Object Distortion

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greglab61
Posts: 4
Joined: Sun Feb 15, 2015 6:55 pm
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Object Distortion

Postby greglab61 » Sun Feb 15, 2015 7:20 pm

Hello. I am new to this forum and new to DLP printing. I am trying to use a new printer from a company that has designed their machine to build bottom down i.e. build as it submerges. The prints are human maxillary and mandibular teeth arches. We take these prints and makes pressurized plastic formed appliances on them. A plastic blank is heated to temperature and then a machine presses the heated blank onto the mold (DLP print) to form the appliance. Some machines use vacuum, ours uses 87 lbs. of positive pressure.
Our problem is that when we scan a patients arch, we use a very accurate intraoral scanner. Our files are very good, and they are successfully printed by a company we use now. When we attempt to use our own DLP printer, the same file that was printed successfully by another company completes on our machine, but is not the same "size" as the original. In other words, all of the object is there, but if you make a plastic mold of it, it simply does not fit in the patients mouth even though it looks to the naked eye like an exact copy. We have tried 100 micron, 70 and 50, and all of the results are the same. There is a size or definition difference that does not create our prints accurately. We have played with the X, Y, and Z scaling, turned aliasing on and off, etc. etc. but have not been able to duplicate a scanned image accurately enough to work. In dentistry, precision and accuracy are tight parameters in order for an appliance to fit over the various cusps, tooth surfaces and anatomy of each individual patient.
Our machine is being developed by a third party, and they have not been able to resolve this issue either. They are using what I assume to be a custom version of Creation Workshop written for them. I noticed they are now listed in the partners section of the website, without a link.
I am here today to see if someone has had similar issues, or can possibly get me up to speed on this subject. I will be operating this machine, and it is comforting to know that it is open source and supported by a forum and users base.
Sorry to be so wordy, but I hope a good explanation might help someone help me.
Thanks.

Phife
Posts: 239
Joined: Fri Jan 17, 2014 5:24 pm
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Re: Object Distortion

Postby Phife » Sun Feb 15, 2015 9:05 pm

Sounds like a calibration problem, and perhaps resin shrink problem?

You should easily be able to solve both though. Id print a bunch of calibration blocks and prints and figure out exactly whats going on with your prints. Are they shrinking? too big? shrinking in only one direction? multiple directions?

Once you get all that figured out you can properly calibrate your machine so it prints accurately.

greglab61
Posts: 4
Joined: Sun Feb 15, 2015 6:55 pm
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Re: Object Distortion

Postby greglab61 » Mon Feb 16, 2015 1:50 am

Thank you. I haven't had much time to do a lot of tweaking on it. By calibration do you mean the projector and or resin temperature and curing times? I have been watching one fellow trying to compensate by adjusting the scale of the 3 axis. I don't see this problem coming from scale, just build parameters of the machine. I have seen them print calibration blocks, and the blocks are not square or level. I will try and get more information and measurements and get back with some better data.

dangre
Posts: 116
Joined: Wed Jun 25, 2014 4:20 pm
Location: SW Michigan
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Re: Object Distortion

Postby dangre » Mon Feb 16, 2015 9:53 am

I initially adjust my projector (after setting up the software and z-step height with the correct settings) using the calibration function of CW (Projector Control~Show Calibration) which projects a 10mm grid onto your build surface. Use the zoom and focus of the projector to get as close to matching the 10mm grid. You may have to move/angle your projector if you see any 'skewing' or 'keystone' of the calibration grid. I then print a 10mm cube and measure it (X, Y, & Z) to insure I have everything perfect. I can then adjust the CW software settings (Configure Machine~Build Size) to get it spot on.
Dan - mUVe 1 DLP

mhackney
Posts: 18
Joined: Sun Feb 15, 2015 9:27 pm
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Re: Object Distortion

Postby mhackney » Mon Feb 16, 2015 12:07 pm

dangre, I do not see the Show Calibration option in the latest CW. Was it removed or am I missing something?

Cheers,
Michael

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PomeroyB
Posts: 168
Joined: Thu Mar 27, 2014 9:51 pm
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Re: Object Distortion

Postby PomeroyB » Tue Feb 17, 2015 8:54 pm

See the bottom picture in to locate the "Show Calibration" option. If you don't see the "Projector Control" area in the control tab, you need to enable it in the configure tab.

mhackney
Posts: 18
Joined: Sun Feb 15, 2015 9:27 pm
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Re: Object Distortion

Postby mhackney » Tue Feb 17, 2015 9:26 pm

Great, that was it, thanks!


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