Thursday, July 5, 2012

Multiple layers and warping solutions...

...Or, one step closer to being able to print a boat!

We've had a lot of issues with the HDPE not sticking to surfaces and peeling away, and a lot of ideas thrown around as a solution. On Wednesday, we tested printing on countersunk pegboard. The thought was that the plastic would get forced into the holes, and get mechanically anchored, thanks to the chamfer of the holes. We screwed the pegboard down to the print bed to try to minimize warping of the bed. Then the 5" test cube was loaded up, respirators put on, extruder and heating activated, and off we went!

To mash the plastic into the holes, we started off with a breakneck clip of 3 inches per minute. This spread our extruded layer out to nearly an inch thick. We modified our GCode to use a very sparse infill (we actually combined two different slicing configs) on the first layer to avoid unnecessary buildup.

Wonderful! Now up to the second layer and infill.

Looks good so far! And a pleasant surprise; HDPE bridges quite well naturally over gaps. But what about the perimeter? That's what everyone's going to see.

So maybe it's not the prettiest in the world, but at least it works, right?
Wrong. We had some issue with the extruder not being very consistent. It's visible both in the perimeter and the infill. But at least it's not a horrible flaw.
Hold on a second, that doesn't look like a cube! We ended up stopping the print here. This little square was almost exactly a thirty minute print. We'll have to try test printing shells of cubes. Solid shapes just take way too much time!
And, unfortunately, we got some warpage. The good news is that when we flipped the board over, the plastic had done exactly what we wanted and was anchored to the holes. We'd like to try printing with a raft included in the base layer, that way all the warping will happen to a part that is trimmed off.

Rumor has it that our layers are also starting to delaminate a little, but I haven't got any pictures of that so far.

Now for some numbers:
Feedrate = 30 in/min (100%)
Perimeter = 60-70% feedrate
Infill = 60-80% feedrate
Base = 10% feedrate

You may notice that these pictures are screenshotted from a video. I have the entire thirty minute print recorded, but I haven't uploaded it anywhere yet. If there is a huge demand for it I will put it up (It's a rather boring video, with a loud whirring sound the entire time), but otherwise we'll just put it in the archives, so to speak.

That's all for now! More updates as they come!

1 comment:

  1. Excellent post Brandon. As an update, we tried to print a bucket today. After working on the extruder, we managed to nearly eliminate the grey color (metal powder due to auger misalignment). Also, the raft we made today was a big improvement. We had extruder issues on the subsequent layers and only made it up about an inch. Good news is the "bucket" was pretty much water tight. One small crack that could be fixed with a soldering iron. Again the pegboard worked without a hitch.