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UMC - Geometry - Troubleshooting Guide

8.3 Geometry - Troubleshooting

Last updated: 02/09/2021

UMC - Geometry - Troubleshooting Guide

Overview

Before troubleshooting a UMC-750 accuracy or geometry problem, the tech must have a thorough understanding of the following fundamentals:

A problem with UMC-750 machine geometry or accuracy needs to be approached systematically and in the proper sequence. The following information should be adhered to strictly and followed in sequential order.

It is absolutely critical that before any assesment or adjustment is made to the machine geometry that the machine has been checked for proper level and alignment of the rotary axes to the machine

Many errors can be attributed the the machine suffering a crash or problems either with tooling applications or programming issues. Do not attempt to change machine geometry with out completely checking the machines overall level and geometry per the Inspection report. This includes checking the Machine Rotary Zero Point (MRZP).

In the event of a crash there are 4 slip joints on the machine. These areas are the spindle head to the ram, the ram to the saddle, the saddle to the bridge, and the trunnion to the trunnion support.

 Note: none of these joints should ever be shimmed. A machine crash should never change the amount of shims required in the machine from the factory settings.

It is important to remember the Linear accuracy of the machine is 0.0004/10" and the angular accuracy is +/- 15 arc. sec. These tolerances can add up quickly.

Every effort should be exhausted to determine if the machining application is reasonable and within the machine, fixturing, and toolings ability.

Assess Machine Condition

Determine if machine was crashed previously. Review the alarm history; look for physical damage on the sheet metal, table, spindlehead, etc. No matter how "minor" the crash was, it will affect machine's geometry. If the machine has been crashed a full inspection of the machines geometry needs to be performed

Asses the overall condition of the part fixturing and the condition of the cutting tools.

Get full machine backup and error report.

Verify Machine Level and Geometry

Verify machine is level and the rotary axis is aligned to the machine

 Note: do not attempt to make any adjustments to the machine geometry other than adjusting level feet at this time.

If the machine is out of level or the rotary is not aligned, reset level and rotary alignment.

Perform Full geometry inspection noting magnitude and direction of any errors for each axis.

Analyze the inspection report.

If any of the sections of the inspection report is out of tolerance, machine needs to be re-aligned.

Review application

Gather the following information about the part, workholding, and tooling:

  • Which features are out of tolerance, magnitude, direction of the error
  • Is the part machined using 5-axis, 3+2 axis or 3 axis?
  • Review the part and the machining approach
  • Can any of the part accuracy errors be minimized by changing the machining approach?
  • Is the problem a repeatability issue, a size issue, or a geometric issue?
  • Does the Program use TCPC or DWO?
  • Are there any values in the compensation tables?