Retromaster’s Electronics Projects

…related to old computers and other assorted stuff…

Upgrading the MF70 CNC

Posted by retromaster on March 16, 2011

Here is a new post after a litte hiatus.

First of all, let me get the Cumulus news out of the way: Last week, I’ve mailed the very first Cumulus board-set to ibisum for testing. He has five Atmos machines and the necessary hardware for debugging if things do not go as expected, so he is the right guy for testing at this stage. If everything goes smoothly, then I may think about organising a small production run for people who have expressed interest in purchasing Cumulus boards.

And now back to the main topic of this post. For various reasons, I decided to upgrade my MF70 CNC implementation. The aim is to fix some mechanical problems found in my original design, as well as upgrade the motors and the electronics to achieve higher speeds and precision. I even plan to try a split-nut anti-backlash design at some point.

The image above shows the very first parts I’ve manufactured that are intended to replace the current endplates in the X axis. As is evident from the photo, I’ve opted for using plastics this time, instead of aluminium. Although aluminium looks far more impressive, the plastic material I use here (specifically polyamide/nylon) is much easier and quicker to machine (deeper cuts, no coolant required, etc.) with a nice enough finish and they seem to be strong enough for the application (the original parts that come with the MF70 were plastic, too). In any case, if I find that the manufactured parts do not perform to my expectations I can always try out Delrin instead :).

These parts are very similar to the current aluminium parts but there are some differences. The mounting holes have been made into slots for allowing better alignment of the leadscrew with the leadnut. The bearing housing contains an additional 14mm inner groove to allow me to test thrust ball bearings (much higher axial load capacity) instead of the standard ball bearings that I’ve been using so far (I can still use the ball bearings if for some reason I am not happy with the thrust bearings). The motors will be mounted using an additional plate bolted to the motors. That plate and the larger plate in the photo above will be bolted together with a couple of M10 steel screws using the holes on the sides.


4 Responses to “Upgrading the MF70 CNC”

  1. Hi retromaster! Just wanted to let you know that the boards arrived by me (ibisum) yesterday and I will now hunt down the needed cable and power supply to rig it all up and have a bit of a play with it this weekend .. I’m looking forward to being able to contribute to this project, you’ve done a lot of amazing work so far and I’m really impressed with the extent of your progress .. the board looks really pro and I’m very eager to get it plugged into my Atmos collection for serious hacking! More news soon ..

  2. retromaster said

    Great news, Jay. Hopefully, everything will go smoothly. At this stage it would be great if you could test the board with all of the Atmos’es you have so that we can make sure there are no problems with different kinds of hardware revisions/batches (or figure out how we can fix any problems).

  3. tadpole said

    Hi Retromaster,
    I would like to thank you for posting your expreiences with the MF70 conversion. Not all too many people take the time and effort to share their knowledge, and I simply wanted to let you know it is appreciated by many. I was also curious to know if you, or anyone you know sells the end caps you eventually ended up using. I bought a MF70, and after not too long I really was looking to upgrade it to CNC. Unlike most others, I don’t have access to anyone with the tools to help manufacture something of this nature (I’m living overseas in Austria). I thought about trying to mill it out by hand in the MF70, and realised I would be crazy to try. By no means feel obliged to answer if find yourself too busy, but I thought I’d hate myself later for not asking if in fact you knew of the *right person*. I’ve seen some online kits, but I sort of wanted to piece it together myself. Thanks again.

  4. retromaster said

    Hi tadpole,
    I am glad you appreciate the information found in my blog, thanks. I do not manufacture/sell the end caps I use, and neither do I know of anyone who does. But I might suggest you use the same route I did: Try and build something simpler by hand-drilling aluminum profiles. Once you get something that works more or less you can try manufacturing endplates the way did, since it’s much easier once you get a working CNC. I think you should be able to observe the progress of my machine by checking out older related posts in my blog.

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