Titivating A CNC Plasma Table

[awemawson]

In early October I bought a CNC Plasma Table - motivated by needing a few bits cut for that Flail Mower, and always having hankered after one it seemed a good excuse 

It is a home made one with a capacity of approximately 1500 x 1500 (mm) - uses HiWin rails, stepper motors driving rack & pinions and came with a Hypertherm 45 Plasma cutter complete with a machine torch. Also it has an automatic torch height control which is a big advantage.

Although I'm glad to say it worked as bought it was obvious to me that it was going to have to be re-built as the wiring and arrangement of the control box was not at all to my liking.

Now when I got it, it got pushed into a corner of the welding shop where I used it successfully to make the bits I needed, but it became obvious that with it there no improvements were going to happen, as it wasn't very accessible, and it's rather chilly in there at the moment.

So today was the big day to move it - clearing all the odds and sods out of the way in the welding shop and fork lifting it into my operating theatre project space 

So a few pictures for a start:

[awemawson]

When a CNC Plasma table is going full tilt it blows burning metal particles downwards creating much mess, fumes and nastyness, so one of the first things I intend to incorporate is a powerful down draught extract system.

Basically an upside down hood under the bars of the table acting as a funnel to collect all the debris and fumes which are removed by a fairly beefy extractor fan - probably 12" diameter in this case though not fixed yet.

Googling about in various forums I came across a neat layout, and contacting the builder he was happy for me to do a direct crib of his idea - why re-invent the wheel - so these pictures are of his table and extract duct

I'll probably get a local duct work firm to bend it up, as although I've got the bender and guillotine they can probably do it for not much more than the materials would cost me to buy

[awemawson]

Immediately under the support bars I'll fix a mesh to catch the larger 'drops' from cut outs, and the collecting box will have a spark arresting fine mesh on it's output.

So the way it looks at the moment the job list is:

a/ get an extract duct bent up

b/ source a suitable sealed steel enclosure for the drive electronics that can be fixed to the side of t he machine

c/ decide whether to put a PC inside same enclosure (ventilation issues)

d/ incorporate limit switches

e/ totally re-vamp all the wiring to hopefully a rather better standard than currently.

[AdeV]

c/ decide whether to put a PC inside same enclosure (ventilation issues)

You can get some pretty decent fanless PCs these days. If you're not wedded to Windows, you could probably get away with using a Raspberry Pi 3 [and allegedly Windows 10 will run on one, but IMHO that's just cruelty to silicon].

[nrml]

Or one of the increasingly popular DDCSV 1.1 or similar boxes? It would be perfect for this sort of environment.

[awemawson]

No nice as they may be I don't want this to turn into a long & protracted learning curve. I have a spare Dell Optiplex ultra small form factor with an SSD fitted that'll do the job.

I've made a little progress in that I've been spending money on needed bits - I've sourced:

1/ a nice 800 x 600 x 300 Schneider electrical cabinet

2/ a blower that claims to shift 3900 cu/M/ an hour

3/ some jumbo non-flammable air hose 315 mm i/d

4/ some mammoth Jubilee clips to stick them together

5/ and a wall plate to get the fumes outside

Meanwhile my sketch for the under duct / inverted hood thing is with a sheet metal work place I didn't previously know existed only just over 1/2 mile from the house - hopefully getting a quote to me tomorrow 

[awemawson]

A bit more dismantling progress this morning:

The down draught exhaust duct is going in from the top, so the slats that support the work piece need to come off as well as the slat supports. Simple pull out for the slats - these are expendable, and inevitably get cut to pieces in use.

I've furnished myself with a complete new set, but obviously will only introduce them as needed - for the time being I've sorted the old ones into an acceptable pile and a grotty pile, and then removed the box section that supports them. One is rather bowed - not that it shows much in the picture, but I'm going to have to re-work them anyway, as the duct metal will be trapped by them to the frame, so the supports will need shortening by two metal thicknesses. I will probably introduce a third support that will have slots out of phase with the other two, allowing the slats to be held in a curve. This minimises slat cutting when rectangular parts are being cut.

