Adjusting the Z level on Workhorse

Hey folks was having a hell of a time getting this to print. The nozzle would scrape the daylights out of the print. Tech walked me thru changing the Z. It was from factory at I think -.12, we ran adjustments up to +.20, and it seemed to begin printing Polylite PETG, but the print won’t stay on the bed after an hour. Using Elmers glue stick and bed at 60. I tried Polylite PLA, same effect. The PLA won’t stick for more than 30 seconds. I tried painters tape. I raised the Z as high as +.30, lowered to +.15, ran PLA at 210 at 220. Nothing seems to be working, Bed level seems to be working. Went back to the glue, cleaned the bed with windex and then alcohol. Still won’t hold. The filament binds up at the nozzle, then drags across a printed area and rips it off. Any help would be appreciated. Tech is emailing me back and forth and that may help. Thanks

There are several things to check…

Z-offset is one of them. But so are things like print temperature and first layer speed and build plate temperature.

PolyLite PLA will work best if you print it at 230°C (I’ve done the temperature tower for that filament on the Workhorse a few times and each time the 230°C works best. 225 isn’t quite as good. 235 is also not as good. Anything below 220 is noticeably poor.

With the PLA… set the bed temp to 55°C and leave it there… do NOT let it cool down to 45°C for subsequent layers. That will cause some part contraction (filament contracts as it cools) and break the bond it has with the build plate. I used to have parts break away from the plate in mid-print until I learned this. The default profile does drop the temp to 45°C and that may be your issue.

First layer speed should be slower… I print 15mm/sec on the first layer then speed up for subsequent layers. I typically do 40mm/sec but use 35mm/sec for outer walls. You can print faster than 40mm/sec but generally if you’re not in in a hurry you get better part quality by printing just a little slower.

For PLA you want a bit of “squish” on the first layer. Watch the skirt as it lays it down before starting the part. It’ll do a couple of laps of filament around the build area before it starts on the part. The skirt should have even thickness all the way around (otherwise you didn’t achieve a good “level” on the bed). You don’t want it over-squished… if the filament looks “flat” with frayed edges as it lays down the skirt, it’s too low. The idea is that filament that isn’t squished at all (as if gently laid on the bed) will have very little surface area touching the bed. A bit of squish flattens it gently into an oval shape and that increases the surface area touching the bed which helps with adhesion.

My Z-offset is typically -0.13 with PLA.

PETG is a bit different… it wants to stick to EVERYTHING. PVA glue-stick (e.g. Elmer’s) is necessary – but not to help it “stick” to the bed… to help it release from the bed. I flip the bed over and use the glass side with Elmer’s when printing PETG.

I use IC3D brand PETG and if I use the LulzBot Cura Edition profile for it (on the “standard” quality setting) it’s perfect. But I increase the z-offset to -0.12 or possibly even -0.11 … PETG should be gently laid onto the bed as it prints the first layer.

Again… I dislike letting the bed cool after printing the first layer.

PETG normally prints at a slower speed… about 30mm/sec (and 15mm/sec for the first layer.)

These days I use the glass side of the bed for pretty much everything and I use MagiGoo for PVA (but I still use PVA glue stick for PETG). MagiGoo is more for the easy of pulling the part off the bed. It sticks about the same as Elmer’s … but once it cools it contracts so much that the parts practically lift off the bed with almost no effort at all (Sometimes my parts are completely broken free once they fully cool down. Sometimes they just need a very gentle tap to break them free.) I only use MagiGoo (so far) with PLA … not for the PETG (I still use Elmer’s for that).