At Premier Equipment for many years now,We have been inspecting, maintaining and operating CNC machines. The CNC guideways are one of the critical components that are often overlooked, but tend to be a concern. And these are the backbone of your CNC machine’s precision and efficiency. Guideway wear signs are important to know to continue optimal performance and prevent expensive downtime.
The Importance of Guideways
Linear tracks that smooth and precise movement of machine axes are called guideways. However, they are critical to ensuring the cutting tool moves accurately by path programmed moving so that parts can be produced to tight tolerance. With constant use over time, environmental factors and lack of maintenance care, guideways can wear over time.
Common Signs of Wear
Early signs of wear can save you from bigger headaches later. Here are some indicators that your guideways may need attention:
1. Reduced Machining Accuracy
A decline in machining accuracy is one of the most obvious signs of worn guideways. You may also find that finished parts are no longer meeting specified tolerances. It can appear as being off in dimension or parts that shouldn’t be different being different in consistency. Unexpected marks or roughness is another red flag… a deteriorating surface finish.
2. Visible Surface Damage
Look at the CNC guideways closely. Abusive wear, if you see scoring, scratches, or grooves along the tracks. Damage such as this often occurs from contaminants such as dust or metal particles between the moving parts, or from lack of lubrication. If you find pitting on the surface or rust spots the culprit may be chemical wear resulting from moisture exposure or exposure to corrosive substances.
3. Abnormal Movement
Watch how the axes move when operating the machine. Uneven friction from worn guideways is often seen as a jerky or uneven movement — ‘stick slip‘ — in this case. Wear can also be indicated by excessive play or backlash—when the movement command doesn’t happen for a noticeable amount of time between the command and the movement.
4. Increased Friction and Heat
After the machine has been running, feel the area around the guideways. Worn surfaces cause increased friction, and a sign of excessive heat. Also, if the lubrication oil or grease looks burnt or degraded, it’s not reducing friction effectively, and can accelerate wear.
5. Unusual Noises
When it comes to diagnosing machine problems, your ears can be as valuable as your eyes. If the sounds are grinding or scraping, this signals metal to metal contact, which shouldn’t occur if both the guideways and the table are well lubricated and if in good condition. This can be squeaking or creaking noises indicating that there will not be enough lubrication, or that surfaces are wearing down.
6. Wear Patterns
Look at the wear patterns on the CNC guideways. Localized wear may be caused by repetitive movements over a limited range of movement if certain areas wear more than others. Another sign that material has been worn away unevenly is step wear—noticeable steps or ridges on the guideway surface.
7. Contamination
Wear is exacerbated by accumulation of debris like metal shavings or dust on or around the CNC guideways. Less effective contaminated lubricant can cause extended friction and wear and be cloudy with particles.
8. Performance Alarms
In most modern CNC machines, the diagnostics are built in. If you’re getting a lot of machine errors related to axis movement or positioning or if the servo motors are overloading more than usual, it could be that the guideways are worn and are causing more resistance.
Types of Guideways and Specific Concerns
The types of guideways used on different machines are different and have different wear characteristics.
- Box (Sliding) Guideways: They are known to be rigid and load bearing. Wear signs include galling, where material is transferred from one sliding surface to another, and the loss of low friction coatings such as Turcite or Babbitt material.
- Linear (Rolling) Guideways: These rolling elements are balls or rollers. Brinelling, indentations on the rail surface from excessive loads, and damage to the rolling elements themselves, are all to be looked out for.
How to Inspect Guideways
A thorough inspection combines visual checks with physical tests.
- Visual Inspection: Examine the guideways with a flashlight and if necessary a magnifying glass. Remember to look under protective covers, but do so carefully, and make sure the machine is powered down and locked out before removing any guards.
- Physical Testing: When the machine is powered off manually move the axes to feel for resistance or decide to make sense of what is happening. Dial indicators can measure deviations in straightness or parallelism.
- Lubrication Assessment: Check the lubrication system. Are the lines in place and clean? Is the lubricant clean and is there enough of it? Guideway wear, both a cause and a symptom, is poor lubrication.
- Operational Testing: Write a test program to move all axes through their full range of motion. Look for movement that is smooth, listen for unusual noises. Monitoring the load meters can also be informative, as high loads may mean higher than normal friction caused by wear.
Preventing Excessive Wear
Prevention is always better than cure. Here are some steps to minimize guideway wear:
- Regular Maintenance: Follow a strict maintenance schedule. Clean the machine regularly and inspect critical components, replace or filter lubricant.
- Proper Lubrication: Check that the lubrication system runs properly and that the right lubrication was employed.
- Environmental Control: Never expose the machine to dust, moisture, or very extreme temperature.
- Operator Training: All operators should be trained to run the machine, as well as basic maintenance and to look out for signs of wear.
When to Seek Professional Help
If you see several of the signs above, or you’re not sure how healthy your guideways are, it’s time to call in the professionals. Operating a machine with worn guideways can continue to add damage and safety risks.
Conclusion
Your CNC machine’s precision and longevity depend on guideways. If you’re proactive and can recognize the signs of wear, then you’re saving yourself time, money, and a lot of headaches. Inspections and maintenance are just as important as they extend the life of your machine, and help your parts to meet the highest quality standards, and keep your production on track.
A productive machine is a well maintained machine. If you have any questions or need help with your CNC equipment, please don’t hesitate to contact us at Premier Equipment. We want to help you keep your operations running smoothly.
