garyhlucas
Stainless
- Joined
- Oct 17, 2013
- Location
- New Jersey
I am posting here because I am trying to learn about the technical aspects of ram EDM. The hobby sites haven't answered my questions.
It occured to me the other day that my homebuilt CNC could maybe make a pretty nice EDM machine since all the homebuilt EDM machines I have seen look fairly crude. So I thought I'd list what I have to work with and get suggestions on how I might go about this. My machine is about minimill stiffness but has very precise THK ball ways and ball screws on all axis. The table does not move, it is built like a boring mill, and measures 18" x 24", the spindle moves and work envelope is an 18" cube. I have large steppers and a 1500 watt 68vdc power supply for the steppers as well as a 12 vdc 30 amp power supply which runs the heaters for the 3D printing attachment.
I have 5 stepper drivers and can run the 3D printer extruder or the lathe attachment large stepper spindle motor with the 4th axis. The machine can move quite fast, 300 ipm with no problem and is microstepped down to 0.0015mm per step with the usual caveats about microstepping. The CNC control is Mach 3. However, I also have a Do-More BRX PLC in the machine. I have high speed digital pulse outputs to 250Khz. Analog current or voltage inputs, and analog voltage or current outputs, serial, and Ethernet ports. Behind the spindle I have 0xa Tormach QC lathe tool post which makes it really easy to mount the EDM tooling, and there is the spindle for EDM drilling too.
So what am I missing to do this? It seems I can read the discharge voltage and current with the PLC and control it too, along with pulsing the output. Mach 3 might not be able to run the Z axis slow enough but I can easily switch it over to driving it from the PLC where I can go as slow as I want. The PLC is connected to the Mach 3 computer for programming and the PLC talks Modbus too so I can interface it directly to Mach 3 as well.
What voltage and current does the tool see when cutting? How slow does the Z need to be able to go? I understand flushing is very important. Is flushing done by rapiding the tool up and back again? Or is fluid just pumped around the tool? Is the 250Khz pulse rate high enough, or is a much higher rate used?
I am more of a controls guy than a CNC guy and I think this might make a nice addition to what I call the Ifactory, the personal machine shop. It is currently a vertical mill and the head can be rotated 90 degrees to use as a horizontal mill. I have a router spindle and an R8 spindle. I have a 0XA size tool post behind the spindle that holds lathe tooling so I can machine parts on the lathe bed with spindle and tail stock that bolts to the table. The lathe spindle can work as a fourth axis with a large stepper for position with substantial timing belt reduction drive. The tool post also holds the 3D printer extruder and the heated build plate attaches magnetically to the build plate. I am looking to get a small laser attachment and EDM seems like it would pretty much complete the machine.
It occured to me the other day that my homebuilt CNC could maybe make a pretty nice EDM machine since all the homebuilt EDM machines I have seen look fairly crude. So I thought I'd list what I have to work with and get suggestions on how I might go about this. My machine is about minimill stiffness but has very precise THK ball ways and ball screws on all axis. The table does not move, it is built like a boring mill, and measures 18" x 24", the spindle moves and work envelope is an 18" cube. I have large steppers and a 1500 watt 68vdc power supply for the steppers as well as a 12 vdc 30 amp power supply which runs the heaters for the 3D printing attachment.
I have 5 stepper drivers and can run the 3D printer extruder or the lathe attachment large stepper spindle motor with the 4th axis. The machine can move quite fast, 300 ipm with no problem and is microstepped down to 0.0015mm per step with the usual caveats about microstepping. The CNC control is Mach 3. However, I also have a Do-More BRX PLC in the machine. I have high speed digital pulse outputs to 250Khz. Analog current or voltage inputs, and analog voltage or current outputs, serial, and Ethernet ports. Behind the spindle I have 0xa Tormach QC lathe tool post which makes it really easy to mount the EDM tooling, and there is the spindle for EDM drilling too.
So what am I missing to do this? It seems I can read the discharge voltage and current with the PLC and control it too, along with pulsing the output. Mach 3 might not be able to run the Z axis slow enough but I can easily switch it over to driving it from the PLC where I can go as slow as I want. The PLC is connected to the Mach 3 computer for programming and the PLC talks Modbus too so I can interface it directly to Mach 3 as well.
What voltage and current does the tool see when cutting? How slow does the Z need to be able to go? I understand flushing is very important. Is flushing done by rapiding the tool up and back again? Or is fluid just pumped around the tool? Is the 250Khz pulse rate high enough, or is a much higher rate used?
I am more of a controls guy than a CNC guy and I think this might make a nice addition to what I call the Ifactory, the personal machine shop. It is currently a vertical mill and the head can be rotated 90 degrees to use as a horizontal mill. I have a router spindle and an R8 spindle. I have a 0XA size tool post behind the spindle that holds lathe tooling so I can machine parts on the lathe bed with spindle and tail stock that bolts to the table. The lathe spindle can work as a fourth axis with a large stepper for position with substantial timing belt reduction drive. The tool post also holds the 3D printer extruder and the heated build plate attaches magnetically to the build plate. I am looking to get a small laser attachment and EDM seems like it would pretty much complete the machine.