Thursday, April 3, 2014

Delta Bot Build: cooling fan & magnetic bearings

Finally- more progress on the "snowstock" delta bot 3D printer! 

I've uploaded the files of all parts shown in this blog post to the "Snowstock" page on Thingiverse.

.STL and solidworks 2013 .prt files are located at:

Cooling Shroud
One of the things I learned from using and modifying my MendelMax 1.5 is that a cooling fan really, really helps with part quality- particularly with bridging and small features. So, the snowstock will have a part cooling fan from the start. 

Fan shroud wth 40mm fan mounted and ready to go

Mounted and ready to go

The assembly looks great, but the Traxxas rod ends introduced much more slop than I'd like. Ideally there should be zero backlash / slop in the print head. As assembled, it had at least a quarter inch of total play at the nozzle- unacceptable for a quality print. So, I decided to implement magnetic bearings right away and not as a future upgrade.

Assembling and  installing the magnetic bearings 

I chose to design and print ABS endcaps to epoxy onto carbon fiber rod to hold the M5x15 SHCS's. Other examples of magnetic bearings I've seen online have glued the 10mm spherical magnets to the ends of the carbon rods. That might work, but it seems less secure and messier than just using two screws per joint, one on each side of the ball magnet. Each screw is then threaded into the respective component.

Endcap ready for screw installation and epoxying 

M5x15 SHCS installed- note head was dished out using a 10mm ball end mill for a higher strength joint with the 10mm rare earth magnets
The 10mm ball end mill was sourced from ebay- about $10 including shipping from China. The M5x15 SHCS were from McMaster Carr. One note- you'll want to use black oxide coated steel screws- not stainless steel. Stainless screws are not very magnetic, and you'll probably have problems getting your system to hold together if you try them. The cheap 10mm ball end mill was barely good for dishing the heads of the 24 screws, even with good lubrication.

Dishing out the M5x15mm SHCSs

All 6 rods, assembled and ready to go
Carriage mount installed

Joint detail shown- the silver ball is a 10mm spherical rare earth magnet from e-bay
There are plenty of sources for 10mm spherical magnets on ebay, just search for: "Nickel plated Neodymium Sphere Magnet 10mm N35 balls"

Magnetic arms assembled
I have yet to actually power up and run the printer- I still need to design, print and install the extrusion mechanism. But, even so, I think the magnetic bearing upgrade was worth while. The Traxxas rod ends had far too much slop, I'm sure it would have been very difficult to achieve a decent print quality. The magnetic bearings have zero slop, and also very securely hold the mechanism together. As long as there isn't any sort of long term wear issues I'm sure they will work great. 


  1. hi there! Are there any further developments on your SnowStock design?

    I'm thinking of printing one, and if you have improvements over what's currently published.. this would be the good time to know :)


    1. I'm not working on any changes to the parts currently on Thingiverse, but I am working on adding some parts to finish out the build. The next parts I'll be posting will be some braces to stiffen up the frame- as currently designed it flexes too much for my liking. I'm currently printing and iterating those- I hope to post the .stl and .prt files for the braces this week.

      Now that fall is coming I'll be motivated to finish up the design and get it running!

    2. M- just uploaded the brace files to thingiverse.