Jeff,
On the 250 w/ the doctor blade, lower the platform to a position just above the resin. Go into the elevator mover (under utilities), change the velocity to .1 and lower the platform into the resin approximately 10-15mm below the surface. This will prevent (or significantly minimize) bubbles generated when lowering the platform before beginning a build. NEVER let the platform lower itself into the resin at full speed. When you add resin, always poor in the right rear corner at a slow rate. When the desired level is reached, a blank business card or something similar can be used to "rake" the bubbles to the side of the vat where it is easy to pop them.
Another helpful hint - As always, you must sweep in odd numbers. Three (3) sweeps would be the minimal that I recommend with the doctor blade. To minimize and prevent bubbles, use a blade gap of 200% on the first sweep, 999% on the second sweep, and whatever you desire on the third sweep (I always used 100-120%). This technique sweeps bubbles to either the front or back of the vat on the first sweep, breaks the bubbles on the second sweep, and leaves the desired layer of uncured resin on the third sweep. This technique worked extremely well when I had the doctor blade recoat system.
On the zephyr blade, the same blade gap technique can be used as well (three sweeps). Although more than one sweep adds to the build time, the 999% blade gap provides the opportunity to suck bubbles up into the zephyr blade on the second sweep. Additionally, be extremely careful with the vacuum pressure on your zephyr system. You can actually suck up fine point supports if the vacuum is excessive.
Hope this helps...
Allen W. Brand, Sr.
Technical Supervisor / Lab Manager
Motorola Energy Systems Group
1700 Belle Meade Court
Lawrenceville, Georgia 30043
Phone: 770-338-3088
Fax: 770-338-3455
email: Allen.Brand@motorola.com
-----Original Message-----
From: Jeff Toole [mailto:jtoole@morristech.com]
Sent: Wednesday, March 28, 2001 10:55 AM
To: Rapid Prototype Mailing List
Subject: Bubbles in Resin Vat
I have a problem with bubbles in the resin during builds. I know it sounds a
little silly at first, but this does have consequences in part quality and
personnel utilization (someone has to be on "bubble popping patrol" at the start
of builds).
I am running SLA-250's with Doctor blades and SLA-500's with Zephyr blades.
Resins are Somos 7100/7110/7120, 8110/8100, and 9100. Supports are Finepoint
via Lightyear 1.1 w/ SP1.
The problems are twofold. First, during the initial support building phase, a
lot of bubbles can knock out supports and cause "mounding," leading to a crash.
Second is the problem of small bubbles becoming cured into the parts. This
seems to happen most with the Doctor blades as the tend to comb larger bubbles
through the Finepoint supports to create ever smaller bubbles. These small
bubbles are virtually impossible to clear from the vat once they have formed.
This doesn't seem to occur with Zephyr blades as a single pass (maybe two)
usually clears all bubbles.
Does anyone else have trouble this? Has anyone come up with any good solutions
for it?
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