The chap who built this welded a bit of 75 x 4 mm plate to the side frame to aid aligning big sheets - this will need cutting off before the duct is installed as it's in the way, also there are mysterious 'lumps' welded on in places that need dressing off for the same reason

[awemawson]

So now I need to work out how to temporarily hook it back up to it's drive electronics so that I can move the gantry up and down, while I wheel it outside to attack those extraneous bits with an angle grinder 

(The angle grinder is banned from the 'clean' workshop  )

[awemawson]

Well looking again at the plate he'd welded on the solution was obvious 

He'd not made it full length as obviously the gantry was fitted before he fixed it, drive the gantry down the far end and all is exposed. OK still meant lashing the electronics back on, but no need to make them 'portable' when I drag the table outside for fettling 

[awemawson]

Not a lot done today - the morning was taken up by an interrogation by the local Planning Authority's consultant 'farming adviser' over my application for planning permission for a tractor shed. I wasn't looking forward to it, but in the event he went away convinced it WAS needed for agricultural purposes (honest!) and I almost managed to sell him a freezer pack of lamb 

By the time he'd left, the heavens opened and there was no chance of pulling the table out side for grinding - so how to proceed Then I remembered a recent 'impulse purchase' of a rather nice electric Die Grinder - this was occasioned by not being able to dress welds back as neatly as I'd wanted to on the Flail Mower - the usual 'fixing the previous problem' purchase 

...well the Die Grinder hasn't been banned from the clean workshop, as after all it doesn't chuck grinding dust everywhere, only filings, and as it's Tungsten Carbide bit is a small diameter they don't go far anyway 

So I ground back the welds aiming to weaken them enough to break them and leave the parent metal untouched - largely successful but a bit of filler before a coat of paint will hide any imperfections.

The locating bar came off nicely, then I attacked that odd 'lump' on the inside of the frame only to discover that in fact there were three of them. I suspect he had had the slat supports running at right angles to where they are now, and these are the artefacts surviving his re-make. Well off they came and with a bit of hand filing everything got dressed back to an acceptable level allowing the duct to fit (I hope - still not got the quote yet)

Anyway - have some pictures

[millwright]

And so another saga is unfolding, looking forward to reading of your trials and tribulatations on the way, and your triumph and the end of it all when another piece of equipment is resurrected Andrew. i always enjoy your projects. 

John

[Pete W.]

And so another saga is unfolding, looking forward to reading of your trials and tribulatations on the way, and your triumph and the end of it all when another piece of equipment is resurrected Andrew. i always enjoy your projects. 

John

 

I agree.                        

[awemawson]

Kind words, and much appreciated chaps 

[DICKEYBIRD]

Holy cow Andrew; do you ever sleep?  Watching what you get accomplished in one day tires me out.  I need some of whatever vitamins (or drugs) you take.  I don't care if they're legal or not!

Seriously, thanks for posting your work in so much detail.  It's very inspiring to watch you do all of these amazing projects.

[awemawson]

Nothing physical on the Plasma Table today - resting up after quite a hike yesterday round Virginia Water / Windsor Great Park with the dogs and an extended pleasant lunch with my son and his fiancee preceded and followed by rather too long on the M25 !

However cogitation time ... I wanted to look at limit switches ... this table has switches on all three axis, however they are not wired in, and one is physically broken (he hit it with his fork lift he told me) 

Now I want active limit switches, but I hate the way these have been mounted - they are the normal roller type but are effectively being used as 'long stops' - if an axis does over travel it will squash the limit switch and break it. In my book there should be a physical / mechanical stop at the end of axis travel - possibly with a buffer of some sort, but this should be preceded by a limit switch THAT CAN BE PASSED so a bar or ramp or what ever operates the switch in such a way that the roller ISN'T a physical stop. Re-engineering this is not going to be easy as it isn't how he designed it, and will probably involve a few bits bolted on to change the way the switches are triggered. (Space is tight on the Z carriage and gantry.)

First step was to locate a replacement for the IMI IMP switch that was broken, and fortunately it's an RS Components stock item so one should be here on Monday.

