Ultimaker Hot-end Rev. 2 released

The release of a revised hot-end by Ultimaking Ltd is significant for two reasons, first it shows that they have acknowledged the poor design of the original, and second it means we’ll hopefully be printing without blockages very soon!

According to the Ultimaker blog, these things are what make the new hot-end special:

• Retrofit: All existing users can benefit.
• Fool proof when assembling: There is only one way to assemble it, no (more) small differences.
• Leak free: No more need to use teflon tape or ABS to make the extruder leak free.
• Free of plugs.

We ordered one straight away and received it a few days later. Here are the parts on the desk ready for assembly. It’s funny to think how such a small and simple assembly can make such a large difference in print quality. 

Don’t be fooled by the simplicity of the parts however! Retrofitting the new hot end was a long operation. It involved disassembling the entire x and y axis and hot-end sections. Below you can see the beginning of the disassembly. The wires also had to be re-routed and belts re-tightened.

Below is the new hot-end being assembled. Note the fan in the picture with a few missing blades, casualties of accidentally sticking a finger in whilst it was on. I ordered some replacement fans off eBay for $4 (!) and replaced it without a hitch. Also notice the melted section of the white fan shroud from where it came into contact with the aluminium heat block during a routine hot-end disassembly. I haven’t been bothered to order a new fan shroud as it seems to be working fine. 

Re-assembly was a bit of a drag, but went smoothly. You can imagine my excitement to get printing after so many frustrations with the previous hot-end! 

I was not disappointed. Here is the Ultimaker back up and running on its first print with the rev.2 hot-end.

And here is the result. 

The good news is that since the upgrade, we haven’t had a single blockage. The not so good news is that it still leaks a bit (despite Ultimaking’s advertising) and hasn’t solved all of our problems yet. Despite this – I can safely say the rev. 2 hot-end solves the biggest and most frustrating problem with the Ultimaker design to date. 

The problem(s) with the Ultimaker

As it stands we have a few problems to solve with the Ultimaker:

1. We need to prevent blockages at the hot-end.
2. We need to push the filament at the extruder section with enough even force to prevent skipping and grinding. 
3. We need to find a way to adjust the Z-stage quickly and accurately. 

These three problems all lead to an unsuccessful print. Below you can see a part that would have otherwise printed successfully if the filament hadn’t skipped in the extruder gear. As a result of the skipping you can see that a few layers didn’t receive enough filament, and so immediately broke when handled. 

In the part below you can see the difficulty of setting a level Z-stage. Some of the filament has printed normally, but some has encountered a lack of clearance between the nozzle and the bed, causing an uneven, lumpy surface. Ideally, you want the first layer of the print to look uniform. It allows the part to build more accurately and means it will stick more firmly as well (important for taller parts). In the below example, the lumped PLA hardened and caused unpleasant grinding sounds as the extruder passed perpendicular to it. 

Currently, if you want to adjust the z-stage to account for this, it’s a process of loosening the screws holding the stopper switch and manually moving it up and down. As the machine auto-homes, it meets the switch and resets at 0. The problem with this is for ideal printing conditions, you want the nozzle to be exactly 0.2mm from the bed, and adjusting the switch by hand means its basically impossible to do accurately. In looking for a solution I found this fantastic object on thingiverse which allows you to fine adjust the z-stage with a screw. 

In the picture below you can see the printed red part with the vertical screw, ready to meet the black switch above. Adjusting it is very easy. Why the Ultimaker didn’t come with a fine adjuster like this, I do not know – I think printing successfully without it is almost impossible. 

This solved the z-stage zeroing issue but still leaves room to improve on the actual levelling of the bed. This is less of a pressing issue however, and I might leave it until we deal with some of the bigger problems, like the hot-end and extruder.