Retromaster’s Electronics Projects

…related to old computers and other assorted stuff…

Archive for March, 2011

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.

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