Dave, you wrote:
Hope you can shed some light on this.
Sorry, what your about to read may seem harsh. I'm frustrated, and I
would like some real answers. I know there may not be any direct answers but
I'm trying to reach out to as mush help as I can. Thanks in advance.
We've been running this equipment for 5 weeks and there seems to be a high
rate of failures. These failures conclude in a sweeper stall.
(typical right?) 3D Systems has gone through all the settings and tests
and seem to not be able to give me a definite "here is the problem" type
response. We/they change a setting and run it again. The build may work or
fail, or it fails on the next build, which indicates the changed settings
where not the problem. We've had 5 consecutive good builds within this time
period which to me is unacceptable.
Now for my questions:
Has any other SLA5000 users had similar problems?
If so what did you do for it?
What is the acceptable build failure rate for SLA machines? (I know
failure happens)
One concern is our power source. It will fluctuate from 207 to 246
volts. does any one have any data on what effect this has on 1) the
laser as it draws, 2) the life span of the laser, 3) the mirror servo
motors during the draw, 4) other parts of the operations? I can not fine
any suggestion in the site preparation guide as to supplying conditioned
power. Do you have condictioned power for the SLA5000? What kind, maker,
size, and where?
Knowing that 3D Systems monitors this list, is there someone there that has
any input to this situation. Please respond to me directly. I'm
trying to keep my managers and VP's calm but there is a lot of money
involved and you can see their concern. Meantime promises where made to our
costumes and those are not being met.
****************************************************************************
****
Dave:
We recently installed a SLA-5000 in March 1998 and have had some similar
start-up problems. It took several weeks to sort them out, but now we're up
and running fine, although the 3D field service engineers had to make
several trips out. Our FSE's and installers were Dennis Van Zante (out of
St. Louis) and Tony Roldan (out of Chicago) and they were very good at
diagnosing and solving the problems. If all else fails, maybe you can talk
to them directly about your problems (just call 3D's hotline and they will
page them to call you).
Regarding your sweeper stalls. We had problems with resin starvation
(especially on large surface area parts) in the Zephyr blade which we traced
to resin blockage of the vacuum supply lines to the blade. Due to vacuum
fluctuations (high vacuum condition), resin had been sucked up into the
lines, blocking the vacuum necessary for the recoater action. It was fairly
easy to take the lines off (the metal one on top of the blade and the rubber
hose going back to the vacuum pump) and clean them out with isopropyl
alcohol (99% purity lab grade). The real trick is the vacuum adjustment,
you can do this yourself (or have the 3D FSE do this), but it's real
sensitive and it's real easy to apply too much vacuum and you'll be cleaning
the lines again. There are two adjustment knobs (one for coarse and the
other for fine adjustment) behind the lower back panel directly behind the
vat. If this isn't it, you might have 3D check the blade gap again,
sometimes after a good crash the blade adjustment is knocked off (usually
the blade will be crooked, one side may be fine but the other side could be
higher having been pushed up by uneven resin build-up due to failed
supports. etc.).
Regarding your second problem on laser power stability. We haven't had the
fluctuation go up and down, our power only went one direction - down. From
246 to 207 mW (after about 2 months of continuous operation) which
consequently slowed the drawing speed which in turn slowed the build times
WAY down. According to 3D's field service spec's, if the laser power drops
below 210 mW, this is below spec. and adjustments should be made. A 3D FSE
came out and reoriented the laser crystal (to avoid a burnt spot) which took
about 3 hours (we scheduled him to come in right after a build finished so
as to minimize down time).
Another problem we found as a cause for crashes was excessive blade speed.
Ciba's resin parameters recommends 2 in/sec. for SL-5195 but this is too
fast for this resin, especially for large surface area parts. We found that
using 1 - 1.5 in/sec. worked best.
Another problem could be the resin you're using. If you're using Ciba
SL5195, this resin is rather touchy as far as modifying the processing
parameters such as Z-level wait time. You can't stray too far from the
default settings in the zeal to reduce cycle time but this is also part
dependent, if you're making large surface area parts you want the resin to
cure longer than thinner walled parts. You may want to consider using other
resins such as Dupont Somos or another Ciba resin.
Another problem we found was inadequate support generation if you're just
using the Maestro default supports, especially as far as tangent curves and
knife edges (such as making a wing) are concerned. Failed supports have
caused us many a failed build. It takes more time, but check out the
supports on questionable geometry and if necessary go into "Custom Draw
Supports" in Vista and draw some better supports. Or you could check out
alternative support generation software such as SolidWorks. If possible,
get Mark Abshire, the "Maestro Ace" (3D application engineer) to spend
several days with your Maestro operator to show them numerous ways to tweak
Maestro to make a successful build. This software has a number of
irritating bugs that you have to watch out for.
We currently do not have conditioned power, but in the long term to save
laser's and power supplies, I would recommend one. From what I've heard,
Liebert and Toshiba both make excellent UPS's but they're not cheap. You're
probably looking at $5,000-$10,000 for a good quality one (what's critical
is good response time to immediately protect the sensitive electronics from
brownouts, not just blackouts) with enough capacity for expansion (to put
computers and possible future machine additions on it also). This could be
a tough sell however since you just spent $500,000+ for the machine (I know,
I've tried). You may have to wait for an expensive laser failure to
convince management that it would be more economical in the long run to
condition the power. In other words, sometimes it's easier to beg for
forgiveness after the fact than to get everything you want upfront.
>From one who has been there and done that,
Good Luck!
Glenn Whiteside
Cessna Aircraft Company
e-mail: siderwhite@worldnet.att.net
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