village idiot builds a plasma table.........

[warwick]

ok to start...this is going to be picture heavy!..anything you see here is how iv done it and it doesnt mean its the right way.....
A year or so ago id seen a few videos on youtube and thought id really love to have a cnc plasma table.....
i had a look on the internet and most seemed mega expensive and made out of pressed tin...
i decided id build my own table to be able to cut an 8x4 sheet of 12mm mild steel.....I HAVE NEVER HAD ANYTHING TO DO WITH CNC EVER,
the table is fabricated out of 80x80x6 mild steel box...a few photos of the table
a huge thankyou to julian

[warwick]

after welding the table up i mounted some 80x80x6 angle to the side making the base for my y axis 16mm linear rails..i drilled and tapped the three legs of the table and then slotted the angle iron so i had plenty of adjustment

[warwick]

next i needed to drive the y axis so after alot of advice i opted for rack and pinion,it came in 2m lengths and i needed two 3m pieces... (lee roberts look away for the next few photos )

[warwick]

now having two pieces of 3m rack i needed to attach it to the y axis angle iron i used 4mm counter sunk brass machine screws..iv used these as it was 10pm and thats all i had in the shed.....

[Robin Hewitt]

How clever are you? Do you actually need any help? Here is a bunch of stuff, feel free to tell me where to go if I am teaching granny to suck eggs.

Joining two bits of racking is easy, you just put a third piece on top an it gives you the perfect spacing while you nut up.

You want to cut 12mm steel, is that a specific job of a theoretical maximum?

An 8 x 4 sheet of 12mm is a fearsome thing. If you are actually going to be slicing 2mm while planning for 12mm, maybe you want a smaller, less vigorous torch to start with, or have you already been on CNC Zone and been convinced HyperTherm is the only option?

Possibly not because you don't have a monster water bed

It might be too late to mention that you do not need huge motors because there are no cutting forces. The only thing you have to push against is the weight of metal in the gantry when you reach a pointy corner. Weight is your enemy.

If you start using the same motor to lift the torch as you use to move the gantry expect derision.

[magicniner]

If you start using the same motor to lift the torch as you use to move the gantry expect derision.

That's an interesting speculation, HTF would one go about doing that BTW?

- Nick

EDIT: Or did you mean "the same model/specification" of motor rather than "the same motor"?

[warwick]

How clever are you? Do you actually need any help? Here is a bunch of stuff, feel free to tell me where to go if I am teaching granny to suck eggs.

Joining two bits of racking is easy, you just put a third piece on top an it gives you the perfect spacing while you nut up.

You want to cut 12mm steel, is that a specific job of a theoretical maximum?

An 8 x 4 sheet of 12mm is a fearsome thing. If you are actually going to be slicing 2mm while planning for 12mm, maybe you want a smaller, less vigorous torch to start with, or have you already been on CNC Zone and been convinced HyperTherm is the only option?

Possibly not because you don't have a monster water bed

It might be too late to mention that you do not need huge motors because there are no cutting forces. The only thing you have to push against is the weight of metal in the gantry when you reach a pointy corner. Weight is your enemy.

If you start using the same motor to lift the torch as you use to move the gantry expect derision.

hi robin,
its in my nature to bite off more than i can chew and blag my way through, bright or stupid?
yes i need help and adviice really, im a first time builder with no expierience of cnc or computers....
iv never even seen r&p until a friend showed me what to order,so yes clamping a piece to the two parts that need joining to get distance right is easy aslong as someone tells you the method of doing it...my original question re.welding rack ...was can i tack it to the frame rather then drill and tapping,its a part that has a sprung loaded gear pushing into it so didnt see any issue??...
iv messed about and built a few narrowboats on the bank without fancy over head cranes or lifting gear so any 8x4 sheet seems easy to handle compared to a 10mm base plate 50ft long.........
everything has always been EYE right as now with this project its 0.5mm is sloppy but ok for a plasma.you never see both sides of a boat at the same time........
i want to be able to cut 10/12mm but also thin stuff like 3mm.....


next part of the build is the x axis gantry..what are the best options for a gantry???iv got some 20mm supported rail and 2m of r&p

thanks in advance for your help..........

[Robin Hewitt]

I tried and failed, my gantry was 2.75m of 4" square aluminium box section and it did the long axis. I started out by taking a 4m length of the stuff, supporting it at the ends and dumping weights in the middle to see how far it bent. Hardly at all. You don't need to swing huge amounts of iron just to move a torch. It had a 15mm profile rail along one side, screwed from behind so the black dust could not sneak in past the wipers.
I threw the towel in when I discovered the T5 belting and pulleys I had bought were unbelievably slack.
If you have pinions at either side of the gantry connect them with a low inertia shaft. Thin walled aluminium tube perhaps.
I could ramble on all day, it was fun.

[warwick]

not a huge amount done today, anchored the table to the floor and adjusted it for leval and true,,,iv gone with 80x80x5mm box for the x axis....the brackets are just 2" of 50x6 angle welded to the legs still need to round the brackets off and repaint....

[Robin Hewitt]

Slats, you will support the work piece on slats. Think how you will support your slats. If they have to flex a bit to fit they are more likely to behave themselves.

If it is a small piece of metal you will need the slats close together with more support from below. If it is a large sheet the slats can be further apart. Why not put slats close together in one corner and further apart over the rest of the table?
The other slat function is the tilt. You cut a complete part and instead of resting flat on two slats or falling through it tilts and jambs itself at an angle. The tool slams in to it on a rapid transit and does hideous damage to itself. You would need vast numbers of slats to avoid this but it is quite predictable. You can put a bumper ring around the tool tip to spot them and apply the brakes.