Plasma table build, first question....

[Davek0974]

Thanks,
i am looking to add a z-axis after watching some videos on YouTube and playing with sheetcam and mach3.

It it will at least give me the option of adding THC later on with little hassle.

my torch does have HF start but not pilot arc.

[Boyan Silyavski]

You will need this Complete Compact THC MD system ( CNC Plasma Z axis controller ) | eBay, or at least half of it, it works with both type plasmas. Look at the videos in You tube or their web.

As to 0.02 precision, with a build like the one inspired you, you will be happy to stain in the 0.5mm ballpark. But having many alu profiles as you say, you could do far more precise build. Something like the cncrouterparts kits. Or round shaft inserted at the slots, could make cheap and precise rail

You can clock the belts on the long axis via shaft at one of the ends. In fact you should. My current machine is build like this.

[Davek0974]

Thanks, the proma THC is the unit I am thinking of using when I fit THC, the THC and driver does not seem to be available anymore but the THC on its own is.

0.5mm or better is plenty good enough I think.

[Boyan Silyavski]

0.5mm or better is plenty good enough I think.

Errors accumulate in the build :-) , its not only one thing. I strive to make everything perfect in my build, even knowing that could not be.

Also accuracy is ok when depends for whom and for what purpose.

FYI after reading your answer i went in the garage and started precisely measuring the 10mm thick steel elements that ordered lasercut for my build. I haven't done it before as everything fit nice together. Guess what - 0.01 -0.03mm at the most, different from the drawing.

A properly constructed , aligned and calibrated belt driven machine can offer real life precision in the ballpark of 0.05mm. Yes, even with roller bearings and belt. This for the unbelievers. My machine uses V bearings / roller bearings inside- 608/ on supported rail. When i bought it new it was in the 0.5mm ballpark, a couple of days thinking and bettering it and now is in the 0.05 -0.1 mm , i am talking about router not plasma.

So, take your time and strive, you could make a very precise machine if you invest more time and precision right now when building it.

[Davek0974]

Here's the reduced frame with side tracks fitted...

And the two Y-axis trolleys...

Coming along nicely.

[Davek0974]

Yes, someone else has just suggested a sprung loaded torch as well, I am fitting a stepper drive z-axis so I can get the torch clear while rapid moving, a floating or gravity/sprung head sounds a good addition.

[Davek0974]

Sound advice.

im trying to build as controlled and tight as possible, but this is a learning machine and never having seen one up close, I have no idea of speeds, acceleration, deceleration forces etc so maybe it will work wonderfully first time or maybe I will need to rebuild bits of it.

one thing I am surprised at is how difficult it is building small - every millimetre of axis travel counts and things keep getting in the way - gantry mounts, trolley brackets and so on.. Building a nice big table would have been much easier but I have nowhere to put it :(

[Boyan Silyavski]

As it would be only plasma machine, you could go light and simple on everything. Take a look at the ebay kits they sell and improvise. The Proma kit they sell at they web also. I pointed it to you as the second piece is the Z driver and will simplify things even further if you have not bought the drivers for the motors. Look at his simple Z axis.

it not my machine, cause the part i want to show you is hidden inside, so i can not make photo of it but that's what i meant for clocking the gantry belts:





that is good idea for simple Z DIY CNC Plasma cutter axis rail car for nema 23 stepper motors | eBay



If i were at this point where you are, i would buy a 1 second hand wide type square rail with bearing block or two for around 100-200eur shipped to you from ebay for the gantry, as it will be far better than the other solutions. This wider type of rail will hold a very light z perfectly, move it fast and precisely and simplify a lot the build.

something like this LAW21EL+710-2 Linear Bearing 1Rail 2Block NSK Used Wide type K1 lubricate seal | eBay

[Davek0974]

That picture is almost identical to what I have built :)

i have designed a carriage for the x axis on the gantry and will start machining it as soon as the aluminium arrives. It rides directly in the gantry beam, pretty much like the one in the eBay listing you added, but mine is made out of aluminium slab, same sort of bearing layout though.

hopefully have it made by Monday as I'm still finishing the gantry trucks and motor mount.

[Davek0974]

Made the X-axis trolley today, came out lovely...


The motion is smooth as silk and no twist or slack at all, very happy with that. The front plate is drilled for the motorised Z axis I have already waiting.