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Author Topic: Bridgeport Knee Mill Conversion?  (Read 158994 times)

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Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #170 on: May 25, 2016, 04:26:21 AM »
Wiring check...

Power supplies, one for the CSMIO and one for the inputs/outputs to maintain isolation?

The outputs on the drive are sink outputs so i would connect the +ve pin on the CSMIO input channel to 24v and the -ve to the drive?

Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #171 on: May 25, 2016, 06:28:23 AM »
Also...

The cable from the drive to the CSMIO - probably about 2' long at most, shows twisted pair for the encoder lines - is shielded multi-core ok here?

I have a pile of Centronics printer leads in the box, these have nice moulded DB25 plugs on the end - saves soldering those horrible plugs up.

Fully wired so all 25 cores are connected, any good??
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline dude1

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Re: Bridgeport Knee Mill Conversion?
« Reply #172 on: May 25, 2016, 06:41:00 AM »
shielded is good just have the shield connected at one end only going to your common 

Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #173 on: May 25, 2016, 10:21:37 AM »
Limitations of the system?

When i was building the large scale traction engines, everything was made with a tolerance of only 0.1mm or better - easily obtainable on a hand controlled Bridgeport with a three digit DRO. It really was not needed to go tighter on these engines and many say that if too tight they never worked properly due to expansion when running etc.

Anyway, the third digit on the DRO was pointless as you could never set that precision by hand and merely looking at the mill out of the corner of your eye made it wobble more than that!

So, now (when done) I will have ball-screws and servo's with Mach3 acting as my DRO display - this is all running on my bench very nicely now.

But - the encoder/motor is connected to the screw via a toothed belt - surely this must introduce an error possibility, especially with a 100kg sitting on the bed??

My main point here is - If i want to use the mill manually, say to drill some holes without cam-ing the job, I can put Mach into reset, this drops out the servo motors and i can spin the handles like before and Mach tracks the position on screen - I am hoping here that this is a workable situation with decent accuracy when positioned manually??
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline dude1

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Re: Bridgeport Knee Mill Conversion?
« Reply #174 on: May 25, 2016, 03:50:18 PM »
I have heard of people saying they are going to do this but never do

Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #175 on: May 25, 2016, 03:57:05 PM »
Thinking on it more - the hand wheels are on the screw ends so when using it manually, all the torque goes straight to moving the load - the belt only transmits position back to the encoder/motor.

I am confident it will work out fine, just over-analysing as usual :)

I've just about pulled everything off the mill now, DRO will be sold to raise funds ;)
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #176 on: May 26, 2016, 09:26:34 AM »
Ok, where did I slip up...

Previously had the motor tuning set as book, 2000 steps per (10,000 / 5mm pitch)

When I fit this on the machine it will be at 2:1 ratio so i set steps per to 4000 (10,000 * 2 / 5mm pitch) and set velocity to 7500 (3000rpm / 2 * 5mm pitch) acceleration is at 750mm/s/s

Works ok in jog mode, works ok in code mode at speeds up to 7500mm/min

If i do a "Goto zero" it runs for a while then stops with ePid fault.

It also allows me to set feed higher than it can handle and then goes into ePid fault.

Is there a reason here?
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #177 on: May 26, 2016, 10:53:26 AM »
Ok, found it - it seems it does not like running right at the limit of max speed - if kept just below max it all works perfect.

If I set the max at 7500 and command a feed at 7500 it faults, if I set 7400 it works perfectly in all modes.

Wont get that high in real life as the mill bed is not really big enough.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Hood

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Re: Bridgeport Knee Mill Conversion?
« Reply #178 on: May 26, 2016, 02:01:02 PM »
Just catching up, so you say that you do not have any means to tune the servo other than what it automatically chooses when entering the model number?

Regarding the manual usage, MDI I find is much easier and cleaner than winding handles. When I did the manual conversion I went out of my way to keep the handles, hacked them off with a grinder a week or so later as they had never been used and really were just a hazard.
If determined though then I am not sure why you think there would be an issue even if the handles were on the motors, timing belts should not have any stretch in them at all as they are reinforced with fibreglass or kevlar strands or some even steel.

Encoder wiring should be fine with shielded multi-core but best is definitely twisted pairs.

Sounds like it may be a tuning issue if you get  the PID error at max RPM.

Hood

Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #179 on: May 26, 2016, 02:10:50 PM »
Hi Hood,

I'm not too sure re the tuning - i mailed the seller who asked the supplier and the reply was that it was set by entering the motor code. There may be parameters but thats way beyond me.

yeah i think it will be fine, probably just didn't have enough coffee that day ;)

The wiring will only be a foot or so long and seems to work ok on the bench at 5' long so will give it a go - looks neater with moulded plugs too.

The error may also be because of running flat out with no load on the motor maybe?
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives