A Technical Guide to Packaging and Calibration of Coordinate Measuring Machines
SECTION 1: INTRODUCTION TO CMMs
1.1 What is a Coordinate Measuring Machine?
A Coordinate Measuring Machine (CMM) is a device used in manufacturing and assembly processes to measure the physical geometrical characteristics of an object. It ensures that the part or assembly conforms to its intended design and tolerance specifications. CMMs use a probe, which touches the object to collect precise coordinate data along the X, Y, and Z axes.
1.2 Types of CMMs
- Bridge CMMs: The most common type; provide high accuracy for medium to large parts.
- Cantilever CMMs: Ideal for smaller parts; provide good accessibility.
- Gantry CMMs: Suitable for very large parts; often found in aerospace or automotive industries.
- Horizontal Arm CMMs: Designed for measuring long and flat components.
- Portable CMMs: Include articulated arms and laser trackers; used for on-site or in-process measurements.
1.3 Components of a CMM
- Structure (base, bridge, columns)
- Probe system (touch-trigger, scanning, optical)
- Scale system (encoders)
- Controller and software (data acquisition and interpretation)
1.4 Applications and Importance in Quality Control
CMMs play a vital role in quality assurance, providing accurate measurements that ensure parts meet design intent. They are widely used in aerospace, automotive, defense, medical device manufacturing, and general precision engineering.
SECTION 2: PRINCIPLES OF CMM CALIBRATION
2.1 Why Calibration Matters
CMM calibration ensures that measurements are accurate and traceable to national or international standards. Calibration helps maintain compliance with ISO, ASME, and industry-specific standards. Regular calibration prevents process drift and measurement errors.
2.2 Calibration Standards
- ISO 10360: International standard for performance verification of CMMs.
- ASME B89.4.1: U.S. standard for CMM performance evaluation.
2.3 Environmental Factors
Environmental conditions such as temperature, humidity, and vibration significantly affect CMM performance. Ideal calibration conditions include a controlled temperature of 20°C ±1°C, minimal vibration, and dust-free, dry environments.
2.4 Calibration Tools and Equipment
- Step gauges
- Ball bars
- Laser interferometers
- Gauge blocks
- Certified artifacts
2.5 Step-by-Step CMM Calibration Procedure
1. Clean the CMM and calibration tools.
2. Allow the machine to acclimate to room temperature.
3. Level the CMM using precision leveling instruments.
4. Use certified artifacts to measure and compare against reference values.
5. Adjust and fine-tune software settings or hardware alignment.
6. Record calibration results and issue a certificate of calibration.
2.6 Establishing a Calibration Schedule
Most CMMs should be calibrated annually or semi-annually depending on usage. High-use environments or critical inspection tasks may require quarterly verification.
SECTION 3: PACKAGING A CMM FOR SHIPPING OR STORAGE
3.1 Risks of Improper Packaging
Improper packaging of a CMM can result in:
- Vibration damage to sensitive electronics and mechanical systems
- Moisture ingress leading to rust or corrosion
- Dust contamination
- Physical damage during handling or transit
3.2 Pre-Packaging Inspection Checklist
Before packaging, perform a thorough inspection:
- Verify the condition and operation of the machine
- Document current calibration status
- Secure and back up all software
- Clean machine surfaces and components
3.3 Disassembly Guidelines
Depending on machine size and model, partial disassembly may be required:
- Remove probe heads and store in padded cases
- Detach moving components if applicable
- Label all connections and cables
- Use anti-static bags for electronics
3.4 Protective Materials
Use the following to protect the equipment:
- Industrial-grade foam inserts
- Moisture barrier bags with desiccants
- Shock-absorbing crates or skids
- Plastic wrap and corrosion inhibitors
3.5 Custom Crating Techniques
Build custom crates:
- Ensure the base can support the full weight without flexing
- Use cleats and blocks to prevent shifting
- Install shock indicators and tilt sensors
- Clearly mark the crate with 'FRAGILE', 'THIS SIDE UP', and 'DO NOT STACK'
3.6 Securing Fixtures and Cables
All probes, fixtures, cables, and accessories should be:
- Individually wrapped and padded
- Stored in labeled containers inside the crate
- Inventoried and documented for traceability
3.7 Documentation for Transport
Always include:
- Bill of lading
- Equipment inventory list
- Calibration certificates
- Contact info and reassembly instructions
SECTION 4: RE-INSTALLATION AND RE-CALIBRATION POST-SHIPPING
4.1 Unpacking Procedure
Upon arrival:
- Verify crate integrity
- Open crate slowly to avoid sudden release of tensioned parts
- Remove components carefully and check for damage
4.2 Environmental Reconditioning
Before use:
- Allow 24–48 hours for machine to acclimate
- Re-level the base
- Ensure stable ambient temperature and humidity
4.3 Verifying Alignment and Leveling
Check for alignment drift:
- Use leveling tools or onboard system diagnostics
- Adjust leveling feet accordingly
- Confirm X, Y, Z accuracy using gauge blocks or test parts
4.4 Re-Calibrating After Transit
Recalibrate using certified artifacts to:
- Validate and reestablish measurement traceability
- Update software configuration
- Reissue calibration certificate
4.5 Performance Testing and Certification
Once calibrated:
- Run verification routines
- Check repeatability and linear accuracy
- Save a baseline diagnostic report for future reference
