The Craftmans Shop > New from Old
Titivating A CNC Plasma Table
awemawson:
Since I first got this machine I've not been overly happy with the Z Axis. It's main mounting plate had been bent at one time, and both the normal Z movement and also the 'floating Z Axis' used for material sensing only ran on single linear rails, resulting in a bit of side to side wobble and tilt. Don't get me wrong - it works - but it's not overly robust in it's design and there were features that I wanted to incorporate - namely:
A/ Dual parallel rails for the main Z and the floating Z movements
B/ A Magnetic Breakaway Torch Mount
C/ Emergency Stop to be asserted if the Magnetic Breakaway is triggered
Now this is all very well, but I didn't want to strip down the existing Z axis and hence stop me using the machine, while building the new one. So I decided to start from scratch and make a modular Z axis that would be on plugs and sockets and fit existing mounts on the machine.
I procrastinated for a long time, looking at economical ways of getting the linear ways, ball screw and nut, bearings etc until eventually a 'Prototype Z Axis' turned up on eBay. It had been put together but obviously never used, and would need re-making, but it had the linear rails, ball screw and nut, bearings, stepper etc just as I wanted, but for far less than the total of buying the separate items :clap:
awemawson:
The end mounting plates will need re-making to spread the rails further to suite the existing machine mounts, the coupling between the stepper motor and ball screw was rigid, and I'll have to mount a new floating Z axis on it with suitable magnetic breakaway torch holder and limit switches.
So - buy an Oldham coupling and bore it to the correct sizes - simple (and done :ddb:)
Draw up a CAD drawing to show how all the components potentially interfere with each other, to make sure that the new upper and lower plates will work - done :ddb:
Buy a handful of limit switches - done :ddb:
awemawson:
Buy a big slab of 10 mm thick aluminium alloy ground tooling plate to make the bits - done :ddb:
Source a (VASTLY EXPENSIVE :bugeye: ) Magnetic Breakaway Torch Holder - done and customs duties paid :ddb:
(I had intended to make my own, and even drew it out in CAD and bought the magnets, then I realised that the 'real ones' had been carefully developed to hold on in normal situations, and let got if the torch catches the plate and the amount of magnetic force needed was a great imponderable, and with torches about £600 each I didn't want to carry out tests !)
awemawson:
Source some smaller THK-10RM rails and sliders for the floating Z - done but will need cutting in half :ddb:
So now it is a case of making the end plates - (simple but need doing accurately) so I extracted them as individual parts from the CAD montages and will probably CNC machine them.
Still quite a few details to work out re the floating Z and limit switch mounting, but I'll get the end plates made so I have something to prod and poke !
awemawson:
Incidentally, the pre-existing mounting slots that I previously referred to are these:
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