Power feeds for Chinese mills

[Speedy Builder5Participant @speedybuilder5]

Why have you gone for a closed loop motor with feedback ? If you are not measuring distances and only using the stepper motor to power your leadscrew, its an additional non required expense. You could use an Open Loop stepper and controller.

[not done it yetParticipant @notdoneityet]

While I had the table off my Raglan (some time ago), I drilled and threaded the feed screw at the non-drive end.

I have very vaguely followed Phil Vandelay’s youtube video titled “Building a Power Feed for my Milling Machine (with a Wiper Motor)”.

I have used a 12V wiper motor (because I had one), but the controller will easily cope with a 24V item which would provide a higher power at lower feed rates. Easy enough to make (my next one would be an improvement🙂 ). Cost me less than £13 (for the speed controller), above the bits I already had in stock.

A simple add-on will be limit switches at the table extremities and/or adjustable ones for limiting the travel either side/end of a cut.

[Terry KirkupParticipant @terrykirkup37827]

Thank you Gents for the responses. Speedy, I watched a couple of Tube vidz that discouraged the use of Open Loop stuff, I didn't have a clue but was happy to be guided by their opinion on the advantages of Closed Loop over t'other type. I hope to still save a lot over a ready made hunk of steel like William's photo above and electrics from the likes of Axminster and others.

Not done it yet, I did consider that simpler approach but again there are so many folk pushing steppers as the ultimate solution I decided to go that way.

Martin, wow, that's a conclusive answer I think, thank you. May come back to you if I get tied in knots when the bits arrive, if you don't mind.

Edited By Terry Kirkup on 05/07/2021 19:30:53

Edited By Terry Kirkup on 05/07/2021 19:31:48

Edited By Terry Kirkup on 05/07/2021 19:32:10

[Ady1Participant @ady1]

You can use a portable drill with a hex socket as a good bodge for zipping the table up and down

[Terry KirkupParticipant @terrykirkup37827]

Haha, cheers Ady1. Or at a stretch I could use someone else's arm to crank it .

As it happens I'm going to be tight on sideways movement and even though I do have an unused Makita angle drill I think I'd like the setup to look a bit more business-like for when the time comes for Wifey to flog all my kit! (RIP Me).

[William AyerstParticipant @williamayerst55662]

Posted by William Chitham on 12/11/2020 15:31:31:

Plus one for cheap and cheerful, install was easy and seems to work well enough, not sure if these are available in the flat orientation though.

Edited By William Chitham on 12/11/2020 15:33:03

This looks the business, is it one of the fleabay specials? Is it self contained (i.e. just needs a 5/12/20/24v power supply?)? I'm not looking to get a power feed on anything yet, but knowing is half the battle!

[Martin ConnellyParticipant @martinconnelly55370]

The photo of the hanging variable speed unit shows the type that are usually 110V and require a suitable transformer in the UK. Some have a different output gears to bring the unit up to a horizontal position.

Martin C

[old martParticipant @oldmart]

The unit that William Chitham has looks like one of the ebay type which sell for under £140. I have been thinking about getting one, they use 230V which might be of concern. I would like to hear about how easy they function and whether the stops allow you to repeatedly cut up to a shoulder. There are two types, similar in price, but one is 135lbin and the other is 450lbin.

[Ron LadenParticipant @ronladen17547]

I have thought about adding a table drive to my small mill but havnt got around to it, if I do I will go down the route I took when I added a power cross feed to my Warco 918 lathe and that turned out to work very well.

I kept it simple and used a MFA 975D 12 volt motor with an inline 104/1 epicyclic gearbox which proved to have excellent torque for its size and I,m sure would be more than enough to drive a hobby mill table back and forth including milling and not just table movement.

I used an inexpensive PWM controller which comes with a Fwd/Neutral/Rev switch plus a variable speed pot and powered that with an inexpensive 12 volt supply of suitable amperage. Total cost including cable, switches etc was around £75.

Apart from the motor mount and the leadscrew connection I fashioned a simple dog clutch to disengage the drive from the hand wheel for manual operation.

