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Author Topic: Bridgeport Knee Mill Conversion?  (Read 158948 times)

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Re: Bridgeport Knee Mill Conversion?
« Reply #590 on: October 30, 2016, 06:57:15 PM »
Hi Dave,
I, years ago, put cnc on my ancient Henry Milnes knee type mill. When it came to the z direction I reckoned that the weight of the table,cross slide and knee (probably 250 lbs or more), would take care of any backlash in in the set-up so that I connected a fairly hefty stepper motor with a 3/1 stepdown that has worked perfectly for the last 6 years. It would be a very strong tool and motor that would lift any backlash into the system using the stepper onto the original windup on the mill and has proved to be troublefree, saving the expence and work of installing a new screw. Gravity wins!

another Dave.

Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #591 on: November 15, 2016, 12:17:47 PM »
Steps-per or measured?

Considering I have ballscrews with a pitch of 0.2" or 5.08mm with a connection ratio of 2:1 and encoders with 10,000 pulses (all edges), should there be a reason to stray from a purely mathematical steps-per setting of 3937.00788 ??

I have no way of mapping the screw so measuring at one point seems like it could cause some variation at other points no?

Is it best to stick with calculated steps or try and measure using the axis calibrator??
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives
Re: Bridgeport Knee Mill Conversion?
« Reply #592 on: November 15, 2016, 03:19:27 PM »
Hi Dave,
I have used the recommended method with the Mach 3 whereby you go to settings page, do a run, and check out what is with what should be and set up to suit. I have found in use that that is way easier to do and likely more accurate (at anyrate with my maths!). I have used this for several years without accuracy problems. Worth trying before you get knee deep in numbers.

cheers, Dave.

Offline dude1

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Re: Bridgeport Knee Mill Conversion?
« Reply #593 on: November 15, 2016, 03:55:25 PM »
just use the auto feature but do big runs 4in or so it makes it a bit easyer and faster

Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #594 on: December 09, 2016, 08:54:09 AM »
Was there ever a fix or reason for the random "script compiler error in m3.m1s" issue?

Had it again today, first time in a fair while now, no idea why. Half way through a job, code starts with spindle not running because of the error but Mach happily runs the code regardless, bang goes the cutter :(

Restart Mach and all is good again as usual.

Why does Mach know there was an error - it puts the error message on screen - but happily runs on without the motor running?

No global error trap??
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Hood

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Re: Bridgeport Knee Mill Conversion?
« Reply #595 on: December 09, 2016, 01:28:57 PM »
Seems some people get that problem and others, like me, never do but now I have said that ::)

Anyway maybe adding this to your macropump would help, it should stop the machine if the spindle is 10% out from commanded speed.
http://www.machsupport.com/forum/index.php/topic,16290.msg110182.html#msg110182

Hood

Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #596 on: December 09, 2016, 01:54:12 PM »
Nice one, thanks Hood, that looks like a nice little fix.

Hope the plasma is running well ;)
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Hood

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Re: Bridgeport Knee Mill Conversion?
« Reply #597 on: December 10, 2016, 03:25:50 PM »
Hopefully it works for you Dave.

Plasma is cutting well although today I discovered the X axis is not right. Cut panels from 5mm Alu to make a water cooler tank for the tig and the X axis is short. On the 300mm x 300mm panels were only 295 or so on X.
Checked my steps per unit and they are correct  for 100mm per rev on rack and 10:1 on the gearbox so it looks like the gearbox is not exactly 10:1 like I thought. It can't be the rack/pinion as it is the same as on Y and it is spot on. Easy enough fix, just need to adjust the steps per unit.

Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #598 on: December 10, 2016, 03:56:37 PM »
You mean after giving all the advice, you didn't do a steps calibration yourself ;) ;)

As you said, easy fix though.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Hood

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Re: Bridgeport Knee Mill Conversion?
« Reply #599 on: December 10, 2016, 04:02:05 PM »
My advice is almost always to calculate rather than use the calibration utility :) Seems like this time it is not working out by calculating, either I just presumed the gearbox was a 10:1 or it says it is and it is not that accurate.