Switching from PLA to ABS: Beginner's guide?

[3design 0]

I just tried to print with ABS after having two months of experience with PLA.

I took a black ABS filament from fabbster, diameter about 2.9mm, temperature 220°, packing density 0.85.

It seemed to harden much more faster than the PLA before, and after some layers the print started to mess up and look like a plate of spaghetti.

Re-inserting of PLA was troublesome as well, because the ABS nearly blocked the nozzle (extruding via Ultimaker controller, until the extruding wheel rubbed off too much filament, then cutting out the damaged part, re-inserting), and making a test print which was polluted with ABS.

Before trying a second time I'd prefer to ask you for your experience: What is specific for printing with ABS; do you know any beginner's guide?

 

[cora111 0]

You used round filament and not their sticks, didn't you?

I had no problems so far between switching between ABS and PLA, even as I switch a couple of times in one week.

Try to increase the fan speed and decreasing the speed of extrusion.

 

[3design 0]

Yes, it is a reel with round filament, diameter constantly between 2.8 and 2.9mm (rather 2.9).

What settings do you recommend for the fan speed and the extrusion speed? Or just by "trial and error"?

 

[owen 17]

Haven't used ABS myself but I thought 230 was about minimum.

Also I believe Joegren uses a packing density of 0.97.

You could just write gcode to squirt about 20mm of filament. Start at 250 Degrees and repeat while lowering the temp by 5 degrees each time until it starts to extrude a bit less. Then choose a temperature 5 or 10 degrees hotter than that.

In your first print of PLA after maybe go a bit hotter? Also look for posts from Joegren about his printing with it, he has probably written some of the various settings he has used.

 

[owen 17]

Sorry I spelt Joergen's name wrong. :oops:

 

[calinb 10]

I never print ABS below 240 and I print Ultimachine ABS at 275 (as displayed on my machine, obviously). I like to live on the hairy edge of jams in order to get maximum strength in my commercial parts, however. I've also taken to printing on Kapton tape and cranking my 160 mA fan to 100% after the first couple of layers (original fan was 100 mA and noticably weaker). Putting layers down as hot as workable minimizes the Achilles heel of FFF/FDM--weak "grain" (incomplete layer to layer bonding) strength. Cooling layers quickly after they are deposited reduces stress accumulation in the part as many layers cool (all layers have to cool sometime). Strain (warping) results when the stress overcomes the bond to the build surface. Actually, strain occurs anyway (like Z-shrinkage); it's just not as bad when the part stays firmly fixed to the build surface.

Like most people, I've tried countless combinations of things (bubble wrap/heated build chamber to 50C, different bed and nozzle temperatures/ fan profiles, etc. But this approach seem to be the best for my large parts, which span the diagonal of the bed and can be several cm tall. With the best Kapton tape I've ever used, I could actually unplug the heated bed after the first few layers and run the fan 100% and the part still remained stuck and warping was minimized! I found that about 60 - 70 C (the same temp I use for PLA directly on glass) resulted in the best Kapton to glass bed bond and it's quite good after cooling to room temperature too. At times, it's what gives rather than the ABS to Kapton bond.

I've yet to print a part hotter that wasn't stronger but eventually, you run into problems.

I'm certain everyone else's mileage will vary!

 

[3design 0]

As to cleaning the nozzle from ABS remainders (after swiching back to PLA), I was told to heat up the extruder on 260 C an extrude manually until the outcoming PLA is clean from ABS leftovers. Works pretty good.