Author Topic: Mill power feed  (Read 3338 times)

Offline John Stevenson

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Mill power feed
« on: July 14, 2012, 06:46:07 AM »
Just a generic question.

How do the Align etc. power feeds work in relation to engaging and disengaging when making manual moves ?

They must have some way to disengage the worm drive as they can't be wound backwards manually.

Reason I ask is getting fed up of winding this POS Bridgy knee up and down all the while and toying with either buying the align unit which over here always comes as a 110 volt unit and you use a transformer, or using a 3 phase geared motor and inverter.

If I use the geared motor it will be in mesh all the while but I very rarely use the knee for cutting. I had thought about fitting a handwheel on the fan end of the motor for turning it for accurate placement. I know it will be low geared but with the inverter the handle possibly won't be needed.

I would sooner use a geared motor as I have loads of them or can get then easily for little or no cost from one of the rewinders. Got inverters on stock. The Align unit would need to be bought, a knee one which is bigger ? costs about 350 over here and they I have to piss about with a transformer and from many posts I have seen they often pack in or burn out and my machine often has to carry max weight bed loads hence the pain of winding the knee up.

I have more or less made my mind up but would appreciate any insight from anyone who has done this or researched it.


John S.
John Stevenson

Offline BillTodd

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Re: Mill power feed
« Reply #1 on: July 14, 2012, 08:57:11 AM »
I've replied on another forum but...

The Servo type have a 'clutch' that disengages the bevel drive pinion (they don't use a worm drive, just a large reduction gear)

It had occurred to me that it might be possible to use a variation on a typical VCR fast wind mechanism:  These have a idler gear engaged with the motor pinion mounted on an arm that pivots on the motor shaft axis.  The idler has a spring loaded fiction plate that ensures the arm will move the idler gear to the left or right (depending on motor direction) to engage with one of the two cassette hub gears.  With the motor not under power the idler is easily pushed out of engagement buy the motion of the hub gears.

If a similar arrangement were made using two idlers engaging with one output gear (driving the knee jack-shaft or handle) if would operate as a fairly simple automatic clutch.



Offline Lew_Merrick_PE

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Re: Mill power feed
« Reply #2 on: July 14, 2012, 01:40:07 PM »

So the real question is: Do you want functional, or do you need neat?

A rather kludgey means of adding a power knee-feed to a turret knee mill I have run across is to add a timing-drive pulley (large) to the knee handle-shaft and mount a motor and timing-drive pulley (small) to a pivot mechanisms some distance away (and out of the way).  The motor is mounted on a pivot such that it can be (manually) swung to engage/disengage the timing belt.  Two idler pulleys are used -- one to force the belt away from the motor to give you working "slack," and another radially sprung to engage and "lift" the belt to prevent it from hanging onto the drive pulley when disengaged.

This was a fairly common modification done to turret knee-mills back in the 60's and early-70's before power feed units became commonly commercially available here in the NW portion of the U.S.  I never saw one that was "pretty," but they really were a back-saver when working with large delta-Z moves common in aerospace parts.

The manual crank handle is re-positioned to the "outside" of the (large) timing belt pulley.

Offline John Hill

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Re: Mill power feed
« Reply #3 on: July 14, 2012, 11:04:34 PM »
For what it is worth John:-

Worm and peg wheel by aardvark_akubra, on Flickr

This is the power feed I made for the X axis of my mill.  The motor drives the worm which in turn drives the peg wheel.  The peg wheel is loose on the shaft.  The dog clutch locks the peg wheel to a collar that slides on the shaft and drives the shaft via a sliding keyway.  I have a handwheel what attaches to the collar when the cover is on, I pull/push this wheel to engage the drive and I can turn it when disengaged to manually move the table.
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