PDMS tearing

Hardware issues, problems and solutions
jbin
B9 Maker
B9 Maker
Posts: 193

PDMS tearing

Post#1 » Wed Feb 04, 2015 3:02 pm

I have been doing a lot of printing over the past week and twice now have had the PDMS tear during a print. Very small areas but ruins many of the parts and messes with my schedule. On my V1.2 machine I seem to be seeing more pronounced fogging sooner and there is actual swelling of the PDMS in the heavily fogged areas these tears are happening after only 6 or 7 print runs. I am printing Cherry with factory settings except the attach layers where I am using an attach multiplier of 5. Any thoughts on what might be happening. I have never had the PDMS tear on my V1.1 machine.
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jbin
B9 Maker
B9 Maker
Posts: 193

Re: PDMS tearing

Post#2 » Wed Feb 04, 2015 7:27 pm

In examining everything about what I am doing to try to see what might be at issue I was looking at weighing/mixing the PDMS. I use two plastic containers, a 8 oz one for the resin and a 2 oz one for the catalyst. I am using 30 grams of resin to 3 grams of catalyst or so I thought. Tonight I put the small container back on the scale after pouring it into the larger container. I noticed that about 0.3 gm of catalyst was still in the container. This means that my PDMS is about 10% under catalyzed. I am wondering if this could be the reason for it tearing more easily? With these tiny amounts of resin and catalyst it is real easy to be off the optimum ratio. Any thoughts?

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akgold
B9 Wizard
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Posts: 2071

Re: PDMS tearing

Post#3 » Wed Feb 04, 2015 8:30 pm

The way I do it is all in one container.
to make sure of mixing I would add the resin to the container by weight and then pour the catalyst in to bring the total wt up to 3.3 grams
so 3 grams of resin
and .3 grams of catalyst right out of the bottle.
then mix thoroughly
I'm so far behind I think I'm First !!

jbin
B9 Maker
B9 Maker
Posts: 193

Re: PDMS tearing

Post#4 » Thu Feb 05, 2015 10:58 pm

Thanks, that is simple. I mixed a new PDMS batch this way and we will see if it helps.

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tim.yoshi
B9 Master
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Re: PDMS tearing

Post#5 » Fri Feb 06, 2015 8:59 am

But maybe you just overcuring it?
Maybe lower MSM to 0.9 or even 0.8. See if it works (models came out good), then it will def lower the PDMS fogging and sticking.
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