Avoid the Biggest Pothole for Automation: Process Variability | Rob Tracy Consulting

Avoid the Biggest Pothole for Automation: Process Variability

by | Jun 2, 2021 | Operations

Many companies want or need to embrace automation to address chronic labor shortages, improve quality and safety, and reduce labor costs.  If your company is seriously considering automation or are in the midst of implementing an automation project of any type, this article should be a “must read”.

The Top Reason Automation Projects Fail!

Process variability is THE NUMBER ONE reason automation projects fail, hands down.  Most automation engineers and system integrators fail to understand and address this fact, and the issues arise during system run off and/or during commissioning when most of the money is spent, timetables are slipping, and tempers are flaring.

Sources of Process Variability

Process variability is manifested in a number of ways:

  • Part Dimensions – key fit up dimensions or part features that impact part feeding vary significantly within a batch or between suppliers, causing machine jam ups, work cell downtime, and loss of productivity. These can range from flash on an injection molded parts so features on a stamped steel part or casting that varies between batches.

For this assembly operation part dimensional variations or flash will result in mis-feeding, mis-placement, or failure to complete cycle.  All will cripple the assembly output.  This is true of any assembly process including welding.

  • Fixture Condition – part positioning is critical to maintain the proper orientation for processing during the cycle. Fixtures wear, are modified to make parts fit, and are poorly maintained.

In this example maintaining the condition and dimensional integrity of the weld fixtures and welding head are crucial to ensuring that parts are welded consistently right.  Slight mis-alignments, weld spatter build- up on the fixture or mis-alignment of the weld head can all lead to scrap and downtime.

  • Process Variability – every manufacturing process has process variability. From an automation perspective, understanding the magnitude and type of process variability is key.

In this example a blow molded part that was automatically lanced is being checked for the proper position of two holes that are critical for final assembly.  If the part is cooled too slowly or quickly after molding the hole locations change, causing defects.  This type of phenomenon occurs in all molding processes, MIG and TIG welding, and castings.

How Do I Use This Information?

This insight is critical for all three phases of an automation project:

  • Project Selection & Preparation – conduct machine and process capability studies on key characteristics of part to assess variability and share with prospective automation integrators
  • Project Planning & Implementation – test parts and materials from different lots and suppliers during the approval process to root out issues and determine the best course of action.
  • Commissioning and Project Rescue – first look to process or part variability to address machine faults and downtime during commissioning.

Understanding and minimizing process variability is THE KEY to avoiding automation failures.

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