New Build-12x6ft Plasma Table

[Davek0974]

Yes I was thinking of an adjustable 'Z axis', the diagram of the table was only a rough idea.

If by adjustable, you mean a torch height control, then I would say for a build of your size it would be essential, not just a thought ;)

My biggest problem of the whole build is the motors and the rails setup. The fabrication of the table and the separate supports for the gantry is the reasonably easy part?

One thing I have learnt so far is to take it all into consideration, but build it in parts.

Do I have to buy the rails as a one piece or can they be joined?? Also how many do I need??

Liner rail like HiWin can be butt-joined if carefully aligned, longest bit in one length I think is 3m. As to how many, if you take a look at the specs, they can take a massive load, the 15mm section am looking at can roll a 1500kg load! It must be fitted correctly though with side support etc.

This lad used angle irons and rollers like a roller gate set up for the liner rails will this system work?? is it a cheaper method??

Cheaper, yes, better, no.

I would look at proper linear rails, one per side probably 25mm size, but thats just a guess. Get the carriages fitted with wipers and scrapers.

[Boyan Silyavski]

What i said in the long post before is still valid, so maybe read it a couple of times more, cause you will get there if you think more and more deeply

for example:

-Hiwin 20 size rail/ or MGW15/

If it was ok Hiwin 15 size rail, i would have told you that. The savings from HGR15 to HGR20 are very small if none, but with the small blocks on the 15 size rail you will have much more problems designing the thing.

I was talking that if you design it properly you could even use 4 rails and only 4 blocks in the whole machine. Using the long HA blocks, where each block is 90mm long. And for sure 4 rails and 8 blocks if you dont feel like minimalist design is for you. After all if you buy from China 4 bearing blocks more, it will be only 120 euro more in the whole build.

As you were told, there is no problem connecting Hiwin Rails, especially in plasma build.


-While on a small table speed is no problem, on such a size you need things to be really fast. I would go as far as to say that you need 800ipm real life speeds with serious acceleration there . Cause bad things happen on plasma when deccelerates and you have crappy THC . You will need to cut thin stuff something like more than 10000mm/min

-Again - THC is a must


So , make the machine separate from table. Forget the stupid table for now. Invest money and effort in the actual machine. Later having THC you can support and cut the shit on a basic frame, which once you start earning money can upgrade as per your desires.

How hard could be to sit down and design a modular sides design from that 75x75x5 or whatever. Like at the photo bellow. As i said personally will use at least 100x100x3 . You are talking about 3.6meters long+ 4 legs 1m high each side. But size really it does not matter if you use THC and simply is strong enough not rack the gantry.





-simple 1 beam gantry with one rail. Similar to the video before. Forget about the monstrous machines from pictures. they are made to route and drill also, driven by powerful servos, etc...

[F1transportationserv]

yes brilliant thanks the previous massive machines (first images i found of the type of design) were only generating ideas ie separate table and rails of that type design.

so whats my next step start drawing? or what do I need to do?

something similar to the image above is what I'm looking to put together.

Also sorry if I seem eager I'm just unsure what way to go with things :)

[Robin Hewitt]

so whats my next step start drawing? or what do I need to do?

I think that first you have to understand the problem

Your problem is the change of direction on thin sheet and is all to do with accelerations.

For a first machine you will probably build your gantry out of 75x75x5 and fit enormously powerful motors to overcome the inertia. Strangely you might use the same motor for the Z as you do for the other axes. You might even use 2 motors for the long axis and try to connect them electrically

1 Newton force will accelerate 1 kg mass at 1 m/s/s

[cropwell]

Strangely you might use the same motor for the Z as you do for the other axes. You might even use 2 motors for the long axis and try to connect them electrically

I can see that a plasma machine won't need heavy lifting capability on the Z axis but why does slaving 2 motors for the long axis merit a ROFL, unless you mean connecting two motors with a choc block

[Robin Hewitt]

I find lots of things funny, especially since the blood supply to my brain failed last year. In fact I find it difficult to take most anything seriously

We must remember that the decision to use 2 motors usually follows a failed Google search for extra long timing belts. You have to be oblivious to the problems it can cause or you would not give up that easily.

How many people check the driver initial step pattern on power up before they shop for this? Do they fit a stall detect system to ensure that both sides fail at the same time? Do they fit one location sensor and pray or two sensors and then decide prayer was the easy option?

[Davek0974]

The reason I have chosen to use two motors is because I have a belt drive machine with one motor and it suffers belt issues and does not go fast enough, along with the fact that there are many many commercial build tables with slaved motors and AFIK no hardware or software fitted to check for a failed move on one motor i.e. racking the gantry.

With steppers, its a moot point to a degree as they will not do any (or much) harm if stalled, a servo on the other hand will happily destroy itself and/or its driver when jammed. Gantry damage is possible with both systems i guess but to different degrees.

My motors have dual shafts so I guess I could install slotted opto-discs and detectors on each motor and a small logic board that trips the E-Stop circuit if one side does not move - could be an interesting project one day.

Power-up IS however one issue I am looking at, I know my steppers jump into lock when powered up, but what are the chances of BOTH jumping into the same lock position ?? Zero, 50/50 ????

That is the main point I think