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Author Topic: What Steps/ Units Settings for Z-axis (Quill) of CNC Retrofitted Radial Machine?  (Read 21071 times)

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Offline khalid

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See my following thread, I have converted the Radial Drill and now tweaking the controls..
http://www.cnczone.com/forums/showthread.php?threadid=105247
I have used Ball screw and i have backlash compensation enabled in Mach3 due to some backlash in those screws... Now I am getting 0.009mm accuracy and repeatability..

Currently I am getting problems in calibrating the Z-axes... When I using Mach3 to setup it in 'MM' metric mode..I am getting 12.344 steps/mm... This is very coarse I don't know why?

My Motor is = 200 steps
Gear Reduction 3: 1 attached to QUILL mechanism
I am using 1/2 step mode...
I don't know what is driving the quill but it is something Rack and pinion, i don't know the specification..

so the mathshould be simple...
200 x 2 x 3 x Y= 1200 x Y. (Where 'Y' is the Quill rack and pinion I don't have informations about)
but Mach3 only returning me 12.33 steps!!!!!

What should i do?

Offline RICH

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KHALID,
You could make a circular paper template of know size and tape/attach it to the shaft of the stepper. Then see how far along the circumferance it takes to move the Z a mm by jogging the stepper ( i am assuming that it's double shafted). You can get rather close on the number of steps. Then just check over a longer Z travel.  The bigger the template the more accurate.
That will give total ratio ( would include the rack and pinion ). Poor mans encoder.

IE: 6" circle  C= 6x 3.14= 18.84"        18.84/200=  0.094"  so that distance along circumferance equals one step

RICH 
Early this was my problem.
please set unit to inch and test . i sure not problem when you use inch.
**Even a clock that does not work is right twice a day**

Offline stirling

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We know that 1200 steps turns your pinion exactly once. So to get your 'Y' you could set your steps/per to 1200 initially and code g0 Z? where ? is some suitable integer and hence allways turns your stepper full turns. Obviously bigger ? gives you more accuracy in measurement. Measure travel and stir in a little maths to taste.

Ian

Offline khalid

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RICH:)
Thanks for informations... I will certainly drive the Pinion and see how much the quill goes down with one revolution.... I discussed with one of my friend about his drill and he said that with one revolution of drill-arm, the quill goes down about 4 inches... I will check with my drill, if this is the case then the steps may be very Coarse...

MANMARDAM...
Thank you for the information... I understand what you means to change the Units...If the unit set in 'INCH' then it may be by simple math (1200 steps/INCH).. Do you belive this will solve the problem?.. I really want to know what problem you were facing?... and How much this problem was resolved at your end?.... Please help me providing more information about your experience...
thanks

IAN:)
Thank you for the response...but if lets suppose the One turn of Pinion drive the Rack down to 5inches..then this will be coarse or fine?


TO ALL:)
I am still puzzling about Turning the UNIT from 'MM" to 'INCHES'.. How does this problem can be resolved by changing the UNIT?

Best Regards and waiting for yours response SIR.


PS:
to find the Pinion-Rack ratio or travel:
200 x 2 x 3 x Y= 12.344
Y=0.010286666666666666666666666666667  What does this means???
i think when set unit to mm ,Calculations are done wrong.
Maybe I'm wrong :)
**Even a clock that does not work is right twice a day**

Offline khalid

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Manmardam.. currently what Steps/Unit you have kept for Z-axis in Mach3?.. and do you have snaps to share... Again thanks for the quick reply :)
MANMARDAM...
 I understand what you means to change the Units...If the unit set in 'INCH' then it may be by simple math (1200 steps/INCH)

i mean : change "select native unite" to INCH
**Even a clock that does not work is right twice a day**

Offline khalid

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Yes I clearly understood your previous post for changing the Unit to INCH in MACH3 and try recalibration....I will try that too..but logically, it will have no effect on the setup... This is because whatever steps/unit i calculated in 'MM" mode, Mach3 will simply multiply them into 25.4 to get in 'INCH' mode...

Regards and thanks for your valuable time...
yes , this calculate is simple but ...
**Even a clock that does not work is right twice a day**