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Tips on Correcting an Unbalanced Spindle

One of the leading causes of machine tool failure is imbalance. A spindle can become unbalanced due to a variety of causes, which can result in damage to other components. Spindle imbalance occurs when a spindle’s center of mass is not aligned with its center of rotation, causing the energy to transfer to the tool and work piece. A few causes of imbalance include thermal fluctuation, improper/inattentive maintenance, poor tools, bent or bowed shafts, and occasionally, product build-up.

To fix a spindle that has become unbalanced, the axis of inertia must be restored to nearly-perfect alignment with the axis of rotation. While the effects of imbalance are slightly less noticeable on low-speed machine tools, it is critical that high-speed spindles be balanced to ensure optimal performance and a maximum lifespan.

To fix spindle imbalance, a balancing system is required, specifically one that has a two-plane function. For these tips on correcting spindle imbalance, we will be describing a common balancing system setup that features a tachometer, an accelerometer, and two-plane balancing software with a digital data readout display (i.e. an iPad tablet).

Once you have a setup like this in place, the following tips will help you conduct the balancing process and minimize potential errors:

  • Weight Recommendation – Spindles come in a wide range of weight-ratings, some weigh less than 20lbs while others can weigh more than 100lbs. The software will recommend the exact recommended trial and correction weight, based on the estimated rotor/shaft weight.
  • Rotation Direction – Ensure that your spindle and software are set for the same rotation direction. If your device is set up for clockwise rotation, it is important that your software is set up to gather data according to clockwise rotation. This is a common error made when balancing machine tools.
  • Tachometer Signal – Verify that your tachometer is exhibiting a signal. It is common for tachometers to lose their signal due to being bumped or moved. It is also common for the reflective tape to fall off during the process of balancing, so be sure to monitor tape placement.
  • Tachometer and Accelerometer Alignment – The setup of your tachometer and accelerometer is key to the proper balancing of a spindle. Ensure that your tachometer is facing the accelerometers, on the same side, and on the same horizontal or vertical plane.
  • Misalignment and Tool Looseness – A spindle that is misaligned or loose is virtually impossible to balance. It is critical that you check for these two factors before attempting to balance a spindle.

The benefits of regularly balancing a spindle include enhanced machine accuracy and efficiency, longer tool life, and increased life of related components such as bearings. Balancing will also decrease the noise and vibration levels created by machine tools during operation.

These are general guidelines for balancing a spindle. For specific spindle balancing needs, contact an experienced professional with the correct equipment and expertise.

About GTI Spindle Technology

At GTI Spindle Technology, 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.