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Silent CNC - Wire EDM Machine

Cut metal parts precise and silent using Wire EDM

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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.






  • Marlin Feature for Closed Loop Control

    Dominik Meffert01/09/2022 at 23:36 0 comments

    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.

    Here is the code that I wrote:

    https://github.com/DerM4209/Marlin_ECM_EDM_Mode

    If you are good at coding and want to integrate this feature into the Marlin Firmware, it would be nice if you could help me to clean up the code, to make that possible:

    https://github.com/MarlinFirmware/Marlin/issues/22849

    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.

    I will keep you updated....

  • Arc Generator Circuit

    Dominik Meffert01/09/2022 at 21:51 0 comments

    Here is the circuit that I used for creating the EDM arc:

    I only used parts that you can buy as a whole, so that you only have to connect them with wires for building this circuit.

    Here are the parts that I used:

    Connected to 230VAC:

    - 60V 10A power supply

    - 12V 5A power supply

    - SSR

    Connected to 60VDC:

    - 6x 12V 40W heating cartridge

    - ACS712 current sensor

    - 100V 100uF "low ESR" capacitor

    - IRFP260 MOSFET

    - XL7015 step down converter

    Connected to 12VDC from XL7015:

    - 12V fan

    - IRF520 module

    - 10k resistor across V+ and V- of the IRF520 module

    - LM2596

    Connected to 5VDC:

    - Arduino Nano

    Connected to Arduino Nano:

    - D9 connected to signal pin of IRF520 module, which is connected to the gate of the IRFP260 MOSFET

    Connected to 12VDC from PSU:

    - Arduino Mega & Ramps 1.6 plus

    Connected to Ramps 1.6 plus:

    - SSR on pin D65 and GND

    - 12V fan

    - thermistor on T0

    - thermistor on T1

    - ACS712 on 5V, GND and T2

    The Arduino Nano is used to switch the IRFP260 at a high frequency.

    Here is the code for it:

    #define PWM 9
    #include <TimerOne.h>
    
    void setup()
    {
      pinMode(PWM, OUTPUT);
      Timer1.initialize(100);  //100us = 10khz
      Timer1.pwm(PWM, 800);    // 0 to 1023
    }
    
    void loop()
    {
      // do nothing
    }

    And that's the whole circuit.

  • The Water System

    Dominik Meffert01/09/2022 at 11:58 0 comments

    Here are some pictures of the water system:

    - 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

    - It has an outlet that leads to the lower container

    - 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

    - I inserted just one at the time

    - TDS sensors for in and outlet

    - Flow sensor for the cleaning filter to check if the filter needs to be replaced

    - 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.

    - Plug for the aquarium pump and power supplys for the gear pumps

    - 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. 

    For now it's ok, but if I cut more parts in the future it will likely need some improvements to filter out more dirt before the filters need replacement.

  • Hi, Everyone...

    Dominik Meffert01/08/2022 at 19:56 0 comments

    Hi,

    sorry for being so quite about this project.

    I'm working on it for quite a while, but first I wanted to make sure that I can get the critical parts to work which could have lead to failure like:

    - the water system

    - the arc generator circuit

    - the Marlin feature for motion control

    Now it can be used for sinker EDM or EDM drilling without a problem and I'm currently working on Wire EDM for precisely cutting metal parts.

    I will post a description of all parts that I've got so far and if you are interested in testing it out or if you need more infos, let me know.

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