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Author Topic: Warco VMc /Chester 626 knee mill CNC conversion  (Read 45997 times)

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Offline Perfo

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Warco VMc /Chester 626 knee mill CNC conversion
« on: July 13, 2008, 12:19:42 AM »
http://www.chesteruk.net/store/626_turret_mill.htm Sorry I'm not sure how to post the picture yet.

I'm hoping to CNC this mill and have already started to get a few bits and pieces together which is probably the wrong way to go about it as I won’t profess to know much about the whole conversion business.

Parts list so far is:-
CNC4PC  Bi directional buffered break out boards X 2
CNC4PC  Charge pump board
Motion control products (MCP)  MSD542 micro stepping driver X 3
MCP  34 frame (86BYG450B-011) steppers 3 Nm X  2 for X and Y Axis
MCP  23 frame (FL57STH)  Stepper motor  X 1 for Z axis
Power supply supplied by MCP for the above steppers and drivers.

I started building the box of bits as I had in mind to build a Router but when this Mill came up as a damaged unit in an auction I couldn’t resist and thus my project has now changed with the idea that once I get a CNC’d Miller it will make it a lot easier to make the router table.  In the same auction I also got a Chester Craftsman lathe which I may CNC later depending on my success with the mill.
That’s as far as I’ve got.

What I need to do now is:-

1, Build a base with casters on to actually get the lathe and miller in to my work shop    as I can’t lift the things once inside.

2, Ask some learned fellows a few questions to get me started.

One problem I’ve got is I can’t get Mach 3 to run on my Vista machine ( the driver test fails) but I’ll go through all the set up install steps again as I’ve probably missed something (I’ve installed the memory override dll)

With reference to number two above:-
What sort of drive ratio should I have on the X and Y axis ? I was thinking of using the steppers in 400 pulse per rev mode and each rev (using the standard ACME screws) gives me 3 mm travel.
As the longitudinal travel is 365 mm and I guess it would be nice to be able to travel this distance in high speed non cutting mode (Jog mode ?) in about 30 seconds this would mean 120 ish revs per traverse and 48 K pulses or 1.6 Khz (please tell me If I’m talking utter rubbish here) . If my calcs are anywhere near correct then I could afford to have a 10:1 reduction ratio on the stepper as it should be about to run at 16 Khz no problem (shouldn’t it ?).  Cross travel is half the distance but the same gearing would be ok. The thing that worries me is looking at some pics I’ve found on the net, some folks seem to have coupled the steppers direct or at least through a 1:1 ration pulley system. Surely this would give you an unusable traverse max speed and need you to get bigger motors….hmmmmm…
Last question. I’ve seen a Mill doing thread cutting under control of Mach 3 on you tube and it looks very impressive but how does the Z axis the cutter and the rotating work piece stay in sync ?? I can see how the Cutter and Z axis does but the spindle is free to rotate, Isn’t it ?
Anyway thanks in anticipation for any help or suggestions anyone has.

Offline Hood

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Re: Warco VMc /Chester 626 knee mill CNC conversion
« Reply #1 on: July 13, 2008, 07:24:35 AM »
Would recommend you go higher than half stepping, probably best 10x. You should manage to go 1:1 with these motors if the mill had ballscrews, not sure with the acme's thouggh. Wouldnt go as high as 10:1 as I dont think your motors will turn fast enough but you never know.
 The thread cutting thing depends on what you have seen, if its thread milling then the spindle speed is not important, reason is the cutter is spinning round but the X, Y and Z moving in sync with one another is what controls the dia and pitch. Rigid tapping is a whole different ball game, for that youneed prcise spindle control, you can also use a floating holder and do semi rigid tapping but you will still need spindle control (Speed,Fwd and Reverse)

Hood
Re: Warco VMc /Chester 626 knee mill CNC conversion
« Reply #2 on: July 13, 2008, 05:16:07 PM »
I converted a Warco VMC which is the same machine as the 626
I used the Motioncontrol MSD542 with the 86BYG stepper on all axis
Which includes the Knee. The reason for this was that the play on the rack and pinion on the quill is rather large (I tried),  where as the weight of the knee pushes all the play to one side.

The ratio used is 3:1 as this works well with the lead screw 3mm pitch
The Z runs on a 6:1 due to the weight
It all runs happily at 600mm/minute which I regard as about the limit for soft cast-iron ways.
The screws are frequently adjusted and lots of lube is required on them

I “customized” three large transformers to give 50V DC at the drives

The machine runs at least 2 days a week production work 8 hours long, and not a beat is missed.

I have been able to fit all the motors in such a way that the machine is not bigger…
I turned around the X axis screw and then fitted the X motor “under” the table
This is done so I can fix a scale on the other side of the knee.
The Y axis also lives “under” the knee, and finally the Z axis. I removed the hand crank
and fitted the toothed wheel on the Z screw the stepper sits on a plate inside the Knee
which is fixed in place of the crank bearing plate. In this way the envelope is not larger due to the stepper motors, which you often see in conversions
when you remove the screws to install wheels, check the bearings and how they are fitted
the Chinese have a thing against finishing…..

