Power Feed to Milling Machine Table

I suppose you could say it's a steady medium you're aiming for, basically fast enough to keep a cut going, it should be working its way through the material, not dragging at snails pace, at the same time forcing the tool to work is quick way to not blunt it, but break it!

I find that for most turning cuts are done in a continuous motion and drilling or parting off can be interspersed with occasional retractions to ward off heat or apply oil.

Michael W

nothing too complicated to set up .

The complication is simply that of disconnection so that the manual feed wheel can be used. Most are satisfactory at slow feeds, but fast traversing is not always fast enough.

Most could easily be converted if the manual wheel was removed and replaced with a power drive. But shifting the table by a tiny amount might be problematic.... Clearly, tables with wheels at both ends are easier conversions and retention of manual adjustment is necessary.

Another approach is to use a stepper motor. This is not the cheapest route but is still a lot cheaper than a commercial one. This is the one I made, complete with clutch, for a Myford VMB mill and it works very well.

Doug

Thank you to all Forum members for the replies and various suggestions. Much room for thought here.

I tried the wiper motor last evening and blow me down it was seized ! So back to the drawing board.

Jonathan

In some ways a stepper may be easiest because more or less off the shelf parts could be used. To avoid using a huge one a gearbox could be added. They can be bought with them but the costs tend to escalate and it's probably well worth buying or making gears to form your own.

I assume just like other drivers the TB6560 boards just need pulses for the drive and have a direction input. There are chips about that can produce a variable frequency output at the turn of a knob. I doubt if it would be much of a problem with these to cause them to run faster for the return feed if that is needed.

What I don't know is how fast the steppers can be made to rotate at. All I know on that score is that higher voltage ones such as 6 and 12v can produce a lot more torque but for a given supply voltage can't match the speed of lowere voltage ones. 24v volt for the supply is sensible anyway. Higher voltage drivers tend to be much more expensive.

The cheapest drivers I could find that really are in the UK are these

**LINK**

Not so sure about the others as RM are likely to deliver them where ever they come from. The above actually shows the connection details in the listing as well.

John

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Toothed-belt drive, from an off-axis motor would probably be cheaper/easier/quieter.

MichaelG.

Did you notice feeds and speeds cropped up again Michael ? Cutting tools can't rub unless something is loose. Something usually is due to flex rigidity or what ever so there will be a min feed rate. + and depth of cut.

I thought gears so that it could be a nice compact unit. 1/2 or 1/4 stepping maybe to reduce noise but plastic gears are probably feasible.

Clutch - swing said motor in and out of mesh. I see that as an advantage as it's easy. Doing that with a belt wouldn't be so easy. I have a telescope drive that uses single stepping and brass gearing though and it isn't half noisy especially when it's quiet at night. Annoyingly it's the best one I have - old Vixen

This is on the back burner for me due to lack of info on max rotational speed. Not worth measuring the torque at my feed handle until I can get some info on that. At some point I will probably finish up buying to find out.

The wiper motor is for raising and lowering the head. Actually cost of a decent 24v wiper motor is likely to be similar to a 3" Nema 23. I had to look hard to get a new one at that sort of price.

John

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Edited By Ajohnw on 03/08/2016 12:35:47

The 12v wiper motor that I use is run on 18v, 12v automotive electric motors are usually quite ok at up to 24v. i think the speed at the worm wheel is about 120rpm, that gives 60rpm at the lead screw, and 3 mm per rev. It's a Lucas motor, probably at least 40 years old, with a wound field, not like some /most with permanent magnet field, so the power supply doesn't need too much smoothing. I don't think a rough supply is very good with permanent magnets.

Ian S C

Would using a DC shunt motor be a good idea, if not a little big?

Michael W

Hi all, The 24 volt truck wiper motor I used was new and cost around £ 100.00 . it only draws around 1/2 amp at 24 volt so a small power supply is all you need. I guess you could find a cheap one on ebay but I happen to have it lying around. They are used in tv studios a lot to lower and raise lights from the ceiling, I was in that game for years and had one on the shelve, the problem is its too slow, you need a motor that can go quite fast to quickly move the table from one end too the other as well as fine slow adjustment.

Interesting. I expect a wiper motor to draw over 10 amps really well loaded. May be wrong, have to see. In my case I want to raise and lower more than I can comfortable lift to any height. I know that because I had some trouble fitting the head and only just managed with the motor off.

When the supply arrives I can see what the stall current is.

I found a 24v NOS motor on ebay for about £20. Lucas. I may have to remove any built in gearing. They did make some that were just a bare motor but no luck finding one. Actually I am not at all sure what is in this one. Finding out what it does can wait for the supply to arrive.

John

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More Bollocks - not what I actually said

John

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Many wiper motors have brushes designed only to run in one direction as a recent correspondent to MEW pointed out.

Neil

I built my original version (before I got "the real thing"  ) that way and just as you say it was cheaper/easier/quieter. I cobbled together a 555 timer circuit, controlled by a pot, to generate pulses. Regular NEMA-23 stepper. I didn't have any form of clutch but I did incorporate a switch to disconnect one side of each winding during manual feed and it wasn't too bad. (A number of experts, elsewhere, told me that was a Bad Thing for any number of technical reasons but it worked just fine for me - I'll take my practice over their theory any time).

(Edited to remove phantom smiley)

Edited By Bandersnatch on 03/08/2016 17:25:45

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You being ish again Michael. I'm not biting otherwise I would post 2 shots showing what happens when I run the same cut on my Boxford. JS is more or less correct but lathes vary. Until my bearings warm up mine tends to take a very light cut, a better one if it is warmed up but then any vibration in the machine also shows up in the finish. Some rubbing too at times when they have warmed up.

I did mention flex and etc when I originally posted and min depth etc. Hence use of Bollocks with a big B.

John

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John ( Ajohnw)

I was sat here musing about your prolific posting on this site and ( as one does!) I wondered how much time you spend at it.

Now I'm on here fairly often - and have been since the site first started. You will see my current number of posts on the left <.

I calculate that, at your rate of posting, I would have made around 17,000 posts in that time. Good grief man when do you find time to eat!

Norman

Or do anything in the workshop