If you want to go with the auxiliary slide idea you can often pick up short linear slides off eBay for peanuts. Bolt on your torch, add a switch and the job is done. I have some nice 100mm long THK rails here that I bought for this purpose.
I have been thinking about this for some time and a while back I came up with a very different design to all of the others I have seen. First of all, you don't need or want a ball screw on Z. Z doesn't need to be hugely accurate. It needs reasonable resolution and it needs to be dirt resistant. Plasma generates a lot of very fine abrasive dust that gets everywhere and will wreck ball screws fairly quickly. My plan is to use a simple winch. Think of a drum with a coarse thread machined into it. Wind some flexible wire or heat resistant cord on the drum and control it with a stepper or servo. This is simple, dirt tolerant and provides good enough accuracy. Run the wire over a pulley at the top of the Z axis to lift the torch. The weight of the torch and slide should provide enough tension. For touch sensing, mount the pulley on a spring loaded arm with a hinge at one end and a switch at the other. As the weight comes off the cord the pulley will lift and trip the switch. Alternatively you can have a fixed pulley and a separate spring loaded pulley and switch to measure the cord tension. The main problem I can see with this setup is the possibility of the cord coming off the drum. This can happen if the cord goes slack. There are a few ways to get around this. One is to add some guides so there isn't room for the cord to lift out of the grooves. Another is to stop the machine if the touch sensing switch trips and you aren't seeking the top of the work. This is worth doing no matter what touch off mechanism you use. I have used the grooved drum setup for position measurement and have had very few problems with the cord coming off. After initial calibration they maintained surprisingly good accuaracy. > I dont think your idea is a good practical idee for a production > machine. The torch does touch off thousands of times and the loose nuts > will wear out in no time. There is nothing wrong with a well designed > floating head and in my opinion it is the best possible pactise to date. I can't see why the nut would wear. There is very little load on it when it moves on the pins. Instead of bolts you may want to use hardened pins as they can be made a better fit and will wear less. Les ------------------------------------------------------------------------------ Everyone hates slow websites. So do we. Make your web apps faster with AppDynamics Download AppDynamics Lite for free today: http://p.sf.net/sfu/appdyn_d2d_nov _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
