Homebuilt Plasma Table Modifications

[Normsthename]

I built my CNC Plasma Table about two years ago and it has really earned its keep in that time
It was originally built as a Wood Router, but all it ever made were Freebies for everyone else!
Because I run a small business making small Motorcycle parts, I decided to convert the machine over to Plasma.
The machines current cutting size is 985mm x 585mm and I want to increase the cutting size to accept a standard off the shelf sheet size.
I originally thought about increasing the table size to accept a 2000mm x 1000mm sheet, but now I think I can fit a 2500mm x 1250mm machine into the available space I have.
Here is a video of the Plasma machine working in its current state.



I use a Hypertherm Powermax 1000 which has a cutting capacity of 12.7mm maximum.
It also has a Torch Height controller (THC) that measures the Tip voltage and adjusts the Z axis to maintain the optimum cutting height.
The machine uses a water table to keep the dust down and also to keep the steel cool so it does not warp while cutting.
I plan on building a new water table for the new machine where I will be able to raise and lower the water level using compressed air

These are the Mods that I have in mind, this is the original machine



First I plan on removing the gantry and cutting the top off of the original table



I will then build a new frame to fit onto the existing table.



I want to build a lightweight gantry, the old machine has a heavy steel gantry that was designed for Wood Routing.
Because of this I have to keep the acceleration speeds right down which affects the cut quality on the corners.
When I cut 1.5mm Stainless Steel it cuts at 3810mm / Minute but if I used a 60A tip on thin material you need to almost double that speed :surprised:



Here I have used 25mm round supported rails for the X Axis and 15mm Hiwin Linear rails mounted onto a 30mm Aluminium Extrusion for the Gantry.
I would like to change the design of the gantry so I can use supported round rail because it is a lot cheaper than the Hiwin Rails, but not sure how I will mount these.......
I will be driving the Y axis using the existing tables X Ballscrew.
I am not sure how I will drive the x axis yet, I have a spare motor so I can have two motors driving.
I was thinking about using rack and pinion for the x axis but I am all ears to any other suggestions
That's it for starters now, all comments appreciated

Andy

[Ross77]

Hi Andy.
Nice machine. I see what you mean about the over kill for the plasma, thats a big gantry.

I would like to change the design of the gantry so I can use supported round rail because it is a lot cheaper than the Hiwin Rails, but not sure how I will mount these.......

You can get double slot profile to be able to mount the supported rail but this is obviously bigger and heavier than the 30mm you planed to use. I would think about using some more steel box for the gantry, smaller thin wall would be about the same weight as the double Ali extrusion and much cheaper.

You could also look at Ali box and tap it or use a tapped steel plate on the inside to bolt the rails to.

I was thinking about using rack and pinion for the x axis but I am all ears to any other suggestions

Not used it myself but I think its what most people use for long lengths, don't forget belts as well, both suffer from poor resolution so if you need 0.000000001mm accuracy :heehee: then it will need gearing. But don't forget that this will also improve the rapids so a balance over resolution and speed needs to be considered.

[Tom]

Nice machine Andy, it looks productive!

What power supply arrangements do you have for the powermax? Presumably it's running on a high voltage, high current shop supply? Is it 3phase?

[Normsthename]

You can get double slot profile to be able to mount the supported rail but this is obviously bigger and heavier than the 30mm you planed to use.

Any links to the double slot profile?
I would like to keep as much of the build 'Nut a& Bolt' to save time

What power supply arrangements do you have for the powermax? Presumably it's running on a high voltage, high current shop supply? Is it 3phase?

Yep, it runs on 3 phase.
I have a small business unit (400sq. Metres....) and it has 3 phase electrics.
There are plenty of single phase Plasma cutters that would do the same job
Andy

[Ross77]

Any links to the double slot profile?
I would like to keep as much of the build 'Nut a& Bolt' to save time

Whats the bolt spacing on the rail support?

[GeorgeD]

Thought you might of seen this link what I posted sometime ago Andy? problem is you have to spend a minimium of £100 and there's a 4% surcharge on CC transactions.
Good site though evey piece of Ally extrusion imaginable,fill in the form and they let you download the price list and extrusion products in PDF format,both are seperate PDF's.
http://www.valuframe.co.uk/

[Normsthename]

Whats the bolt spacing on the rail support?

SBR16 has a bolt spacing of 30mm
TBR16 has a bolt spacing of 37mm
Both types have a 5.5 Diameter hole so I will use a M5 bolt / Screw to secure into position

Andy

[routercnc]

Hi Andy,

With regard to mounting the supported rail onto Ali profile, this was something I was pondering over a while back in case I upgrade to supported rails. I have pretty wide Ali sections with double slots, but they do not line up with the bolt spacing. I had decided that I'd probably line up one set of holes over one slot, sliding a long steel tapped nut plate into the slot to bolt into, as Ross has suggested. For the other side, I'd just drill and tap direct into the Ali. My profile has quite a thick wall section, so I think I'd get away with it, but the sort of part you might end up buying might be a bit thin. Some people use the 1 - 1.5xD guide for depth of thread vs diameter of bolt.

Another option would be to bolt a plate (say 6mm thick) to the single slot profile, using countersunk bolts into a nut plate inside the slot. The plate would be wider than the profile, and be wide enough to bolt the rail onto. Less stiff than some other options, but a possibility.

Or maybe you'll get lucky with an off the shelf double slot part.

[Normsthename]

Done a bit of research and found there is a 30mm x 60mm double slot Extrusion that has the exact 30mm centres of SBR16



Shouldn't be too heavy........

Andy

[Ross77]

TBR16 has a bolt spacing of 37mm

Thats a pain, you have couple of options but they still require a bit of tweaking if you use this one http://www.aluminium-profile.co.uk/acatalog/40x80.pdf then the 40mm spacing with the 10mm slot gives you 30mm edge to edge which should be just enough to get the bolts in.

The tricky bit is the fasteners, most have a rebate on the edges so they centre in the slot which is no good. if you look here http://catalog.item.info/Onlinekatal...00020610/37344

The nuts are just flat bar with cut corners and m5 thread, this means you can move them over a bit to suit your spacing. Ideally you could make your own with offset holes that fit the 10mm slot.

Item also do a 12mm slot version that might work with the offset idea.

Another option is to remove the bolts that hold the rail and support together and replace with longer ones drilled all the way throught the profile, I have some 16mm rails mounted like this but using soilid Ali square section, very strong.

As always there are lots of ways of acheiving the same goal but ulimatley if you want easy go with the hiwin profile rails, if you want cheaper then I'm afraid it means improvising a bit