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FIRST

Using a CNC router to cut parts from sheet materials

This article describes how to convert g-code into physical part from sheet materials (aluminium or polycarbonate).

The notes here do describe a specific application with a specific CNC Router (OMIO X8-2200L-USB) and specific controller software (Mach3Mill).

NOTE #1: "Inventor HSM" is now known as "Inventor CAM"

Pre-requisites

Before commencing this article you will need:

Hardware required to complete this process:

  • PPE ...
    • ear muffs
    • safety glasses or goggles
    • gloves
    • face mask
  • OMIO X8-2200L-USB CNC router including:
    • CNC router bed, gantry and spindle
    • CNC router control box
    • Z depth probe
    • "USB-Receiver"
    • Remote control handset
    • 4mm single flute bit
    • collet to hold 4mm bit
  • Coolant tank with pump
  • Compressor
  • Blue USB cable to connect laptop to CNC router control box
  • Laptop with Mach3Mill installed (we're using "Yogi")
  • USB Stick containing the g-code
  • Power cables to suit all of the above
  • Cleaning gear
    • Dustpan
    • Brush
    • Vacuum cleaner
    • Cloth/rag

Disposables:

  • Water for coolant tank
  • Cutting oil for mist spray
    • we use "Kool Kut 1"
    • diluted with water in a 1:30 ratio
    • Kool Kut 1 is available at Total Tools in Australia
  • Stock material, one or more of:
    • 3mm Aluminium Sheet
    • 6mm Aluminium Sheet
    • 3mm Polycarbonate Sheet
    • RHS 50mm x 25mm
    • SHS 25mm x 25mm
  • Spoil/Baseboard, one of ...
    • 19mm MDF
    • 20mm Rigid PVC Foam

Overview

The steps involved in this article can be broken into the following sections:

(a) pre-flight steps and checks

(b) CNC router setup

(c) Load g-code

(d) Kick off the initial machine run

(e) Kick off the final machine run

(f) Shut down

(g) Clean up

The sections that follow elaborate on each of these steps. The final section provides some troubleshooting hints.

Pre-flight steps and checks

Sorry, there are a lot of checks. Following this lot will keep the troubleshooting section much smaller!

1: Check that you have all of the PPE on yourself not the hook!

2: Make sure the following emergency stop locations are visible and accessible:

  • big red button on the front of CNC router control box
  • mains power wall switch for CNC router control box

3: Check baseboard:

  • if using MDF you may need to sand down and/or dry out after previous run

4: Set up stock on baseboard:

  • grab self tapping screws that are shorter than baseboard + stock
  • secure stock to baseboard using the self tapping screws
  • check that stock is secure and level

5: Check the following connections are NOT in place:

  • compressor line to misting system
  • this is not automated in our setup at this point in time

6: Check the following connections:

  • laptop connected to CNC router control box with blue USB cable
  • USB stick is plugged into laptop
  • "USB-Receiver" is plugged into the laptop
  • Z depth probe is plugged into CNC router control box

7: Check the following tooling and coolant:

  • correct router bit is in place and secure
  • adequate coolant in tank (top up with water if pump is not totally covered)
  • adequate cutting fluid in misting tank (top up with water mixed with "Kool Kut 1" in 30:1 ratio if tank is not at least half full)

8: Check for mains power to:

  • CNC router control box
  • laptop
  • compressor
  • coolant pump

9: Switch on:

  • laptop
  • compressor
  • CNC router control box (both green and red switches need to be on)
  • coolant pump

10: Software checks:

  • login to laptop as Admin user
  • check for "Mach 3 Mill" desktop icon and double click
  • window will open, check that text "Emergency Mode Active" is reported in the ticker tape next to the big red "RESET" button 

CNC router setup

1: Login as admin user on the laptop

2: If "Mach 3 Mill" is not already running, then start using the desktop icon

3: Select the "RESET" button on the left of the screen to clear the text message "Emergency Mode Active"

4: Check the bed area for spare material, tools etc ... we are about to move the CNC router head for the first time so pay particular attention for misting bottle if that is perched on the CNC router bed and also any cables / tubing that may have shifted when topping up fluids etc.

5: On the remote press and release button 1 once - the head will move to machine home.

