From: Miller, Michael W (michael.w.miller@boeing.com)
Date: Thu May 02 2002 - 22:48:02 EEST
In general, the part bed needs to be as hot as possible without causing the
whole part bed to sinter, which really makes breakout tough. By having the
part bed as hot as possible, you can minimize the laser input and achieve
flatter (less curl) in the parts. The same can be said for the feeds... As
hot as possible without disrupting powder flow. The downside is that powder
quality will degrade faster at the higher temps.
Disclaimer: Engineer and out the other!
Experience is something you get right after you need it.
Michael W Miller (michael.w.miller@boeing.com)
The Boeing Company M/C 17-PE B-2T65
Propulsion Experimental Hardware 206-655-3289
Rapid Prototyping 655-4366 Lab 655-4365
-----Original Message-----
From: Roger Spielman [mailto:RSpielman@regale.com]
Sent: Thursday, May 02, 2002 10:21 AM
To: 'Brian Caulfield'; Rapid Mailing List
Subject: RE: SLS Part/Feed Bed temps?
Hello Brian
Hopes this helps (read inserted text below). Another good source of
information is the folks at 3D Systems (formerly DTM). Give them a
call....they can be a great resource.
Roger Spielman
Regale Inc.
-----Original Message-----
From: Brian Caulfield [mailto:brian.caulfield@nuigalway.ie]
Sent: Thursday, May 02, 2002 8:53 AM
To: Rapid Mailing List
Subject: SLS Part/Feed Bed temps?
I am just curious about a few aspects of the SLS process as regards
temperatures.
> What is the ideal Part bed temperature?
Whatever works best....realistically this variable will change with respect
of material and material condition. Recycled material will react slightly
different than virgin material. Keep in mind the temperature displayed is
ONLY a reference. This is not calibrated and is determined from your IR
sensor feedback...which can be altered by many things - including IR coolant
flow rate. Not all machines will register the same value.
> For PA we have the part bed 12 degrees C below the Tm (Approx PB temp of
150-153), can anybody tell me why 12 degrees?
This is a starting point determined by DTM/3DSystems for this material. It's
a good reference to start with, but the temperature you end up with may be
slightly different. Keep in mind as your powder ages this variable will
change as well.
> What is the ideal Feed bed temperatures?
Depending on the platform you are using, this could be determined from an IR
sensor (2500+ and Vanguard) or type K thermocouples (2000 - 2500). The
thermocouples will give you an accurate temperature on the display, while
the IR loop is subject to other influences as described above. Machines
using IR sensors may not reflect accurate temperatures and should be
considered reference points. Possibly a more accurate way to monitor your
feed temps is by watching your duty cycles. Setpoints that average from 20%
to 25% usually work well, but again are influenced by your material and
that materials condition (virgin vs.. recycled).
> Should the part bed temperature be proportional to the energy density
from the laser i.e decrease as the ED increases?
Somewhat. This is a good ground rule to follow, but there are distinct
limits you will reach in either direction. Some basic tests upfront such as
part appearance, part strength, density and accuracy are needed to establish
your specific operating parameters. These will change somewhat from machine
to machine in the number displayed, but if you work from discreet values (
temperature drop from material glaze) the information should transfer
platform to platform with good predictability.
If anybody has an ideas on this topic or knows a bit more than me on it I
would love to hear it.
Regards
Brian Caulfield
-------------------------------------
National Centre for Biomedical Engineering Science
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