Titivating A CNC Plasma Table

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awemawson:
Tywrapping the hanging support allowed me to determine the correct height for the new rear cross member, so when that was clamped up tight, I could then adjust the fore and aft position of the hanging fan support rail.

That done I had a trial fit of the fan to check that the measurements were correct, and all was well :thumbup:

Then it was a case of drilling and tapping to permanently fit the rails in place. Getting the flexible trunking over the lip on the fan was a nightmare - it's just too tight - it's 'on-ish' but I'm not happy with it - looks like it needs a slightly fatter trunking.

Powering up the fan it caused a huge draught in the workshop which I stunk out holding a smoking paper roll over the table to track the down draught. It's excellent apart from the extreme corners, which is perhaps not surprising.

On the subject of the fan - it's making funny noises for all the world as though its speeding up then slowing down. The rating plate says 2,800 to 3,300 rpm which I'd assumed was for 50 or 60 hz but just maybe it's a universal motor with some sort of speed monitoring. Normally if you block a pump or fan it's load (slightly against instinct) decreases. This one draws more current (1.7 amps as opposed to 1.5 unblocked) and the speeding up / slowing down stops - odd. It claims to shift 65 cubic metres of air a minute, which is quite possible from the blast it produces :bugeye:

awemawson:
Today has hopefully seen the last of he 'mechanical' side of things - I've been pondering how and where to mount the monitor and keyboard - it's not possible to put them on an adjacent wall, and really I want this table to be self contained and able to be moved about without too much hassle.

I obtained a wall mount monitor / keyboard swively thing which is not ideal but was a good starting point. Clamping some flat plate to the frame of the table I experimented with various positions trying to find somewhere that would clear all the moving bits, and yet still swing out of the way allowing plates to be loaded onto the table.

Ended up with a reasonable compromise which suited 'stand up typing' so I went ahead and fabricated a weldment - really a darn great bracket

awemawson:
Now although this weldment is made from 6 mm plate I was expecting some tilt or twist, and sure enough there was a bit too much to tolerate. My fall back plan was to incorporate a 'torque tube' made from heavy 40 mm box welded on the back to resist the twist.

Worked well and made things very rigid. So it was a case of drilling mounting holes, clamping it in place and drilling and tapping the table frame.

Then of course the obligatory coat of Ford Tractor Blue to add a bit of bling - well in all honesty actually to slow the rust down :clap:

awemawson:
This morning I attached the monitor bracket gizmo and cut a bit of melamine chip board as a keyboard / mouse table (hate the stuff but it was all I had to hand.

The table is looking more and more like an oil rig out of the water, with all sorts of things hanging off it :lol:

... anyway this means no more procrastination, I need to get on with drawing up a wiring schedule of the current set up, so that when I pull it all apart and mount things in the new cabinet I stand some chance of getting it right :bugeye:

It's not that complicated, but as the various settings are already up and running I want to keep things 'as is' rather than re-invent the wheel.

Over the next few days I will go through the rest of the original wiring documenting it and try and decide how to implement the limit switches he currently ignores (he's only wired one on X, one on Y, and one on Z and I suspect that only -Z is actually used by the software) and also how to build in an eStop in a sensible fashion.

First thing - try and identify the stepper motors. X, X-slave, and Y are all the same - "Astrosyn MY259RE" and quote 0.8 ohms 4.3 amps on the case - can't find details of them on the web but they seem to work. The Z stepper carries no markings what so ever :bang:

So far I have traced the stepper motor wiring from each motor back to the appropriate AM882 driver in his box of tricks, and also traced out the limit switch wiring back to the break out board and drawn out tables as a record. Initially it puzzled me that X and X-slave were wired differently, then I realised, as they face each other they must rotate in opposite directions :med:

It seems he has implemented all limit switches as normally closed, with the exception of Z- which is wired normally open, but held closed by gravity assisted by a spring, until the torch touches down for height setting purposes.

I've attach the tables but really only to keep a record, pretty boring for anyone else !

awemawson:
I >>>THINK<<< I've completed documenting the existing wiring to the extent that I can pull it apart and start re-locating the various modules into their new places .... time only will tell if I've forgotten something :bugeye:

Anyway the document has grown to 8 pages and I attach it here for reference, but it's pretty dry stuff :med:

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