Titivating A CNC Plasma Table

The Craftmans Shop > New from Old

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awemawson:
So I've decided to rip out all the stepper motor and limit switch wiring from the table and re-run it, and that's today's job. The master plan is to re-wire, then temporarily hook up to the existing controller box to prove all OK before pulling the controller box to bits, thus cutting down on fault finding (hopefully)

Firstly some little things to overcome:

a/ Z-Down limit switch is only fixed by one screw and has no cover as everything is very inaccessible

b/ How to run the wiring from the (missing) X-Far limit switch as it's a long way from the 'power chain' ducts

c/ How to connect to the stepper motors as present chunky car type plugs and sockets are not acceptable

d/ Best position to move the power chains to for threading, as as soon as I start removing wires I can no longer move the carriage about :bugeye:

Starting with the Z-Down limit switch, I decided that the best course of action was to carefully measure up and drill a pair of access holes, allowing a screw driver to access the M4 mounting screws. Having done that and removed the single screw currently fixing the switch it turns out he's not drilled or tapped the hole for the other screw :bang:

Now M4 needs a 3.3 mm tapping drill, and a standard 3.3 jobber drill is far too short to reach the plate that needs drilling. It just so happens that when I was rebuilding my Dominion Super Elliot Woodworker I'd had the same problem and had made an extended 3.3 mm drill - result :ddb:

But what about an M4 tap 100 mm long - well extend one ! Across the 'points' of the square shank of the tap I chose measured 3.85 mm, so I drilled a 3.7 mm hole in a bit of 6 mm mild steel rod and used the lathe to press the tap into the undersized hole - worked a charm and ensured that they are concentric - problem solved :clap:

As for the X-Far limit wiring, having thought about drilling the frame and threading the wire through I've come to the conclusion that it might as well be Tywrapped.

The power chain issue I think is OK as one side has 'open fingers' to allow wires to enter

Now the stepper motor connections call for a neat little 4 way junction box that can be fixed to the body of the motor - not sourced any yet and would welcome suggestions

awemawson:
Right-ho, that's all the wiring off the table :clap:

Cropped off the original ends at the stepper motors so that there can be no confusion which core is which on replacement, but unscrewed the limit switches individually. For some reason best known to himself the wires had been stripped for about 2 inches and wrapped round the terminals about 10 times :bugeye: They will go back with crimped on 'boot lace ferrules' with about 6 mm sticking out !

Removing the cable from the gantry, I realised that he'd left the angle iron support in bare metal and it was already getting rusty, so another job - remove, clean and paint - which I did. It's fixed into the slotted extrusion of the gantry with Tee nuts of the type that you can put in and twist - handy, but he's spaced it down about 1/2" using a pile of 6 washers on each bolt - so it looks like I'm turning up eight spacers this afternoon !

awemawson:
So after lunch an off cut of 19 mm hex aluminium was turned into eight spacers - much nicer to handle than a pile of washers !

Waiting for paint to dry - already touch dry but pushing my luck to mount the chain support until the morning. At the moment I'm thinking I'll just use crimps to couple the stepper motors - much rather use a small junction box but every thing on the market seems to be far too big. I'll try and leave enough cable in the system that I can re-terminate in the future if anything suitable turns up.

... so it looks like re-wiring can't start until tomorrow ... :med:

awemawson:
Late on Friday afternoon I located some small clip together boxes on Toolstation - not ideal as they aren't sealed, but definitely functional. Ordered on line and they arrived first thing this morning - pretty good.

I re-fitted the 'power chain' support now the paint has dried.

awemawson:
So I was able to start the wiring - so far the four stepper motor cables are pulled through, as are the six limit switch cables. The motors and limit switches are all connected and the controller ends brought back to the cabinet in flexy conduit awaiting drilling the cabinet bottom plate - a job for tomorrow.

Another job tomorrow is to finish off securing cables with 'P Clips', and binding the various bundles with spiral wrap.

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