeable waterfall, and the surface was near flush.

I used sylgard 184, with a 10-1 ratio measured out on a digital kitchen scale.

I tried is twice, and Both times were similar, so I am obviously doing something wrong. Hope someone can offer some advice, as I need to know how to properly fix the PDMS...

Thanks!
Jason

maetti
B9 Maker
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Posts: 140

PDMS curing

Post#2 » Wed Jul 17, 2013 6:45 am

Hi Jason

I too had this problems at the beginning. The PDMS was completely flat after one day.
Today I have a solution it works great with the waterfall and after one day all is perfect cured.

I pour the silicone into VAT, then swifel it from right to left so that all the surface was once covered, too about 1cm to all side walls. Then I let flow all the silicone to the build side and lay the Vat to a completely flat surface (I made it flat with my Iphone, worked quite well).

Now the most important: Directly after laying the VAT to the flat surface, I switch on a 250W headlight adjusted to the VAT with a distance of about 20 to 25cm. So it cures with the heat of the light and the waterfall comes great like it has to be.

This worked great for me and the prints are always fantastic.
Mat

jbryant
B9 Maker
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Posts: 89

PDMS curing

Post#3 » Wed Jul 17, 2013 6:59 am

There is a video on you tube of how you are supposed to do it. Temperature definitely has a lot to do with cure time. If you have it in a cool basement or something, it will take longer.

I've recoated several times and have had no issues, other than the first time the waterfall came out a bit thin. Now I coat the whole thing and tip it up to let the mass go to the high side for about 5-10 minutes. That seems to do the trick before laying flat for final curing. I also cover it with a piece of printer paper to keep dust out but allow it to breath.

http://www.youtube.com/watch?v=q3Aw_ZG4V4E

jasonspyke
Newbie
Newbie
Posts: 7

PDMS curing

Post#4 » Wed Jul 17, 2013 7:41 am

Thanks for the replies, I will try the lamp, maybe add a space heater too.

form
B9 Maker
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Posts: 134

PDMS curing

Post#5 » Wed Jul 17, 2013 6:51 pm

Lamp works really well for me too.
I use one called a par38 (not sure what you have there).
I lay my vat on a glass sheet (level it with a spirit level on the vat first) and put the lamp underneath shining up.
You can buy a cheap thermometer and pop that on the shelf next to the vat and your good to go.
Mine dries in about 4 hours and gets a really nice waterfall (which I think is important).

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tim.yoshi
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PDMS curing

Post#6 » Wed Jul 17, 2013 7:34 pm

Sounds like you haven't mixed components well. As Mike describes it should be mixed thoroughly for few minutes.
Image

jbryant
B9 Maker
B9 Maker
Posts: 89

PDMS curing

Post#7 » Thu Jul 18, 2013 3:33 am

Also, be careful not to cure it too fast or all of the bubbles won't have a chance to rise out of it.

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noahbern
B9 Maker
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Posts: 374

PDMS curing

Post#8 » Mon Aug 05, 2013 5:19 am

Any pictures of people's setups to cure the pdms I could use some help! Thanks

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tim.yoshi
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PDMS curing

Post#9 » Mon Aug 05, 2013 6:16 am

I made it in ordinary cooking oven set on the absolute minimum temperature.

Image

But make sure that you place under and over it some cooking paper to prevent melting from contact with metal and from dust.
Image

zanderscreations
B9 Maker
B9 Maker
Posts: 40

PDMS curing

Post#10 » Wed Oct 23, 2013 7:03 am

What about keeping it level during the curing/heating process? I am having difficulty doing so.

I used my oven to cure the PDMS and it appeared to work great. But after a super failed print where everything was off, I noticed the pdms was tilted more to one side than the other. I did remember to calibrate my build table after though so not sure exactly what went wrong.

has anyone used a toaster oven or something like that for curing the pdms? I would like a easier and more accurate way to regulate the temperature and level the VAT than my oven.

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noahbern
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Posts: 374

PDMS curing

Post#11 » Wed Oct 23, 2013 7:48 am

I use this now

http://www.b9c.com/support/?mingleforumaction=viewtopic&t=914

bryce@forgejax.com
Newbie
Newbie
Posts: 6

PDMS curing

Post#12 » Wed Oct 23, 2013 8:15 am

Image

Here's our Hotbox. We're around 25 cm away and no problem with hot spots.

