I'm currently working on a Wire EDM setup, which I want to use for precise cutting of metal parts. Wire EDM is able to cut even thick metal parts without force using a thin wire and a high frequency arc that erodes material every time the arc ignites. It is also not as loud as typical CNC machining and does not cause vibration, so that it should be easier to reduce the noise enough for working at any time of the day.
To get a continuous arc the electrode or wire has to keep the right distance to the workpiece at any time. For keeping the arc at the right distance I wrote some code for the Marlin Firmware that measures a voltage provided by a current sensor to move the electrode towards the target position as long as the current is lower than a defined value. If the electrode touches the workpiece the current increases above the defined value and the electrode stops and moves back to where it came from until the current is again below the defined value. This gets repeated continuously until the electrode reaches the target. The electrode does that very fast at a low feedrate, so that it does not move a large distance in every direction and so it keeps the right distance at any time what leads to a stable arc.
I think with the infos about the water system, electronics and the closed loop control you should be able to build your own sinker or drill EDM machine.
Because I want to use EDM as a more silent and more precise alternative to plasma cutting and CNC milling, I need to upgrade the machine so that it is able to cut out workpieces. The current problem with that is the wear of the electrode and so I need continuous refreshing of it, for what I will need a wire EDM system.
There are some good Wire EDM designs out there and I will try to build something like that by myself in the next days and weeks.
- Deionization Filter for making the water less conductive
- Some filters in different sizes for testing
- They are used to keep the water in the reservoir clean
- Whole water system
- The lower container is filled with clean deionized water and contains an aquarium pump to pump the water through a filter
- Aquarium pump
- Outlet of the DI filter (blue tube)
- The outlet of the cleaning filter and inlet of the gear pumps with a petrol filter and a weight on it
- Tube from the upper container to the lower container
- The upper container is used to store and mount the most parts and also to collect some of the dirt from cutting that settles down on the ground
- TDS Meter to measure the conductivity on the in and outlet of the DI filter
- To check the conductivity in the system and check if the DI filter needs to be replaced
- Hand TDS Meter
- Conductivity at the EDM machine
- PWM controllers for gear pumps to control flow through DI filter and to the electrode flusher
- Gear pumps with common inlet and check valve. Because for the DI filter and electrode flusher a higher pressure is needed than aquarium pumps can provide and because diaphragm pumps are too noisy, I choosed gear pumps for this.
- DI filter
- TDS sensors on in and outlet of the DI filter
- Everything is mounted on top of the cleaning filters
- Cleaning filter
- Outlet of the EDM machine with weight
- I used paper towels to filter out most of the dirt, but while cutting they get clogged very fast.
- I think this needs an improvement, maybe some sort of continuous paper roll that slowly rolls under a waterfall into a waste bin.
- Inlet from the reservoir to the gear pumps
- The right pump goes to the DI filter
- The left pump goes to the electrode flusher
- Here you can see the cooling block for all parts that will heat up during cutting. It is placed between the gear pump and the electrode flusher
- Between two cooling elements there is an aluminum bar in which six 12V 40W heaters are placed, that are used as resistor for the arc generator circuit
- There is also a IRFP260 MOSFET placed on top of it, also from the circuit
- The temperature of the cooling block is measured with two thermistors for redundancy
- In the rare case that the cooling should fail at the time when there is a short on the workpiece what would lead to overheating of the cooling block after some time, an emergency stop would be called that would cut off the power to the arc generator circuit.
- Electrode flusher to flush out the dirt from cutting
- Outlet of the EDM machine that leads to the paper towel filter
So, that's the water system that I use for testing at the moment.