Can I do This?

[Kipper]

Only having given nested .DXF's to the laser cutters in the past....I decided to cut them out of the loop and build a plasma cutter for my "things" (cutbacks you know!) Sooooo what's with this here THC? I've tried one cut after setting the machine as I would my mill or router....result was a nice round circle of 25mm diameter....without any type of THC. Next I decided I wanted to go one step further and have the plasma "engage" as it touches the sheet to be cut automatically...hence my finding the THC talked about quite often... So to the point at last :naughty: Can I use a floating Z and have the trigger make a contact on shiny metal sheet using the ball tranfer units I'm using? or should I keep the microswitch I used for the test set at a predetermined depth?

Advantages of a THC would be?

It has six legs because that was the price break

[jimcolt]

Roller ball plate riders for plasma cutting have been used for many years to control the torch to work distance of a plasma torch. They are still used extensively on plasma machines used for cutting thin plate with low accuracy requirements such as HVAC ductwork.

The biggest problem with this type of height control for plasma is that there is no IHS (initial height sensor) for setting a higher pierce height. Without pierce height (which is typically 1.5 to 2 times the recomended cut height) consumable life is very short. A good THC will find the surface of the plate before each cut, rise to the pierce height, fire the torch, as soon as pierce is complete will index down to cut height, and will then use AVC (arc voltage control) feedback to maintain proper height without contacting the plate during the cut. On plate thicker than 3/16" (4.5 mm) you must pierce at a higher distance from the plate as compared to cut height...or damage to the nozzle and shield will occur.

Other drawbacks with the rollerball plate rider:

-scratching the surface of the plate
-physically moving the plate
-buildup of pierce splatter on rollers requires attention

The WA Whitney punch plasma uses a roller ball plate rider, but always punches a hole so the plasma can edge start on thicker materials.

Jim Colt

[Kipper]

Thanks for the explanation Jim! I'm going to muddle along a little with this system....If it works the Plasma cutter will be upgraded and a "proper" THC system may very well be in order....One of the items this has to be able to cut can't stand too many scratches!

:beer: