Trouble with threads

[Fiddler2070]

Hi guys,

I am having problems printing threads (like on a bolt). It just doesn't come out right. The threads come out blobby. I'm using kisslicer.

8 loops (4mm skin), 0.2mm layer thickness, 0.5 mm nozzle. Infill set at 33% (but it never infills anyways because the loops and skin thickness takes care of it). I've tried a bunch of settings and it just doesn't come out right no matter what I do.

Everything else I print comes out great. The twisted vase looks incredible. I just can't seem to print threads for some reason. anyone have any experience with this?

Thanks.

Fiddler

[Captain Starfish]

thread size and a photo of the b0rk3d print would help.

[Fiddler2070]

thread size and a photo of the b0rk3d print would help.

I'll post it tomorrow. There's lots of them! Thanks.

[Polygonhell]

The most common issue when printing 100% infill, either withe the setting or just lots of perimeters as you are is over extrusion, it only has to be very slight to mess up a print.
Having said that threads aren't a particularly easy print, they require a very well calibrated printer, and good cooling.

[Fiddler2070]

The most common issue when printing 100% infill, either withe the setting or just lots of perimeters as you are is over extrusion, it only has to be very slight to mess up a print.
Having said that threads aren't a particularly easy print, they require a very well calibrated printer, and good cooling.

I figured I was doing something wrong, I just couldn't figure out what it was. I tried 1mm skin 33% infill, 2mm skin, all the way up to 4mm skin and it still looked like shit. I print with ABS so no layer cooling.

Everyone is asleep so I can't go digging for the old prints. I will post the prints tomorrow and the vase I printed using the same calibration on the printer. It's making me crazy! Mostly because it's going to be for a commercial product. I figure I am going to have to use a tap anyways to make sure the threads are good but the closer I can make it the better. Less work to tap the thing and faster time.

Thanks for the help. I really appreciate it.

[Captain Starfish]

I find that threads go to crap if I don't have at least 10 layers per revolution and, even then, it's a bastard of a compromise with ABS. Nice and hot (around 260º) means layer adhesion is really nice BUT it sags worse than grannie's bewbs. So when the layer comes around to that next bit of overhang, it droops. And the layer after that drops on top. And so on. On the other hand, printing at 230º means the overhangs cool quick enough to not sag so much. But the inter-layer adhesion is rubbish.

Go with a layer height of pitch/10 (ie a 1.0mm pitch needs at most a 0.1mm layer height) and slow the print down. If it's blobbing out looking like some case of boils then polygonhell has identified the most likely cause: you're overextruding slightly and that extra goop has no-where to go. Definitely worth doing another filament length calibration (extrude 100mm, measure it eg 100.3mm, change your stepper ratio for the extruder by 100/100.3), definitely worth doing another filament diameter calibration (measure 4 times along a 100mm length with a micrometer, load the average into your filament settings, guaranteed it won't equal 1.75mm).

[Jimustanguitar]

I've had great luck with threads that I've designed, but it's one of those things that varies greatly by software. I printed threads on a part for a friend, and they came out almost like teeth on a gear. I thought something was wrong, but they're that way in the STL file, and the slicer exaggerated them.

[img]http://i.imgur.com/edmedWs.png[/img]
[img]http://i.imgur.com/yfgga5e.png?1[/img]
[img]http://i.imgur.com/7FytHoX.png?1[/img]

It turns out that the way he did threads in OpenSCAD made the threads a series of triangular prisms instead of a smooth helix.

For comparison, here's the STL of some threads I created in DesignSpark Mechanical.

[img]http://i.imgur.com/RdSPcns.png?1[/img]

[Fiddler2070]

Ok here's the pictures. I think you guys may be right. It's over extruding on the threads.

So this is a print from the same printer. No changes except to the slicer settings. The inside is just as clean as the outside. A little acetone vapor and it would look like it was injection molded.

Here's the frustrating parts.

It's gets all blobby on the inside and the threads are blobby. Not only that the printer is doing some sort of circular fill in the wall. It does these little circles inside the walls of the cylinder. I've never seen it do that before. So it makes the wall layers uneven layer wise.


Here are some prints of the Xnaron mag arm parts for comparison. Again no changes to the printer extrusion settings, just the slicer loops, skin width, etc.

Here are more thread type prints. You can see the size in comparison with my hand. These are a little bigger than the one above so theoretically it should be better or easier. I went from 4 loops to 8 loops to 10 loops and it doesn't seem to help.

Smaller threads just to see what happens and it the threads still come out blobby. These are normal threads.

This is the inside of the previous pic. Just a seam but otherwise no blobbing like the big thread ones.

You would think bigger is less blobbing but no.

So I can't seem to figure out the settings. I will check the extrusion and the size of the filament but it has been very even. The only trouble I have had is with the threads. Everything else comes out great.

[Fiddler2070]

The vase was printed using vase setting in Kisslicer. The others were not 100% infill. They vary from 33% to 75%. It doesn't seem to matter. I'm curious what settings you guys use for your slicer to do threads.

I'm using the stock hotend at 0.5mm nozzle. It drools a lot. I have a E3D V6 that I will install after I get the Xnaron Mag Arms ready.

The first layer is at 0.17mm all the way around. The first layer is a little squished but It has taken me more time than I want to say to get this far so I am happy with a slightly smaller first layer since the other layers are at 0.2mm.

I got an inclinometer the other day and found that the Y tower is 2.5 degrees off 90, while the other ones are 0.5 degrees off. I will have to adjust the Y tower at some point but at these short print heights it shouldn't make a difference. The vase came out great and it's taller than anything else I've printed.