3d printed dies undersized, a mystery for the ages.

HonestAbe

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The Problem: I design and mill zirconia crowns, they get sintered, and when placed on the single dies we print, it looks like the crown is too big. Turns out they're fine in the mouth, but for whatever reason these single dies seem to be coming out wrong. I'm trying to pinpoint why but I can't figure it out.

We know the scan files aren't corrupted because we're designing on them and the crowns are coming out the right size. I took the raw .stl from a scan, made my own die, printed it on different printers (Form 2 at work and my own Anycubic Photon S at home). I compared those dies to ones that had been through Sirona's model app (cleans up model, ditches die and makes it removable). The crowns look the same on all of them. The really weird part is that the rest of the model seems fine and accurate. We're checking our interproximal contacts on solid models that we print and those seem fine. If the whole model was distorted or wrong-sized then the other dimensions wouldn't fit our crown.

We print them on rafts with supports but for some of my tests I printed them directly on the build plate and the issue was uniform. I wanted to blame the Sirona software but when I got the same results after cutting them out of the picture completely it made me thing something is going on in the 3d printer side of things. The fact that we have the same issue on two different printers is what's throwing me for a loop. The Form2 can do 25 microns, and my Photon S can to 50 microns. Is there some parameter I might be messing up where the margin tapers down thin enough to be like, not printed?

Apologies in advance if I didn't include enough info, I didn't have the presence of mind to take pictures as I went but I wanted to just throw it out there in case other people have had a similar issue or ideas of different ways I could narrow it down that I haven't thought of yet. Much appreciated!
 
KingGhidorah

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Are you designing based off the digital files or are you scanning in the models after being printed?
If you’re designing based off the digital files the first place id look is at whoever is setting the margins for the dies. Is there a potential for whoever is marking the margins to be rolling it up too high on the tooth, thus ditching out info where normally the margin would extend out more?
 
CoolHandLuke

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you are using two different printers that use the same resin printing technology.

the center of the plate in any resin printer will always be more accurate than the edges of the printer.

have someone print for you using an Objet printer for comparison. not another resin printer.
 
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I have Nextdent printer and I'm also facing the same issue . We design crowns and 3d models on Exocad by importing raw stl files from Trios .
No matter how thin I set the cement gap of crowns over printed dies, they always come out loose, yet the margin line is fit .
I once set the cement gap at 0.001 and still no satisfying retention over the printed dies. I was thinking of calibrating the printer but my supplier said
that if the machine hasn't been moved from its place then it doesn't require calibration.
 
HonestAbe

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Are you designing based off the digital files or are you scanning in the models after being printed?
If you’re designing based off the digital files the first place id look is at whoever is setting the margins for the dies. Is there a potential for whoever is marking the margins to be rolling it up too high on the tooth, thus ditching out info where normally the margin would extend out more?

I've tried it every which way. Three docs send scans to us, one is from a prime scan/sirona connect, two from Itero. The weird thing is that one of the Itero docs just sends us the scans and the other one's scans take sometimes up to 24 hours. They go to Itero for... some reason? Then they are sent to us through their web portal with margins marked and dies already ditched. I'm trying to sort out why they're even involved as we want to be the ones to mark the margins for obvious reasons. You'd think that would be easy to sort out but Itero's systems have been down for a couple of days or something and communication with the doc to them to sort it out has been challenging. I'm just the low level newbie (3 years into being a tech) that's trying to figure all this out.

Even the ones that we mark have this issue so although I don't see any reason for Itero to be involved in marking margins, I hesitate to blame them since it's only one of the three sources of these dies.
 
HonestAbe

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you are using two different printers that use the same resin printing technology.

the center of the plate in any resin printer will always be more accurate than the edges of the printer.

have someone print for you using an Objet printer for comparison. not another resin printer.

Not familiar with Objet, but is that something we can just outsource to get a test from them? Supposed to be more accurate than a DLP resin printer?
 
CoolHandLuke

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Objet or 3dsystems are still producing material jetting printers, i.e. it comes out of a nozzle and is flattened. material jetting instead of projected light cure is just a different way to accomplish the same goal. the advantage material jets have over dlp printers is only that the table is equally acurate all around. material in the top corners is equally as accurate as objects in the center of the table. not so in dlp printers that have laser light bouncing off a gimballed mirror.

other than that material jet printers are massively expensive and high maintenance. dlp is so much more widely adopted simply because its cheap. its garbage for print accuracy but its dirt cheap. so close enough must be ok.

which is why i am so opposed to it to begin with.
 
HonestAbe

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It makes me wonder if our solid models are undersized as well. Had an issue yesterday with an essix retainer being too tight, got multiple new impressions from doc and poured those to compare, the essix which we originally made on a 3d printed model didn't fit at all, was visibly shorter. This is so difficult to test because there's so many variables.
 
Affinity

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Take 2 of any alginate or pvs impression and they will not be the same. Now you can confirm it digitally.
 
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grantoz

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As i have said in a previous thread something happens with omni cam scans when you convert them to a printed model via sironas portal or stl export. All other scanners work fine with my asiga including primescans from sirona. One of my clients had great fits for years with his omni scanner once the sirona portal changed to accommodate primescans the omnis didnt fit i found this with other omni uses also .The client went and purchased a new Medit I700 perfect fits and in his words the best fits ever he has had . Another purchased a new CS3700 and apologised for giving me a hard time. We solved the problem by getting the doc just to mill a temp crown on his cerec then checked it against the printed model it was very different. This is how we diagnosed the problem and avoided anymore grief about it being our fault.
 
