Corner slow down for plasma, laseroxy fuel and waterjet cutting?

How can I get some kind of corner slowdown in Mach3?

Peter

write it into your code?
Hood

Hi

I cut with plasma, and I want constant speed - better cuts. All other cuts should also be better with constant speed (laser,water ...).
Can you tell why do you want so slow down ?

Thanks

Hi ftomazz,

You say you cut plasma.  How thick are you cutting?

Yes keeping the travel speed constant is critical.  But  this is only noticable really on the thicker steels,  ie the thicker you go the more obvious it becomes.

Plasma, abrasive waterjet, laser and oxy are all what you would call a flexable tool.  To illustrate it more clearly, imagine squeezing out some honey out of a squeeze bottle on your toast.  Now imagine you are a cutting machine, and move in the shape of a square.

You will find that when you go to each corner you will have to wait for the "lag" of the honey to catch up to that corner, yeah.  Now imagine using plasma or waterjet but you are cutting say 1" thick steel.  What will happed is the top surface of the plate will cut spot on and the square will be perfect.  But underneath on the bottom side the same corners will become radius corners because the plasma at the bootom has not yet gotton to the corner when all of a sudden the machine changes direction.  Yes the top has got there but the bottom has not.

On thin sheet steel this is not really an issue., but on thicker plate it becomes a pain in the A**.  Even when just cutting a radius, the top of the part will be accurate but the bottom will not.

So yeah, that's why you would want a "corner slowdown feature", but if you havent the need for it, don't worry about it.  It is just that I'd like to start one day making a few cutting machines and this would be a feature that I would definantly need.

Peter

I cut up to 16mm (0.62")
After it the cut turns bad, but I have cutted 20mm.
Normally I get better results if I use a constant speed, but as you say in corners the botton stays behind of the top as thickness grows. Normally I lower the speed of cut of all the piece (all the gcode) not only in corners, if you get behind in corners then it means that you are getting behind in the rest of the cut, but for example, you do not notice it because you are on a straight line.

Filipe

If you slow the whole g code down, technicaly you are not traveling as fast as you could along the straights.  Therefore your parts throughput per hour will be much lower.  Also the slower you go, the wider the kerf.

Still would be a nice feature to have, rather than editing every corner in gcode.

I see thinks in a different form than you.

For me a cut should be as close to have 90º in relation to the face of cut, this is: when you are cutting in a XY position in the upper plate, you should also have the bottom cut at that position at the same time (or with a very slow gap of time - only enough for the energy of the plasma or the flame reaches the bottom plate). If you have this, then you will have it on straight lines, corners, anywhere and you will want constant speed.

See below:

TOP PLATE
   ||||||        |||||||
 ///////         ||||||| (Desired 90º)
//////           |||||||
BOTTOM PLATE

You can have this with a slower feedrate. But it is how you said: "Therefore your parts throughput per hour will be much lower"
But that is easy to solve: Invest in a higher AMP plasma, if you are using plasma.
As an example, with my 100A plasma I cut fine 12mm (1/2") at 500mm/min. It is not fast, but the result is good.

Filipe

Yes I agree a cut should be as close to 90degrees as possible.  Yeah using a bigger powered plasma is another way around it, then you can even to an oxygen plasma and use Hi def plasma etc etc.  Anything is possible  with $$$$$$$$$$$$$.

And then if you say you cut at 500mm/min and the result is acceptable then it suits you fine.  Just the next person might not be happy with the result.  Really in my opinion after about 3/8" to 1/2" I would start to use an oxy if I was cutting that thickness and more.

What machine do you use?

Lincoln electric PC100 (5-6 years old now)

Very good investment, one of the best in my workshop. Made in Italy (broken 3 times - I only had to replace diodes inside of it)
For 12mm I would use plasma for sure, better result and much less expensive, less dangerous, never have to replace bottles ...
For sure plasma.