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Post by mrguesp on Nov 21, 2016 18:37:12 GMT -5
Hello! When casting with Water Clear I've noticed that the resin often recedes significantly while it is curing. For example: If I pour into a one piece mold right up to the top of the mold, after the resin has cured the bottom of the cast will be several millimeters below the top of the mold. My process involves both vacuum degassing of the resin as well as pressure casting, though the receding has also happened when I cast without pressure.
I have two questions:
1. Is there anything I can do to the resin to avoid this problem?
2. Do all of your other clear resin products display this behavior or is there an alternative?
Thank you!
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Post by mike on Nov 22, 2016 8:37:02 GMT -5
Good question. What you are noticing is shrink. All casting resins shrink to some degree ... even filled systems which shrink much less still shrink. The larger the part or mass you are pouring, the more it will shrink and be noticed.
The best way to over come this and make sure it does not effect your part is to make a slightly larger reservoir in which you pour into. Then the material will shrink and draw down from the over pour area inside the reservoir and eliminate the shrink from effecting your part.
If you do not have an area to open up or cut the reservoir larger in your mold, you can add a clay dam around the pour opening to artificially construct a larger reservoir. Then simply trim this area off after demolding as you would flash or a sprew hole.
Mike
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Post by mrguesp on Nov 22, 2016 16:00:09 GMT -5
Hi Mike, thanks for the advice. Actually just tried casting with a clay dam yesterday and it worked fairly well. Nonetheless I'd like to avoid it as much as possible. Is this determined by the "Shrinkage" as listed in your TDS? If so I'd like to learn about this quantity and how to use it to calculate the proper resin quantity to mix. Is it basically (MixedVolume - CuredVolume)/(MixedVolume)?
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Post by mike on Nov 23, 2016 9:23:12 GMT -5
The best way to do it is the pour one piece with a reservoir as full as needed to NOT shrink or without it receding into your part ... causing a short shot. Then simply demold it and weigh it. Then you know exactly how much the mold will require to pour a good part. I'd then add a marginal % that will be left inside the cup. For example, after demolding and before removing any flash or the sprew ... weigh the part and if it is, for example, 200 grams, then I'd mix up between 105 and 110 grams of each side to mix, pour the next time to make sure you have enough.
Hope this helps.
Happy Thanksgiving!
Mike
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Post by bailey3 on Dec 10, 2016 4:02:13 GMT -5
Thank you so much.. Your advice helped me too.
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Post by adaline3 on Dec 14, 2016 8:06:45 GMT -5
Thank you guys for this info  |
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