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Print Could Use Some Analysis

Posted by bbriggstkd 
Print Could Use Some Analysis
December 26, 2010 12:30PM
I got a vertex to print but I'm getting a small gap between the infill and perimeter on some parts of the object. I've seen it on other objects too so it's not just the vertex. I've got the infill overlap set to .6. I'm getting warninging from Skeinforge about that high a number so I don't know if bumping that more would help. I've tightened the belt trying to reduce backlash but I don't know if that is the problem.

I've also got a spot around one of the horizontal holes where the perimeter seems to be offset just a bit but is fine on the back side.

I'm using Skeinforge 31 with the TechZone electronics.

I've included some pictured, can some of you more experienced folks take a look and see if you can tell me what I need to do to fix this?
open | download - Vertex Top.JPG (46 KB)
open | download - Vertex Side.JPG (42.9 KB)
Re: Print Could Use Some Analysis
December 26, 2010 12:42PM
I don't think this is filament drag. I have unwound a bunch of filament so the extruder just has to feed it thorough. It doesn't have to pull it off the reel.
Re: Print Could Use Some Analysis
December 26, 2010 05:28PM
0.6 is very high for infill overlap. I have never used more than 0.15 and prefer 0 as it the infill distorts the outline if it is rammed into it. Problems on the layers below can cause the infill not to stick to the outline. Make sure you have three solid layers, solidity no less that 0.25 and interior over exterior density 1.

It does look like backlash to me though. Does the carriage glide smoothly with no belt? Friction will cause backlash as well as a loose belt.

The problem at the side could be that the outline has not stuck to the layer below so has taken a short cut round the corner rather then being extruded in the wrong place. Inconsistent filament flow can cause that.

Re: Print Could Use Some Analysis
December 26, 2010 05:54PM
My solidity is set to 0.25 but the interior over exterior density was 0.9. I do have it set for 3 solid layers. I see this even on the first layers and even if I don't use a raft. I haven't had a successful build without a raft but I do get through the first couple layers.

Since this is my first 3D printer and I have nothing to compare it to it is hard to say if the carriage glides smoothly. What I think is smooth may not really be that smooth. I'll try to adjust it and see if I can get it smoother that what it is now.

On the side problem, I see what you mean. It only seems to do it in that one spot. I looked at other vertexes that I printed and it is there also. If it were inconsistent filament flow, wouldn't it randomly show up on other builds too? I'm trying to get the drool to stop with the retraction settings but I can't get that to stop. I have it set to 3mm and it still drools. I know that is a great deal more than what nophead uses. It may not be reversing correctly. That may cause the pressure to be off and the extrusion to be inconsistent.

Thanks for the help. I'll make some adjustments and post the results here.
Re: Print Could Use Some Analysis
December 27, 2010 04:49AM
Perhaps the filament on the side is just ooze, i.e. an extra filament rather than some outline that is displaced.

I think perhaps the SF retraction distance is referring to extruded filament rather than feedstock. I.e. I retract the feedstock about 0.75mm. If I was extruding say 0.5mm filament that would be 27mm of extrudate. If I was extruding 0.6mm filament then it would be only 18.75mm, that is why I specify feedstock rather than extrudate in my software as I run builds with different filament sizes even for the same size nozzle.

Re: Print Could Use Some Analysis
December 28, 2010 03:42PM
I had something very similar to this backlash that I think I finally fixed when I tightened the grub screw on the shaft of the motor pulley.

Tony Buser http://tonybuser.com * http://reprap.org/wiki/User:Tbuser#Projects
Re: Print Could Use Some Analysis
December 28, 2010 06:07PM
I'll look into the pulley. If I slow down printing, will that help with backlash?
Re: Print Could Use Some Analysis
December 29, 2010 10:29AM
I had the exact some output on my Makerbot with the vertexes (every single one), but when I searched for pictures of other printed vertexes, I noticed that they all had the same problem. I figured it was a software issue because it only happens on the layers where that edge is complete, as opposed the layers where it open for a rod to go through. My layers rotate at 45 degrees, but it the output is the same is consistent on every layer, regardless of angle, which is why I just assumed it was the way Skeinforge calculates. I'll have to look at the simulator and see if I can confirm it's a software issue and not hardware.
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