Rejections on the Floor

An inevitable fact of life in operations is the occurrence of errors or rejections on the shop floor,  Upper management is always striving to "eliminate rejections", "work smarter", or some other catchy slogan to eliminate errors.  But the best you can do is to implement checks and balances in the process to help reduce the error count.  What you do when you have an error on the floor is just as important as trying to avoid it initially.

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Many medium to large companies have an error reporting system established whereby standard rules are followed when a rejection occurs.  Once an error is reported or written up (usually by Quality Assurance) it is essential that the information is accurate.  Some key things to check:

• Are the correct part numbers listed in the rejection write-up? I have seen many error reports (often called rejection tags) that have the incorrect part numbers and or descriptions in error.  This is a problem if there was ever a need to go back and look at a repair later and the records were in error.
• Is the error write-up clearly written? If there is confusion on what is really in error, then the incorrect analysis and repair methodology will not effectively address the issue.
• Will a repair impact downstream users?  If your repair will effect any downstream users you must coordinated before you provide your repair fix (disposition).  Otherwise bigger problems may occur that will adversely affect schedule.

For those weighing on the repair, be certain they have the necessary skill and experience to effectively analyze the problem.  An inexperienced mechanic or engineer may have good intentions, but a lack of experience in a key juncture of the operation could be a problem further down the process.

Finally it is essential to keep a record of the different rejection scenarios that one encounters on the shop floor.  Some times repairing the error requires a unique fix that should be shared with others to help educate them.  This is most important if it is second shift or a weekend and subject matter experts are unavailable.  A good database will help locate a similar issue to consult for you rejection at hand.

Rejecting discrepant parts is a fact of operations management
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Engineering Drawings in Operations

Operations struggles without  a clear set of engineering drawings or processes which define the part and its integration . The blueprint for making a quality product has particular characteristics depending on the type of drawing: 1) detail drawing used to define how a basic part is built, 2) assembly drawing used to show how two or more details are mated together, 3) installation drawing used to show how an  assembly is located in a final installation.

The detail drawing will usually contain the most technical information since it tells how to build the part from scratch using raw materials.  It is important to know all the correct (and up to date) processes and call outs listed on the bill of materials (BOM) or parts list.  I have seen many detail parts get held up in the quality assurance (QA) inspection because information was not current leaving the inspector to hold up approval of the detail part.  Also clear and complete drawings will alleviate any misinterpretation by the machinists or those who will fabricate the part.

A typical engineering drawing
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The assembly drawing will bring two or more details together.  Again clear drawings help immensely as well as keeping up to date on processes.  These drawings will show many detail parts so it is essential that all detail part numbers are correct on this drawing.  QA will stop an assembly from moving if the incorrect part numbers are listed on the BOM.  Also special consideration must be given to how parts are mechanically attached to each other and if necessary put precautionary notes on the BOM.  

The installation drawing will show how an assembly is located into a final product.  Installation drawings are used in the aircraft and automobile industries due to the enormous number of parts required to build the product.  Again clear and complete definition is essential for installation drawings.  In addition, the topic of tolerance analysis must be addressed.  Many times the tolerance stack up will be too far in one direction and the assembly will not properly install in the installation drawing.  This is usually discovered in the factory and requires immediate attention to fix the current unit and others behind it in the factory queue.

An engineering drawing has many downstream users
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