Ultimaker Original 1.75mm filament conversion

Contributed by

Neotko's little workshop
Neotko's little workshop
Converting an Ultimaker to 1.75mm filament is pretty high on quite a few users’ wish-list, but if you want to continue using the print head designed by Ultimaker, the modification is rather tricky. So before you start taking things apart, we recommend you sit down for a minute and read about the pros and cons of converting your Ultimaker Original to 1.75mm filament in the first place. Below I’ll summarize what the advantages and disadvantages are of completing this mod. But please note, this is just one way to convert your Ultimaker Original to 1.75mm filament and you will be relying on third-party products. Due to our open nature, there are many alternatives. Let us know if you have found another way.

We're confident that you'll be able to successfully convert your printer to 1.75mm by following this tutorial, but as this conversion relies on parts that have to be sourced from third parties Ultimaker can't be held responsible for the results should you choose to modify your printer.

Advantages to using this mod:

  • You can lower the retract distance to 3.2mm (instead of the 4.5mm for 3mm). This means you can retract less material, i.e. you can do more retracts without grinding.
  • Less drip and stringing. This is good not only because you can print at lower temperatures, but the nozzle receives less material than 2.85mm. Less material versus gravity equals less drip.
  • It’s easier to print at 20 microns.
  • In some regions in the world 1.75mm is more commonly available than 2.85mm filaments.

20 micron prints
20 micron prints

Disadvantages to using this mod:

  • Your feeder must move more to print the same, this means there is a higher chance of some vibrations reflecting in your print surface and more noise.
  • It’s harder to print flexible materials compared to 2.85mm flexible filaments.
  • You have to rely on third-party products, which sometimes require additional processing. Depending on execution this can affect the reliability and print quality of your Ultimaker.
  • Generally speaking you can print faster using 2.85mm filament.

Flexible material
Image credit: ideato3D

Neotko: This is a collection of my personal experiences modding 3 Ultimaker Original+’s, both good and bad. I’d like to share this with you so everyone can learn from each other. First of all, when I bought my Ultimaker Original+ preassembled from iMakr a year ago, I spent at least three months reading all the posts on the forum, digging up information, asking around and getting overly prepared. I soon realized I shouldn’t have bought a preassembled Ultimaker Original but a DIY-kit instead. The amount of experience and insight you gain from building one is invaluable. I would have learned exactly where everything was supposed to go, what it’s supposed to do and how things are constructed. The time building is a small investment for the knowledge I’ve gained.

A year ago, not many people were talking about using 1.75mm filament on Ultimaker and the only source I found at the time was the mod that Scottmayson published on the forums.

ScottMayson uses a hot barrel from e3d, a new feeder (without spring tension) and a lot of m4/m5 nuts. Even though it was a source of inspiration for me, it turned out to be overly complicated, not reliable and quite problematic. I contacted him later and he told me that he did update his mod but he never published it. So I started to think about tackling this myself.

It was clear to me that I had to change the key components to allow me to use 1.75mm filaments. I’ll save you the full list of mods I experimented with, and trim it down to a summary of what did and didn’t work. After all, failure is our greatest teacher, is it not? And we shouldn’t be afraid to make mistakes.

One of my first attempts was just feeding 1.75mm filament in the stock set up. Would that work? Maybe. But probably only for a short time. The first problem you’ll get is that the filament can snap inside the Bowden tube. It twists and turns because the pressure of the Bowden system and also because it has too much ‘space’ for it to roam and move around.

The second problem you’ll find is with the original Ultimaker Original feeder. In the feeder is a lever that applies pressure on the filament and teethed sleeve, however, if you reduce the filament diameter from 2.85mm to 1.75mm the force it can apply significantly reduces. You are also more likely to get more grinding issues due to the smaller contact area between the filament and teethed sleeve.

Broken 1.75mm filament
Broken 1.75mm filament
1.75mm grinding
Image credit: S3D

The third problem you will probably encounter, and maybe the biggest one, is the extra 1mm of open space that’s not being used inside the print head. It leaves room for the heat to travel up from the hot end, causing clogs inside the Bowden tube and blocking the retractions made. When the retractions do go well they contribute in helping the heat crawl up. So let’s solve each problem through modifications.

As a heads up, if you want to fully tackle this mod you may need to modify some parts yourself. However, I would only recommend you attempt this if you’re an expert user who understands the purpose of each part. If you have questions during the modification, feel free to engage with our community of experts!

Step 1. A new Bowden tube

Solution A

Use the standard Bowden tube with 6mm outer diameter / 3.14mm inner diameter and insert a 2-3mm PTFE tube. Glue these together with a special two-component glue suited for PTFE materials. The result is a smaller Bowden tube which eliminates your first and partially fourth problem.

A world of Bowdens
A world of Bowdens

Solution B

We recommend solution A over solution B because the quality of a completely different Bowden tube is not proven to be reliable. Alternatively, you can buy a special PTFE with 6mm outer diameter and 2mm inner diameter. They are quite hard to find, but can be found in charlies3dt shop. If you decide to go for this option, get your calipers ready!

