Table of Contents
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Background
Each machine is tuned at the factory to meet or exceed certain precision metrics. These metrics are indicated on the Certificate of Inspection that is included with each mill, along with the actual values measured for each metric as part of Tormach’s Quality Assurance program. The following advanced maintenance procedures may become necessary over the ownership lifetime to maintain the original factory precision:
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A properly adjusted gib minimizes lost motion by balancing conventional backlash and sliding friction. A gib that is too loose results in excessive conventional backlash; a gib that is too tight cannot adequately support an oil film resulting in excessive sliding friction. The position of the tapered gib plate is controlled by two screws on either end of the gib that capture the position of the gib with respect to the saddle. These screws can be adjusted (as a pair) to tune the tightness and sliding friction of the dovetail way for each axis.
Definitions
The following definitions are important to the advanced maintenance discussion.
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Space between gib and way needed to support an oil film. This is tuned by tightening the gib.
The space between the ball bearings and races in the angular contact bearing pair that supports the ball screw. This is tuned by increasing the angular contact bearing pair preload.
Tools
Flat-bladed screwdriver
Dial Indicator (.0005” resolution)
Magnetic Base
Metric allen keys
Table of Contents
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Measuring Lost Motion
Correctly measuring lost motion is critical to successfully undertaking any of advanced maintenance procedures detailed in the following sections. Mill setup and tuning is done under no-load conditions. The precision measurements recorded in the Tormach Certificate of Inspection are taken under no-load conditions. The accuracy of a machined feature is not an indicator of machine precision. Tool flex, workpiece flex, fixture flex, thermal expansion, and other factors contribute to the overall machined-part accuracy.
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