1 Topic by HestonKent

  • HestonKent
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Topic: Extruder slows down while printing small cylindrical objects

So I have a model of a simple cylindrical object that has a gradual progression of expansion around 100 layers or so at .3mm layer height. The diameter of the base should be around 5mm, but it's coming out to 6mm due to the over-extrusion of the printer. For some reason, the G-code is slowing down the extruder when the object has a diameter of less than 10mm, which is odd. I cannot find a setting in slic3r that changes the speed of the extruder when printing an object that small.

So in essence, the g-code appears to be slowing down the speed of the extruder, but not the flow rate of the filament which causes it to heavily over extrude and completely mess up the print. I need a way to be able to keep the extruder at the 30mm/s speed that it maintains with all the other objects it prints much larger than this so that not only will it print faster, it will keep a solid print.

I'm attaching my slic3r settings, along with a picture of the screwed up cylindrical object I was trying to print. I'm on a Solidoodle 2 expert model, using Repetier and Slic3r, of course. Any help would be greatly appreciated! smile

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2 Reply by IanJohnson

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Re: Extruder slows down while printing small cylindrical objects

It slows down the extruder with tiny objects, because each layer takes so little time that it is still soft and melty when the next layer goes on.  The still soft lower layers get squished and pushed around by the layers above.  It slows down to try and give the layer time to cool, but at some point (as in your model) it isn't enough.   The best solution is a gcode controlled fan on the nozzle.  You can tell Slic3r to turn on the fan when a layer is going to take below a minimum amount of time, which works great.

If you can't use the fan, the best approach is to print another object at the same time.  If I have something small to print, I will stick a cylinder on the bed next to it, scaled up to the same height.  Then the object has time to cool while the cylinder is getting printed.  It uses up more plastic, but that is better than not getting it to print at all.

3 Reply by n2ri

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Re: Extruder slows down while printing small cylindrical objects

Ian is correct. slicer determines such settings for G-code to prevent bad prints or worse. its like a service company used to say on a sign.

fast, friendly, fine. you can have any 2 of these options. ;^P

Solidoodle 2 with Deluxe kit cover & glass bed with heater. and 2nd board SD2 used not 3rd and alum platform not installed yet still wood. also need cooling fan installed to board. use Repetier Host couple vers. Slic3r also have all free ware STL programs

4 Reply by Hazer

  • Hazer
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Re: Extruder slows down while printing small cylindrical objects

In RH you can change that 'minimum print time per layer' setting under your filament tab in the cooling section. I believe the default is like 30 seconds. There is also another setting which is minimum print speed somewhere that is default of 10mm/min. That one I  leave alone though. When the print job is small enough, the minimum print speed wins out over the minimum print time since the layer being printed can be so small. There is a real limit to how slow the extruder can extrude accurately vs linear travel. Ians suggestion is the best at handling this problem, print another object next to your primary job.

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5 Reply by HestonKent

  • HestonKent
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Re: Extruder slows down while printing small cylindrical objects

You guys were absolutely right! Thanks so much for helping me! Cooling is everything as far as layer adhesion goes with PLA, to which I was previously ignorant about prior to this.

My prints have come out fantastic as I have about a dozen printing on the build plate now and they all are meeting the expected diameter and everything. Thanks so much again!