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Thought I would post my recent progress with the CNC mill for cutting gears and crossing out the gears with the new setup.  Since I have a long post with history I'll just provide the URL but towards the end you will see the gears recently cut and they turned out nice.  Certainly would not have been possibel without the help of the Mach team.


Best Regards.


General Mach Discussion / CNC Gear Cutting
« on: October 06, 2008, 07:16:15 PM »
I'm in the middle of converting one of my manual Carroll Dividing Heads to CNC when it occurred to me I may have a problem with resolution so I was hoping someone may be able to provide some insight.

My dividing head has a 20:1 reduction.  I was planning on mounting a Nema 23 stepper with 1.8 degree steps using a timing belt and pulleys with a 3:1 reduction for a final reduction of 60:1 at the spindal.  When I tried to calculate some of the common tooth cuts I would make I found that some would not fall nicely into the resolution of this setup.  While I could change the gearing which would help in some cases it would eliminate others from what I can tell.

For example, to cut a gear with 34 teeth using my existing 20:1 reduction dividing head I would use a dividing plate with 17 divisions and index 10 positions each time.  This would equate to 10.588235294117647058823529411765 degrees per tooth.

Trying to calculate the steps for the 60:1 reduction CNC dividing head I get 3529.4117647058823529411764705882 micro steps.  It's my understanding that I can not move the stepper the fractional part so I would basically have .4117647058823529411764705882 x 34 = 13.99 steps lost which would be 0.041999 degrees lost.  This would create 1 tooth that is either too fat or too thin if I'm not mistaken which isn't good for time keeping.

Am I totally missing something or do I need to take another approach?

Any feedback would be greatly appreciated.

Best Regards.


General Mach Discussion / Progressive Move Error with X and Y
« on: June 29, 2008, 01:38:43 PM »
I'm not sure how to word this and read through some of the posts but didn't see anything that applied.  I finally got to cutting some parts after many tests and realized I have a problem when moving both the x and y axis in G90 or G91 mode.  If I move each axis independently, it always returns to the exact same point.  However, if I move from x0y0 to x1.5y1.5, and back to x0y0 and then finally to x1.5y1.5 I will be off by about 0.042 thousands.  If I repeat this, it is progressive and goes to about 0.084 thousands roughly.

I just don't know where to start with this problem.  The independent x/y movements I believe indicate that my basic motor setup is correct.  So I'm not sure how the xy movement together can cause a progresive move error.  Is the computer itself suspect and possibly not sending the right information or could it be missed steps for some reason when doing both axis?  If it were missed steps, I would have thought it would show up when doing single axis movements too?!

If anyone has any ideas, it would be greatly appreciated.

Best Regards.


General Mach Discussion / Step Pulse Won't Save
« on: May 28, 2008, 08:21:09 PM »
I just finished converting an Enco tabletop mill to CNC and have gotten the x/y axis working fairly good but I have been unable to save the recommended Step Pulse setting.  I'm using Nema 34 steppers (4 wire type from Homeshopcnc) and Gecko 201s and it's my understanding that the Step Pulse should be set to 2.  When I enter this setting and save it appears to work but when I return to the setup screen the value is 1.  Any feedback would be greatly appreciated.

Best Regards.

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