So I had an incident with my Ubis all metal the other day...

@Alan_Thomason The NFPA 704 health rating for MEK is a 1 (out of 4). This is defined as:

Exposure would cause irritation with only minor residual injury (e.g. acetone, sodium bromate)

Really not terrible, antifreeze and diesel fuel are in the same class. Wouldn’t want to breathe either on a daily basis but use in a well ventilated area doesn’t pose much of a risk.

@Tim_Elmore thank you for proving him wrong. I am not stupid lol

Have you tried heating the hot end and use a small Allen wrench in the tip to force the plastic out? There is also a guide for removing the nozzle on the Printrbot support site that may allow you to get to the extra plastic. There is really no reason to use solvents or torches. That is a bit on the exteme side until you try the easier troubleshooting options.

@Abc_Def of solvents, I wouldn’t keep mek in my house… But it isn’t bad in the garage.

I store all chemicals in the garage

Heat it up to 250 or so and try to push it through. If it’s heated to 200, you can always disassemble it. Every part is replaceable and removable.

If you damage it, we are happy to get you what you need to get it up and running. That goes for all All Metal Ubis hotend owners :wink:


Btw- checked with customer service today. About 5 reports of jamming in 3 weeks- not bad!!

Known causes:

Retraction above 1mm… We recommend .3-.5mm

Running your bot at high temps and too fast. We recommend below 60mm/sec w .4mm tip for worry-free printing

Filament (usually pla) that has absorbed too much moisture- just bake it for a couple hours at 150F for a couple hours

Crappy quality filament. We stand by our filament, and there are many quality vendors. But ultra low cost filament is often really bad quality and could clog your tip. Try the cold pull method to clean your barrel and clear your tip.


@Brook_Drumm ​ much appreciated!!! I have been using them for the last couple months with the same retraction settings without issues (I run bowden and it’s still working well).

I have been using Toner plastics filament so shouldn’t be an issue there as I believe you guys use the same.

I’ll try to fix it myself with your suggestion and if it doesn’t work I’ll give you a shout.

Btw really impressive hotend. I have an earlier version that has the bare metal barrel/heatsink and have had 3 jams in the last 6 months that were not from cheap filament. Two were before I figured out retraction settings and the third is this one.

The accuracy is awesome and ad always the build quality is top notch.

Awesome as always Brook!

I messaged support again about when it will be back in stock (for no more than a few minutes no doubt)

We have 500 all metal hotends hitting the store on Monday! Itty bitty little subtle changes that should only improve manufacturability are all incorporated on the latest ones.

I spent time with Carl today doing extensive tests on one of the hotends in the shop that was jamming. Always good to experience the problem myself! We did several things:

Tested temps against a highly accurate thermocouple : everything was fine.

We cleaned the barrel with a cold pull: almost no carbon deposit. Check.

Measured the tip with exact pin gauges: .38mm, not .4 (fixed on new ones releasing Monday)…, but we adjusted our slice accordingly.

We measured the filament and concluded it was moisture swell. Switched out filament and no jamming! We will bake the swollen filament tomorrow and retry. We expect good results.

The good news is no mechanical or electronic issues, just filament.


Does that mean that the hotends that go into the store on Monday will have thermocouples.

MEK is something I use all the time, nearly daily. Ddon’t get it in your eyes (watch any splashing), avoid contact because it will burn though not too aggressively unless get more than a splash on you. IOW, don’t stick your hand in the container. Like any other solvent, don’t let the fumes build up and if you need to breath around it for more than a few minutes get a respirator. Depending on your exposure you’ll get a headache. Kleanstrip sells an MEK based product in quart sizes in many states. It’s in the paint section.

For more intense stripping there are commercial powercoat dissolvers like Rapid Strip or Ben 17 that are far faster and more aggressive than MEK. However, they’re expensive and much more hazardous to handle than MEK or acetone.

@Alan_Thomason MSDS are meant to comply with OHSA standards and typcially always take PPE to the maximum level even for small exposure. All things equal the big hazard for MEK is combustion. I use safety glasses and gloves and unless you spill several oz on you (or get a bit in your eye, it can really burn your eyes) you’ll be OK.

Take that baby apart! What’s going to happen? Your going to learn something new is all. Take plenty of pictures and read the forums beforehand.

set it to 5 degrees hotter then you usually print and wait for it to get good and hot, then jam a paperclip down the hot end from the top (where the filament goes in) and it should slowly push out (NOTE! the part thats stuck is above the hot end so it might take some force to push it down) and once you go thru it should really start coming out the end, use the paper clip up and down a few times then while its hot put it back together and put some filament in and push it thru by hand

@Brook_Drumm I disassembled it and tried to jam it down. Im gonna give it a try in the oven and if that doesnt work mek.

My question for you is this- I was able to take the hotend apart without heating it and really with litte strength. Is this normal??? I was trying to get it back together to match the other one I have but that one seems really tight.

We recommend heating it to avoid cold plastic from seizing the operation. The assembly procedure used torque wrenches and very exact instructions- like “finger tight, then 1/8th turn…” It’s possible things were not assembled properly or that repeated heating and cooling effected the tightness. But I don’t think your problem is indicative of improper tightening. I could be wrong, of course, and welcome any feedback. If we can, we will learn from your experience.