Improving small sphere quality

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mike.stanley
Posts: 53
Joined: Thu May 12, 2016 8:06 pm

Improving small sphere quality

Post by mike.stanley » Wed Jun 08, 2016 8:34 pm

Modeled a few chess pieces in openscad and printing with Cura. Using only one of the extruders of the flexy dual extruder and printing in ABS. Layer height is 0.15mm, 20% infill, 235 temp and 90 bed. The quality of the print overall is great. But the top sphere keeps coming out crappy and not sure what to do about it.

Any suggestions?
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kcchen_00
Posts: 1705
Joined: Thu Feb 19, 2015 12:42 am

Re: Improving small sphere quality

Post by kcchen_00 » Wed Jun 08, 2016 11:01 pm

Hard to explain, but basically its due to the small surface area of the object. The printed area is not cooling enough before the next layer is being deposited.

There may be a setting Cura, but its not my normal slicer... maybe another community member can tell you how to add the delay. The other thing you could try is increasing the cooling through the "Tweak at Z" plugin... I guess you could also use the plugin to slow the print down at the top.

If you don't mind a bit of filament waste, you could try printing a pillar of the same height next to the chess piece. A 5x5mm square pillar should work (and hopefully stay stuck to the bed). Essentially, printing the pillar layer and the toolhead movement time will allow the chess piece layer to set.

Try the Tweak at Z plugin and slow down the print towards the top. Then try the pillar...

Hope that helps.

ohhorob
Posts: 11
Joined: Tue Jan 05, 2016 4:41 pm

Re: Improving small sphere quality

Post by ohhorob » Wed Jun 08, 2016 11:07 pm

If you're watching the print, when it gets closer to the top layers, gradually slow down the print with the dial next to the LCD screen.

Although the indicator says the "FR" is changing (Flow Rate?), it really just slows down the whole process, allowing more cooling time for each layer.

If you just crank it down to say 66% in one go, the difference in speed will show up in a subtle difference between the fast and slow layer. I normally change it by ~5% every couple of layers..

Farris
Posts: 36
Joined: Sun Jul 19, 2015 5:30 pm

Re: Improving small sphere quality

Post by Farris » Thu Jun 09, 2016 3:59 am

There is a setting in Cura for minimum layer time under the advanced settings. I think the 2nd tab. Near the check box for the cooling fan.

nopick
Posts: 1004
Joined: Mon Sep 09, 2013 11:14 am

Re: Improving small sphere quality

Post by nopick » Thu Jun 09, 2016 11:22 am

ohhorob wrote:If you're watching the print, when it gets closer to the top layers, gradually slow down the print with the dial next to the LCD screen.

Although the indicator says the "FR" is changing (Flow Rate?), it really just slows down the whole process, allowing more cooling time for each layer.

If you just crank it down to say 66% in one go, the difference in speed will show up in a subtle difference between the fast and slow layer. I normally change it by ~5% every couple of layers..
FR on the lcd stands for feed rate. That will adjust the speed of entire printing process. The flow rate adjustment in the lcd menus and in the print control software adjusts only the extruder flow rate.

idiot
Posts: 122
Joined: Thu Jul 02, 2015 7:53 am

Re: Improving small sphere quality

Post by idiot » Thu Jun 09, 2016 5:26 pm

I have had small sections like this in the past. The way I dealt with it was to either print multiple copies, or if it was something I only wanted 1 or 2 of, printing another object at the same time that I wanted to print anyway.

Obviously that object has to be as tall as the thin sections on the other part(s) and big enough so each layer has sufficient cooling time.

Just like the pillar idea really.

mike.stanley
Posts: 53
Joined: Thu May 12, 2016 8:06 pm

Re: Improving small sphere quality

Post by mike.stanley » Fri Jun 10, 2016 6:49 am

Perfection!

Thanks everyone for the suggestions. The "too fast to cool" makes a lot of sense (but was not obvious to me). I adopted two suggestions:
1) I adjusted the min layer time from 10 to 30 seconds
2) I used the tweak at Z plugin to slow down total speed by 50% when it gets near the ball at the top of the bishop.

I'm sure I could have gotten by with just the second one, but didn't see a harm in doing both. I didn't try them in isolation, but together they worked like a charm. Also, given that bishop's do come in pairs, I could have printed two at a time as well, but for the sake of learning, I went with the above. Having never used the tweak at Z plugin, I wanted to explore it.

Here's pictures from the latest print:
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mike.stanley
Posts: 53
Joined: Thu May 12, 2016 8:06 pm

Re: Improving small sphere quality

Post by mike.stanley » Fri Jun 10, 2016 3:22 pm

Oh, and please critique my print! The quality shown in this print is amongst the best I've been able to achieve with the unmodified Taz 5 / flexy dually v2.

I think it's pretty good, but always looking for tips and suggestions for squeezing more out of the printer.

I know there are a number of mods to help with Z wobble, x sag, y stability, etc, and also different nozzle sizes (the 0.6mm is relatively large for fine features). Without going the mod route, I'm curious if there are obvious adjustments I could make / glaring omissions in my tweaking. In other words, I'm just trying to level set my expectations. (Again, happy with current quality. Call me fanatical).

kcchen_00
Posts: 1705
Joined: Thu Feb 19, 2015 12:42 am

Re: Improving small sphere quality

Post by kcchen_00 » Fri Jun 10, 2016 9:42 pm

Glad you figured it out.

The print looks great. You have a little Z-banding, but that's hard to get rid of... try a quarter turn on one of the screws to get it out of phase.

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