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6.0 - CNC Operation

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Lesson overview

• 6.1- CNC Process• 6.2 – Machine & Tool Offsets

If running a Haas mill print the Lesson 6 PDF file and use it as a reference at the machine. For other machine makes, refer to the machine owners manual or instructor-provided operating procedures.

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objectives

• List the steps to set up and operate CNC Mill.• Identify location and purpose of operating controls on CNC mill

controller.• Start and Home CNC mill.• Load tools into CNC mill.• Set Tool Length Offset registers.• Set Fixture Offset registers.

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objectives

• Load CNC program from PC to CNC control.• Safely run new CNC program.• Adjust offsets to account for tool wear and deflection.• Shut down CNC machine correctly.• Properly clean CNC machine.

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Overview

In this lesson you will work at the machine to set up and operate a CNC mill to make your first part.

Your instructor will provide you with the specific operating instructions for your machine.

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Overview

• Work safely.• Obey all shop rules in Safety Contract.• Wear safety glasses at all times.• Kindly point out any safety issues to others.• Watch carefully the instructor demonstrates and as other

participants work before you.• Work methodically.• Think about everything you do and why.• Precision is more important than speed.

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Safe practices

• Only one person operates the machine at a time. A CLEAR procedure to hand control to the next person is to be used: “Your Machine/My Machine”.

• NEVER have one person working control while other is working in the machine envelope.

• Operator to remained focused. Do NOT look away from work or allow yourself to be distracted.

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Safe practices

• Observe what the person operating the machine is doing. Learn as you observe as you will be next.

• Kindly point out any safety issues.• Others should remain quiet and talk ONLY when necessary.• Do NOT engage in non-work related talk, horseplay, or anything

else that will distract the machine operator.

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6.1 - CNC Process

1. Pre-Start.2. Start/Home.3. Load Tools.4. Set Tool Length Offsets.5. Set Fixture Offset XY.6. Set Fixture Offset Z.7. Load CNC Program.8. Run Program.9. Adjust offsets as required.10. Shut down.

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Step 1: Pre-start

• Ensure oil and coolant levels are full.• Ensure work area is clear of loose tools or equipment.• Ensure air supply is on and adequate pressure (if required).• Ensure main power disconnect is on.

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Step 2: Start/home

• Turn on CNC machine.• Close protective doors.• Execute machine Start/Home sequence.• Wait until machine completes cycle before proceeding to next

step.

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Step 3: Load tools

• Load tool(s) into machine carousel for machines with tool changer.

• Load first tool into spindle for machine without tool changer.

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Step 4: Set tool length offsets

• For each tool used, set Tool Length offset.

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Step 5: Set fixture offset xy

• Use Edge Finder or Part Probe to find and set Fixture Offset XY.

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Step 6: Set fixture offset z

• Use Dial Indicator and 1-2-3 block or Tool Probe and 1-2-3 block to find and set Fixture Offset Z.

This is just one way to set TLO. Other methods may be easier or more appropriate to your situation.Appendix E describes other methods.

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Step 7: Load cnc program

• Use RS-232 communications (DNC software and cable from PC to CNC), USB flash drive, Ethernet, or other communications method to transmit your G-code program into the CNC control memory.

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Step 8: Run program

• Run your program.• Use extra caution when running an unproven CNC program.

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Step 9: adjust offsets as required

• Adjust Tool Length and Diameter offset registers as required to achieve part tolerances.

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Step 10: shut down

• Move spindle near home position.• Remove tools from spindle.• Place a clean rag in the spindle hole to prevent chips from being

ingested.• Clean the CNC machine.• Sweep and mop as needed.• Put away tools and equipment.• Turn off machine power.

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6.2 - Machine & Tool offsets

• Tool Offsets (H1, H2, H3, etc).• Compensate for varying tool lengths.

• Fixture Offsets (G54, G55, G56, etc).• Compensate for distance from machine home to CNC program

datum.• Diameter Offsets (D1, D2, D3, etc).

• Account for tool diameter wear.• Covered in Lesson 3.

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Fixture Offset XY

• Delta-X | Delta-Y• Machine Home to CNC Program

Datum.

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Fixture offset xy (plan view)

• G54 XY Shown.• G54-G59 Available.• Shift values stored in memory

registers on CNC control.

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Fixture offset z

• Used to set Delta-Z from tool set position to Part Z-datum.*

• Use Dial Indicator (See Lesson 6: “Set Fixture Offset Z”).

*There are many ways to use Fixture Offset Z and TLO. This works well and is consistent with machines with Tool Probes.

Please see Appendix E-Alternate Tool Setting Strategies for other methods.

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Set tool length offset (TLO)

• Set all tools from G54 Z Position.

• TLO and Fixture Offset Z work together.*

• See Lesson 5 “Set Tool Length Offset (TLO)”.

*For Haas controls, control parameter 64 (T OFS USES WORK) must be set OFF to use this method.

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warnings

• Never operate a CNC machine or any shop equipment that you have not been properly trained to use.

• Observe extreme caution at all times.• Follow all safety rules.

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summary

• Follow the general steps listed in this presentation, using instructions for you particular make and model of machine.

• Work safely.• Work methodically.• Learn from others.• Point out any safety issues.• Clean up after yourself.