Wednesday, November 28, 2007

Update on upgraded motor installation

After fixing the motor to Sherline, I notice that the max rapid with bipolar series configuration was around 30ipm only! After a quick rewire to half coil excitation, I was able to get over 50ipm with ease. The result just goes to show that spinning air is very different from actual load... frictions, vibrations, leadscrew efficiency, so on and on... Currently still running at 2A/phase @44V... Will re-set the driver for 3A/phase when I have the opportunity...

Photos below show my current setup and the motor tuning parameters...

Tuesday, November 27, 2007

Upgraded stepper for the Sherline

Took delivery of new set of motors yesterday. It is model KL23H276-30-8B (8-wires, 3A/phase, 280, ordered direct from China. Several US online sites also sell identical motors.

I'm yet to fix it to the Sherline. Tried hooking up to the driver (PICStep+Mach3) and result as follows:

  • With 2A/phase @44V, bipolar series, 1/4 step: reached more than 2000rpm (80ipm) before stalling.
  • With 2A/phase @44V, half coil, 1/4 step: reached more than 1250rpm (50ipm) before stalling.
With the above results, I'll be fixing it to the Sherline as bipolar series for high torque at low speed yet yield acceptable (>50ipm) rapids. I'm just too lazy to change the current setting resistor of the PICStep to try half coil with 3A. Probably give better, or equal, rapid speed compared to the bipolar series.

Photo below show the two motors side by side for comparison.

Tuesday, November 20, 2007

Build CNC in a flash...

Found the following video from which may be of interest to some of you...

Thursday, November 15, 2007

Spindle Index Addition to Sherline/Mach3

I've been wanting to add a spindle speed sensor to my Sherline/Mach3 setup for a long time. After several failed attempt of using reflective IR optical sensor, I managed to locate and procure a hall effect sensor (from RS Electronics) to settle the matter once and for all. I had two different sensors, proportional output sensor and latch sensor. Looking for easiest way to setup the sensor, I went with the latch sensor approach.

For such setup, I only needed the sensor (Allegro UGN3177UA), a pull-up resistor (10k) and two small magnets. Three wires goes from the sensor to my driver board and PC (+5V, GND, Sensor Output). Since the sensor output is toggle using magnet polarity, the magnets are mounted to the spindle as shown below, one polarity facing up per magnet, giving a consistent 50:50 duty cycle on the output. The pocket for the magnet were milled in the acrylic using the Sherline, of course. Works on the first power up. Mounted to the Sherline using scrap acrylic, double sided tape and cable ties. Now... the DigiSpeed controller looking very tempting... hmmmm....

Thursday, November 1, 2007

Video of my Sherline in action

Uploaded the video below to show the speed of my current Sherline setup. Though cutting air (the artwork was cut earlier... forgot to capture the video) the rapid speed can be seen. Current rapid is 25ipm with Sherline-supplied motor. Driver is bipolar, 1/4-step, 2A per phase, 35V supply (PICStep).