Heavy Duty Plasma - Ball Screws

My company is looking at making out own cnc plasma table because non we see on the market are what we are looking for. Unless they go over a 200k machine. We are a family business we work with stainless steel and brass, we make beer towers.
Anyways what we want to do is have 2 x axis motors powering ball screws, 1 y axis and a Z. We want to be able to cut a 5x10 area and im wondering what kind of motors I will need to be able to travel at least 325imp cut speed. Also if it is possible to do this with emc2.

Unlike a mill or lathe, the only forces you have with a plasma table are friction and inertia. The bad thing about plasma is abrasive dust.

Belt drive positioning accuracy is well within the requirements of a plasma table and the belts are practically immune to abrasive wear. I built a positioning table for automated spot welding a few years ago. It performed at twice the design spec and the belts were still good after three years.

Doug

Ok well this was the table we were looking at buying problem with it is one big ball screw down the middle of the table drives the x axis and from what we see when its out at the ends it will wiggle too. So we want to put 1 on each side to make sure each side is strong.
Our table now is rack and pinion the repeatability is very poor. Here is my table running

The reason we want to use ball screws is we feel they will be more accurate, we want to put a router on it and later down the road we want to get a fiber laser.

On the equipment i want to use Im not sure yet, trying to figure out what servos and guides I need and how to lay them out with accordion covering on all axis.

Here is another video i just uploaded, one side gets alot of whip

Ok so I was thinking would it be better to mount a low watt laser next to the plasma instead of a router? We would use it for cutting insulation and engraving serial number/part numbers.

ocpistol wrote:

My company is looking at making out own cnc plasma table because non we see on the market are what we are looking for. Unless they go over a 200k machine. We are a family business we work with stainless steel and brass, we make beer towers.
Anyways what we want to do is have 2 x axis motors powering ball screws, 1 y axis and a Z. We want to be able to cut a 5x10 area and im wondering what kind of motors I will need to be able to travel at least 325imp cut speed. Also if it is possible to do this with emc2.

Are you sure you want ballscrews? Many plasma machines have been built with rack and pinion drives.
The large sizes typically used as well as the high feeds make ballscrews a poor choice. You need either
huge diameters of very coarse thread pitches to keep the long screws from whipping.

Probably servo motors are a good choice as you get more power per weight and sustained high
speed operation. But, lots of these machines have been built with modern steppers, too.

Jon

BigJohnT wrote:

I used timing belts on my design but sized them one size too small ...............

John

I commend you for recognizing the real problem. Most builders blame the concept and abandon belts altogether. The two most common mistakes are inadequate belt width and trying to use fabric reinforced buna-n instead of steel reinforced urethane belts. The other mistake is using a closed loop belt which effectively doubles the stretch problem.

I repaired three 10 foot traveling head surface grinders that each used a single 50mm wide belt to pull a 10HP spindle. The machines run 60-100 hours a week. The belts last 3-5 years.

No industrial plasma table that I am aware of uses ball screws. Every one I have seen or worked on had belt or rack and pinion drive. The better quality systems use double preloaded pinions on each rack to eliminate backlash.

Doug