How to use the CNC Router

Training Requirements

Before operating the ShopBot CNC machine, make sure you have passed the CNC Router Certification Course and had an in-person CNC training. Contact soatechdesk@utexas.edu to find out more.

Revision Date

Guide last updated 06 Mar 2025 . This is an interim revision for the Spring.

Troubleshooting

Solutions to common troubleshooting issues are located at the last page of this guide or soa.utexas.edu/cnc

Command Quick Reference

Command	Function	Example of use
C1	Automatic Tool Changer (CNC #2 ONLY)	Chooses a new bit (1-9) from the Tool list.
C2	Z-axis Calibration (CNC #1 ONLY)	Calibrate the Z-axis for the bit with the help of the Z-zero plate.
C3	Home Calibration	Carriage will 'Home' itself to 0,0
C5	Spindle Warm-Up Sequence	Spindle will cycle from low, med, high to warm-up, Takes 6-Minutes. Only required for the first cut of the day. If others are using the CNC prior to you; this has already been done.
J2	Dual-Axis Jog (X,Y)	Jogs the carriage by 2-axis, using the format X-axis then Y-axis Example: enter 'j2 12, 24' to send the carriage to 12" on the X-axis and 24" on the Y-axis
JX \| JY \| JZ	Single-Axis Jog (X, Y, OR Z)	Jogs the carriage by 1-axis, specify which axis by 'JX' or 'JY' or 'JZ'
Z2	Sets temporary 'Home' position	Change the 0,0 reference point from the default corner to the current location of the carriage.
JH	Jog Home	Moves the carriage to the designated 'home' position from any point.
FP	File Part Load	Opens a ShopBot.sbt file to run from the start. (default)
FG	File Load in Goto/Line mode	Opens a ShopBot.sbt file to run from a specified line. For use when restarting a failed/paused job part way through. (additional troubleshooting on last page)
TR	RPM Spindle Controller	When this window is open the spindle will be able to read the RPM from your file.

Input Quick Reference

Input	Function	Example of use
1	Aluminum Z-plate	*Only on CNC 1*; for manual Z-axis calibration
2	X-axis Proxy	Proximity sensor for X-axis
3	Y-axis Proxy	Proximity sensor for Y-axis
4	Emergency Stop Button	Big red Emergency STOP button located above the workstation
5	ATC Z-plate	Only on CNC 2; for automatic tool changer Z-axis calibration

ShopBot CNC Process

Double-check that the bit you are using is the exact type of bit mentioned in the CNC Templates page. If you don’t use the right bit, your part will not come out correctly.
The ShopBot CNC will perform ANY command given without question. It is important that YOU question every command to ensure no damage is done to the machine or to the surrounding shop patrons.

Part 1: Machine Calibration

Sign-in to the CNC Workstation using your EID credentials
Clear the CNC bed off to ensure no collisions occur
Ensure that the brush is magnetically attached to the end of the CNC router
Ensure that the dust collection gate is open and clear of obstructions; feel for airflow to ensure dust collection system is working
Turn on the ShopBot using the red switch on the control box
Press the blue, reset button (middle) on the ShopBot pendant located at the workstation
Check the fan above the spindle and ensure that it is powered on
On the workstation, launch the ShopBot 3 program from the desktop or search 'sb3' on the start menu

Next, perform the homing calibration; this process differs depending on which machine you're on.