6: Wait for the home process to complete, this may take a minute or two as it works through each of the XYZ axes

7: In "Mach 3 Mill" make sure the "Soft Limits" button has a GREEN box around it and the "Machine Coordinates" button has a BLACK box around it

8: In this configuration the coordinates being displayed are the XYZ working coordinates

9: On the remote press X+, X-, Y+ and Y- buttons to manually jog the head to the front left of the stock (roughly where you plan to start cutting)

10: Place the Z-probe on the top surface of the stock directly underneath the bit

11: Connect the crocodile clip to the router bit

12: Hold the z-probe in place by firmly pressing down on it

13: While still holding down the Z-probe on the remote press button 3

14: The head will slowly move down until it touches the sensor and will then back away 10mm

15: On the laptop, check that the Z axis value should be reported as 31.28 - this is because "Mach 3 Mill" has been pre-configured with the z-probe height which is 21.28

16: The controller now knows that the top surface of the stock is 31.28 mm below the tip of the bit.

17: You can confirm this if you carefully jog the head down using the Z+ button on the remote so that the bit is almost touching the stock surface. At this point the Z-axis on Mach 3 Mill should be reported as zero (or very close to zero)

18: Now use the X+, X-, Y+ and Y- buttons on the remote to position the head to a sensible start position to commence the cut

19: On the remote press button 4 then press button 5

20: Check that X and Y in Mach 3 Mill are both now reported as exactly zero

Load g-code

1: In Autodesk Inventor, open IPT file for the part to be cut and double check that:

  • the XYZ origin is on the front left corner of the stock
  • X is increasing from left to right
  • Y is increasing from front to back
  • Z is increasing from bottom to top

2: Generate the NC files "run01" and "run02" as described in the article ""

3: Note that the default file location for these NC files is: "%LOCALAPPDATA%\Inventor HSM\nc" (see note#1)

4: Copy the files to a USB stick and transfer USB stick to the CNC router laptop

5: Copy files onto desktop of the laptop

6: In "Mach 3 Mill" select the "Load G-Code" button

7: Navigate to the run01 NC file and select "open"

8: The G-code will now be displayed in the top left of "Mach 3 Mill"

Kick off the initial machine run

We are ready to commence the cutting. Note that the misting system is manually controlled at this time so the first two steps here need to be completed at the same time or as close as possible!

1: In "Mach 3 Mill" press the "Cycle Start" button

2: Connect the pneumatic tube for the misting system to the compressor

3: Wait while the magic happens, at the end of the run the head will stop and the spindle will wind down and stop

4: Disconnect the pneumatic tube for the misting system from the compressor

5: Jog the head away from your part using the X+, X-, Y+ and Y- buttons on the remote

Kick off the final machine run

1: Secure the part to the baseboard using screws in at least two of the holes cut in Run01

2: Now repeat the steps in the previous two sections for Run02

Shut down

1: Turn off both green and red switch on the CNC router control box

2: Turn off power to the compressor

3: Turn off power to the coolant pump

4: Power down the laptop

5: Release pressure from the compressor

Clean up

1: Sweep or vacuum off the swarf from the CNC router bed

2: If necessary dry off the baseboard and remaining stock that is on CNC router bed

3: If this is the last cut on this stock then unscrew from the baseboard and stow in the supply cupboard ;)

4: Sweep and/or vacuum the floor around the CNC router

5: Turn off the lights, close the door . . .

Trouble shooting

This section suggests some things to check for if OMIO is behaving unexpectedly. Unexpected behaviour includes but is not limited to:

* reset being triggered during Z-zero procedure (e.g. head lowers to Z-probe plate and stops but fails to move up)

* during cutting process the head moves to a random location

Suggested checks are:

1: Check temperature of the head - if too hot, is the coolant level good and circulating?

2: Check misting system - is enough mist being generated? Is nozzle clogged? Is tank empty?

3: Check blue USB is routed as far as possible away from OMIO the control unit - there appear to be EMF issues from the inverter inside the left side of the controller box.

4: Check limit switches. Is there and swarf under the mechanical lever of any the limit switches? Is there swarf between connection points and/or OMIO frame?

5: Check "status" report (bottom center) of the Mach3CNC window on the laptop - this may provide some indication of the problem (e.g. limit switch triggering reset)

6: Check "Task Manager" on laptop. Are there any unnecessary processes that are consuming CPU or memory or disk either continuously or periodically? For example, Windows Defender and Virus Scanning software may be periodically placing a load on the disk IO which can cause the OMIO to pause due to lack of data.