FORGE
http://forgejax.com/

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Burnsjt
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Posts: 128

PDMS curing

Post#13 » Wed Oct 23, 2013 8:25 am

I'm building a hotbox as well, I will post photos of the finished product when I get a chance.

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perpetual_dreamer
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PDMS curing

Post#14 » Wed Oct 23, 2013 9:54 am

anyone use a simple cardboard box and hair dryer? xD

Bitter Jeweler
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Posts: 47

PDMS curing

Post#15 » Fri Nov 01, 2013 7:34 am

I recoated my vat today, and for the first time used heat (two 75W bulbs, in a cardboard box).
Temp slowly got up to 140°F, and within 2 hours the PDMS was set, but tacky in two corners.
The problem is, for the first time, I have no waterfall.

I've done this before, curing at room temp for 2 days, and had a slight waterfall. Not like original, but it still worked.
I followed the WIKI directions and used a total of 50dwt's of PDMS. As I type this, I realize I used too much, and forgot to switch my scale to grams. DOH!

But still, given that I barely had a waterfall in the past, should I use a total of 45 grams of PDMS, instead of 50g?

(funny how sometimes the process of asking a question, finds your answer for you)

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Robert Howle
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PDMS curing

Post#16 » Fri Nov 01, 2013 3:05 pm

If u follow the video and have a truly level surface (x and y) u should have no problems. You don't have to be in a hurry to mix, because you've got hrs. before it's going to start to set. I always mix longer than I think is necessary. I use to get a tear at the waterfall after several prints. That has stopped because i had read on the forum about smoothing the sharp edge at the waterfall. I sanded it to remove the sharp edge and this has not happened since. I used 600 grit wet dry paper. I have a good toaster oven for curing, but since I have the extra vat, I just let one cure at room temp for 48 hrs., while I work with the other one. Every recoat has been just fine. Don't forget that u need an oil free surface when u coat. After washing with soap and water and a final rinse with distilled water be careful not to touch the floor or walls on the inside. I think I touched the bottom of the vat once, or missed a spot while cleaning, and it gave me an unattached bubble in that area. Has only happened one time.
Dance like nobody's watching!

Bitter Jeweler
B9 Maker
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Posts: 47

PDMS curing

Post#17 » Sun Nov 03, 2013 2:09 am

I feel so stoopid. Recoated the vat using a total of 45 GRAMS of PDMS, and it came out perfect.

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perpetual_dreamer
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PDMS curing

Post#18 » Sun Nov 03, 2013 8:01 am

I'm really really surprised my PDMS has held up so strong for the past 3+ months after printing about 50 prototype rings.. I used a higher ratio of initiator. Its still going strong, shows no sigh of breaking apart aside from the first signs of clouding now.. Part of it could be because I take time to make sure my parts and supports are slanted to minimize any areas being continously exposed too repeatedly. I'm sure it could last much much longer if clouding wasn't a problem.. I can't wait for Kirk to offer the projector mod soon so I can get 4 times the usage with each coating of PDMS. I was worried I'd have to replace the PDMS too often.. guess not *fingers crossed*

Anyone have thoughts about the PDMS while using the MakerJuiceG+ resin which has very short exposure times? Does that make your PDMS last longer and reduce clouding?

tribetype40
B9 Maker
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Posts: 59

PDMS curing

Post#19 » Sun Nov 03, 2013 11:33 am

Wait till the misses is out :-) and I put mine in the oven, set to 110degrees and im ready to go in 40 minutes. Did measure the shelf to ensure it was level first though!

ah3000mk1@sbcglobal.net
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Posts: 88

PDMS curing

Post#20 » Sun Nov 03, 2013 3:08 pm

I've also had multiple successes using the kitchen oven, and a dial thermometer. About 3.5 hrs at 160 deg F. A bullet level is used to assure a flat vat. As noted above, sloshing the material up the sides & ends of the vat, and allowing it to pool in the build side before leveling, leaves a thin layer of material around the walls. I now try for 3/4" or so up the sides, and I believe this has extended the life of the PDMS applications be preventing resin from wicking under the silicone layer and initiating peeling from the sides.

Also, I concur with re-coating while the Missus it at the mall.

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