CNC 1

CNC 2

Ask a Build Lab staff member to install your router bit
Enter command 'C3'
1. ShopBot will home in the X-axis and Y-axis
Place the aluminum plate on the table underneath the spindle
Enter command 'C2'
1. ShopBot will home in the Z-axis
ShopBot is now homed

Open the keypad
1. Jog the Z axis up and remove the PVC pipe from underneath
Enter command 'C3'
1. The software will tell you that there is no tool loaded, hit Enter
2. ShopBot will home in the X-axis, Y-axis and Z-axis automatically
Enter command 'CN' then '72' hit Enter
1. Enter the tool number that you will be using for your file
2. If you need to zero another bit, enter 'Y' otherwise, enter 'N'
  1. Enter the next tool number
  2. Repeat until all tools that your file will use have been zeroed
ShopBot is now homed

Enter command 'JZ 4' then 'JX 80' to jog the spindle to a safe location in preparation for loading your stock material
Enter command 'TR' to open the auto RPM Spindle Control window

Part 2: Spindle Warm Up Sequence

The operator is responsible for ensuring that the warm up sequence has been ran at least once that day. If the sequence has already been ran, you may skip to 'Part 3: Loading Stock Material'

The ShopBot CNC MUST go through the spindle warm up sequence to prevent damage to the spindle.
This process takes 9 minutes and only needs to be done once per day.
1. Enter command 'C5' to start the spindle calibration routine
2. A dialogue box will pop up asking you to start the router/spindle with 'start' button; DO NOTHING and proceed to next step
3. Press the green, start button (right) on the ShopBot pendant located at the workstation to turn the spindle on
4. Verify VISUALLY that the bit is now rotating in the spindle
5. Click 'Yes/OK' to start the spindle warm up sequence
6. Once the operation is complete, proceed to the next step

Part 3: Loading Stock Material

Stock material should be at least 20" x 20" or larger in size for the vacuum table to perform correctly.
Smaller footprints will require an additional plywood sheet be mounted beneath your stock to create a larger surface space for the vacuum table.

Place your stock material on the home position 0,0 reference point
Ensure that the bleeder valve is OPEN to relieve pressure from the vacuum system
Open/Close the appropriate zones for your stock material, ensuring uncovered zones are turned off at the ball valve to provide the best vacuum hold down to your stock.
Turn on the vacuum table with the red switch on the blower control box mounted to the wall
Ensure that 1 or more zones are open, then close the bleeder valve; failure to perform this action correctly will result in damage to the blower motor
Give your stock material a solid push to ensure that it is held down tight with the vacuum table suction
1. Use the provided airflow redirect sheets stored against the wall to block off and redirect airflow to your stock
If your stock material budges after the last step, you should redo the steps for 'Part 3: Loading Stock Material'

Part 4: Running a Job

Download your ShopBot job file or transfer it from a USB drive and save the file to the desktop to ensure that no errors occur during the operation.

Ensure that your file is saved locally to the desktop
Enter command 'FP' to load your file
A yellow notepad window will appear, you can ignore this and click the green 'START' button on screen
Pay extra close attention to what the dialog boxes tell you on these next steps
1. If a box pops up asking if the right tool is in the spindle; verify that it is and click 'Yes/OK'
2. If a box pops up asking if you have zeroed the bit; click 'Yes/OK'
3. If a box pops up asking you to start the router/spindle with 'start' button; DO NOTHING and proceed to next step
Press the green, start button (right) on the ShopBot pendant located at the workstation to turn the spindle on
Verify VISUALLY that the bit is now rotating in the spindle
Once the spindle is on and spinning you're ready to cut!
Click 'Yes/OK' while keeping your hand near the red EMERGENCY STOP button while the operation starts
Your job will now start!
Keep an eye on the cuts to ensure they look accurate to your original file and the simulation. If you notice something, it is best hit the EMERGENCY STOP and review your file and or calibration steps.

Shutdown & Cleanup Process

The dust collection system does not collect 100% of removed materials.
Please spend time at the end of each CNC session to clean up the surrounding space using the Build Labs shop vacs, brooms and dustpans.

Jog the spindle out of the way if it is blocking you from retrieving your part 'JZ 4' then 'JX 60'
Open the bleeder valve and turn off the blower motor using the blower control box switch to release your cut part from the CNC bed

Depending on which machine you are using...