KingGhidorah

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I've tried it every which way. Three docs send scans to us, one is from a prime scan/sirona connect, two from Itero. The weird thing is that one of the Itero docs just sends us the scans and the other one's scans take sometimes up to 24 hours. They go to Itero for... some reason? Then they are sent to us through their web portal with margins marked and dies already ditched. I'm trying to sort out why they're even involved as we want to be the ones to mark the margins for obvious reasons. You'd think that would be easy to sort out but Itero's systems have been down for a couple of days or something and communication with the doc to them to sort it out has been challenging. I'm just the low level newbie (3 years into being a tech) that's trying to figure all this out.

Even the ones that we mark have this issue so although I don't see any reason for Itero to be involved in marking margins, I hesitate to blame them since it's only one of the three sources of these dies.
Nothing wrong with being a newbie, I’m a newbie too, just about hitting 3 years myself as well.
If that’s the case with what’s going on I doubt it’s the margin marking then, but something important to note is that itero reallllllyyyyy sucks at marking margins. Like they are beyond bad at it, I always preview in the itero software and look at the thing pre ditching to make sure they did it correctly. Back at my old lab I had to call and complain like once every week until finally they told me they were putting a note on my account for only one of the managers to mark margins for our cases. Then they ended up being fine after that, but I had too complain up a storm.
 
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grantoz

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Just a side note with Asiga style printers you dont loose accuracy printing around the side of the build plate its accurate all over.
 
tehnik

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I had exact opposite problem with my brand new asiga 4k pro. Crowns did not fit on any dies. As I also have asiga max and there are no problems with that, I knew there is something off with the new printer. I got some suggestions from support and eventually got it working by changing printer internal parameter. The printer test screen was not sharp and that caused the bigger model and dies, after the change it is all good.

Sidenote: form2 and anycubic are not something to benchmark anything, you need better printers for that. I had both printers and they are now in garbage bin.
 
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hmartek

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I had exact opposite problem with my brand new asiga 4k pro. Crowns did not fit on any dies. As I also have asiga max and there are no problems with that, I knew there is something off with the new printer. I got some suggestions from support and eventually got it working by changing printer internal parameter. The printer test screen was not sharp and that caused the bigger model and dies, after the change it is all good.

Sidenote: form2 and anycubic are not something to benchmark anything, you need better printers for that. I had both printers and they are now in garbage bin.
In our lab we had used form2, but not any more being so slow. It just sits on a shelves for decoration. We switch to Envision, faster. We had a problem once, all they did was calibrate and change parameters on the printer itself.

You should call support and try tell them to look into that.

edit: also let us know the reason if you had solved the problem.
 
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mmbh

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The Problem: I design and mill zirconia crowns, they get sintered, and when placed on the single dies we print, it looks like the crown is too big. Turns out they're fine in the mouth, but for whatever reason these single dies seem to be coming out wrong. I'm trying to pinpoint why but I can't figure it out.

We know the scan files aren't corrupted because we're designing on them and the crowns are coming out the right size. I took the raw .stl from a scan, made my own die, printed it on different printers (Form 2 at work and my own Anycubic Photon S at home). I compared those dies to ones that had been through Sirona's model app (cleans up model, ditches die and makes it removable). The crowns look the same on all of them. The really weird part is that the rest of the model seems fine and accurate. We're checking our interproximal contacts on solid models that we print and those seem fine. If the whole model was distorted or wrong-sized then the other dimensions wouldn't fit our crown.

We print them on rafts with supports but for some of my tests I printed them directly on the build plate and the issue was uniform. I wanted to blame the Sirona software but when I got the same results after cutting them out of the picture completely it made me thing something is going on in the 3d printer side of things. The fact that we have the same issue on two different printers is what's throwing me for a loop. The Form2 can do 25 microns, and my Photon S can to 50 microns. Is there some parameter I might be messing up where the margin tapers down thin enough to be like, not printed?

Apologies in advance if I didn't include enough info, I didn't have the presence of mind to take pictures as I went but I wanted to just throw it out there in case other people have had a similar issue or ideas of different ways I could narrow it down that I haven't thought of yet. Much appreciated
Have you tried printing solid model with a separate solid die instead of removable die?
 
HonestAbe

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In our lab we had used form2, but not any more being so slow. It just sits on a shelves for decoration. We switch to Envision, faster. We had a problem once, all they did was calibrate and change parameters on the printer itself.

You should call support and try tell them to look into that.

edit: also let us know the reason if you had solved the problem.
Thank you I will be sure to do this. Was out sick for a few days (whew not covid..) and back on it now.
 
HonestAbe

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Have you tried printing solid model with a separate solid die instead of removable die?
Yes and every which way between. We stopped bothering with the removable dies entirely and were doing just a solid model and an individual die for checking margins.
 
JMN

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Keep in mind that there is a limit to how much fiddling of settings will help.

When you get right to it, there is a voxel printed or not. If it is, it's limited to making changes in a recticuloid cube addition only.

If the build plate is, oh, 40 micorn by 40 micron and the z is set to 10 micron steps you can only add or remove a 40x40x10 object.

That's if you have the detail turned up the highest this theororetical machine can achieve.

How many are set at 100micron? Many.

there's lots of other things, but be aware of the voxel size your machine can produce and if your setting fiddling even gets noticed by the output.

edit:This applies to the ones with a screen under the vat. Ones like Form makes have other issues to be aware of when fiddling.
 
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grantoz

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what resin are you using honestabe
 

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