First weekend with Dual Extrusion
Well, I dropped offline for a couple of days, and it wasn’t just the turkey. I’ve been working with the new Dual Extruder I just got for my LulzBot Taz4, and wanted to share an in-progress report on how it’s going.
Dual extrusion has been on my to-learn list for a while – I want to use HIPS for support material with my ABS prints so I can just dissolve it away in Limonene (I may also try PVA with PLA, but that’s another story). A lot of the models I’m working with have interior support required, and it’s rather painful (or even impossible) to remove. And then there’s the idea of printing a candy cane – in white and red, right out of the shoot. I just have to make sure my young nephew’s don’t get a hold of it.
The folks at Aleph Objects did a great job on the step-by-step instructions to get everything installed. I followed all the instructions (or thought I did), plugged everything in and turned it on…and promptly got a MAXTEMP error. Hmm. Well, as Jerry Pournelle always says, “It’s probably a cable.” So I unplugged everything, plugged it back in, and sure enough it worked – I must have gotten two of the plugs exchanged. So far so good.
Next, it’s time to build and then install new firmware. That sounds more difficult than it is, since they provide really good step by step instructions for that too. I plan to keep the firmware builds stored away and just upload the right one as I switch between extruders (there’s that flexy dually in the other box that’s itching to be installed). It’s not quite as easy as changing a setting, but it’s not too bad. Still, I plan to batch up prints to minimize the back and forth (and calibration needed on each switch).
When building the firmware, there’s one place where the instructions say to combine two folders together (merge). That works great on Windows, but on the Mac, for some reason that’s beyond me, finder only replaces folders and won’t merge them. There’s a hidden option to merge, but it’s not the same true merge that Windows provides (don’t even bother trying it). All the gory details can be found in a great blog post on How-To Geek. Plus, the target location is inside the Arduino bunder itself (more on that later), which causes other challenges.
My UNIX days are long past, but I remembered how to do it from Terminal with the CP command, but ditto is definitely the easier path. Assuming you’ve copied the Arudino application into /Applications, and have the ArduinoAddons.tar file expanded in your Downloads Folder, you can use this terminal command to merge the two folders together:
ditto ~/Downloads/ArduinoAddons/Arduino_1.x.x /Applications/Arduino.app/Contents/Resources/Java
Then continue on with the rest of the steps as shown. If OSX complains about Arduino being corrupt and refuses to open it, it’s Gatekeeper (Apple’s application security module) getting finicky – just open system preferences, security, and set it to ‘allow from anywhere’, then run Arduino, and then immediately change the setting back. It’ll remember that this app is OK from now on.
So once that was all done, I leveled the two extruders and printed the calibration squares to set the proper offset. That worked – sort of. I was able to get decent prints out of the printer, but found that the offset kept changing. I decided to try something a bit more cutting edge.
That seemed to give me a more consistent set of squares, and the Lulzbot calculator still works just fine.
I got all that dialed in and my next print turned out with great alignment. This is a 3D scan that Carrie did of a conch shell my folks brought back from the Bahamas when I was a kid – you can see in the center where the HIPS support material would be a real bear to remove. Now I just have to wait for that gallon of Limonene to arrive and see how the HIPS dissolves.
It’s pretty good, but I’m still dialing things in. Here’s my to-do list for the next phase:
- Change to dual ABS extrusion for the offset calibration. I think the HIPS shrinks at a different rate and oozes a bit more than the ABS. Once dialed in, I’ll switch back.
- Try using Ooze Shield and/or a wipe and prime tower (thanks to Ben & Ray at LulzBot for the suggestion.
- Change the z-hop value in Cura. I’m getting extruder strikes during travel, and suspect that’s why my offset keeps changing.
- Level – and I mean really level the bed. I have the impression that there’s enough sag with the dual extruder on the x-axis that I need to level in the center, but it’s just as possible that the bed isn’t really perfectly level – need to nail this one down.
- Add white marks to the dial on the front of the dual-extruder. This is used to set the vertical offset between the two extruders – the marks will help me see if it’s actually moving during printing.
- At some point I need to add cooling fans to the extruders so I can work with PLA – I hear that there’s other folks working on that, so I’m waiting to see what they come up with.
So that’s my first weekend with dual-extrusion. Not bad overall, and a ways to go, but I’m pretty happy with how things went so far.
If you’re headed down the same path, drop a comment here and let me know what your experience has been.