Prusa i3 MK2(s) & MK3 Spool Holder - Frame Mount - Top Loader

Update 2022/04/19

I've created a version of the Mark 3 arms for 2020 VSlot aluminum extrusions. Check out the remix section!

Update 2019/10/18

I've imported this project from my Thingiverse account. To make things clearer, only the Mark 3 version is available here. Note that Mark 3 stands for the iteration of the spool holder. It is compatible with all metal Z-frame printers from Prusa Research, i.e., Mark 1, Mark 2 / 2S / 2.5 / 2.5S, and Mark 3(S).

If you are interested in the older iterations, please visit Thingiverse: https://www.thingiverse.com/thing:1832235

Interactive 3D Modell:

https://a360.co/2DbpG7G

This SpoolHolder's history goes far back into mid-2016 when I received my first Original Prusa i3 MK2 with its terrible spool arm. It was a pain to switch spools, primarily if their width differed. Adjusting the arm on the frame was tedious, and one arm even broke at some point.

Therefore, I looked on Thingiverse for alternatives and found the top-loader spool holders like mine ended up being too. However, all of these designs back in the day had some flaws that bothered me — for example, some needed tools; others required hardware like real screws. However, the most significant weakness was the design of the mounting mechanics for the frame assembly. There was always that tight fit and the force one needed to clamp the arms onto the frame.

So I designed Mark 1 of the arm, which you can still see on most of the pictures and downloads as a legacy zip archive on Thingiverse (link above).

I was surprised by the success of my design throughout the community. However, this supported my bad opinion of the stock spool holder arm.

The Original Prusa i3 MK3 is out for sale, with some significant geometrical changes. My Mark 3 version of the arm takes them into account and also fits nicely on an MK2 and MK2S (most probably even on an MK2.5, but mine is still not delivered).

I hope you like my continuous efforts to make this arm better. I read every comment coming from you and try to react quickly. Many thanks also to the incredible Thingiverse community for providing a lot of derivates of my designs for other machines and purposes.

I also have a side project where I release arms for other machines. I do not test these arm derivates because I don't own all of these printers. The process is that you send me your request for such an arm derivate and the measurements of the frame of your machine, and I try to provide you with the best experience.

You can find these arms here: https://www.thingiverse.com/thing:2356183

Please also look at my other designs, printer parts, and tools.

Support

If you like to support me and my work, please consider following me:

- MartinMajewski.net - Twitter - Instagram - YouTube If you like to buy me a coffee to stay productive and creative, you can do so by sending a tip via Prusaprinters.org or PayPal...

PayPal.Me

... or by using one of the following affiliate links below (without any additional costs!).

Products seen or related to this project

- Amazon.de: 8x 608 ABEC 9 bearings as used on my prints - Amazon.co.uk: 8x 608 ABEC 9 bearings, similar to the ones I used Generic Affiliate Links

- Amazon.de - Amazon.co.uk - eBay Germany - GearBest.com Thank you very much, and happy printing, Martin

Print instructions

- The printer I used: Prusa i3 MK2S - Rafts: No - Supports: No - Resolution: 0.2 mm - Infill: 10% for all small parts, 20% for the arm, and 100% for the bolts (optionally). Notes

You'll have to print the following parts in the following quantities.

1x Mark3_SpoolHolder_HexStyle_ArmRight.stl 1x Mark3_SpoolHolder_HexStyle_ArmLeft.stl 4x Mark3_SpoolHolder_Bolts.stl 4x Mark3_SpoolHolder_Spacer.stl 4x Mark3_AxisNut.stl 4x Mark3_SpoolHolder_HexStyle_Tire.stl

Note: users have reported that the bolts break easily during the assembly. To avoid this from happening , I highly suggest that you print them with 100% infill!

To make the spool holder work, you need four 608 bearings for one set, which you can get from a local skate shop or from Amazon (by using the provided links, you can support me and my work):

- Amazon.de: 8x 608 ABEC 9 bearings as used on my prints - Amazon.co.uk: 8x 608 ABEC 9 bearings, similar to the ones I used You often find eight bearings inside a set, enough for two spool holders. The spool holder is designed to use all parts on both sides of the holder and switch the axis bolts from back to front and vice versa. If you like to have the "smooth bedside" oriented to the outside, you have to mirror the right arm along the x-axis.

For the infill, I used a honeycomb pattern because it matches the hexagonal style of the holder, and my filament is quite translucent. Honeycomb gives good mechanical support in general.

I printed three perimeters for all small parts. Four parameters were used for the arm and six perimeters for the wheels to avoid infill there. Each part has four top and bottom layers on my prints - except for the arms, where I printed without any top and bottom layer to achieve the honeycomb look.

Even though I printed my final design in 200µm (0.2 mm) layer resolution, I also tested 100um (0.1 mm) for the wheels. That gave them a smooth finish, but it did not affect the mechanical properties. You can also use smaller layer heights for the bolts to make the threads more smooth.

Post-Printing

Bolts, Nuts, and Spacer

The bolts, nuts, and spacer should fit nicely with a small clearance. Nevertheless, it can be hard to get the nuts screwed onto the bolts the first time around. So give them a gentle press and try to find the sweet spot where the threads match up.

If you still want to use grease to get an easier fit, here is my recommendation:

Finish Line Fett Synthetik Casual Grease

- Amazon.de: http://amzn.to/2eawdDU - Amazon.co.uk: http://amzn.to/2ee64Bn This PTFE-based grease is also very useful for other mechanical components.