Problems with down facing fill

From: Jason Williams (Pennsylvania State  University at Erie), Kamesh Tata (Plynetics Express  Corporation), Tim Caffrey (The Boeing  Co.)
To: RP-ML
Date: Wednesday, December 6, 1995
Subject: Problems with down facing fill
     Ok, I'm having troubles...  We've got an SLA-250 and are using Allied Signal's X-actomer 2202SF resin.  My parts were coming out fantastic about 3 weeks ago (laser power ~16mW) and then I had a jump in laser power (~25mW) and my down facing skin fill vectors went to heck.  I'm thinking the problem might be in the laser or in the sensors.  The laser has about 1,800 hours on it.  My down facing skin fill vectors look like they are not connected and are 'wiggly' and nasty.  I've played with increasing my cure depth of the down facing vectors and it really hasn't made much of an impact.  I did discover that if I increase the overcure on the hatch vectors it helps seal up the parts better, but my warpage becomes unacceptable.  If anyone has any solutions or recommendations please let me know.  Thanks ahead of time!
thanks,
Jason

Date: Wed, 06 Dec 1995 11:55:52 -0500
     One reason could be a change in the beam diameter. It might be worth trying a closer hatch spacing. I would also check the power with a laser power meter (don't trust the screen reading).  
Kamesh 
PS: please let us know when you find the cause. 
Kamesh Tata
Prototype Express, Inc.
ktata@proex.com

Date: Wed, 6 Dec 1995 14:38:11 -0800
From: "Tim J. Caffrey" <tjc8347@proplab2.ca.boeing.com>
     Two items:
     I agree with Dave Flynn and Todd Stalhut. Please tone it down.
     Second, Jason "doh" Williams says his laser power on the 250  "jumped" to 25 mW. I suspect his laser power hasn't changed at all, as Kamesh suggested. The villian is one of your sensors, sensing a much higher power than actual, and increasing drawing speed accordingly, causing the poor builds....Do let us know what you find out.
Tim Caffrey
Boeing