Re: scale and warpage of sls

From: David K. Leigh (
Date: Mon Apr 02 2001 - 16:26:29 EEST

There are several ways to skin this cat:
* You can shell the part in software and have a wall thickness instead of a
thick part.
* Rotate the part slightly and build at a low laser power at the highest
part heater setpoint that will allow you to break the part out.
* Have the part built in a 2500 or 2500plus.
* Add stock and post machine the bottom/curled surface.
* Warpage can be eliminated 90% of the time by lengthening your cool-down.
Let the build sit over the weekend after it's finished.

Horizontal holes - Drill bits work great. You will always get a flat area
to a hole on the upper surface of that hole, but that is really the only
problem. . . unless your scales are way off.

As far as improved accuracy for the SLS 2000, don't hold your breath.
You'll have to purchase a new system to get the latest bells and whistles,
just as with most RP manufacturers.
David K. Leigh ph (254) 933-1000
Harvest Technologies, Inc. fax (254) 298-0125
Rapid Prototyping Services

----- Original Message -----
From: "Miller, Michael W" <>
To: "'RPML www Mail List'" <>
Sent: Friday, March 30, 2001 5:29 PM
Subject: scale and warpage of sls

> Dear rpml,
> I'm looking at using my sls2000's to make some simple tooling out of
Duraform GF. My experience so far has been that the process is not quite
accurate enough. I'm looking for suggestions that might improve the parts.
> 1) Curl- The parts I'm making our relatively bulky.... 1 inch section
thickness. Even though the build looks dead flat, the finished parts are
warped or curled. I feel that this is an endemic, direct result of the
process, adding heat on top of the part and then subsequently having it cool
and shrink. Any thoughts on how to reduce this persistent phenomena? I
know orientation on a corner helps a little. What about designing the parts
for reduced mass without sacrificing stiffness by using a web and flange
philosophy... like I-beams? Alternatively, has anybody had much luck with
the outline feature? My experience has been that it's unreliable, at least
on the 2000's. Perhaps shelling the part with outline but filling the core
with lightly sintered material would alleviate the 'curl'. Unfortunately,
on the 2000's, this is quite slow because of the delay while the scanner
loads with new parameters. Are the 2500's fraught with curl?
> 2) Scaling- Has anybody developed non-linear scaling parameters? I
utilize a one dimensional Z-scale as a function of Z. For the GF I vary Z
scale 1.012 @ Z=0, 1.010 @ Z=3, and 1.008 @ Z=5. For X and Y I use a
constant scale, 1.023. Has anybody tried varying Z scale 3 dimensionally...
as a function of X,Y and Z?
> 3) Z adjust- I believe the z-adjust parameter in the 2000 software is
lousy. Horizontal holes do not come out round. Solid View has a z-shift
function that is fully adjustable as a function of downfacing angle that
results in much rounder rounds. Concur?
> 4) DTM- Does DTM have anything in the works to improve accuracy?
> Thanks for your insight,
> Disclaimer: Engineer and out the other!
> Experience is something you get right after you need it.
> Michael W Miller (
> The Boeing Company M/C 17-PE B-2T65
> Propulsion Experimental Hardware 206-655-3289
> Rapid Prototyping 655-4366 Lab 655-4365
> For more information about the rp-ml, see

For more information about the rp-ml, see

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