Which Plasma Cutter to buy?

[AndyG]

I have been doing a LOT of research into building my own 4'x4' plasma cutting table. I've just about worked out the mechanical side of things and the only question I cant seem to find a definitive answer to is... Can I use an HF pilot start inverter plasma unit ?

I have seen a lot of information that says I'll get a lot of interference from an HF unit.

I cant afford a very expensive unit such as a Hypertherm and have been looking at this unit from R-tech welding. http://www.r-techwelding.co.uk/weldi...r_R-Tech_P40HF

Would this unit be suitable if I make sure I use a local earth rod and use shielded cables to all steppers and home/limit switches etc?

I have lotts of questions but this is the main one thats bugging me at the moment,

Thanks,

Andy.

[Web Goblin]

Using an H.F. start plasma unit should not be a problem if you get your grounding correctly installed. As you say shielded cables will be a requirement. You will need to get your grounding cables back to a star point and connected to an earthing rod would be a good idea but just make sure your earthrod is installed in a position where the soil does not dry out too much.
Try to avoid any parallel paths for your grounding cables.

Regards

Ian

[John S]

I bought the 236 pound model from these people.

http://www.cut40.com/secure/

Not got it working under CNC yet as it wasn't bought for that but I did test it cutting on a piece of plate tight at the side of the CNC mill when it was air cutting a part to see if it affected it, It was fine which is far better than the old Cebora plasma which crashes everything electronic in the workshop when it runs.

John S.

[AndyG]

Thanks for the info chaps! It has helped a lot and is just what I was looking for.

I have seen the cut40 plasma demonstrated on youtube and it looks quite good for a Chinese made machine. It's like a lot of far eastern tools thats badged under a large number of brands.

Cheers for now,

Andy.

[CLAYTON]

Dear Andyg you may use HF pilot start inverter plasma unit which will work well instead of using other units here . you may need to install the shielded cables on the back side of the starting point . I hope that you will sort out your problem .

[WSD]

Its good to hear what you guys think - ive been looking at a few models now and i just get so confused. I too don't have a fortune to spend and have been looking at the £582 model on here - is this a good buy or not? :confused:

[Web Goblin]

Before you go spending your cash you need to have a good thinkabout what you are going to be cutting and how much you will be using the plasma power source. Alot of the smaller portable plasma will not have a high duty cycle so this will limit the amount of arc time you get. You might not get "hold" or "delay" contacts from the power source to connect to your cnc machine. These contacts normally allow the plasma power source to pierce through the material and ramp up the current to the set level required for the material thickness before allowing the cnc machine to start motion. Also they wont have any Arc Voltage Control systems. This allows the plasma unit to monitor the arc voltage across the plasma arc then adjust the height of the torch holder, ie the Z axis, to keep the cutting height the same. If you dont have this you will have to watch the cut continually to make sure it stays roughly the same height. If you are doing this you need a full face helmet with a good quality glass it in to stop damage to your eyes and skin from the plasma arc. Decent gloves as well. A fume extraction system is a must, plasma fumes from cutting are lethal and you should filter the fumes as well to remove particulate matter before dumping it to atmosphere. I will presume that you will be cutting air plasma/ air shield which is using compressed air for the plasma and shield gases. Your air supply needs to be oil and water free for the plasma to work correctly.
John, the Cebora plasmas were dodgy and expensive. I also remember looking at a small profile machine which sat in between two Miller snycrowelds. When they fired up the poor cnc controller went nuts due to the RF.

Ian

[John S]

Ian,
Fortunately I don't use the Cebora much, it's a "get John out the $hit machine" when I need a thick part I can't wait to get laser cut.
It will handle 16mm with ease and the odd time it's used it earns it's keep.