I,m sure it doesnt have to be complex or expensive to add a drive to the table.

Ron

[David George 1Participant @davidgeorge1]

Hi I have a Chester 16VS mill and the Z axis is behind the column and being not a tall person I decided to move the handwheel to the side and at the same time use the space left by the handwheel to put on a variable speed drive. I replaced the leadscrew with a ballscrew at the same time and used a stepper motor. The handwheel has a bevel gear which I can now see and use easier and the drive gives me the slow feed for fine boring and faster traverse when needed.

David

[William ChithamParticipant @williamchitham75949]

Posted by old mart on 11/07/2021 14:01:36:

The unit that William Chitham has looks like one of the ebay type which sell for under £140. I have been thinking about getting one, they use 230V which might be of concern. I would like to hear about how easy they function and whether the stops allow you to repeatedly cut up to a shoulder. There are two types, similar in price, but one is 135lbin and the other is 450lbin.

That's right, 230v 135lbin, still working six months on. Powerful enough to feed smoothly even if I forget to unlock the table properly which I never do of course. Powered through a normal 13A plug and since I fearlessly use mains voltage power tools all the time I'm not concerned about that. I can't say how accurate or repeatable the limit stops are, I have never tried them for cutting to a shoulder but the mechanism is simple so should be reliable I would think. I will do some experiments.

William.

[duncan webster 1Participant @duncanwebster1]

Many moons ago I made a drive for the Naerok miller using a DC motor and a train of gears. This had two disadvantages:

1. When the cut started and more load went on the motor it all slowed down, by quite a lot, in fact if set for a very slow feed it would just stop.. I can wax lyrical about why, but not here
2. you had to disconnect the drive to do manual feed.

I overcame the first by incorporating a feedback loop. I suspect people using windscreen wiper motors just have a lot of oomph to spare so it doesn't slow down as much.

The setup on my Centec uses a stepper with tooth belt drive. It is so much easier. If you use one of the pulse generator things referred to above it is just buy some bits, make up a mounting bracket, join the bits together and go. No need for a clutch, just wind the motor round. No need to know anything technical about steppers or controllers. Mine is a bit cleverer as it incorporates acceleration ramps

[John BaronParticipant @johnbaron31275]

Posted by duncan webster on 12/07/2021 11:42:34:

Many moons ago I made a drive for the Naerok miller using a DC motor and a train of gears. This had two disadvantages:

1. When the cut started and more load went on the motor it all slowed down, by quite a lot, in fact if set for a very slow feed it would just stop.. I can wax lyrical about why, but not here
2. you had to disconnect the drive to do manual feed.

I overcame the first by incorporating a feedback loop. I suspect people using windscreen wiper motors just have a lot of oomph to spare so it doesn't slow down as much.

The setup on my Centec uses a stepper with tooth belt drive. It is so much easier. If you use one of the pulse generator things referred to above it is just buy some bits, make up a mounting bracket, join the bits together and go. No need for a clutch, just wind the motor round. No need to know anything technical about steppers or controllers. Mine is a bit cleverer as it incorporates acceleration ramps

Hi Duncan,

I made mine using a car window screen wiper motor. They just don't stop, at all ! They are amazingly powerful.

I actually twisted the centre out of the primary gear on mine by forgetting that I had locked the table. Fortunately I had a spare gear.

I drive mine from a 3 amp 30 volt variable voltage power supply. Usually at about 7 volts. But I have put the full 30 volts on the motor several times for rapid feed without any issue.

[Terry KirkupParticipant @terrykirkup37827]

Well, I've managed to complete the X-axis drive apart from tidying the cables. It works very well, hope it still does in 10 years' time! (if I'm still around…)

Edited By Terry Kirkup on 22/07/2021 21:23:10

[Terry KirkupParticipant @terrykirkup37827]

 

Edited By Terry Kirkup on 22/07/2021 21:18:57

[Terry KirkupParticipant @terrykirkup37827]

Well then, six months down the line before disaster struck! Rightly or wrongly, and opinion seems to differ on here, I am now in the habit of locking the head while shaving metal horizontally.

