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jean-baptiste

Dental model problem

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Hello everybody,

Last night i try to print a dental model with a UM2, but this morning the printer was bugging. The printer has stopped printing on a full teeth, nozzle pressed against.

I don't understand why, he is my four files (corrected with netfabb or not).

I have try the last file no corrected because it is the only one who posted the the piece on coutour cura during the pre-prod. You now the light blue line.

https://mega.co.nz/#F!owJi2DzJ!HiHXo7ch1kLbTQVYf1IvGw

If you can help me, Thank you very much in advance !

Jean-Baptiste

 

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I downloaded your model (4-fixed) and sliced with Cura and it looks good. The digital model is excellent quality.

 

The printer has stopped printing on a full teeth, nozzle pressed against.

 

There is a bug where sometimes the printer stops early. This is fixed in the latest firmware. Install the cura and then install the firmware from Cura.

 

For example, this kind of faults is not possible

 

The red circles are showing areas that are pretty good and I'm not sure what the problem is. The final tooth printed (#23?) has a little spot that can be improved with "cool head lift" but only slightly and this won't affect the other teeth.

I don't think you can get much better than this. Also when the tooth gets thinner than .4mm the nozzle can't print any thinner than that so it stops printing the top most layer sometimes as it is thinner than .4mm. You can see this in Cura before you start a print. You could by a UM Original and a smaller nozzle (say .25mm) but of course this means it would also take longer to print.

 

(40 per week)?

 

I think you know the answer. With no infill (I dont' think you need infill at all) and no infill bottom and .8mm shell at .2mm layers at 50mm/sec Cura says:

48 minutes to print.

With .1mm layers at 30mm/sec (better quality) Cura says:

93 minutes to print

If you remove the bottom half of the model (Quality - Cut off object bottom: 10mm) .1mm layers 30mm/sec Cura says:

57 minutes to print

I guess in theory it's possible. You would need someone to check the printer every hour to make sure the printer didn't fail, mark each print, and start the next one.

Maybe after a week you could get good enough to print 4 at a time over night?

You could even program it to let the suface cool for 5 minutes, then knock the part off the platform and then reheat and then start the next one. That way you could print all night long and all day long.

 

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You might want to print it in this orientation. This will give you much better quality at the tops of every tooth - but the red areas (overhangs) will be worse quality (bumpy). Note the parameter circled in green to help it sit flat on the glass:

 

 

gallery_1527_132_3664.png

 

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I think you could improve the top teeth just by dropping the nozzle temp a little for the entire print.

0.06mm (or maybe 0.07 or 0.08) will show a slight improvement... beyond that I think you're way beyond diminishing returns.

40 a week sounds easy enough... I have a UM1, but there have been stretches where I ran consecutive 20+hour prints every day for weeks.

 

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The nozzle is a separate and fairly standard part on a UM1, so it's relatively easy to find a compatible smaller nozzle. Although using it will slow down your print speeds a lot, as the pressures will be much higher for a given volume per second. On the UM2, the nozzle and heater block is a custom piece that comes pre-drilled to 0.4mm, so finding smaller sizes will be quite hard.

I've been doing some dental prints like these for someone else lately, and have been pretty satisfied with the resulting print quality, although I can't speak to their suitability or usefulness for actual dental applications. But to a lay person, they look like they should work well. I'm finding that a typical print takes about 90 mins or so. So, 40 per week out of a single printer during regular office hours might be a bit of a stretch. But you could do multiple prints in one batch overnight - or just get a second printer. Compared to more traditional methods, or outsourcing to a 3D print bureau, the savings would still be massive, I would think.

As others have noted, you can probably print a bit cooler and slower, and with more careful retraction settings and get some pretty good results. The problems you highlighted mostly don't look too bad - it would probably be simpler to inspect the finished pieces and perform minor clean-up on them with a scalpel. What exactly are the parameters of what you need from your finished prints?

 

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Thanks for you answer illuminarti !

The dental model must be perfect on the teeth because i am using it to make some braces (prepare the model), or other appliance which need precision :/

Can you tell me about the retraction setting ? About the nozzle in 0.45, if i good understand, it's not very possible on a UM2. Too complicated fot nor sure best result ?

