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Author Topic: Using_MM_Ballscrews_with_Inches  (Read 2616 times)

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Offline Garyv

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Using_MM_Ballscrews_with_Inches
« on: April 06, 2008, 09:54:14 PM »
I_have_been_looking_on_ebay_for_router_parts_but_have_not_read_anyone_ask_if_you_can_use_a_Metric_ballscrew_
on_a_system_running_inches_and_how_can_you_calculate_steps_with_Metric_threads_and_still_run_Inches_in_Mach3
Thanks
GaryV
Re: Using_MM_Ballscrews_with_Inches
« Reply #1 on: April 07, 2008, 12:44:07 AM »
No problem, GaryV.  When you calculate the steps per inch, you just include the 25.4 factor for converting from mm.

I have two linear slides with 1mm pitch ballscrews.  My motors are 200 step per revolution and I'm 1/8-stepping them.

So the steps per inch is ( 25.4 x 200 x 8 ) / 1 = 40640

If the screws were 5mm pitch, the steps per inch would be ( 25.4 x 200 x 8 ) / 5 = 8128

Hope that helps. :)

Randy

Offline Chaoticone

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Re: Using_MM_Ballscrews_with_Inches
« Reply #2 on: April 07, 2008, 12:54:59 AM »
Here is how you do the math. I will give you mine as an example. What we need to know is, How many pulses from Mach will it take to move the machine 1 of your units? (inch,mm) Mine is in inches. 1 inch = 10,000 pulses on mine. This is how I came up with the number.
My steppers have 200 pulses per revolution. ( 360 degrees divided by 1.8 degrees = 200 )
Micro stepping = 10. So 200 X 10=2,000
Motor to screw gearing is 1-1. So 2,000 X 1=2,000
Screw lead is .200 of an inch. My screw will have to turn 5 rounds to move the nut 1". 1.0 divided by 0.200=5. So 2,000 X 5=10,000.

Brett
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Offline Garyv

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Re: Using_MM_Ballscrews_with_Inches
« Reply #3 on: April 07, 2008, 06:03:29 AM »
Thanks_for_the_info_guys_the_25.4_and_odd_number_of_pulses_is_what_concerned_me...
Thanks
Gary

Offline jimpinder

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Re: Using_MM_Ballscrews_with_Inches
« Reply #4 on: April 07, 2008, 09:50:34 AM »
It doesn't honestly matter if you set up in mm - as long as you do it all in mm - i.e. tool offsets etc as well as your motors.

I am changing my leadscrew and crossslide to ball screws - and they are metric, so I will probably set up in mm's

if you are running your code in inches, Mach3 just converts it anyway, and vica versa. I don't know which country you are in but in the UK there is more metric stuff about here, and really metric is the one to set up in.

So - if you buy your parts in metric - maybe your tools are metric diameters as well - set up your machine in metric.

When you use G20 in the code, Mach 3 changes all the DRO's etc to inches, and also brings out all offsets from tool tables etc in inches. It is then, to all intents and purposes an imperial machine.
« Last Edit: April 07, 2008, 09:55:17 AM by jimpinder »
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