Mike's ORDish Bot build

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Re: Mike's ORDish Bot build

Postby mike » Mon Mar 05, 2012 5:02 pm

Many thanks for the cooling tips! Looks like adding a cooling fan needs to be one the next additions to the printer.
For Slic3r, are you talking about the "Slow down if layer print time is below" parameter?

I'd call this my first "successful" print -- I'm not using a heated bed yet, and on the first try the print popped off when it was about 10mm high. I ended up using a heat-gun to pre-warm the bed and periodically throughout the run.
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Re: Mike's ORDish Bot build

Postby Zat German » Mon Mar 05, 2012 6:49 pm

If you don't have a fan, another trick with PLA is to print multiple things so that your smaller parts have time to cool off by the time it gets back around to it on the next layer.

Blue painter's tape and no heated bed is supposed to work really well for PLA too. This is what I am trying first once I get my Hadron.
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Re: Mike's ORDish Bot build

Postby JeremyBP » Tue Mar 06, 2012 4:35 am

Mike: that is the parameter I meant. The example squirrel I printed was also at 60% scale to make it go faster. For PLA, blue tape on an unheated platform does work very well. I've printed over 10lbs of PLA on an unheated bed with no issues to speak of.
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Re: Mike's ORDish Bot build

Postby mike » Mon Mar 12, 2012 4:11 pm

Just wanted to report great success with the blue painters tape -- it's actually surprisingly hard to remove the parts... got to keep a chisel handy to get them to pop off.

I've also jury-rigged a 40mm fan on the carriage which has mostly eliminated the blobbing -- next up is printing a duct to mount the fan permanently.

Quick question: I'm getting fine threads/strings on the inside of vertical holes/cavities while printing -- any suggestions on parameters or process changes to reduce this?
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Re: Mike's ORDish Bot build

Postby JeremyBP » Mon Mar 12, 2012 10:25 pm

Try speeding up the reversal. What are your reversal settings right now?
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Re: Mike's ORDish Bot build

Postby mike » Mon Mar 12, 2012 10:37 pm

JeremyBP wrote:Try speeding up the reversal. What are your reversal settings right now?

Thanks, I'll give that a try. Currently I'm running with the stock Slic3r retraction settings.
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Re: Mike's ORDish Bot build

Postby JeremyBP » Mon Mar 12, 2012 11:37 pm

Try 2mm retraction at 30mm/s to start off. If that doesn't work, make it faster, longer, or both.
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Re: Mike's ORDish Bot build

Postby mxk » Mon Mar 12, 2012 11:48 pm

If you are not getting stringing between objects, only on the insides of circles or corners, then try turning the heat up a small amount and/or slow down the head movement. It sounds like you may be stretching the extruded filament.
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Re: Mike's ORDish Bot build

Postby JeremyBP » Tue Mar 13, 2012 12:01 am

MXK made a good point. Do you have any pictures of the objects?
Try printing an object with towers and observe the stringing (or lack thereof). That should tell you a lot about where the strings are coming from.
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Re: Mike's ORDish Bot build

Postby mike » Tue Mar 13, 2012 4:28 pm

A couple of breakthroughs -- looks like my problems are being caused by the cooling fan placement & speed.

First off, I noticed I was getting some "cold extrusion prevented" msgs after the cooling fan turned on -- don't know how I missed seeing those before. After jury-rigging some ducting to redirect the airflow, there's still a temperature drop, but not enough to prevent extrusion.

I was printing small hollow tubes, varying the retraction length from 1mm up to 2.5mm -- slight differences between prints, but nothing noteworthy.

I had a lucky accident here -- I was using a 40mm fan from my parts box, probably pulled from an old PC. The fan died during the next test print :( , and the rest of the print came out looking great, no threads... :D

My ToDo list for tonight:
  • replace the fan
  • fine tune the fan placement & speed
  • more test prints
  • pictures
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