Melted plastic bunching up on the print head?

I've been calibrating my reprap for about a week now, and I'm just about at my wits end here. I at least expected to be printing a weighted companion cube by now.

Right now I'm working through the reprap calibration page on the wiki: [reprap.org]. The bed is level, and all the motors work wonderfully. When I try and print the 0.05 mm thin wall box file, all the melted plastic bunches up right after I lay it down. I'm using white 3.0mm PLA filament. The temperature is 180 degrees on the hot end. Right now I'm just producing blobs of plastic.

Here's what I'm currently working with: Reprap prusa with a sanguililo and sprinter firmware. Lulzbot Budaschnozzle with a 0.5 mm hole, no heated build plate but I've got blue 3M painters tape on by bed. On the computer I'm using SFact and Pronterface. I can control all axes and the extruder manually. Everything works perfectly, I'm just making giant blobs of plastic.

Is there anyway to reset my SFact settings?

Any help would be appreciated.

How close to the bed is the nozzle it sounds like its not sticking to the tape. I find you should just be able to slide 2 thickness's of paper under the nozzle to get the right height

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Experimenting in 3D in New Zealand

If I fold a piece of printer/copier paper and slide it under the nozzle, I can feel the drag on it. I'm pretty sure the z home position is nailed down pretty well.

What is your layer height?
What is your nozzle size?
What is your print width set at?

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Layer Height = 0.4 mm
Nozzle Size = 0.5 mm
Extrusion Width (under Skeinforge/Carve): 0.60 mm

Although hose number are within "normal range" I would recommend going to layer of 0.3mm with a width of 0.5mm. I find I get a much smoother finish with the same width as nozzle diameter. Which makes me think it does not drag the nozzle through the plastic as it prints at all. And that would stop the build up of plastic on the tip.

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FFF Settings Calculator	Gcode post processors	Geometric Object Deposition Tool Blog
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I bumped the layer height down to 0.3 and the width down to 0.5. I'm now the owner of a 20mm calibration cube:



I think the problem I'm having is that the layers aren't cooling down when the next layer is being printed. Is there any way to slow down or stop the extruder in between printing layers.

Also, is there any wiki/manual for Skeinforge? Most of the guides I've seen either go into too much detail on a few things, or not enough detail on everything.

Edited 1 time(s). Last edit at 12/25/2011 04:31PM by wanderingjew.

This is the wiki/manual for SF [fabmetheus.crsndoo.com]

I personally only use [fabmetheus.crsndoo.com] which are the settings for skeinforges slicer. The rest of the wiki is to do with it many other functions which are overwhelming and have very little or nothing to do with printing.

The cool plugin can be used to slow down the machine or to orbit after each layer. The problem with orbit is you can have ooze during the orbit and and then you don't get any material on the next layer.

It would be best to try printing at 20mm/s constant and see if that improves things. At 20mm/s it should have plenty of time to cool.

Also PLA likes being cooled by a fan when printing small items or quickly.

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FFF Settings Calculator	Gcode post processors	Geometric Object Deposition Tool Blog
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Sublime Wrote:
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>
> It would be best to try printing at 20mm/s
> constant and see if that improves things. At
> 20mm/s it should have plenty of time to cool.
>
Could you please clarify which setting would be at 20mm/s? There are so many it is hard to be sure I'm thinking the same one as you.

thanks

In Skeinforge it is the feedrate/flowrate they need to be both set to 20 or whatever speed you want.

I SFact I think it is just feedrate and you set flowrate to 1 (1 = 100% of the feedrate)

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FFF Settings Calculator	Gcode post processors	Geometric Object Deposition Tool Blog
Tantillus.org	Mini Printable Lathe	How NOT to install a Pololu driver

You can also try upping your hot end temp. I usually print at 200 C in PLA. you might even want it a bit higher for the first layer.

Another thing that works to help the filament stick is wiping the tape down with some acetone (actually i'm using nail polish remover, so not very concentrated acetone) right before i print.

You may want to check out slic3r to use in place of skeinforge/sfact. Some people find it easier.

[www.slic3r.org]

-Jeff Moe

Edited 1 time(s). Last edit at 12/29/2011 02:35PM by jebba.

Looking at your picture i think you have several problems.
1) you have a big hole in the middle. If your fill is 1.0 yor must have non consistent flow.The most prominent causes are:
a. Your to cold. (I need to print PLA between 200 and 220 deg. depending on color.)
b. Your extruder isn't powerful enough and misses steps.
c. Any other kind of mechanical extrobles problem causing missed steps.

2) look like to much material caused by:
a. Your flow rate is to high. Did you do the calibration ? Check your values in Dimension plugin.
b. your fill is to dense. At the Fill plugin: increase "extrusion lines extra spacing"