Monday, March 30, 2009
I am also working on a CNC table which I will document on hear as soon as I can. It is going to be a 4'x4' table with dual drives. I plan on attaching my laser a router and plasma/Oxy-fuel for the heads. I have wrote my own control system for an automated drill a while back I will modify to control this system. The software was written on linux using a real time kernel. All loop calculations are done in software. I am using a Mesa 4I65 with some custom FPGA code programmed on it to control IO and ADC/DAC's. The drill software was only a single linear axis with a programmable spindle speed so programming the arcs on dual axis is going to be the fun part. Pic of the drill below..
Anyone have expericence writing velocity profilers for more than 1 axis? I think I figured out how to do it but I would like to discuss this with someone who has experience in the field. I would like to program it for 3 axis motion so I can do some 3D routing. I thought about just using a CNC program like EMC but I like the experience I get when trying to do these things on my own.
I just stopped by the pipe place today and picked up all the couplings I need. I also picked up all the tubing as well. Next time I go to work on a plasma table I will cut up the blocks i need for the mounts and start machining them. This project has been on the back burner for a while due to money and life getting in the way but I will get it done one day. My final plan is to have it run for an entire day without over heating or loosing mirror alignment. Then mount it to a CNC table. I have been collecting parts for my CNC table, drew up some plans and have a few controllers lying around which will work great for this….. One Day…..
On a side note I tried adding a little extra CO2 to the mix and the increase in power was noticable. I was removing the gas line and sticking it into a CO2 bottle quickly so I know I was most likely sucking in O2 & N2 at the same time. If I actually properly increase the mix I can just imagine the power I will get….
Here is a idea I have to try to make the laser more rigid.
In this design I split the tube so I can have the vacuum in the center and gas inlets on the end. This will help cool the gas as it effectively cuts the distance the gas travels in the tube in half. I also had a couple ideas to convert this to a fast flow laser in the future so I increased the diameter of the gas and vacuum hoses to allow increased flow If I ever want to. The new design is totally removable and the mirror mounts are sturdily mounted to a piece of steel. I don’t know if I will stick with an I beam but you get the idea.
I have removed the water jacket and removed the epoxy from the heads. To seal the laser tube to the heads I have placed an o-ring on the od of the tube. I then mounted the heads to a 4×4 wood block and strapped them down tight. It’s pretty crappy but It works very well. I have also since acquired a 15Kv/60mA NST. This seems to effectively double the output power but damn the tube gets hot quick. I have finished one head of the cooling jacket but haven’t had time for the other.
Well so much for 3rd times a charm. After I attached the coolant lines and pumped water into the cooling jacket the plasma just stops. That tells me it is transferring through the water, the other give away was water on the rear mirror. Damn…
So I decided on a solution which will work guaranteed, maybe I shouldn’t use that word… should work. I removed the end caps put them back on the lathe and placed an o-ring on the inner diameter against the discharge tube. I will make a separate water insulator totally isolated from the end caps and use o-rings to seal it against the discharge tube. This way there is no connection between the water and end caps other than a piece of glass.
Well now that I have actually got this thing to work I need to fix a coulpe things. First of all the flow regulator has to go. I just assembled a pressure regulator from pieces I had lying around and will give that a shot when I get home. The mirror alignment issue is quite annoying. I am going to build a mount from steel and strap the tube down by the mirror insulators. I am also going to try using spring loaded mirror mounts to try to keep a more constant pressure on them and also reduce the sensitivity of the screw adjustment. Third I havn’t pressure tested the system with water yet. I just picked up the final pieces I need to finish that part and will try it soon.
I have called about getting a proper sized transformer for this tube so I will be able to run it at it’s full 60mA capability. I am also trying to source some high voltage rectifier diodes to try running this on DC, I already have a suitable sized filter capacitor bank rated at 30kV for the job aswell.
I have a variac which will allow me to adjust the output. I’m not sure how well adjusting the voltage with a variac will work while still runnning AC. The arc seems to just barly start at 15kV and with a reduced voltage and a zero cross it may not restart. Running DC should be fine although, once the arc is initiaded the DC current should keep the path ionized as the voltage is dropped.