Tag Archives: skeinforge

Slowdown

As I mentioned in my previous post, I had issues with the last print due to the high speed. I thought I’d slow this one down.

I also thought that I should be more meticulous about keeping records of the changes I’m making. In keeping with the original ‘lab notebook’ idea for this blog, here’s the settings.

Original settings:

From ‘Speed’

  • Main Feed Rate – 60 mm/s
  • Perimeter Feed Rate – 30 mm/s
  • Travel Feed Rate – 130 mm/s
From ‘Raft’
  • First Layer Main Feed Rate – 35 mm/s
  • First Layer Perimeter Feed Rate – 25 mm/s

 

Changed Settings:

From ‘Speed’

  • Main Feed Rate – 20 mm/s
  • Perimeter Feed Rate – 15 mm/s
  • Travel Feed Rate – 30 mm/s
From ‘Raft’
  • First Layer Main Feed Rate – 15 mm/s
  • First Layer Perimeter Feed Rate – 15 mm/s

And the result:

As you can see, it came out looking nearly identical to the first part. So it looks like speed isn’t the problem. As another test, I decided to print out the ‘single wall calibration piece’. It came out beautifully.

Then I thought I’d try the 10x40mm piece. I stopped that one after about 8mm, it was just turning into a sludgy mess. I thought then that to print a piece like that, I’d need to turn down the temperature, or use active cooling. I thought I’d try turning the temp down.

To get a better picture of what was happening, I thought I’d print out the ‘ultimate calibration piece’. To start with, I turned the temp down to 225 degrees, (from 230).

You can see in the picture, that the first couple of ‘hanging beams’ are sagging a bit. I then turned the temp down to 220. The remainder of the object printed fine, but the sagging was noticeably reduced.

I stopped the print at that point, since the ‘shelling’ problem (can be seen in the problem above) was distracting me. It’s clearly seen in the ‘reprap shot glass’, and it looks like SF is not correctly shelling the object, and creating proper G-Codes. I thought I’d better fix that problem first, before messing with the temperature.

Overthinking the Problem

One of the things I try and teach younger engineers (whenever they’ll listen – damn Gen Y’ers) is that it’s possible to over-think a problem. You end up burrowing down so much that you become entangled in the work, and generally end up with a much more complicated solution than what’s actually required.

When thinking about changes that I had to make to skeinforge, I realised that I had too many variables – one of the classic symptoms of over-thinking. I had made too many changes to the original settings, and I wasn’t sure which ones I needed to change back, or other ones to change.

So I decided to take a step back, approach the problem from the start again. To do that, I deleted the skeinforge directory, and re-installed from latest download – going back to the original skeinforge settings, no adjustment at all. This would allow me to approach the problem fresh. I went back and re-did the shot glass.

┬áIt’s looking great. Still a bit strange, but vertically, it’s just about perfect.

Emboldened by this success, I thought that I’d try and print out a useful part – a LM8UU Y-axis bearing holder. After looking at the options on Thingiverse, I finally settled for Digifab’s design.

Classic overspeed melted mess. That makes sense. When I did the shot glass, it was at original SF speed, up to 60mm / s. That was clearly way to fast for such a small piece as this. I’ll try it again tonight, but at a much slower speed.

The heatbed is working great. No problems at all getting the prints to stick.