Plasma Torch Height Controller - DigiCut Plasma THC 1.4

Digicut Plasma THC 1.4


Fully standalone Plasma Torch Height Control
Controls the Z axis directly and independently of the CNC Control
Microcontroller based digital design
Seperate Voltage Divider and control units to avoid Plasma Noise. Works with HF pilot based Plasma Power Sources
Stepper / Servo motor based Z Axis control for higher precision and higher resolution with acceleration. Does not offer DC based motor control.
Dual Speed Initial Height Sensing for both Ohmic and Floating switch based Ihs.
Advanced PID loop for dynamic correction during Automatic mode
Adjustable pierce height and cut height in 0.1 mm intervals
Dynamically adjust pierce height
Dual IHS - Ohmic and Proxy Switch based. (floating)
1 Volt accuracy (+- 0.5v )
Settable pierce delay in 0.1 sec intervals
Able to cut Currogated Steel

User Adjustable dead band adjustable in 0.5 volt to avoid over corrections
User Adjustable AVC Response time
User settable Proxy switch based offset for Floating switch IHS
User adjustable Z Axis speed with acceleration and de-acceleration for smooth operation and to reduce cycle time
User definable slow speed for Ohmic IHS to protect plasma torch, shield and nozzle.
User definable speed changeover location
User definable partial raise height to reduce the cycle time
User definable full retract delay to protect the plasma torch from accidental damages during plate loading / unloading
User definable correction speed during Automatic mode
Full diagnosis of Input and Output signals for quick interfacing

Several user settable parameters.
4 Line (20x4) Backlight LCD display

Dials avaialble to quickly set
    Pierce delay
    Pierce height
    Cut Height

Intutive HMI for
     Single click Initial Height checking
    Arc Output testing

6 LED's for the easyily checking system status.
1. Cut Signal
2. Up Motion
3. Down Motion
4. Plasma start
5. Motion Start
6. Auto / Manual

General Working principle of our Plasma Arc Voltage THC

1. CNC Controller sends a start signal to the THC unit.

2. The unit initiates its internal routine, which will find where the Material (plate to be cut) is (Called IHS: Initial height sensing) by loweing the torch until Ohmic Contact is established or Floating switch is triggered, then raises to pierce height. Also there is compensation for preset height for floating switch which will be added to the raising of torch. The lowering is done at a lower speed and raising is done at full speed.

3. The THC sends Plasma Start signal to the Plasma unit to start the plasma arc after IHS is completed.

4. The THC waits until "pierce delay" then returns to "cutting height", starts reading voltage from the Plasma Unit, Once a sufficient voltage is reached the THC Outputs ARC OK signal to the CNC Controller that it is set and ready for motion or job start. The THC can also take ARC OK feedback signal from the Plasma Power Supply (if available).

5. The THC then continuously reads the DC voltage and compares it with the Arc voltage [set by user] then raises the torch if actual voltage is less than set voltage or lowers the torch if actual voltage is greater than set voltage accordingly until START signal is available from the CNC Controller. If the voltage gap is suddenly more than ARC VOLTAGE CONTROL LIMIT volts it performs nothing until normal voltage range is resumed (kerf crossing etc..)

6. If the Corner signal is sent by Controller (or Enable signal withdrawn) the THC stops raising / lowering the torch for the particular time.
7. If ohmic contact or collision (signal) is detected during cutting (START+ARC OK) the torch is immediately raised to avoid nozzle damage.

8. Once start signal is withdrawn by CNC Controller (means cut is finished), the THC waits until Retraction Delay and then retracts torch to "Partial raise height" at full speed. The THC then waits for Torch retract delay and if START signal is not received raises torch to the top most position (until top limit is triggered) (The THC remembers the distance travelled so that it can speed up next IHS). Partial raise height is used to avoid delay in next pierce.

Remembering height logic: The idea to remember the distance travelled to the parking position or top position is that during next IHS the torch shall be lowered at full speed until 90% of the last travelled height and then the remaining 10% be lowered at a much slower speed.

Also following features are available:

1. When initial power is applied to the THC, the thc moves the torch to the top most position available. (until up limit triggered)
2. At all times when start signal is available from controller the HMI displays the actual voltage and the set voltage, up down indicators when the motor is in motion and the actual distance in mm of the motor from the plate. It also show ARC ON.

3. ARC OK is withdrawn on collision input being detected. HMI displays collision.

4. The system is able to control a stepper / servo motor using positioning mode and is able to issue pulses at the minimum rate of 10k pulses / second.

5. When user presses the IHS button IHS [Initial Height Sensing ] operation takes place. After HIS is complete the torch retracts back to partial retract height after a delay of 5 seconds.

6. If the user presses the AUTO button the auto operation of THC start's / stop's. The indication of this is shown via a LED. If auto is disabled automatic THC corrections would not take place. All other operations would continue as normal.

User settings – POT’s (Dials)

* Arc Voltage from 100 to 250 volts in .1 volt increments using a POT
* Pierce height 2 to 5mm increments in .1mm intervals
* Pierce delay (time before torch moves to the cutting height) 0 to 3 seconds settable in .1 increments.
Above three settings are controlled via 3 pots (Dials)

Following settings are available in our THC

* Manual travel speed mm / sec. 10 to 100mm / second settable in 1mm intervals
* Plate sense speed during initial height setting (IHS)
* height compensation for floating switch. 0 to 10 mm settable in .05 increments using a POT
* Cutting height (torch moves to the cutting height after the pierce time is complete but before the arc voltage control (AVC) mode is activated). 0 to 5mm settable in 0.05 increments.
* Minimum step count. The minimum number of steps that are issued to the motor at a time. (for motor step output. e.g. 10)
* Partial raise height (retract distance from the last cutting height). 15 to 100mm settable in 1mm increments
* Torch retract delay. The time that the THC waits until it retracts the torch completely (until the up limit is triggered). 0 to 120 seconds settable in 1 sec interval.
* Corner AVC delay (delay time from the removal of a corner AVC disable signal and the resumption of arc voltage control)
* High to low speed crossover point during IHS. The position in % at which the IHS speed is lowered. 50 to 95 % settable in 1% increments
* High speed: 10 to 100 mm / second settable in 1mm intervals
* low speed: 10 to 100mm / second settable in 1mm intervals
* Retraction Delay. 0 to 2 seconds settable in .1 second interval.
* AVC Average Count: The number of voltage reading to take and average before giving up/down to the motor.
* ARC VOLTAGE CONTROL LIMIT: Settable voltage 0 to 40 volts during in 1 volt intervals.
* Resolution: the amount of motion achieved with 1 step output to the motor. 0.0025 to 0.01 settable in increments of 0.0001

User settings are written to EEPROM on any changes done by user.

This product is developed by NT Engineers, Nasik. Proudly made in India.

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