Re: Wiper Arm Question

From: Doug Mitchell (
Date: Wed Feb 19 1997 - 21:20:42 EET

On Feb 19, 10:15am, wrana jeffrey scott wrote:
> Subject: Wiper Arm Question
> RP'ers:
> I was wanting to build some small parts on an SLA-250 without the use of the
> wiper arm. However, I'm not quite sure how long of a time period to wait
> between the build of each layer. I will be using 5170 epoxy resin.
> Does anybody know how long of a time period to wait after the build
> platform has lowered into the vat before the next layer is built to
> insure the liquid level is at steady state (without the use of the wiper
> If someone has tried it, how were your results?
> Any comments would be useful.
> Thanks,
> Jeff
> _________________________________
> Jeffrey S. Wrana
> Graduate Student
> Dept of Bioengineering
> Clemson University
> Clemson, SC 29634
>-- End of excerpt from wrana jeffrey scott

As an old-timer on SLA, (I first learned on the SLA-1 - NO wiper), it
would depend on the cross-sectional area of your parts. ISTR that
we used anywhere from 30 second dip delay up to 15 minutes. I quote
from the 3D SLA-1 Training Manual:


The amount of time required for the surface of the resin to level and
settle after a part is dipped is dependent on the geometry of the part
and many other factors.

They went on to recommend a ZW (Z wait) of 30 to 60 seconds for supports
and 45 to 180 seconds for normal part building. We on occasion used
a much longer wait for a large surface area. I believe that the maximum
was 900 seconds, and we used that much. I don't recall what the max is
any more, but you can play with the numbers and see what happens.

Keep in mind that the resins are thinner today, so the 900 second dip
delay may be overkill.

Doug Mitchell
Ford Motor Company

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