bdring wrote:While I want to be able to support a really cheap plasma as an option, I am thinking about going with the Hypertherm Powermax 45 with the machine torch option. It has a very good reputation and brings out all the controls necessary for a CNC system onto a connector. Most cheaper systems you have to do some serious hacking. I like the machine style torch too.
The torch has a built in rack, but I cannot find any decent dimensions or specs on it. It would be cool to use the rack, but a more universal Z might be a better idea.
Powermax45mechanizedtorch.jpg
HYP088012.jpg
I really don't see cutting anything thicker than 1/4", so it should be plenty powerful.
I have heard the cheap harbor freight type plasma have come a long way recently and have a decent pilot arc start and don't blow out all the electronics in the room every time they start anymore.
good choice on the Hypertherm. I used to be a service tech for welders and plasma equipment. Hypertherm is still made here in the US by an employee owned company. They really make the best machine out there.
A friend has a Hypertherm Max 200 for a cnc machine, though that might be too big for you! It will cut 2" steel.
The torch is made to pretty standard specs on the OD and the pitch of the rack. They are, for the most part, interchangeable with Oxy-acet torch heads for gas burning. It is mainly used for adjusting the torch when you set it to a 45 or something to cut a bevel. Also us used for gross height adjustment, say you need to cut a piece in a structural shape piece of steel.
Most lifters use a generic ball screw, nothing fancy, just the cheap black rolled screws. One other thing a lot of people forget is a collision stop. This stops the machine if the torch runs into something, which can save a lot of money in the long run. They are very easy to build. The simplest uses air. Basically two plates are sandwiched together with three steel ball in a triangle. The balls (Or cones) are attached to one plate. On the other plate there are holes with an o-ring seal on the surface where the balls or cones sit into creating valves. The holes are all paralleled together by either small hoses or the plate is drilled to create a manifold. The two plates are held together with a through bolt, spring and a nut to adjust the tension. This all comes together to create something like a touch probe for a cnc machine but pneumatic. On the line that feeds the 3 valves is a low pressure regulator and a pressure switch. The switch is just a simple on/off that opens at 1 or 2 psi and the regulator is set just above the pressure needed to close the switch.
Operation is simple. During normal operation all the valves are sealed. If the torch is hit from any direction one or more of the valves are opened and there is a pressure drop at the switch which opens and triggers a stop.
This can also be used to help set the initial height. The letter drops the torch down till it senses a touch with the collision detection and then moves it up a set distance. Some of the commercial height controllers are very, very simple. They are nothing more than a DC motor on the lifter screw. The control box after touch off just sends power to the motor for a short predetermined period lifting the torch. The actual distance is not very critical. Then the torch fires and the box just uses a comparator to control the motor up and down. There is a basic filter to smooth out the movement and some thumbwheel pots on the front to set the voltage for the comparator. Often you do need to install a voltage divider in the plasma cutter which is nothing more than a power resistor and a filter cap.