RE: scale and warpage of sls

From: Miller, Michael W (
Date: Mon Apr 02 2001 - 18:51:41 EEST

My feeling is that the "curl" effect is a basic function of the process. As mentioned in earlier responses, adding heat and subsequent cooling causes the deformation. Short vectors would help this but DTM has never offered anything other than the basic raster scan. I suggested to them years ago that perhaps wiggling the Y mirror to produce a zig-zag on the part would help alleviate curl without stepping on 3D's toes. I'm sure there must be other possibilities.

        1) I agree shelling the part will likely help a lot.... although there will be loss of properties. Hence my comment regarding the outline function utilizing a lower level sinter of the interior. My experience with the 2000 is that it's slow (not true on the 2500's I hear) and that it unreliable... ie crashes often. What about the 2500's? Are they reliable when using outline?
        2) Rotating and low laser/high part bed temp helps.
        3) I presume 2500/+ will only benefit through the improved scanning.
        4) My parts are curling both top and bottom so I believe the middle of the part is curled also.
        5) I've never noticed that letting the part cool over a weekend helps compared to overnight.

I would like to know what "bell and whistles" are on the 2500's. Are they really that much more accurate?

Thanks for all the great responses!

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

> ----------
> From: David K. Leigh[]
> Sent: Monday, April 02, 2001 6:26 AM
> To: Miller, Michael W; 'RPML www Mail List'
> Subject: Re: scale and warpage of sls
> 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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