Servo Driven 4th Axis for CNC Mill

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awemawson:
Then the second bit of good luck today:

I wanted to sort the air solenoid that drives the 4th axis table brake - it needs to work off 24 v DC and the original is 100v AC. I fired it up via the variac, and although it works it hums like an angry wasp. Pulling the coil off it, it became obvious that it wasn't viable to re-wind the coil as I had intended as it was a sealed unit :( I considered using it via it's own transformer arrangement, but I really don't want 100 v AC in the environment that it will have to live in with coolant and swarf flying everywhere.

:scratch: So what to do. Well it's obvious really - chuck it out and start again. Now the original sits on the end of the operating cylinder, and the valve ports directly link to the cylinder so unless I was VERY lucky and found a similar one, I need to make a simple adaptor to clamp on the cylinder end to take normal push fit pipe unions, and use a standard air valve.

ebay provided me with a brand new one with 24v DC operation for the princely sum of £9.99 including postage :ddb:

awemawson:
Today was really a day for plotting and scheming.

Firstly to decide on how to get cables in and out of the unit. The encoder has an umbilical cord which I don't really want to re-make, and the servo motor, inbuilt tachometer, in built thermal alarm, coil for the brake solenoid, and magnetic sensor that says the piston has moved, along with the reference micro switch takes 12 cables, however due to some being common we need a ten pole connector. So I will make up a second umbilical cord and have a box mounted on the machine with chassis mount sockets. Decided on the Amphenol '97' series connectors as I already had the plug, just need the chassis mount socket. Order placed with RS components promised delivery Monday.

Secondly, how to adapt the end of the pneumatic brake cylinder to give me a standard 1/8" BSP port where previously the solenoid valve mounted.

A bit of poking around convinced my the easiest way was just to clamp a suitable adaptor on the end using the existing mounting screws and gasket.

So adaptor turned up out of a convenient aluminium bar end:

awemawson:
Then I needed to decide how things like the new pneumatic valve, cable clamps and covers would be mounted. First off I set too cleaning up the original mounting bracket so I could see what was what, and how the original cover was retained.

awemawson:
I will probably retain the original bracket, cutting a few bits off where it fouls the encoder cable, and extending it to give more support for a far larger cover and the cable clamps.
The original cover is far too small. I want it to extend over the rear to afford protection to the encoder and servo motor, and be stout enough not to suffer when the 4th axis is lugged about. It is a VERY heavy beast, and it's hard to be delicate moving it. :ddb:

I'll probably use the existing cover as the start of a pattern to develop the new one. Knowing how, when the machine is in full flight, chips go absolutely everywhere and coolant gets splashed over everything, it needs to be all embracing, but with an open bottom for anything that enters to fall out :lol:

Can't do much more to this until the new pneumatic valve arrives, as the bracket and cover need to be designed to fit round it.

Pete W.:
Hi there, Andrew,

That project looks to be coming along fine.

Have you decided what sort of a test-piece you're going to set it all to to try it all out?

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