CNC 1	CNC 2
Asked a Build Lab staff member to retrieve your bit from the spindle	Jog the spindle to the resting home position by entering command 'J2 5,5' then place the white PVC tube under the Tool. 5, 5 is outlined on the table with a blue circle.

If no one is in the queue to use the machine after you
1. Turn off the Vacuum Table system
2. Turn off the ShopBot control box
3. Close the dust collection vent
4. Log off of the CNC workstation
Use the shop vac, broom and dustpan to cleanup the CNC bed and the surrounding areas

Troubleshooting

Did an error or sudden stop occur during your job? did you have to press the emergency stop? Try some of these solutions!

CNC Troubleshooting | Router | Nudge / Nudging

Problem
Your print is not cutting through to the desired depth; this can be caused by a file issue, tool tip calibration or a worn table surface.
Table is surfaced once per semester and should be assumed flat
Tool tip calibration parameters may be incorrect
File issues can cause unrepeatable damage to the CNC machines and if the issue is suspected due to a file you should stop you cut immediately and fix the problem in Fusion360.
If you experience any of these issues please send an email to soatechdesk@utexas.edu to ensure that a staff member is aware of machine or table damage.
Solution

Proceed with caution when using the NUDGE command. Any damage to the spoil board should be reported so that it may be addressed prior to the next CNC user.
The goal is to cut 100% through your material and not to go deeper than 1/32 of an inch into the spoil board.
Stop your job
record the line # if you're expecting to resume
Type MN (Move, Nudge) in the command box
Nudge the Z-axis by -0.015 or 1/64 of an inch at a time
each time a nudge command is given it will be relative from the current point. i.e. if you nudge by -0.015 then again by -0.010 you will be -0.025 from your original start point.
Rerun your file with your newly calibrated Z offset position.
Proceed to CNC Troubleshooting | Router | Resuming a stopped job if you recorded the Line # that your job stopped on.

CNC Troubleshooting | Router | Resuming a stopped job

Problem
This guide is intended to be used to start a job that was inadvertently terminated.
A Job may stop or fault for a variety of reasons. The '-- Unexpected Output Fault ! --' error is caused by a miss-step in communications from the workstation to the Shoptbot controls.
Solution
If you receive a '-- Unexpected Output Fault ! --' error, make sure to note down the line number in the 'Current Line' box.
Enter command 'FG' to resume a job at a specified line in the code
Click 'Setup a Re-start of this file'
Enter your desired starting point in the 'Line Number' box
Click 'GO' and allow the ShopBot to move to the desired start position
Click 'Run from Here'
The ShopBot will notify you to turn on the spindle by pressing the green 'start' button (right side of ShopBot pendent)
Verify VISUALLY that the bit is now rotating in the spindle
Click 'Yes/OK' while keeping your hand near the red EMERGENCY STOP button while the operation starts

CNC Troubleshooting | Router | Axis Limiter Sensor

Problem
If you see this error it is because the ShopBot CNC hit a limiter sensor or proxy switch that caused a fault in the calibration and requires re-calibration.
Solution
The Shopbot CNC machines are designed with a limit sensor for each axis. One of the limiters is a physical stop to keep the gantry from walking off the rails; if you hit these you will have to re-initialize the Shopbot CNC machine. The other limiter is a light sensor to assist the machine with it's 'homing' function (C3). It is important to not enter commands that are beyond the limits of these machines. For example; both of our CNC machines have a 60" Y axis and a 96" X axis beds. pushing either of these numbers beyond their limit will incur a limiter switch error.
Turn off CNC Control box
Close ShopBot3
Fix axis proxy switch (lowering spindle 1")
At least 30 seconds should have passed since turning off the CNC Control box so that it forgets its settings
Start CNC Control Box
Press Blue Reset button
Launch ShopBot3
Enter command Z3 to zero all 3 axis (X, Y, Z)
Enter command C3 to calibrate machine
Proceed back to 'Part 1: Machine Calibration'