Trouble Printing A Dome

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pottsjr
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Trouble Printing A Dome

Post by pottsjr » Mon May 12, 2014 3:10 am

I just acquired the MakerGear M2 and am not yet proficient with it. I leveled the glass platform of my new MakerGear M2 using a piece of paper 0.25 mm thickness and was able to print a dome shell with wall thickness 2.0 mm and hole in the top. The sides (with steep slope) printed very well, however, the top part of the dome (with diminishing slope) printed poorly, especially the inside surface, and I'm not sure exactly why. The picture attached shows the inside surface at the top of the dome. Is this printing problem due to insufficient leveling of the glass platform and if so would using a better technique for leveling the glass platform (using a dial gauge) improve print quality?

I created the 3D STL file using TurboCad Pro 19 and Simply3D program to print.

Comments would be greatly appreciated.
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jimc
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Re: Trouble Printing A Dome

Post by jimc » Mon May 12, 2014 3:24 am

the top of a dome is very difficult. the problem is that the outer perimeter wall begins to step over more and more until there is a gap showing the layer beneath. now on the inside of a dome you need support. anything over about a 45-50deg angle should have support added. i dont know if you printed support or not. if you did and you need that surface cleaner then you need to increase the support density %.

Toby
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Re: Trouble Printing A Dome

Post by Toby » Mon May 12, 2014 3:28 am

The problem is as the dome flattened out the new layers had nothing to stick to. I think what you're seeing there is that the nozzle was essentially printing in air and so it dragged the filament around with it until happened to catch somewhere- hence the lines cutting from one point on the perimeter to another.

The solution for something like that is to use support in the print. Turn on Support in S3D and see what it does in the preview to see what I mean. Only in this case you might want to turn the model upside down so that the support is only needed in the lower layers instead of all the way to the top.

A general rule of thumb is that when an unsupported wall slopes at less than 45 degrees you'll need support.

Toby
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Re: Trouble Printing A Dome

Post by Toby » Mon May 12, 2014 3:43 am

FWIW, I didn't start printing objects that needed support for almost three months after getting going. Likewise for using different materials other than Makergear PLA. There's so many things to learn I figured I'd take it one step at a time and gradually progress. That's worked out well for me.

pottsjr
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Re: Trouble Printing A Dome

Post by pottsjr » Mon May 12, 2014 9:09 pm

Thanks everyone for the prompt and very helpful replies.

I tried both inside and outside supports generated automatically in the Simply3D program and they certainly improved the print quality at the top of the dome. However, separating the supports left the surfaces noticeably marred to varying extents. Would generating the supports manually do much better or do you have any other recommendations?

Generally the inside and outside surfaces at the top of the dome are a bit bumpy, not smooth using supports and will require some type of finishing. I will try using Tetrahydrofuran to smooth the surfaces...any other suggestions?

By the way, the print head generally did not complete a circle and often changed direction at the same point on the circumference leaving a noticeable seam on the dome. Any idea why that happens?

Thanks again.

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jimc
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Re: Trouble Printing A Dome

Post by jimc » Mon May 12, 2014 11:31 pm

well as for the supports, anywhere they contact and need to be removed or broken away will leave a mark. you should have it set so there is a 1 upper separation layer. this basically but a 1 layer gap between the support and the part. if the surface needs to be really nice then the best you are going to get out of it is turning up your support % to about 90. to get the finish any better then you will need to have a dual extruder and print with dissolvable material and have the upper separation set to 0. as for not completing a circle then your coasting is on and set too high and or you have a neg restart distance that to too high. as for the bumpy surface, as i sadi before that is from each layer stepping over more and more until they dont overlap anymore. you cant do anything about it. its the way 3d printing is. you can reduce it a bit by printing at low layer heights. you can do a multi process print and when it gets near the top of the dome set the second process with a layer height of maybe .1

jsc
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Re: Trouble Printing A Dome

Post by jsc » Mon May 12, 2014 11:53 pm

Like every process, there are engineering limitations to the kinds of designs that can be 3D printed on FFF printers like the M2, the biggest of which is, they can't print in midair. It can be disappointing to discover you can't print whatever you want, at the best quality, but that's the nature of the beast. There are workarounds, though. The most useful one is to cut up your model so that every piece is printed in the best orientation for it, then attach them together. Think like a wood worker, or a mold maker. Dovetail joints or mortise and tenons; tiny rare earth magnets are cool, glue is always good, and tetrahydrofuran, if you have it, is supposed to be a good solvent adhesive for PLA. If you want a great dome, try printing it as four wedges up to 45 degrees and bonding them afterwards.

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