[Littlemanweldin]

Hi Folks,
Just joined, not sure how it all works yet (the forum) but will get the hang of it if wife leaves me to play long enough!!!
Hope to be building a plasma table for our works in the new year. Big enough to take an 8x4 sheet (2400x1200).
Have found a good supplier for the control system here in the UK. Was going to bring over a Torchmate but it seems I can't just buy the control system.
I'm sure there will be lots of questions you can all help with once I get going, in the meantime, hello, its nice to be a member.

[cowleym]

Hi
Just wondering who the 'good supplier for the control system here in the UK' is?

thanks

Mike

[Littlemanweldin]

Hi Mike,

That supplier would be Techserv of course, is there another!! Still working on the funding but Jordan Engineering will be getting the cheque book out some time in the new year when finances and boss (wife) permit.
(Marry an accountant, you'll always have money.....but you'll never be allowed to spend it!!!)

Regards
Jerv (Littlemanwelding)

[Littlemanweldin]

Not sure if this should be a new thread or not? Not really a reply, just a continuation. (Too old for all this clever forum stuff)

Moving on from my original post about building an 8x4 plasma table, a few questions now coming to mind. Hopefully some of you experienced chaps can give their views and experiences.

Firstly, what sort of guide rails would perform best on a table of the above size? I tend to favour cam roller bearings on ground rails (a la Torchmate), but it seems a lot of machines are built with "slide" type linear bearings on round rails. The sort of stuff you find from Ondrives, Rhino and Igus etc.
Do they suffer from dirt collection?
They seem to be more suited to cleaner environments than a fab shop full of sparks, smoke and cutting and grinding dust.

Secondly, drive systems. Most "larger" tables appear to be fitted with rack and pinion drives. This would look to be the best method. I'm guessing that screw thread drive is OK on shorter runs, but might bounce or flex over the sort of distance we want to drive. Also again, the issue of dirt could be a problem I think. Which method has the least or most controllable back lash?

Finally for the moment, just how heavy does a table need to be. Some folks seem to build theirs holocaust proof, but as long as it is rigid and can carry the weight of the sheet being cut plus maybe a water table what more does it need?

I look forward to seeing what you chaps have to say.

(Wish I could work out how to start a new thread!)

[cowleym]

Howdy,

I would use linear slides, (trusystems or zapp are our suppliers) if you bung up the screw holes on the slide with the plastic bungers supplied, then it keeps out the muck. They are also availiable with extra metal shields for very dirty applications.

Rack and pinion drive, usually 1.5 mod, making a bit of a special effort with the motor pivot / slide, ( we use 2 slides and a pneumatic ram ). If you are really keen to reduce backlash to a minimum, spend a bit more on a good gearbox and use a helical rack, generally we would not bother with the helical rack on a plasma but would use it on a waterjet cutter. Not too sure about the ballscrew, I always thought it would whip around on longer lengths, the bigger screw machines I have seen used screw supports, or perhaps consider spinning the nut.

Beds: Strong enough to support the material and not skitter around when you load/unload it, you could always make a light bed and bolt it down.

Cheers

Mike

PS glad you like the cnc

www.techservcnc.com

[Littlemanweldin]

Mike,

Thanks for the info. Good food for thought. I am now happy that linear sliders are the way to proceed. If they are good enough for Techserv, they are good enough for me. Certainly there seem to be many advantages over the more "rustic" cam rollers. I've worked with those a lot in the past, typically fitted to the plunger assembly in conventional pick-up balers (for baling hay, straw etc), we also have them as wheels (70mm+) on our works built hoist and the trolley that carries our old Cytringan MMA welder!! (Bought it when I was a young teenager some 40yrs hence)

We run an account with Igus, for bushes and other clever polymer products. I am now very tempted to try their Drylin R-Linear Plain Bearings for the X axis. They have a lot of advantages as "sliders" when compared with normal ball bearing linear systems, or even the improved roller types.
There seem to be a lot of reasons for trying these out. Firstly, they are dry running, and also self lubricating. They are resistant to dirt, dust and moisture, so no worries about crap on the rails. In fact, Igus claim they will move the dirt so it runs through the gaps in the bush, rather than under the sliding surfaces.
They are quiet in use, have a low friction value, resist shocks and when they do expire, are very quick and simple to replace!!
Seems almost too good to be true doesn't it. I need to do a few calculations on load and wear times before I'm totally swayed but they do look attractive, but I'm not fully convinced yet!

