Category Archives: CNC - Page 16

A CNC Cut Geneva Drive

animated geneva mechanismA Geneva Drive is defined by Wikipedia as “a gear mechanism that translates a continuous rotation into an intermittent rotary motion.”  Although replaced by servo drives in many cases, these were once used in movie projectors and to power rotary tables in industrial assembly lines.  This is where I first saw this type of drive, and after redoing practically the entirety of these machines, the venerable Geneva mechanism was still at the heart of it, working like a champ after 20+ years.  Like most cam-type devices, they may not afford nearly the adjustability or the “easy” electrical programming of a servo of PLC controlled device, but they will run for literally decades on end with little maintenance.

So after that introduction, I recently machined one out of MDF on my router.  I plan on making one that works a bit better, and is possibly motor-driven, but check out the video below for my prototype:

This is a crude model a this point, but I’ve included the G-code and DXFs for the mechanism at the end of the article.  Everything was cut with a 5/16 inch bit that I’ve been using as a flycutter on my router, providing a relatively high pocketing speed.  Unfortunately, Read more »

Dramatically Improve Your Zen Toolworks Pocketing Speed with a Dremel 115 “Flycutter”

Today I tried doing a 1/8 inch depth pocket cut with my Zen Toolworks router.  I’ve never tried this particular operation before, but with the new F8 leadscrew upgrades (my latest post on this), I expected it to go pretty quickly.  Compared to the stock leadscrews, the F8 screws are incredibly fast as seen in my pocketing video below.

Although the lateral travel is incredibly fast, the 1/8 inch cutter, although good for many things, doesn’t seem to be the best choice for doing pocketing operations.  With the improved screws, once can easily attain a lateral travel of 100 IPM (inches per minute).  Unfortunately, when the router is cranked up to these speeds, the cutter just doesn’t have the proper rigidity to make good cuts and ends up skipping around and bending during travel.

After trying this operation several times, I eventually was able to cut the pocket at a speed of 30 IPM (inches per minute).  For all of these cuts, I was only taking .015″ per pass which was probably conservative, but using this 1/8 inch cutter, doing a 2 inch circle 1/8 inch pocket took 19:24.  Yes, Nearly 20 minutes.  A long time.

Dremel 115 High Speed Cutter from Amazon

Fortunately, I had a Dremel 115 bit with a 5/16 inch cutting head (I originally used this cutter to mill my router bed flat).  This, like many Dremel bits, fits Read more »

Install a Y-Axis F8 Lead Screw on the Zen Toolworks 7×12 CNC Router

I’ve gone over installing the X-axis and Z-axis F8 lead screws, so now lets check out how to install the Y-axis F8 screw.  One could tear a whole machine up to do this, but after a little thought, the method I used made this lead screw install the easiest of the three.  Check out the video below for most of the steps, explanation to follow.  If you just want to see how fast my ZTW 7×12 is with upgraded X, Y, and Z axes, just skip to 0:32 (original test video at the end for comparison).

To explain the video, in the beginning you’ll need to loosen the set screws on both the driving motor and the collar holding the other side on the bearing.  Remove the circular piece that holds the bearing opposite the Y-axis servo motor.  Once this is done, just roll the lead screw out.  If you have a hand drill available, tighten it down on the end of the screw and reverse everything out. this will speed things up considerably.  After this is out, Read more »