Standalone Torch Height Controller for CNC Plasma Cutting

Hale Design Tech - Torch Height Controller

Added Video Build Guide and Q&A. See Below. 3/3/21

Arduino based THC that reads plasma cutter voltage and send Up and Down signals to Plasma Torch Actuator to adjust voltage to target value. Plus a bonus Breakaway Torch Holder Design

How to Build Video:







Description
Aim is to create a 3D printed low cost and easy to use Torch Height Controller with off the shelf parts, simple easy to read code and as little electronics tinkering as possible. This is a standalone type of THC so it requires an NEMA23 actuator to move the torch independent of the CNC machines controller. If you interface this THC with your CNC Machine please post how you did it!

The unknown we are trying to solve for here is the Torch Height from the Workpiece measurement. It's important for a plasma arc to be stable and be a set height from the workpiece to be cut. The main reason for this is the plasma arc will cut a bevel on the side walls if the height is not set right or crash into the workpiece... This is because the plasma arc is not like a laser with straight edges but more like an egg. Making the problem worse is the fact the metal can warp and contort when a hot plasma arc cuts into it. Using the Arc Voltage is a good way to estimate the distance to the workpiece from the torch head.

The proportional correlation is the longer the arc the higher the voltage. So, we can measure the plasma voltage and feed that into a PID Algorithm to calculate the torch height to change the voltage to a setpoint. It is unwise to measure the Arc Voltage Directly off the plasma torch because the levels there can be deadly. Most CNC ready Plasma Cutters on the market have 50:1 - 16:1 arc voltage dividers built right into the machine. If yours doesn't have this then you will need to do surgery and add a voltage divider circuit to your plasma cutter... Check the Technical Specs of your plasma cutter: Don't Die.

This is completely my own design in not based on any other torch height controller.

Donate:

• HaleDesignTech is creating Technology and Design | Patreon

More info:

• About Hale Design Tech: http://hdt.xyz

3rd Party software used

• Auduino IDE
• FastPID Library
• EasyNextionLibrary
• AccelStepper
• Nextion Editor

Build Guide:

• Video Build Guide:
• Wiring Schematic
• Model STL Files and Software. See Attachments Section Below
  
• THC Fusion 360 Design File: Fusion
  
• Breakaway Holder Fusion 360 Design File: Fusion
  
• Software: HaleDesign/TorchHeightController

known Issues:

• Needs Dust filtering
• Connections rushed and could be better
• Needs raw arc voltage to 50:1 converter and isolation for safety
• Return home after cut finish ( if not could exceed actuator limit ) #! This has been fixed, sketch upload to gethub
• Movement screen some buttons display reversed ( dang it copy and paste ) #! This has been fixed, sketch upload to gethub