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Messages - chrisjh

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General Mach Discussion / Re: PWM Spindle Control using Mach3 - How I did it
« on: September 04, 2014, 07:51:02 PM »
Hi All,

My sins have caught up with me :'(

I have corrected the schematic and published a Parts List (BOM) and attached them below.

To make it easier for others to assemble this PWM to Voltage Converter, I have also attached the photographs showing the Veroboard PCB layout (top and bottom side).


Chris Humphris

General Mach Discussion / Re: PWM Spindle Control using Mach3 - How I did it
« on: September 03, 2014, 01:13:14 AM »
Hi All,

Thanks for correcting my error.  The design intent was to tie all unused inputs to ground (the reason for this is to prevent high impedance inputs from "floating high", thus causing indeterminate output states).  I got a bit carried away when I was drafting the schematic.

The CNC lathe has been operational for quite a few years now, and the spindle control has never missed a beat.


Chris Humphris

*****VIDEOS***** / Re: Video´s from my machines
« on: July 04, 2014, 06:20:33 PM »
Hi Runar,

Excellent use of Mach3 on your conversions.

I like your hybrid amplifier work.  Very impressive.


Chris Humphris

*****VIDEOS***** / Cutting Steel Dovetails with Mach3
« on: July 03, 2014, 01:03:16 AM »
Some Generic QCTP Steel Toolholder Dovetails being cut with Mach3.





I’ve decided to publish my steam engine plans free of charge to anyone who want to download them from my website.

I considered selling them on EBay, but quickly realized that once the plans were sent to a single buyer, “the cat would be out of the bag”, so to speak. 

Unscrupulous buyers would be in a position to pass on the files, cutting me out.

So to minimize the possibility of others making money from my efforts, I will give away the plans. 

Of course, there will be those who try, but they will be up against copies, freely available.

I do like beer however, and would be willing to accept donations of beer, the international currency!!

All pages are A4 size.

So here they are:

Stationary Steam Engine Assembly Drawings (22 Drawings):


Stationary Steam Engine Parts List (3 Pages):


Stationary Steam Engine Parts Drawings (70 Drawings):


Stationary Steam Engine Notes (4 Pages):



Chris Humphris

*****VIDEOS***** / Re: Mach3 Turn CSS Mythbuster
« on: November 13, 2013, 10:00:29 PM »
I’ve been thinking some more and decided to look very closely at some of my parted off material. 

A true G95 motion should have a spiral with a pitch equal to the distance per revolution.  (In this case 0.05mm)

The attached photo shows that the pitch decreases as the parting blade moves from the outside diameter of 38mm towards approx.  Ø12.5, then reverts to a smooth 0.05mm per rev to the centre, when the VFD reaches maximum RPM.

Chris Humphris

*****VIDEOS***** / Re: Mach3 Turn CSS Mythbuster
« on: November 13, 2013, 06:29:54 AM »
Hi All,

I haven't gone to sleep, rather been thinking long and hard, and performing some tests.

My tests (based on blind faith in Mach3's ability to report Feed per Revolution accurately in the F DRO in Mach3 Lathe) reveal that Constant Surface Speed is accurate but, as reported by Hood, Feed per Revolution appears to vary whenever the X Axis is in motion in CSS mode. I have concluded that, in my case, it doesn't really matter, but have proposed a couple of possible solutions to improve constant chip load.

My report is attached.


Chris Humphris

*****VIDEOS***** / Re: Mach3 Turn CSS Mythbuster
« on: November 10, 2013, 04:24:10 AM »
I had assumed that because it appeared to work for me, that CSS capability was an undocumented feature of Mach3. You have aroused my curiosity, so I performed some measurements.
This is what I did.
   Setup some stock in the chuck and calibrated the X Axis.
   Using the MDI, I issued the command G96 M3 S50
   From the MDI, I requested G01 X50, X45, X40, X35, X30 , X25, X20, X15 in succession
   At each of the diameters listed above, I recorded using an independent tachometer, the actual Spindle RPM, and the reported RPM from Mach3 DRO (S True)

Listed below are the results:

Ø (mm)   Calculated RPM   Measured RPM   Mach3 DRO RPM Reading   Tangential Surface Speed (Metres/min)
50   318.31   348   349   50
45   353.68   380   380   
40   397.89   420   420   
35   454.73   471   471   
30   530.52   540   540   
25   636.62   636   636   
20   795.77   785   785   
15   1061.03   1034   1034   

Calculated RPM is from the formula:
 RPM = Surface Speed (in Metres per Minute x1000) / π*Diameter

I repeated the measurements at a couple of random diameters and the results were totally repeatable.  I also noted that the speed transition was very smooth, regardless of whether the diameter was increasing or decreasing.

I think the measurements prove that my combination of Mach3 and USB Smoothstepper is capable of at least approximating CSS.  I am happy it works for me.

One thing that annoys and frustrates me is that at the first use of Mach3 Turn, CSS does not work as intended, and the spindle speed drops to below the Mach3 low speed limit.  The workaround for this is to stop the program, rewind and start again. The lathe then behaves normally for the rest of the working day, even if I change part programs.  I think this is a result of my initial conditioning code, and I haven’t solved this problem yet.  I have simply learned to live with, and expect, this behaviour.

Chris Humphris

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