Yes, I think plain rack and pinion will suffice, as you say, helical is a bit too much for a plain plasma table, and you have confirmed my thoughts about lead screws. They seem OK for short runs but maybe not on a longer table.

I'm gonna' go with 60x60x3.2 RHS for the main frame and X rail mounts, braced lower down with probably 50x50 RHS (whatever is in stock) which will then provide support for the water tray and slat supports.
That should end up "jiggle-free", especially if we rag it to the floor. I don't envisage moving it around much once it's built.

Very grateful for your interest and help. We are slowly working our way towards the purchase of that Techserv control system. It seems to display a lot of logic in its "modus operandi", unlike most of the others I have looked at.
Trouble is, when you have the time to play you have no money, and when you have the money its because you are working flat out with no time to play. Must be a middle line there somewhere but damned if I can find it yet. So much to do and so little time. Apart from normal work (with a full order book till at least april) I collect and restore vintage/classic tractors and combines, commentate at vintage rallys, perform with a charity tractor stunt team (see youtube "Flying Fergies") and get involved in building stupid machines. Next project could be an i/c powered mono-wheel. Ah yes, and there's the "new" annexe on the house that has been underway for around 7+ years. If I live to 100 it still won't be long enough.
Cheers for now

Jerv

[cheetahcnc]

Hi Folks,
Just joined, not sure how it all works yet (the forum) but will get the hang of it if wife leaves me to play long enough!!!
Hope to be building a plasma table for our works in the new year. Big enough to take an 8x4 sheet (2400x1200).
Have found a good supplier for the control system here in the UK. Was going to bring over a Torchmate but it seems I can't just buy the control system.
I'm sure there will be lots of questions you can all help with once I get going, in the meantime, hello, its nice to be a member.

Hello, and welcome to CNC Zone!

[larryy1022]

Hi Folks,
Just joined, not sure how it all works yet (the forum) but will get the hang of it if wife leaves me to play long enough!!!
Hope to be building a plasma table for our works in the new year. Big enough to take an 8x4 sheet (2400x1200).
Have found a good supplier for the control system here in the UK. Was going to bring over a Torchmate but it seems I can't just buy the control system.
I'm sure there will be lots of questions you can all help with once I get going, in the meantime, hello, its nice to be a member.

Torchmate is in US, right?
Why no update of yr plasma building? Or this plan got rejected by your boss wife, hahah?

[Littlemanweldin]

Well it has been a long time since my last post. Been too busy to even think about building our own plasma table. However, we are now about 10 days away from our 3phase supply being finished and coupled up. Power will be supplied by those nice folks at green Energy UK. What a friendly and helpful bunch they are, plus, using their power will wipe out our tiny carbon footprint completely. Have also built the base/legs for our table. Big enough to take a 2m x 1m plate, can't find room for anything bigger at the moment.
Had another word with the guys at Techserv last week, also a friendly and helpful bunch. Paul asked what sort of cutter we were going to be using. It so happens that 18mnths ago I bought a Lincoln Tomahawk 1025 at our local BOC open day. Was offered an amazing deal and even Jools (her that must be obeyed) said it would be a good purchase, although far too premature as we hadn't even got the 3phase sorted, let alone built a table yet.
Told them it must be CNC interfaceable, even came with a machine torch. After talking to Paul at Techserv I thought I would get it out of the box (for the third time since we bought it) and look at the interface. Guess what...there isn't one!! Lots of talks both with Lincoln and BOC finally reveal that neither of the Tomohawks available here in the UK are CNC interfaceable. Whats even more annoying is the fact that the US Tomohawk 1000 is the same as the UK 1025 (both built in Italy) but can have an interface 14 pin plug fitted. But ya can't get it here in the UK. How stupid is that I ask. If you check Lincolns leaflets it even says that they are interfaceable. Don't believe anything you read it seems.
The upshot is that we now have to buy another, different machine, most likely a Thermal Dynamics A80, which is interfaceable I am assured. At least it seems the guys at TD know their products. What a shame that Lincoln don't have the same product knowledge. BOC could do with a bit of training too I think. Sadly many companies become distributors without knowing their product fully. This is why we don't sell our machines through dealers, sadly all they mostly want is the penny at the end of the deal.
This has become a very expensive exercise caused by someones total lack of product knowledge.
Meantime, thanks to Paul at Techserve, who will be supplying our motion control system a little later, and also to Leighton at BOC for soothing the pain of one of his colleagues mess ups. Basically when you ask for a cup of tea, you don't expect to get a cup of coffee. Be warned guys.