Power feed for HM-45 Mill....developments

**Sterob** · 16th April 2007, 11:56 PM

I tried to find the original thread, but alas, could not, so here goes.....
There have been some developments in the last few weeks.
I built MK1 and it worked ok, but the geartrain and motor were noisy (used 2.5 module, straight cut gears) and gearbox output was 420 RPM instead of the quoted 250 RPM and so I had little useful speed adjustment. It used a moving idler gear as the clutch.
MK2 was going to use a stepper motor ( with pulley reduction at first) and then direct drive, due to motor limitations. I got the electronics worked out but the steppers are rather expensive and also tend to be noisy. Also , was not going to use a clutch and thought the indent ( right word?) torque would be too high when driving table manually.This was put aside.....
MK3 used smaller module gears ( 1.5 I think) and a different clutch system( a idle gear that rotated around the table gear, like QC gearboxes on some lathes. I had problems with gear eccentricity due to poor machining methods.( lathe was remote to the job was ONE of the problems...

. Have since rectified this with a lathe purchase. Speed range was ok this time, but gear noise and eccentric gearing made it unworkable.
MK4 will be my last try and will involve using a different 24 V gearmotor (180 RPM) max directly coupled to the leadscrew via a dog clutch. Result: Quiet motor and no gear noise....hopefully.
I know what your thinking, 'why didn't you just buy one?' For fun and experience.....but that's wearing a bit thin now.

Also they are ludicrously expensive for what they are!
So, one last shot at this and I this fails, I'll be ordering one from the US and will speak no more of this......

**Sterob** · 28th April 2007, 08:30 PM

I thought I'd post a couple pics of the Mk3 version. This turned out to be unsatisfactory and has since been scrapped.

**Sterob** · 28th April 2007, 08:40 PM

Have progressed far enough on MK4 to do a test run with the new gearmotor. All seems ok and the motor has enough grunt to do the job. It is very quiet running as well as there is no external gearing like the other designs. The only noise will be the 'squeal' the PWM speed control causes the motor to generate, but it shouldn't be too bad.
As you can see from the pics, it uses a sliding dog clutch, which is prevented from spinning on the motor extension shaft by a key and key way. I'll use a spring to keep the drive engaged and use a fork to slide the dog bad to disengage it, when not in use.

**hux** · 28th April 2007, 08:51 PM

http://www.wcc.net/~jkmccoy/shop/pwrfeed.htm

Not sure if that helps. I read another one the other night (which I failed to bookmark) where the guy adapted a BP style power feed onto the dovetail (or as the yanks would say square column) mill drill. He ended up stripping the gears in it though and hadn't worked out why.
The same guy had a story on building your own power drawbar using some internet plans and an elcheapo butterfly airwrench. Looked sxtremely easy to do and quite neat.

Found it

http://www.thewarfields.com/cnccookb...PowerFeed.html

Hope that helps

**Sterob** · 1st May 2007, 03:06 PM

I've done some more work on this over the last couple of days.
I have to end covers machined up, the spacer beams cut to length and tapped anf the motor mount holes drilled and tapped.
That just about completes the drive part. Just have to design and build the de-clutching mechanism, attach cover plates and rebuild the electrics/ electronics.

**Sterob** · 3rd May 2007, 01:08 AM

I got the motor mounted securely today and gave it a test run from a 24V power supply I have. It ran very quietly and smoothly.I am very happy with it. Next I did a quick speed test and I estimate I have a max table speed of 450mm/min, so that will be plenty, I think. The commercial unit is rated at 500mm/min, so close enough is good enough....
Now I am working on the electrics and have decided to change things a little. I am going to try and use a toggle switch to operate small relays for direction control. This way I can incorporate the limit switches as travel stops. This will mean only low current going through the limit switches instead of motor current.

**Sterob** · 4th May 2007, 10:51 PM

I have made the de-clutching arm for the power feed and it seems to work like a beauty. I have bought some indexing bolts( spring loaded locking pins) from RS and plan to use one of those to lock the arm in the disengaged position. There is a spring behind the sliding dog, so that will keep it engaged without having to rely on the indexing bolt for that part.

**Sterob** · 10th May 2007, 05:12 PM

I made the locking mechanism for the de-clutching arm yesterday and it works pretty good. I drilled a locating hole for when the clutch is engaged as well, although it didn't really need it.
I tested the electrics and it all worked fine. The speed control is very smooth and I can go as low as about 4 rpm on the gearbox output, so it is very flexible as well. The 'whistle' I was getting with the other speed control and less so with this one, is not audible, so that is good. I was worried about that.
On the fabricating side I just need to make a front and rear cover plate ) have to cut a slot in the front one for the control arm) and that is all done.

**Sterob** · 11th May 2007, 09:47 PM

I started making the front and rear covers today and used the PF for this and it seems to handle it no worries. Mind you, I am not taking big cuts in hard metal, so it is early days yet.
The high speed traverse is not as fast as it has been in other versions, but when you look at the handlewheel speed, it is doing a fair clip and would be very tiring if one was doing it by hand, so no problem there.
I'll post a couple more pics in a day or so.

**Sterob** · 13th May 2007, 06:26 PM

I made the front and rear covers up ,and mounted them, yesterday. I milled out a section for the control lever, on the front one. Today I found an old PLC 24V power supply I had lying around, so I have pressed that into service for the power feed. Its rated for 4A so it is plenty big enough for this job.
Thats about it for this epic job. Now to find a job to use it on.

**hux** · 13th May 2007, 07:58 PM

Well done. Now to make serious chips eh.

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