[awemawson]

Well at long last I've been able to place an order for the duct to be bent up. The company I'd discovered very close to here didn't get their quote to me until this morning, and they can't start work until the new year 

So my 'second line of defence' is a small outfit a few miles away that are apparently less well set up looking at their rather shambolic workshop, but were very slightly cheaper and could start next week 

Mean while I'm catching up on a few 'round tuits'

[awemawson]

Still waiting for the duct to arrive, so I decided to make a start on the central third slat support rail. 40 mm square box section fixed on height adjustable brackets at top and bottom of the table, and carrying a 40 x 40 mm x 3 mm angle iron slotted every 50 mm to take the slats. I made the brackets a while back.

Now I'd been wondering what was the best way to cut the slots - the slats are 3 mm thick so a 4 mm slot would be ideal. The original pair of angles are rather uneven and look to have been cut with an angle grinder. I decided to use my Pedrazzoli cold saw, but it has a 2 mm blade, so each slot consists of two cuts carefully spaced - rather fiddly but it seems to have worked OK. I cannot cut the 40x40 support rail yet as it's length depends on how thick the duct ends up.

Then I thought I'd better get a bit of paint on the side rail where I'd cut off the previous owners alignment plate to allow the duct to fit when it comes (I'll bolt a plate back rather than weld it). This is really just to stop things rusting as most of the top of the side rail was bare metal.

Turns out that 'Ford Tractor Blue' in not too bad a match for whatever the frame has been painted in - at least it doesn't shout 'I'm different' and I had 5 litres on the shelf

[awemawson]

A little bit of progress this morning that is actually a big psychological boost as I wasn't looking forward to it -

I've down loaded a legal copy of Mach3 onto a Dell Optiplex Ultra Small Form Factor PC running Windows 7 that I've fitted with a solid state drive, and managed to transfer all the settings from his original set up on a wacking great Dell tower system he was using, AND IT WORKS - happily driving his original electronics. (These will be re-engineered in the electrical enclosure)

All this because at the moment my intention is to house the PC safely within the new electrical enclosure to keep it out of harms way - with just the monitor and keyboard on a stalk somewhere.

Having proved it works I'm now more motivated to plough on with the electrical enclosure.

[mattinker]

I'm looking forward to seeing this when I come over to the UK!

See ya, Matthew

[Pete.]

I have an enclosure here that I believe will suit that, if you want it Andrew.

[awemawson]

That's very kind Pete, but if you look 'up thread' you'll see a picture of the one I've bought 

[awemawson]

Catch 22 rears it's ugly head 

Experimenting with the Dell Optiplex 780 Ultra Small Form Factor, I can set it's power sequencing so that if it looses power it will start up again when power is resumed but the running software may well corrupt. However, if the PC is closed down in an orderly manner by pressing the 'Start' tab then selecting 'Shut Down', when power is resumed the PC doesn't start up and the front panel Power button has to be pressed. Sometimes Windows is happy if it is put in 'Sleep' mode before loosing power, but about one in three times it wants to start in 'safe mode'.

So why does this matter Well if the PC is located in the electrical enclosure YOU CANNOT PRESS THE POWER BUTTON 

Now I've thought of hard wiring an external button, but that's a bit crude as the PC layout doesn't lend itself to this. So I'm coming to the conclusion that the PC will have to be strapped to the outside of the enclosure. Not the end of the world, and in practice means less plugs and sockets, as the monitor and keyboard and mouse are already external, as is the USB socket for transferring files. But it's not quite the neat solution that I'd hoped for.

As it happens I have a 'desk mount sleeve' for the Optiplex 780 USFF so actually mounting it isn't too much of an issue

[russ57]

A long time ago,  I  fixed a "power up after power failure"  on a large fleet of PC's (8000),  by hacking the power on lan feature.  I think we ended up with just a capacitor across the reset button -  it effectively held reset low until power was fully up,  then the pc saw it as the reset button being released .  Did you check through all the bios options?  Sometimes there is a feature to either power up,  or return to the state before power fail.
-Russell

-russ

[awemawson]

Thanks Russ, yes been through all the bios settings and experimented - even tried the 'wake up on Lan' as the 'network' is in fact the torch height controller via Ethernet and an Ethernet breakout board - I'd hoped that their activity might wake it up but no !

[DMIOM]

Andrew - does it have a serial port? - some time ago I did something similar by using the "Wake on ring" feature in the BIOS.

Dave