Change hot ends for ABS?

[dramsey]

I've only ever printed with PLA with my M2, but am ready to start experimenting with ABS. Would it make sense to buy and use a separate hot end for ABS? I worry that the higher print temps will carbonize PLA left in the nozzle; and swapping hot ends on the M2 is so fast that it might make sense to keep separate nozzles for each type of plastic.

[ednisley]

swapping hot ends on the M2 is so fast

Public Service Announcement

Remember to verify / recalibrate the nozzle-to-platform gap with a test square whenever you do that, so as to avoid sharing the heartache and confusion in those "suddenly nothing sticks" posts... [grin]

[dramsey]

Of course, but that's easy with the V4 hot end:

1. Install hot end. Leave mounting screw loose.
2. Get 0.15mm-0.20mm feeler gauge and place under hot end.
3. Home Z axis.
4. Tighten screw.
5. Profits!

(Or print a calibration cube to be sure...)

[ednisley]

(Or print a calibration cube to be sure...)

Always do that, because the difference between "great adhesion!" and "what's wrong with this thing?" is maybe 0.10 mm, tops, and you flat-out can't maintain that accuracy while tightening a screw against a steel cylinder.

Run off a square, measure the height, twiddle the Z offset (not the screw!) by doing whatever it takes with your printer / firmware / software, iterate until the height is correct, then profit!

[dramsey]

But getting back to my original question: does it make sense to have separate hot ends for PLA and ABS?

[Jules]

But getting back to my original question: does it make sense to have separate hot ends for PLA and ABS?

I found it easier to just run the cleaning filament through when switching between hotter and cooler filaments. Hot ends are $70 each.

If you are going to be printing nothing but a specific filament for a while, then it might work to have a separate hot-end for PLA and ABS. Otherwise it takes longer to change out a hot end and re-set your stops and offsets than it does to run cleaning filament through a few times.

[dramsey]

Jules, is there a specific cleaning filament that you recommend?

[Jules]

Jules, is there a specific cleaning filament that you recommend?

Yeah, eSun Cleaning Filament here:

https://www.amazon.com/CLEANING-Filamen ... g+filament

There is a specific way to use it, and you need to be REALLY careful.

1. Heat the nozzle up to extruding temp for the filament that is currently in the machine.
2. Retract that filament completely, and pull as it retracts to remove as much as you can. (You'll get long stringers. Keep pulling.)
3. Cut about a 6-10 inch length of the cleaning filament with a flat end. Check the roundness of the diameter - it tends to get oval shaped rather easily and that hinders feeding. Straighten it gently so it feeds straight in.
4. Try to feed that filament in, 60 to 100 mm total, in batches of 20 mm or so. If it stops, reverse it out, check the Filament Drive Screw tension, (teeth marks need to be about 10-15% or so) and adjust it if needed.
5. Take a fresh piece of cleaning filament, check it for roundness, straighten it out and start trying to feed that in. If it stops feeding, reverse it out.
6. Never try to force the cleaning filament down into the teeth and push it in from the top. It will jam.
7. Repeat the above steps until you start to see the cleaning filament pushing the other filament out of the nozzle below. Eventually you will see clear filament extruding, that is the cleaning filament and it means that you have now cleared the first filament out of the nozzle. Extrude a bit more of the cleaning filament, then retract the remainder out.
8. NOW you can take the temperature up to the higher temp for the new filament. Feed the new filament in slowly, and use the jog controls to purge (20 mm at a time) until all of the cleaning filament remnants have been pushed out.
9. Print with your new filament.

When you go back to the other filament, you do all steps again. Each and every time.

It sounds worse than it actually is - doesn't take more than a few minutes if you mark the correct tension spots for the various filaments on your screw.