 

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I have try to print with no fill (cf gr5), but bottom of the teeth is done into empty :/

Idea to correct that with no fill ? More shell thickness ?

 

Another problem, the end of the two incisors, the nozzle is making a round-trip and continuous to pop out plastic thread more or less, what creates lots of little son between the two :( I have activated the cool head lift.

 

793622unnamed.jpg

 

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The picture above is very tiny and I can't see much of anything.

continuous to pop out plastic thread more or less

It sounds like you are talking about stringing maybe? Are you talking about small strings connecting the teeth? It is possible to get rid of all strings but there are tricks. Most important is retraction:

There are 6 retraction related settings:

1) Make sure retraction is checked on basic/quality

2) In expert settings set minimum travel to 0mm or at least something small like 1mm.

3) In expert settings set "minimal extrusion..." to 0 or something well under .1mm. There is a 160X factor on this for .1mm layers so if you extrude .02mm filament you will get 3.2mm of straight line extruding. So the default is to not retract if you print for less than 3.2mm of linear printing (for .1mm layers).

4) In expert settings you can set "combing" on or off - it shouldn't make a huge difference for this part. Lately turning this "off" seems better in the current version of Cura.

5,6) On UM2: On the printer, you can control retraction there also Leave the retraction speed alone but change the retraction amount from 4.5mm to 5.5mm if the bowden moves up and down at the head (try pulling it a bit).

 

 

 

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but bottom of the teeth is done into empty

Maybe you *do* need support?

You could try top/bottom thickness and change this to be a few more layers. Maybe you are stuck with infill. Those recommendations regarding 0 infill and "cut off bottom" were only to save you time. Not improve quality.

In post #2 above you posted a fantastic picture. Green is much easier to see and also it is a very large picture. In the post above you posted a tiny picture - hard to see anything. Please use green if you can as it is easier to see mistakes.

Did you try printing vertically? I recommend printing vertically.

 

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The dental model must be perfect on the teeth because i am using it to make some braces (prepare the model), or other appliance which need precision

No such thing as perfect. There are only tolerances. For example "need accuracy of surface with roughness less than +/- .01mm and accuracy +/- .1mm.

 

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Regarding .25mm nozzle:

No one has made one for UM2 - they are only available for UM1. No one sells one yet but you could ask Ultimaker for a spare nozzle (I think it's free) and then you could take it to an expert with metals. They could solder/fill the nozzle and redrill it to .25mm.

But printing with .25mm nozzle will take much longer! You have to print at slower speeds (10mm/sec for high quality) and you have to make more passes. But the quality improvement will be stunning! Maybe .4mm is good enough for you? Or .35mm?

 

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Hum ok thanks, I will try !

About the vertically print, i must use the touching buildplate support or everywhere ? The printing time is absolutely not the same :/

About the nozzle, so i must try to have the best quality as i can with .4 and then i will see :)

5,6) On UM2: On the printer, you can control retraction there also Leave the retraction speed alone but change the retraction amount from 4.5mm to 5.5mm if the bowden moves up and down at the head (try pulling it a bit).

I am sorry, i don't understand about that :/

Thanks a lot for you help !

 

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About the vertically print, i must use the touching buildplate support or everywhere ? The printing time is absolutely not the same :/

You should try vertical just to see the quality and worry about speed later.

Support will work but it is faster to simply sink the part into the bed by about 4 to 4.5mm. This will create a new flat bottom.

 

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I am sorry, i don't understand about that

When you click PRINT and then choose a model, before it starts printing, go to the TUNE menu and then go to the retraction settings. Use your fingers and pull up and down on the bowden at the black print head. If it doesn't move then the settings should be 4.5mm retraction. If it moves 1 mm then increase that to 5.5mm retraction.

 

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I think I understand things better now that you explained about the braces. I looked at your green photograph again with the red circles. I now realized you circled "strings" and "bumps".

The "bumps" can be improved by slowing down. Try 20mm/sec. Experiment with different speeds.

I only saw one string at the top most tooth. That can simply be cut off with a razor.

 

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