Just over a week ago I was skimming a piece of aluminium and I inadvertently leaned on the "Down" switch (little aluminium cylinders shown a bit higher up this topic on my control box). The 20mm end mill dug into the workpiece and also managed to mark the top of my lovely, shiny Arc precision vise with a lot of very loud thumping and banging until I gathered myself enough to kill the power. The stepper was powerful enough (9Nm) to overcome the head locks easily and continue to push the head down (28 tooth pulley on stepper, 40 tooth on handwheel). Apart from the mark on the vise there didn't seem to be any further damage done. However when I switched back on to raise the head there was a lot of chattering as the head began to take short, noisy jumps upwards. I was pretty sure I'd smashed a few teeth off the top bevel gears or damaged the leadscrew threads. I removed the drive belt from my stepper motor and tried winding up and down manually. No problem there, it seemed. Taking the top drive box to bits was a chew, as it was during construction with only blind, fingertip access (!) to the hex screws, but at least I could see there was no damage up there.

However, when I went back the next day and reassembled the drive, the stepper motor just flicked and then stopped, and wouldn't work again after that. I thought I'd try it using the controller and driver from the X-axis to see if I'd broken the motor but it then worked perfectly again. I narrowed the problem down to the PWM thingy that @Martin Connelly put me on to (very grateful for his wiring info!) and luckily I'd bought a spare with the rest of the kit so all good again. Except!

Next time I switched on and used the "Up" control, the head started to travel but didn't get very far as the handwheel then popped out of the column! This happened because the lateral pressure of the gear teeth tending to push away from the leadscrew against the handwheel shaft had disengaged the press-fit bearings from the bearing bracket (or Pillow Block as it's named in the equivalent Grizzly parts list). Anyway I solved that by drilling and tapping the bracket and installing two opposing grub screws to bear on the inner bearing's outer race. The outer bevel gear (bronze or brass?) is also an interference fit on its shaft so I drilled that and did the same to it. When I checked the menual I fully expected to see grub screws in there anyway, but no, there aren't any.

Has anyone else had this problem?

[Terry KirkupParticipant @terrykirkup37827]

Actually I think I should have fitted the grub screws to the outer bearing as I look at the photo again!

[Roger BestParticipant @rogerbest89007]

Ouch!

I too am of the ability to press the wrong button at the wrong time. I was especially good at driving an overhead crane in the wrong direction, you would have thought someone was deliberately mixing the buttons up.

Now in later life, I appreciate the principles of electrical control and know that I might need some sort of switching interlock so that only one axis moves at a time, which reduces the chance of an accidental motion, also the principles of ergonomics and putting a control in a suitable place.

All this is very good in hindsight, as I was saying to my brother-in-law when showing him my 1942 lathe, loosing a finger or two is a learning opportunity.

[not done it yetParticipant @notdoneityet]

… my 1942 lathe, loosing a finger or two is a learning opportunity. ….

Hobby lathes of the (later) 1940s mostly had interlocks to avoid long and cross travels at the same time? I would think that many, before then would, too.

Designed-in mechanical interlocks are often not so easy to ‘dis-arm’ by users, than electrical ones, is my thought on the matter.

[Terry KirkupParticipant @terrykirkup37827]

 Ouch! @Roger Best, that cheered me up, thanks!

Edited By Terry Kirkup on 04/03/2022 14:56:43

[Roger BestParticipant @rogerbest89007]

Posted by not done it yet on 04/03/2022 13:46:08:

… my 1942 lathe, loosing a finger or two is a learning opportunity. ….

Hobby lathes of the (later) 1940s mostly had interlocks to avoid long and cross travels at the same time? I would think that many, before then would, too.

Designed-in mechanical interlocks are often not so easy to ‘dis-arm’ by users, than electrical ones, is my thought on the matter.

Yes, I must clarify.

The South Bend does actually have only one lever for cross and long feed, so you cannot do both at once.

The conversation was in the context of the ability to drive into the rotating chuck and the general lack of guarding. There is no mechanical knock-off clutch, that I know of.

Ample opportunity for accidents you only do once.

Sorry for the delay – been sick and busy, bad combination.

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