Milling machine Z axis feed

I'm pondering the addition of a Z axis power feed to my Elliott UO mill. Clearly there are numerousm machine specific detail design
features needed but does anyone have a suggestion of a suitable motor/gearbox that will drive slowly and steadily. Is this best solved by a bespoke stepper setup? I'd rather not use a PC to drive anything though (because I don't have one in the workshop and I'd rather not get one.)
All suggestions from all sources welcomed.
Thanks
Charles
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On Tue, 10 Jul 2007 16:35:23 +0100, Charles Ping

Charles -
It would certainly be possible to build a simple stand-alone stepper-based drive unit - basically all you need is a 555 timer, a small number of discrete components, a reversing switch, a speed potentiometer, a stepper driver, power supply, some sticky backed plastic, some Fairy Liquid bottles...
Seriously, not hard to do.
You could buy a Divisionmaster (Lester Caine will sell you one in kit form) to drive it, and you can arrange it to make simple (and accurate) linear moves, but that is probably overkill price-wise. I have used it to drive my ML7 leadscrew to give electronic "saddle stops" and finefeed to good effect.
Regards, Tony
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wrote:

<snip>
And here's one I made earlier!
Michael
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workshop
Charles,
I'm not familiar with the Elliot UO, but I've had very good work out of the Chinese import Z feeds I've fitted to my manual Bridgeport and my Bridgeport Interact. Both are made by Align and are similar to these:
http://www.atrump.com/product_detail.php?lang=2&pro_id 8
The Interact one took a bit of fiddling as the model wasn't intended for it, but it's a godsend now fitted.
AWEM
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On Tue, 10 Jul 2007 17:34:43 +0100, "Andrew Mawson"

Charles
Is this a quill feed or knee feed? If it's the quill, maybe you could butcher a cordless drill to do the job?
BTW I've got a number of 12V & (mostly) 24V wheelchair-type motors looking for new homes, maybe something like that could be used?
Cheers Tim
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On Tue, 10 Jul 2007 16:35:23 +0100, Charles Ping

    I fitted the standard Chinese add-on drive to the X Axis of my own Elliott about five years ago. It has an infinitely variable speed controller with a press-button over ride to select 'fast' when repositioning the table. Straightforward to fit and no problems since.. I bought it from Warco,(www.warco.co.uk) who also sell a similar unit for the Z axis. There are illustrations of both units in the Warco on-line catalogue. Shout if you need more. --
Chris Edwards (in deepest Dorset) "....there *must* be an easier way!"
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On Tue, 10 Jul 2007 16:35:23 +0100, Charles Ping

Just twigged that the U0 is a horizontal mill, so presume it is the knee you want to feed.
Suppose you had, for instance, a 24V permanent magnet motor supplied from a simple transformer/rectifier/smoothing cap setup, would a 'dimmer switch' type of thyristor control on the mains side be of any use as a speed control? I imagine it would produce some fairly horrible waveforms, so the transformer might need to be well overrated, but would it work otherwise?
Tim
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Second try, first one is not showing up.
Here is about as simple as it gets for a variable speed feed.
View with fixed pitch font.
+ Power + Ref. voltage | | ____________ | ______ \ | |_| | |_______/ __| |______| | \ |__| MOTOR |______| TACH | / | |_ | |_ | |____________| | |______| | | | | | | | | |-| | | MOSFET ||__________| | |-| | | | |___________________| | - Power
The power and ref. voltages depend on the motor and tach. Voltages and can be the same.
The pot should be around 5K to 30K, a resistor between the pot and the ref. voltage can be used if needed.
The MOSFET can be just about anything but I would stay with something with a voltage rating 4 or 5 times the power voltage. Current rating should also be well over rated as it will be operating in the analog range. It should be on a heat sink of some kind and you can parallel them for more current and or less concentrated heat.
Start with the pot set to the lowest voltage and if the motor runs away swap the connections to the tach. Now as you turn up the pot the motor should start turning and within reason it will hold a constant at whatever speed you set.
Add a 4 pole double throw switch or relay to swap both motor and tach connections to reverse the motor direction.
___________ Andre' B.
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Thanks for the suggestions.
I have a Divisionmaster but didn't really plan to tie it up with this sort of work. The geared down motor approach would be OK. I have a spare inverter so a low power size 56 frame motor running at 700rpm would be ok. Finding the motor might take some doing and it will be bulkier than a stepper.
The 24v DC and electronic solutions will need work. I think that I'll go to bed and read the new version of Jim Cox's book for inspiration.
Thanks
Charles
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On Tue, 10 Jul 2007 22:47:44 +0100, Charles Ping

Charles Got some geared motors here what will do the job. Some 440 3~ for invertor and a 110v DC. Not bulky units.
I'll dig them out and send pic's. Won't be until Thursday as I'm installing an X3 in Wakefield tomorrow -- Regards,
John Stevenson Nottingham, England.
Visit the new Model Engineering adverts page at:- http://www.homeworkshop.org.uk /
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uk.rec.models.engineering wrote:

There's a guy flogging new 24V B+D external-battery operated drills around the amateur radio rallies for five to ten quid a throw. Shunt wound .25hp motor, epicyclic box, very well made as compared with the usual DIY junk. They were in the RS catalogue a while back at about 300 quid. I've got one driving a worm box to open and close a half ton sliding door and a few more just waiting until I get the time for CNC.
Regards,
David P .
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You could look for a truck windscreen wiper motor, they are suitably geared down and are rated 24 volts. They go nice and slow on 12 volts powered by an ancient battery charger.
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Charles Ping wrote:

Parvalux - they make a range of small fractional horsepower motors, induction or series wound brush armatures, with integral worm gearbox on the output, which should produce have enough torque. The series wound types in particular are easy to control with a simple thyristor type speed control, say from a variable speed mains drill or modified light dimmer.
Cheap quick solution while you think about how to do it with steppers, and there are a pagefull on fleabay right now, including 3 phase...
Chris
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