A few Plasma Questions.....

[Normsthename]

Hi
Last year I built my own design Steel Frame Router with a 1000mm x 600mm x 150mm Working Range.
After a few teething problems (Motors not being upto the job) etc it is now working great
When I built the Router I built it with the intention of easily being able to convert it to a plasma cutter and back again.
I have a few Questions :-

1) I want to mainly cut 1.6mm 316 grade Stainless steel, will the cut be clean? Any example pictures anybody?

2) What would be the smallest diameter hole I could cut in 1.6mm 316 grade Stainless steel.

3) What size Plasma cutter would be the best for me, it would be nice if it had the capacity to cut thicker materaials

4) I read somewhere about an interface card that uses the Z Axis to control the height & cut on the plasma, any details?

Thanks in advance

Andy

[Torchhead]

Originally Posted by Normsthename Hi 1) I want to mainly cut 1.6mm 316 grade Stainless steel, will the cut be clean? Any example pictures anybody?

The biggest problem will be discoloration and warping. Stainless warps faster than mild steel. You can get pretty good cuts especially if you use the Fine Cut consummables and have everything set right. Clean cuts are a function of several variables:
1. Clean , dry air
2. Correct feedrate
3. new consummables
4. Control of the .040 cut gap (tip to material distance)

Several commercial shops that cut a lot of SS report that having the material sitting on the surface of water (constant level water tray) ends the discoloration and a lot of the wraping and bad cut problems.

2) What would be the smallest diameter hole I could cut in 1.6mm 316 grade Stainless steel.

Well, depnds on how round and how clean you wan the cut. Anything less than and 12mm in dia will cause some problems. You need to slow the cut speed down by a large percentage on holes smaller than about 35mm.

3) What size Plasma cutter would be the best for me, it would be nice if it had the capacity to cut thicker materaials

Any of the 60A units (Hypertherm 1000 has the Fine Cut option) would do that easily and let you cut up to 1/4" without a lot of side flare.

4) I read somewhere about an interface card that uses the Z Axis to control the height & cut on the plasma, any details?

If you use MACH3 as the motion control software and our MP1000-THC it uses the Z axis as the THC "lifter" and gives you full Digital Torch Height Control with toolpath integration. You can switch back and forth between plasma and router (or oxy-acet) just by loading a different software profile.



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[Normsthename]

Thanks Torchhead for the details
Sounds like I won't be able to put the smaller holes in with a Plasma
I have attached a picture of one of the parts I want to cut out in 1.6mm 316 Stainless Steel.
The smallest holes are 5.5mm so by the sound of it, I will have to drill these out?
The larger holes are 14mm.
Do you think this would be possible with a Plasma?

Thanks

Andy

[Switcher]

See http://www.CandCNC.com/THCCompareChart.com for features of a good THC

Maybe this is the link?

http://www.candcnc.com/THCCompareChart.htm



.

[Torchhead]

Originally Posted by Normsthename Thanks Torchhead for the details Sounds like I won't be able to put the smaller holes in with a Plasma I have attached a picture of one of the parts I want to cut out in 1.6mm 316 Stainless Steel. The smallest holes are 5.5mm so by the sound of it, I will have to drill these out? The larger holes are 14mm. Do you think this would be possible with a Plasma? Thanks Andy

Andy, conventional plasma has never been considered a precision cutting operation. It works well on larger sheet stock and decorative cutting where the tolerance is not an issue. You can with trial and error get a setup that cuts cleanly and accurate within .015 BUT change any of the variables and you are back to square one.

Small holes are problematic because they have to be done slowly and maintaining the correct diameter without getting an egg shape is difficult. Fine cut consummables will let you have smaller kerfs and cleaner cuts in thinner material. It all depends on how round and how accurate (tolerances) you have to hold. The flame on a plasma is not rigid and distorts as it cuts. The faster the cut the greater the distortion. On large cuts the distortion is less percentage of the cut area and is less noticeable. If you have a 5.5MM hole and get .5 mm distortion or out of tolerance then it may be too much. Add to that than the direction of the distortion changes as you change direction and you can see why small holes present an issue.

It's fairly easy to peck a center hole with the torch and use conventional drilling to make the holes round. If the other shapes in your design don't have to mate up tightly with matching male shapes then they will cut fine.

Every tool has it's limitations. For accuracy in SS you need to have it waterjet cut or for large Qtys punched. Plasma is well suited to cutting large shapes or smaller ones where the tolerance is not critical.

[Normsthename]

Thanks Torchhead
I have been looking at the Water Tables people are using, and it seems like it would be ideal for my purpose.
Today I have been looking at the available Plasma cutters.
Some of the Plasma's use HF Start, and others use another type of trigger start.
Will the HF type interfere with the Stepper motor operation on the machine?

Andy, conventional plasma has never been considered a precision cutting operation. It works well on larger sheet stock and decorative cutting where the tolerance is not an issue. You can with trial and error get a setup that cuts cleanly and accurate within .015 BUT change any of the variables and you are back to square one.

Tolerance within 0.015" (0.38mm) would be fine for the parts I make

It's fairly easy to peck a center hole with the torch and use conventional drilling to make the holes round. If the other shapes in your design don't have to mate up tightly with matching male shapes then they will cut fine.

A lot of the holes are Cable holes etc, so not that critical.
If you can 'pilot' a hole with the plasma, and I can then drill it out that would be fine.

Every tool has it's limitations. For accuracy in SS you need to have it waterjet cut or for large Qtys punched. Plasma is well suited to cutting large shapes or smaller ones where the tolerance is not critical.

I currently have all my parts laser cut and folded on a CNC Press-Brake.
Last year I paid out approx. £7000 ($14000) on parts.
I have just bought a Fly-Press, and am having some tooling made up so I can fold the parts Just need the cutting process sorting.
You can see why I am looking for a cheap alternative!