I would like to have ball screws, and in time when the machine has earned some of its keep I will fit them. For now I am a happy with the machine and the conversion

Offline Perfo

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Re: Warco VMc /Chester 626 knee mill CNC conversion
« Reply #3 on: July 13, 2008, 09:16:55 PM »
Thanks for your answers. It’s good to see someone has already done it on the same machine and with the same steppers and drives.
Wantcnc did you try to direct couple these steppers?  When you say 10:1 or 3:1 I’m assuming you mean 3 turns of the stepper for one turn of the lead screw. How did you mount the steppers ? Was it with toothed belts ?
Sorry I may be being a little slow but I couldn’t quite follow.

I turned around the X axis screw and then fitted the X motor “under” the table
This is done so I can fix a scale on the other side of the knee.

The X axis screw has a bigger over hang on the right hand side due to it being possible to put a powered cross feed on it. Did you mean reverse this so the extra was on the left ?
Any chance you would have a couple of pics I could see to help me visualise the set up?
You must be happy with the outcome and the machines performance so that’s given me a bit more confidence in surging forward. Motion control products have a few steppers in their clearance section so I may need to get on of these for the Z axis as my Z axis stepper is much smaller than the others. I had thought of putting the Z on the hand wheel purely due to the weight of the knee but I take your point about the play and thus will probably follow your example. I assume you are in the UK somewhere? Anywhere near Bangor N Wales ?

Thanks again Gents. I’m a member of other forums (not CNC related) and have spent a lot of time trying to help others and it’s real nice now I’m a newbie to find a forum where experienced people are willing to help

Offline Perfo

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Re: Warco VMc /Chester 626 knee mill CNC conversion
« Reply #4 on: July 14, 2008, 12:42:13 AM »
I tried to find the thread milling video without much luck. Here's one very similar
http://youtube.com/watch?v=Dlz0EUq6k9M
I can see this fellow has a shaft encoder. Even with the encoder I'm still amazed it gets the start for the thread spot on with every cut. I'm used to lathes where there is a physical connection between the feed and the chuck so it has to line up. I still think this sort of thread cutting would be better on a lathe but if you've got a CNC'd miller then I suppose you are going to use it for everything you can think of.

Offline Hood

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Re: Warco VMc /Chester 626 knee mill CNC conversion
« Reply #5 on: July 14, 2008, 02:34:33 AM »
That guy is basically doing Lathe threading but using his mill, what you need for the is a single pulse per rotation from the spindle so that Mach can calc when to start Z movement and also what the spindle speed is.
 Thread milling is different and probably better suited to a mill, heres a vid of thread milling.
Hood

http://www.youtube.com/watch?v=JA_osyWIEFY
« Last Edit: July 14, 2008, 02:44:40 AM by Hood »

Offline Perfo

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Re: Warco VMc /Chester 626 knee mill CNC conversion
« Reply #6 on: July 14, 2008, 09:35:01 PM »
Oh yes I see the difference. Nice bit of thread milling there.
Re: Warco VMc /Chester 626 knee mill CNC conversion
« Reply #7 on: July 15, 2008, 03:08:05 AM »
work is getting in the way at the moment, will try to post a few pics later this week

motor 3 turns shaft 1 turn....
never tried it 1:1 I would be supriced if it would work, on ball screws it may work...but then that is  ££££
X axis rotate was done since I started to fit the motor on the right side, and then realized I needed that for the scale later on
since the shaft is bigger on the right side, I had no choice but to rotate the screw.
I took of the hand wheels....no point if you have a jog wheel and it only adds to the inertia
I still need to cut of the excess shaft.


I'm in NW London :(

Offline Perfo

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Re: Warco VMc /Chester 626 knee mill CNC conversion
« Reply #8 on: July 15, 2008, 09:04:53 PM »
A pic paints a thousand words as they say. I'd be interested in where you got your gearing from IE did you use toothed belts and wheels ? I'm thinking there's no point reinventing the wheel here and if you are happy with your system and have proven it to work well then that's just where I want to end up :)  Work interferes with all the best past times doesn't it ? I've had one day of in the last 30 days and that is really slowing the progress on my mill conversion. I get down to Hertfordshire every now and then as I come from Stevenage and have family there so not too far from N London.

Offline Perfo

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Re: Warco VMc /Chester 626 knee mill CNC conversion
« Reply #9 on: July 20, 2008, 07:36:08 AM »
has anyone got any suggestions as to a good gearing system to get the 3:1 mentioned above ? I'm thinking of timing belts and pulleys, Where would I get suitable ones in the UK ?
Thanks