Servo Driven 4th Axis for CNC Mill

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awemawson:
There that was easy wasn't it :thumbup:

Well yes, but I confess that is the third flange I made :( First one I broke a 6 mm carbide end mill as it was starting the hold down slots and it left too much mess to re-use. Second one was perfect except when I revised my careful measurements of hole centres and did an average of hole to hole spacing, although my figure was correct I put the wrong one in the CAD drawing :bang:

Still, third time lucky and now we have a flange that fits and looks reasonably presentable. Here it is as a mock up with the motor balanced on top in it's eventual home. Not bolted on yet as I'm awaiting some 5/16" UNF cap head bolts to hold it on.

Brass_Machine:
Your shop seems to be well stocked with tools... I like how you take this problem and solve it taking all issues in stride with a matter of fact attitude.

Eric

awemawson:
Thanks Eric, hills are there to be climbed :lol:

Now I reckon that there is an oddity there :scratch:

If you look carefully there is a horizontal cap screw that used to bear on the original stepper motor flange to adjust gear mesh, but it is pushing the gears OUT of mesh, not as I would expect, INTO mesh. Presumably a pair of gears will tend to separate if anything when they are under load and running, not pull into each other, so I would have expected that adjuster to work the other way. I may bolt something to the side of my flange to take a screw with a pad on the end that would allow uncrewing the adjuster to pull the assembly to bring the gears further together. All suggestions welcome.

awemawson:
So the next thing to sort is the fitting of a suitable pinion to the SEM motor shaft. The original stepper motor had a nice accurate 16 mm shaft, and a 20 tooth 1.5 mod gear fixed by 5 mm key and a grub screw, with the grub screw trapped by a circlip. I would have liked to re-use this gear, if only for economy, but the SEM motor shaft is a rather under sized 5/8" resulting in a 4 thou slop.

I had considered that perhaps Loctite would bridge the gap, but better sense prevailed and I bought a replacement with a 'pilot bore' from HPC gears. Loctite say up to 1.5 thou gap and mine would be 2 thou circularly. Incidentally let me pour praise on HPC. A phone call at 15:30 on Friday resulted in the postman bringing me their parcel on Saturday morning - how fast is that ! They also were able to provide some drive pulleys and a belt that I need for the encoder, but more of that later.

So I need to mount the gear in a collet, bore it to the rather arbitrary motor shaft diameter, and slot a key way to match the 1/8" key in the shaft.

I've also decided to fit a single lip oil seal to the shaft of the motor, as the gears run in an oil bath.

awemawson:
This morning I've bored the gear hub to size, broached it's keyway, and drilled and tapped for a 6mm grub screw to line up with an existing and convenient flat on the servo motor shaft

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