Step 2. A new hot-end


You need a really well-crafted nozzle for good 3D printing, and as Ultimaker doesn’t make them for 1.75mm filament, a reliable alternative would be a 3dsolex/E3D nozzle. They are a little bit smaller in height, so you will have to bend the caps of the fan shroud to prevent them from collapsing with the bed clips. Although if you’ve just executed the dual fan upgrade, you shouldn’t have to worry about the bed clips.

Brass tube

This is one of the key components developed by Ultimaker. Since it’s their design it can be difficult to find a similar part that fits perfectly. For example, if you try to use E3D barrels, they are 30mm long, and Ultimaker uses 20mm (M6) barrels. A 30mm long brass tube can create heat discrepancies, uncontrolled heat inside the peak, and cause possible clogs. A place where you have a chance of finding a clone that fits is on Aliexpress, (Aliexpress is like an eBay of manufacturers and resellers). There aren’t many alternatives to Aliexpress and the overall quality is a bit unreliable. Unfortunately, my first attempts proved me right as the inner diameter was inconsistent. It has to be 2mm and mine had an inner diameter of 1.85mm-1.9mm. My solution was to drill with a 2mm bit, but this is rather fiddly.

Bad barrel 1.85mm
Bad barrel
Good barrel 2mm
Good barrel

But there is another factor that you can’t fix, and that’s the upper part length. The upper part length should be around 11.15mm-11.25mm but the very cheap model is around 10.85-10.90. That’s a 0.20mm gap that will cause problems over and over again, but a really key problem is that it’ll create extra pressure and deform the filament going out. Basically you could print, but not with quality. So how do you know when you buy through Aliexpress that you’ll get a decent part? What I did was send a message to the seller. The bad sellers usually don’t even reply and when you do get a reply you can ask for a photo with an accurate measurement.

Bad barrel
Bad barrel
Good Barrel
Good Barrel

Barrel comparison
Barrel comparison

If you’ve found a reliable seller, feel free to share him with our users on our forum. Expert users, engage! Good luck.

PTFE coupler

Another part that needs to be sourced elsewhere is the PTFE coupler. 3DSolex is a reliable source for supplying these smaller PTFE/TFM couplers. It’s always good to check measurements when you use third party parts. As my grandparents used to say; ‘to measure is to know!’

Good vs Bad PTFE
Good vs Bad PTFE

The feeder

There are many ways to do this. Based on my experience I’d recommend using a different knurled wheel than the default one, because the default wheel is designed for 2.85mm filament and is more likely to grind with 1.75mm filament. I will talk about what I know and what I have tested: IRobertI feeder on UMO + MK7. This is what I used.

IRobert's Feeder on Ultimaker Original
IRobert's Feeder on Ultimaker Original
IRobertI's Feeder on Ultimaker Original

Works like a charm with a small adjustment to the E-steps. On one of my Ultimaker Original + printers I have an Ultimaker 2 feeder motor installed, and I use 195.2 E-steps (0.9º - 400 steps). My other Ultimaker Original+ uses the UMO+ feeder motor (1.8º - 200 steps) using 97.6 E-steps. The exact size of the MK7 is different for each seller so I’d recommend you do a quick calculation on what E-steps value is best for you.

If you want to calculate the steps per E yourself, follow this link and use the Leadscrew driven steps per millimeter calculator to help you out. To get you started here are some of the numbers you’ll need to fill in:

  • Motor Step angle: 1.8º (200º) for Ultimaker Original+
  • Motor Step angle: 0.9º (400º) for Ultimaker 2
  • Driver microstepping: 1/16 Estep
  • Leadscrew pitch: Outer diameter of your knurled wheel (X) * PI (*5,5% too).
  • Pitch presets: Leave it at default
  • Gear ratio: This only applies if you use a geared feeder. If so, count the teeth and put the data in.

Technical Feeder View
Feeder technical view

When using the IRobertI feeder on Ultimaker Original+ with 1.75mm filament, I’d recommend printing the SNAP On guide that comes with the model. The reason for printing this guide is that the filament could slip to one side of the bearing and stop your extrusion.

And that’s all folks!

After changing your filament diameter in Cura to 1.75mm, you’re good to go! Enjoy your 1.75mm Ultimaker, and make sure to share your results with us. If you haven’t installed dual fans, your Ultimaker Original+ with 1.75mm filament should look like this:

Ultimaker Original 1.75mm Fancap

1.75mm modification for your Ultimaker 2

Okay, we also have a little treat for our Ultimaker 2 users. You also have an option to modify your Ultimaker 2 for 1.75mm filament! There is an upgrade kit that can be bought that has the parts you need from Gr5. Hmm, sounds pretty easy!

Ultimaker 2 1.75mm kit
Gr5 upgrade kit