Possible fix for delamination of PDMS layer

Following is an excerpt from an email I received on fixing the problem with the PDMS layer delamination.

Proactive precaution was taken to silicon glue the PDMS vat edges on all new vats before use."

Only question I have is what silicon glue to use for best results.

Is this a statement from formlabs?

Applying silicone to the edge of the PDMS might help preventing resin creeping between the PDMS and the tank, but it won’t stop the delamination. I’ve seen it starting in the center as well. There is still a chance that the PDMS releases from the edges and the silicone preventing resin to creep. However, as the PDMS is loose already, you will still have problems.

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I agree to a point. I’ve watched close and it seems to always start at the “Wiper Edge” of the tray. Once that happens then there is enough give in the PDMS layer that the center can pull up. My info came from Kevin at ALW and from one of his larger customers. That’s how they fixed the problem.

Is this a problem mostly on the F2’s? I have never had that issue with my F1+.
I was thinking what if you used a strip of clear packing tape on a new tank and put it on the edge of the pdms and tank wall. It might be just enough to keep the edge from peeling away and lifting.

My thoughts are that it might be some residual mold release on the tank walls after injection molding causing just enough of a barrier to make some of the tanks having a marginal adhesion to the pdms when it is poured. Just my hunch of what might be happening.

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No, the tape might actually help pull the PDMS layer up. The silicone glue would sink into the PDMS some and adhere best to the plastic walls.

I was thinking of a good way to cure the delamination. If you were to recoat the machine but put a glass insert on the top suspended like an overmold so that the pdms would extend around and up the walls a little it should change the tension spot so it isn’t on an edge.

This would require that the insert be perfectly smooth and have a descent chamfer draft angle so you can peel it out after the pdms has cured. The insert should also be as close to the walls as possible maybe 1/16"-1/8" away. The bottom of the insert should be same Z depth as the pdms currently sits. Filling the tank with the pdms should be easier too since the insert will insure you have an accurate z. I was thinking of doing this on home made tanks where I can use solid acrylic sheets and not worry about their heights as they vary quite a bit. This would have been an easier solution to making your own tanks that are more durable, less expensive and have fewer parts.

Well, not having re-coated the PDMS layer in a resin tray I’m not too sure of that. I feel the silicon glue is a good approach and i will try that on new tanks for a bit. I put two new tanks in December 4 on the December 15 one of the tanks had already started to peel along the wiper edge. I bought a tube of the 100% silicone clear glue and will try that.

Iv’e felt for a long time that one could take an old resin tray and peel the PDMS layer out of it. Then also remove the clear piece in the center leaving just the orange tank frame. To this I would add a bit of an edge, 3/16" square styrene square solid rod around the top edge to reinforce it. Then use this as a master to make a silicon mold. The trays don’t have to be orange. Only reason for that is to protect the resin if you leave the trays out in the light. Best to put them back in the box if they have resin in them anyway. Then cast the tray in clear resin. Add the clear window back and you have a much less expensive tray. Just an idea. Even at the current price the resin trays aren’t that expensive so this is just an idea.

If possible try to clean the walls of the tank to make sure there is no release agent or you will have the same issue. Also make sure the silicone adhesive is platinum cure and there are no contaminants on the pdms like any resin residue. If you try a tin cure adhesive chances are it will not cure.

I’ll only do this on NEW resin trays.

I refer to them as “Trays” as that’s what they are. The Resin Tank is what gets inserted in the back of the printer and feeds resin to the tray. I know FL uses that term but that’s not the only thing they mess up. [grin]

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Intrigued to see how you get on with the glue. Pretty fed up with these so called long life ‘trays’ falling to bits after only a couple of ‘tanks’ of resin…

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