Re: SLA 250 questions

From: Markus Hitter (
Date: Sun Jun 15 2003 - 20:52:20 EEST

As nobody seems to jump in, here's my 3 years aged experience.

Am Samstag, 14.06.03 um 18:47 Uhr schrieb Andrew Miller:

> Build envelope

The name says it: 250 x 250 x 250 mm

> Resolution

With the DOS based build station software the given minimum layer
thickness is 0.1 mm. By creating custom build styles you can go down to
0.0625 mm.

Horizontally, it seems to depend solely on the resolution of the STL

Minimum wall thickness for parts is 2x laser beam diameter. Supports
are about 1x beam diameter. The genuine laser has a diameter of about
0.2 mm. Custom lasers can go down to 0.08 mm. Installing a custom laser
needs some care but isn't rocket science.

> build speed

Slow. Even the smallest part will take at least one hour (machine init
etc.). Bigger parts go up to several days since the standard laser has
a typical output power between 15 mW (time to replace) and 35 mW (new).

My build time calculation software should be still in place, so send me
a STL part and I'll tell you how long ...

> Difference between models

The earliest models had no sweeper at all. Thereafter they had a
"doctor blade", a simple aluminium beam. Later came the "Zephyr blade".
You recognize the Zephyr by the additional vakuum pump and a vacuum
connection to the middle of the blade. For huge cross-sections the
Zephyr will save you a lot of headaches and build time.

Other difference is the fixed/replaceable vat. Depends on your
preferences what you need.

> software limitations

The support generation software needs some experience. All the build
preparation software has a unusual GUI but is OK once you get behind
how it works. Never had a look at "LightYear" (Windows-based), however.

> Maintenace Nightmares

Every once in a while the thing just doesn't work. But only in one of
1837 builds this actually hosed a part. Typical task is to reboot all
the machine, then. I consider this as normal for such a highly complex
and specialized software.

If you do some minor maintenace weekly (cleaning chamber, sensors
etc.), the machine should run smoothly.

Every several month it's time to re-adjust the laser, mirrors etc.
Since there is no info about how to do it in the manuals, you probably
need some service contract.

> The idea behind an SLA machine is a Lights out machine with less post
> processing...

Yes, the SLA runs lights out. Extreme geometries can result in a crash
but since you can't do anything at runtime against it, it's pointless
to attend the machine.

Be prepared to get your gloves on before each build to adjust the resin
level and after the build the get the parts out of the machine. Then
you have to wash them, a 30 minute procedure of handling chemicals ...
Some appropriate washing place is a must or all your workshop will be
sticky and tacky within weeks.

Post processing includes some hours in the UV oven, removing the
supports and some sanding if you want very smooth surfaces. Filling
usually isn't needed but can be required to repair small build errors
(e.g. bubbles).

Part dimensions are very reproducible and can be adjustet to be within
+/-0.05 mm for all sizes. If you recognize a bad measurement you most
likely made a mistake before generating the STL file :-)

Hope that helps,
Markus Hitter

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Dipl. Ing. Markus Hitter

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