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Author Topic: Bridgeport Knee Mill Conversion?  (Read 159127 times)

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Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #610 on: February 03, 2017, 09:21:53 AM »
Hmmm,

Just been playing speeds & feeds for my single flute tool...

Manufacturer specs...
12k Rpm
2.5m DOC
1800mm/min feed - insane i think?

My previous settings...
12k rpm
2.5mm DOC
1000mm/min feed

F&S Calculator recomendations
12k rpm
1.8mm DOC
280mm/min feed - much lower ?

Maybe these lighter settings will be better?
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #611 on: February 04, 2017, 10:20:07 AM »
Ok, did some tests, first was to measure slack in the z axis at the adaptor in line with the high speed spindle - I have 0.02mm vertical (with reasonable force) and 0.15mm rotational around the quill - no doubt the source of my trouble.

Left cuts in the first picture below was at the feed recommended by my S&F calculator shown in the last post, 2 passes of 1.25mm ea, top cut is with me applying pressure to the motor while cutting to remove slack, the lower cut is with it running free as normal.

Both cuts look fine, no burr on the lip and pretty much perfect.

The right cuts in the first pic show results of a single 2.5mm DOC pass, same feed rate, again with hand pressure on the top pass and free on the lower.

Both cuts are acceptable this time but they show signs of vibration on the bottom surface - this is not an issue here as this tool is a roughing tool and will cut right through on these parts.

the second pic is just a closer view of the vibration on the second cuts.

Seems I just have to back off on the fast pedal a bit and let her do her thing, plus fit a bungee cord to remove the slop.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #612 on: December 27, 2017, 06:06:18 AM »
Hi all, I'm getting that itch that can only be scratched by building something so I thought it time to revisit my mill build and fix some issues :)

Issue 1 - poor Z axis travel - avenue being explored = power the knee and feed tool length offsets to that thus retains full Z axis travel on the quill. Does anyone here have any help here - most of the stuff i have found on the 'net has lost all the media links or just get page missing errors. It will be a servo drive, belt reduction, probably best to go direct to the top of the screw rather than via the crank??

Looking for any tips here - software, macros etc

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

Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #613 on: December 27, 2017, 08:14:33 AM »
Driving to the crank shaft seems the way in - simpler and as its only used for TL compensation which is all in the up direction, backlash should not be an issue, a member has forwarded some macros (thanks) and they seem to make sense.

I need to pull the covers off and check i have enough I/O on my CSMIO controller to take another axis and encoder plus limits etc

Seems do-able though.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #614 on: December 27, 2017, 09:09:27 AM »
Managed to dig my way through the snow to the shop, pulled the cover off and happy to see I have no less than three spare axis/encoder inputs and plenty of I/O.

So glad I bought that CSMIO now, I love flexibility :)

Need to order up a servo and drive, probably go China way again, same guy on Aliexpress, couple of pulleys and a belt, good to go i think.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives
Re: Bridgeport Knee Mill Conversion?
« Reply #615 on: December 27, 2017, 05:16:55 PM »
Issue 1 poor z axis travel.  Yep that is the one that makes a knee mill conversion really really suck.  Lots of time and money spent getting short drills, short holders, cranking the knee up and down. Used one for 4 years,  this time bought a bed mill.  For home my homebuilt mini mill has an 18” Z!

Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #616 on: December 28, 2017, 03:29:28 AM »
Yeah, its a real pain - i had to mix-n-match tool holders where possible which helped a lot but the big issue is the Haimer height probe - its the longest by far and really pushes the envelope if the job has short tools!

The Knee shift for tool length offset really sounds good and should help a lot for a very simple fix, cheap too.

I was toying with building from scratch, something like a Fadal VMC which has simple box frame maybe 1/2" wall steel box section, possibly epoxy granite filled, but my sums were not adding to anything that seemed worthwhile - too expensive for a risk project. Most of the money would have been in the steel frame, getting it machined true and some sort of heavy table. Once you get into £5000 plus its worth looking for old machines to rebuild rather than work up a new unknown one.

Would have been a nice project though :)

Have you got any pictures of your 18" Z mill??
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #617 on: December 30, 2017, 04:56:20 AM »
All parts on order :)

Still trying to get my head round how it all plays together but I gather tool length compensation is not really used as the knee sees the length difference and the code just thinks all tools are one length?
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives
Re: Bridgeport Knee Mill Conversion?
« Reply #618 on: December 30, 2017, 12:41:19 PM »
If you want to use the knee for tool length compensation the tool length would simply need to be passed to the knee axis to move it up or down by that amount BEFORE a tool is actually changed so you have room for it at your normal tool change Z height. Then the program sees all tools as the same length.

Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #619 on: December 30, 2017, 12:45:20 PM »
Slowly making sense, thanks ;)

So in the code all tool length compensation would be turned off and I would likely be editing the M6 Start ??
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives