1.75 to 2.85 – Changing Filament Type I3 Mega


In today’s article, we’ll be covering how to modify an FDM printer to take 2.85 mm filament instead of the standard 1.75 and see if it’s worthwhile. If you’re doing this yourself, please keep in mind that I do not take any responsibility for any damages that may occur as a result, so do this modification at your own risk.

To begin, I ordered a new Hot end since I was already looking to upgrade my machine. If you’re doing this modification, all you would need is a replacement Bowden tube, since it will fit into an existing nematic fitting. You’re going to want to pick up a Bowden tube which is 2.85 to 3 mm in width for the inside diameter. Since I was also ordering the components from abroad, I made sure to order 2 along with an extra Bowden tube of the right size. I personally already own a Bowden tube cutter, however you can use the standard filament cutter’s as long as you fix the opening after cutting the tube and make sure that your cut is straight.  

The first step in this project was to look into what component I would need to modify in order to keep the original functionality of the machine. In doing so, I discovered that there would be two main components which would need to be changed. In this, I would need to change the filament guide which is connected to the nematic fitting and modify the housing case for the electronic components of the filament run-out sensor. I will not be going over how to upgrade the hot end in today’s video, but keep an eye out for future videos if you want to see that at a latter date. Important to note, I did discover that this modification works best with a larger nozzle size, therefore you may wish to change your nozzle of 0.8 size since that’s the one I tested and achieved good results.  

When installing the new Bowden tubes, there were a couple of things that I learned throughout the years. First off, you’ll want to make sure that it sticks out as straights as possible otherwise, if you’ve cut the tip of your filament on an angle it will puncture the tube. I tied this tube to the wires which were already secured to the machine and this fixed the problem. When removing the Bowden tube, you will need to press down on the nematic fitting while pulling on the tube without bending it. This releases the mechanism which keeps the tube from being pulled out during normal operations. When using filament which is so thick, there’s a large amount of pressure that’s built up in the tube, which causes the tube to want to deform. You’re better off having a little extra room in order for it to bend around corner’s easily. Too long, however, and you’ll end up wasting more filament when you’re at the end of your printing spool. This filament will be quite difficult to deal with, and you should keep in mind that you will be wasting the amount that you have left in your Bowden tube unless you have a filament welder Connector. This is something that I’ve since ordered and will hopefully be testing in the future.  

When creating this modification, I was only able to replace the guide leading from the gears to the nematic fitting. The area where the filament enters into the gears was too small for FDM printing and therefore a resin print would be required, however most resins remain too brittle. Should I get enough requests to continue this in the future, and I’ll create a follow-up video showing this being addressed with a resin printed part?  I will need to do quite a bit of research to ensure that I use a resin which will remain flexible, so this will take quite a bit of time to achieve.  

The Bowden extruder while simple in design does have a spring mechanism that like to shoot out, so be very careful when removing this component. I would highly recommend using some form of tape to help hold it in place while you work, or remove it entirely to keep losing the spring. With this portion opened up, I was then able to take the two components which I wanted to modify out and replace these with my own. You’ll want to keep these parts in a safe place should you need to switch back in the future. I personally put these into a small transparent bag with all the original components, just in case I required them in the future.  

When remodelling the filament guide leading from the nematic fitting to the gears, I originally attempted to use a Bowden tube for this purpose, however it created enough problems that I ended up extending the part instead. Should any of you decide to use this file, you’re going to want to make sure that you sand down and clean up the printed replacement as much as possible to help reduce any friction that may occur. When re-installing the nematic fitting, it’s important to make sure that the Bowden tube it’s cut flat and that you take your filament cutter to slightly widen its entry point. This will help ensure that it doesn’t get pushed back into the machine and that the filament doesn’t get caught on its edges.  When cutting Bowden tubes, this is a simply trick that will help remove any pleats if you’re using your filament cutter’s. 

 With this portion complete, I was then able to begin working on the filament sensor modifications.  In order to do this, I had to remove the original sensor from is plastic housing to see which portions would need to be modified. In this case, I wanted to keep the pre-existing parts so that I would be able to transition back if needed. What this meant is that I need to recreate the housing to fit its original functionality while accounting from some size changes. With the portion for the circuit board completed, I then changed the filament section to accommodate the new filament size.  I also included the original hole so that it could still be attached to the frame of the machine with a longer screw. This is the final model that I ended up using in the end. 

It was finally time to level the bed, which in my case was pretty close and only required some minor tweaks to get it working. Then came the part of changing my print settings until I had something which was closer to what I had originally had. Now keep in mind that this is a large nozzle size, and therefore it isn’t really designed to get details, it’s best suited for larger prints that you don’t want taking a long time. So in my case, I use this machine to create tools and rigs for my internal manufacturing process. If you plan to sand and finish a piece anyway then this will also still work, but you may want to print a lower height and seal the parts of some form of epoxy based putty too so that it doesn’t take as long to finish.  So in the end, was this mod worth doing? Well, for most of you, it probably isn’t. Unless you happen to get a lot of filaments that’s in the wrong size, then you might want to look into doing this, however there are quite a few issues which could arise. First of, this filament is far more brittle since it has a much larger diameter, so trying to get it to print without interruptions can be a challenge. Secondly, you’ll want to see if you can even print at higher temperatures that will be needed. In my case, I had to increase it by over 15 Degrees Celsius to get completed prints. Anything less and the filament was too prone to clogging within the nozzle, and the extra pressure also caused the filament to break more often. Another important thing to note, is that you’ll have to work with your flow compensation to get it perfect, otherwise you’ll have issues with how it comes out of the nozzle. Removing clogs was often tedious at best since the method I found was to remove the Bowden tube entirely and then do a “cold pull” to remove any residue. I believe that this mod is best suited for filaments which are less brittle but flexible, since these will be less likely to break or bend within the Bowden tube. So if any of you attempt this at home, I’d be interested in hearing what you have to say amount this mod in the future.


Yasmeen completed both the 2D and 3D animation course at Algonquin College and worked in the animation industry as a freelancer for a number of years before being hired to manage the 3D printing services at ItsYeBoi. While using the Alias of "Jenny" during her services, she was responsible for the testing, maintenance and upgrading of the machine while also filming and developing 3D printable assets for various projects.