Mini Project: Monoprice 3D Printer Modification for Flexible Filament

About a year ago I decided to purchase a 3D printer. I didn’t need anything too fancy, and I didn’t want anything too big. I settled on a Monoprice MP Select Mini 3D Printer V2 which is a small desktop printer for about $200.

I’ve been very impressed with it’s reliability – it has only needed to be tuned once since I set it up, and since then it very rarely fails a print using PLA. But for an upcoming project I want to print in a flexible material, so I ordered some TPU filament from Sainsmart.

Having done some research it was clear that by default these printers do not do well with flexible filament – typically the filament buckles somewhere between the extruder and the nozzle. There are many solutions online however I didn’t find anyone with the same extruder design as was on my printer. Generally the solution is to fill up any gaps between the extruder and the nozzle so there is no space for the filament to buckle.

The filament liked to buckle just here where there was a small gap between the wheels and the plastic

In Fusion360 I mocked up the existing design and by tracing out the position of the two wheels in the system I was able to see where there was space to add extra material to fill in the gaps where the filament typically buckled.

Sketch of dimensions in Fusion360

Side-by-side before and after:

Where the extruder transitions to the white tube is a nozzle that fits into the extruder. There was too much space left inside this cavity which caused buckling, so I made the fit around the nozzle tighter too:

I also added a lip around the driving wheel to fill its concave profile:

Improved extruder design bottom half
Improved extruder design top half

And it works! Here is my first flexible component:

The 3d files can be viewed and downloaded: Bottom half, top half.

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