Ever wondered how manufacturers measure parts with pinpoint accuracy? If you’ve heard about CMMs—Coordinate Measuring Machines—but aren’t sure how to use a used one, you’re not alone. Knowing how to operate a used CMM can save money and ensure quality in any workshop or production line.
This article breaks down everything you need: easy-to-follow steps for getting started, essential tips for smooth operation, and practical insights for making the most of a used CMM machine.
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What Is a Used CMM Machine and How Is It Used?
A Coordinate Measuring Machine (CMM) is a precise inspection device used to measure the geometry of physical objects. When you purchase or operate a used CMM machine, you’re using a tool that can deliver the same high accuracy as new models, but often at a more affordable cost. Used CMMs are widely used across industries such as automotive, aerospace, manufacturing, and medical device production for ensuring parts meet strict dimensional specifications.
Understanding how a used CMM machine works, how to use it, and how to get the most value from your investment helps you maintain quality standards while maximizing your budget. Let’s break down everything you need to know about using a used CMM machine, from setup and operation to maintenance and cost-saving tips.
Understanding Used CMM Machines
What Is a CMM?
A CMM (Coordinate Measuring Machine) is a device equipped with a probe. This probe touches, scans, or senses points on a workpiece, enabling the machine to map out the precise coordinates and dimensions of the part. There are several types of CMMs:
- Bridge CMMs: Most common, known for accuracy and stability.
- Cantilever CMMs: Provide open access but typically smaller.
- Gantry CMMs: Ideal for large parts.
- Horizontal Arm CMMs: Used for measuring large, flat panels or assemblies.
- Portable CMMs: Flexible and often used on large, immobile objects.
Why Buy Used Instead of New?
Used CMMs can provide significant savings while offering similar performance as new units. Many manufacturing and metrology providers refurbish, upgrade, and certify pre-owned machines to meet current standards.
Main benefits include:
- Lower upfront costs
- Shorter lead times
- Ability to upgrade or retrofit to fit your needs
- Wide selection of makes and models
Steps to Operate a Used CMM Machine
1. Inspect and Set Up the Machine
Before getting started:
- Visual Check: Examine the physical condition of the CMM, checking for signs of wear or damage.
- Power and Environment: Ensure the machine is correctly connected to power and installed in a clean, temperature-stable environment.
- Level the CMM: Use leveling feet or pads to make sure the machine base is stable and level. Accurate operation relies on proper orientation.
2. Calibrate the CMM
Calibration ensures precision:
- Use certified calibration tools (sphere or block standards) that come with the machine or buy new ones if needed.
- Run manufacturer-recommended calibration routines. Some software assists with guided calibration steps.
- Check probe integrity and calibrate different probe configurations if necessary.
3. Load Your Part Securely
Proper part placement is key:
- Clean the workpiece and fixture to remove dust, oils, and debris.
- Secure the part using appropriate fixturing so it will not move during measurement.
- Align the workpiece with the CMM’s axes. This step helps with repeatability and measurement accuracy.
4. Configure the Measurement Program
Most CMMs are operated via specialized software:
- Import the part’s CAD model if available.
- Set up measurement routines: define which dimensions, points, or surfaces to inspect.
- Configure probe paths and movement thresholds to avoid collisions.
- If needed, use manual joystick controls for single-point probing or testing programs before running automated routines.
5. Run the Measurement Process
Automate or guide the CMM to inspect the workpiece:
- Start the measurement program.
- Observe the machine as it proceeds, ensuring there are no unexpected collisions.
- The machine’s probe will move along the programmed path, collecting precise coordinate data at each point.
6. Analyze Measurement Results
Review data on the computer:
- The software will compare measured values to nominal CAD or programmed dimensions.
- Review graphical and tabular reports highlighting pass/fail, deviations, and recommended actions for out-of-tolerance features.
7. Document and Repeat as Needed
- Save results within your quality management system for traceability.
- Rerun or modify programs as part requirements change or to measure different parts.
Key Benefits of Using a Used CMM Machine
- Reduced Capital Expenditure: Used machines cost significantly less than new, freeing budget for other needs.
- Quick Deployment: Many used CMMs are available for immediate delivery, shortening project timelines.
- Retrofitting Potential: You can often upgrade software and some hardware, adding new capabilities at modest cost.
- Proven Reliability: A well-maintained CMM, even if pre-owned, can provide years of dependable service with proper care.
Common Uses for Used CMM Machines
- Inspecting manufactured parts for dimensional accuracy
- First Article Inspection (FAI)
- In-process quality control in batch manufacturing
- Reverse engineering of components
- Verification against CAD models for critical applications
Practical Tips and Best Practices
Operation Tips
- Train all users on specific CMM control software and safe operation procedures.
- Use certified calibration artifacts and recalibrate routinely, especially after moving the machine.
- Pay attention to the environment: avoid vibrations, drafts, and fluctuating temperatures.
Maintenance Tips
- Schedule regular preventive maintenance—clean guideways, check air bearings or mechanical slides, and inspect electronics.
- Keep machine surfaces and probes clean.
- Replace probe tips and styli as needed.
Buying and Cost Tips
- Source from Reputable Dealers: Find an established metrology distributor who offers warranties, maintenance, and support options.
- Request a Full Service History: Ask for calibration, service, and upgrade records.
- Factor In Installation and Training: Some machines cost less but may require professional installation or retrofitting, which adds to setup costs.
- Shipping Considerations: For large CMMs, factor in crating, transportation, and insurance costs. If shipping across state or country lines, clarify customs, duties, and logistics prior to purchase.
Addressing Common Challenges
- Software Compatibility: Older CMMs may use outdated software. Look for machines compatible with modern platforms or those that support updates.
- Spare Parts: Ensure parts for your model are still available. Bridge models with active support are preferable.
- Integration: Confirm the CMM can interface with your existing CAD and quality management systems.
Tips for Shipping and Setting Up a Used CMM
- Work with shippers experienced in moving precision equipment.
- Document the dismantling process for easier reassembly.
- On arrival, allow the machine to acclimate to your facility’s temperature before power-up.
- Recalibrate after setup and before first use.
Getting the Most from Your Used CMM Investment
- Regularly update measurement programs as parts or requirements change.
- Leverage third-party training if staff are new to CMMs.
- Periodically review results and processes to identify opportunities for improved accuracy or efficiency.
Frequently Asked Questions (FAQs)
1. Can a used CMM machine be as accurate as a new one?
Yes, a properly maintained and calibrated used CMM can match the performance of a new model. The key is ensuring it has been serviced, upgraded as needed, and regularly calibrated.
2. What should I look for when buying a used CMM?
Check for a robust service history, available spare parts, supported software, and physical condition. Buying from a reputable distributor who offers inspection and calibration certificates is also wise.
3. How often should I calibrate my used CMM?
You should calibrate at least annually, and anytime the machine is moved or after major repairs. Some operations require more frequent calibration based on usage and precision demands.
4. Will a used CMM work with my current measurement software?
It depends on the age and model. Some older CMMs may need software upgrades or retrofitting. Always confirm compatibility with your software and CAD file formats before buying.
5. What are the main costs to consider beyond the machine price?
Additional costs may include shipping, installation, calibration, software licenses or upgrades, operator training, fixturing, and maintenance. Make sure to account for these when budgeting for a used CMM purchase.
Final Thoughts
Using a used CMM machine is an excellent way to bring precision measurement capabilities to your business while lowering costs. By understanding proper operation, maintenance, and purchasing tips, you’ll maximize reliability and accuracy. With routine calibration, careful setup, and thoughtful use, a used CMM can deliver years of value for your quality control or inspection needs.