TPU can suck it

Print, print, errkkkkkkk, where's my allan key?...

Table progress has been going okay - mostly. Up until I tried to be clever, that is.

I was printing some bottom rails. These were taking about 8 hours. Set another lot going overnight before bed and woke up to find the printer had been beeping for hours (and had woken up my wife who was not happy). Looks like the Prusament refill for galaxy black is less than ideal for use as there’s a number of bad reviews on the website about it jamming/getting pinched in the sides of the spools.

So I won’t be buying any more of that.

I tried some more TPU after that. The first print of which went fine and I peeled it off the build plate with no issues. So I did a second one with less infill and for whatever reason, the bonding properties of TPU and PEI decided they were going to apply this time and the TPU stuck to the plate like you would not believe.

No matter what I tried, I couldn’t get it off. Found out you’re meant to use glue or similar. My own fault. SO I ordered a gluestick.

Got the buildplate as clean as I could, and decided to flip it. Ran some prints and all was okay on regular filament. Got to the evening and decided that I was going to try and do some feet overnight. Started it at about 9pm, should have been done for about 10am. Did a single foot with glue first, just to check it was doing what it should be doing. All good.

Started the print, watched the first layer, went to bed.

Woke up this morning and checked the camera, expecting to see feet that were 3/4 done. What I saw instead was air printing.


How it looked this morning

I stopped the print and got up and went downstairs to investigate.

There was no filament coming out. I did a filament unload and it snapped away from the hotend. Not a great sign.

Opened up the idler, nothing in the extruder gears at all. No dice.

Tried to load up some PLA to see if I could get anything through. Nothing.

Unloaded the PLA.

Heated up to 280 degrees. Tried to feed some PLA through again.


Found this awesome troubleshooting guide:

Clogged nozzle/hotend (MK3S, MK2.5S)

Disabled the autoloader as suggested, tried to push the allan key through the extruder, couldn’t get any movement on it.

Changed the nozzle, the old one was black.

No change.

Used the acupuncture needle on the new nozzle, could definitely feel some goo up there. Nothing was coming out.

Tried some more PLA to dislodge it.


Before I resorted to taking the hotend assembly apart completely, I removed the new nozzle and tried to push the allan key up from the bottom instead. Struggled to get it in, but did and then got some movement on the second push.

I checked the idler again and could see some TPU!

I pulled it out, this is what was stuck in the PTFE tube:

The culprit

And this was the state of the build plate (mind the glue, and the mess, you can see all of the tools I had to use this morning to try and clear the clog.)

State of the build plate


That was a complete and utter pain in the arse.

I got everything back together, fed some PLA in and it started to ooze out and we got some more TPU clog out. Cleared it through and started a print.

Wasn’t overly happy with the first layer but I let it go. Got a thermal anomaly warning which wouldn’t clear. Accidently hit the X button (which I didn’t even know was a button) to clear it, which actually acts as an emergency stop button and cancelled the job.

Decided to do a heat calibration as the one that I did after the firmware update when I got it was pre case-build, so there was a chance that we were getting a false positive as the radiators had come on in the house and things probably warmed up a little faster than usual in there.

That took 12 mins and was fine. Started again. Still not happy with that first layer.

I cancelled it and started a first layer calibration. Took probably 5 attempts, but got there and got it beautiful. Set off the print again and after 4 hours ended up with some really nice looking game tiles. Everything is back into a good, known working state and everything is okay.

I’ve decided to leave the TPU for now, and am going to print the top rails in a nice PLA blue, they won’t be good to lean on and there won’t be any squish but to be honest, nobody was probably going to lean on it anyways, its fine.

I might come back to it another time - maybe once the rest of the table is done and I’ve got some proper time to sit down and try to get the printer printing TPU without issues.

I’ve bought some rubber feet for the bottom of the legs, cost £3. They’ll be more than adequate for the time being.

Swapped out the filament for some blue and am doing the rails. Doing a couple of corner ones at the moment that’ll finish at about 9pm, then I’m going to kick off an 11 hour set of four card rails that’ll take 11 hours. That’ll give me a few rail pieces to do one edge of the 5x2 table I’m doing, then I’ll do some more brown tiles and then some more rails overnight.

Once I’ve got these in a good place, I’ll start doing some more frames (I need another 10 of those) and the remaining rails I need overnight, swapping out the prusament stuff isn’t too much of a hassle and it seems to fall right back into a print again.

On the subject of Prusa - they sent out a message to say that anyone who had bought an MK3S+ within 30 days of the announcement of the MK4 release would get a voucher. I think I was about 45 days before the announcement but I didn’t receive the printer until about 19 days before the announcement.

They’ve said they’ll honour the voucher offer and I should be receiving it through soon. Which is lovely of them.

I might put it towards the upgrade to an MK4. Not decided yet. It’ll either be that or the next filament order. Problem is, the MK4 upgrade is only about £100 less than just going for the full MK4 kit, I’ll end up with a bunch of spare parts that’ll never get used again.

Will have to have a think on it.

Anyway, hopefully we’re going to have a few good days of printing again now. I’m going to stay away from TPU for a while. Get the table built and hopefully in a position to play small games by this weekend, with a view to having the full thing built for next weekend.

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