January 25, 2018 Spindle Repair No Comments

If you operate a manufacturing plant or similar business, keeping your production line running at maximum efficiency is crucial. Over time, the spindles within your rotating machinery can experience errors that can decrease performance, or in the worst-case scenario, cause complete machine failure. Monitoring the “health” of your spindles is an important part of minimizing downtime.

Here are three non-invasive methods for determining if your spindles are operating at maximum efficiency:

Measure Total Indicated Runout

Measuring your spindle’s total indicated runout is one method of ensuring maximum tool life. Runout can occur when a tool is rotating off its axis, either at an angle from one end of the shaft to the other, or as a whole. This causes it to rotate unevenly and negatively impact tool life. A few reasons that runout can occur include contamination within the tool, improper or subpar tool holders, and/or skewed machinery.

For this measurement, you will need a dial test indicator. After securing the dial test indicator in place with its needle on the shaft, you can rotate the shaft and observe the indicated runout. By placing the dial test indicator on different rotating sections of the tool, you can determine whether your spindle is operating within runout tolerances. To ensure that your spindle is performing at maximum efficiency, you should be aiming for 2 microns or less of runout when performing this test. Anything more than this amount can mean a loss of accuracy, a loss of power, and higher vibration levels.

Check Tool Retention Force

When a drawbar spring within a spindle is not preloaded properly, it can cause a variety of issues and damage other spindle components or complete equipment failure. Drawbar springs are dependent on each other for the tool to function properly, so if one spring fails, the other springs can become overburdened. A spring issue can go unnoticed, but once one fails, the others may follow. Testing the tooling retention of these springs enables you to determine, without disassembly, if your spindle is experiencing a drawbar issue before the issue can affect other components.

In order to measure tool retention, you will need a drawbar force gauge. By inserting a drawbar force gauge into your spindle, you can measure the stress of your springs. The tooling retention force can differ depending on your specific spindle. Most drawbar springs operate with a retention force between 2,000 and 7,000 psi. Be sure to refer to the manufacturer specifications when determining the proper range for a particular spindle.

Vibration Analysis

When a spindle is experiencing an error, it will typically create a vibration signature that is indicative of a specific problem or problems. Vibration analysis can determine which area of the spindle is experiencing damage and/or decreased performance. Vibration analysis can detect prevalent spindle problems such as misalignment, balancing issues, bearing issues, and low drawbar force. In this case study, vibration analysis was able to accurately detect multiple spindle errors including rotor imbalance and a bearing issue.

The most accurate way to identify vibration signatures is by affixing a vibration-sensitive device, such as GTI’s VibePro series, to your spindle. Gathering data and monitoring spikes in vibration levels can help you determine if your spindle is operating within its parameters for peak efficiency. If there is a vibration signature that suggests something is wrong, the signature can be analyzed to determine where the problem is occurring within the spindle.

If you have conducted these tests and did observe issues, it may be necessary to move from non-invasive diagnosis to disassembly and repair. Any invasive work that involves removing a spindle from a machine should be conducted by a trained professional. Remember, keeping your equipment in the best possible condition is critical to minimizing downtime, and minimizing downtime is critical to success.

About GTI Spindle

At GTI Spindle, we specialize in high quality spindle diagnosis and repair. Getting your business back into full operation and minimizing downtime is our mission. We offer in-house, on-site, and emergency assistance for machine tool spindle failure analysis, spindle repair, and complete spindle testing. With an extensive range and expertise in a diverse group of industries, our customers know that they are getting the highest quality of spindle repair and customer service. Click here to find out more.