The Eight Stages of Mold Repair
While the mold was still being disassembled, two “cleaners” began pulling tooling out of plates and putting them into buckets in preparation for a good scrubbing—and I mean a scrubbing. Immersing the buckets into a solvent tank, they used their hands like wire whisks as they swished the close-tolerance ejector sleeves around, effectively removing any trace of vent residue or “track” marks on the tooling—and in the process maybe adding some marks of their own.
Gone were helpful clues for the repair technicians who had yet to begin troubleshooting and analyzing mold performance and wear. So now, how will the repair techs determine if the 63-day production run was too long? Or whether the leader pins, bushings, and interlocks were greased properly during the run? And how will they know if all the swishing during cleaning did not create any “dings” in the sleeves that could be blamed on something else instead of poor cleaning practices? Other questions will remain unanswered, too: Does the mold still have excess vent residue in the top right quadrant? Were all the ejector sleeves numbered and in the proper mold position before they were removed?
A seemingly little thing like working out of sequence can foil our best efforts at mold repair before they begin. Mold maintenance must follow a plan.
KEEP A STRUCTURED SEQUENCE
Structure is a word I don’t care for, but it seems to be required in most everything we do. In mold design, mold building, molding parts, and, yes, in mold repair. As a kid, my dad used to “structure” any rebuilding work on 19th-century gasoline engines that my brothers and I did. Coming home one day to find his super-organized shop littered with pistons, flywheels, crankshafts, and other miscellaneous engine parts and tools, he “structured” an immediate change in our work habits. After that painful experience, we did not have the freedom to just tear into the old engines without first clearing with him our plan for the day—which meant we would always be tested as to what we thought a good rebuilding sequence should be, based on what we know about a particular engine. It took a few rebuilds to appreciate the value of a structured sequence.
So we took pictures from different angles, and then engine components were removed (in the proper order) marked and set aside with some organization in mind. Nothing was ever randomly removed, cleaned, and reinstalled on a whim. As we got better at it, the rebuild stages were always the same—and in the same order.
The U.S. Navy has a similar approach when working on jet engines. Engines requiring repairs are not simply yanked from the air frame and disassembled without first creating, then discussing, the maintenance plan or objectives with the shop boss. This keeps things flowing smoothly in a hanger where there would always be several jets in various stages of repair. It was much the same as a mold shop where a group of repair technicians work on multiple molds during the day or week, sharing equipment, tools, and space.
For the individual technician, working in a structured approach has several intuitive benefits that are good habits to form and critical to daily shop efficiency and mold performance:
- It reduces mental mistakes by working the same format day in and day out. So when focus wanes, force of habit can save you.
- It improves troubleshooting skills and accuracy.
- It reduces repair time through better optimization of equipment utilization, removing bottlenecks.
- It promotes faster, easier, and more thorough training of new technicians.
In mold repair, structure is especially critical when working with many pieces of close-fitting tooling that are nested into plates. Remembering the type, fit, relational position of components, and the sheer volume of tooling in some molds can be overwhelming enough without adding confusion about where you are in the process of the repair. In shops where two repair techs are usually assigned to a mold, time can be saved by working in a organized approach.
Here is an overview of the Eight Stages of Repair and the critical elements of each. The accompanying flow chart demonstrates the order.
1. PM PREPARATION
A critical part of any mold maintenance plan is to provide the technicians a historical summary of past issues and corrective actions so they may be aware of longstanding or unresolved issues during repairs. Unfortunately, some technicians skip this first stage until after they get a mold disassembled—and then they stop to research a problem whenever they see or feel something they don’t like.
For instance, if you remove 16 ejector pins from a mold and notice that a couple of them feel tight, will you remember which ones were tight later on, when you peruse past records to discover that galling pins have been a problem for the past five production runs? Knowing this information before you split or disassemble a mold removes some of the guesswork involved when looking for the root cause.
2. MOLD DISASSEMBLY
Molds should never be arbitrarily disassembled without a specific level in mind. To do so is to invite excessive handling of tooling components or over-maintaining a mold, which increases the opportunity for damage and wastes man-hours. Time-based mold disassembly levels (based on cycles, hours, days, or parts produced) should be established to optimize bench time.
Three disassembly levels are typical in the industry, with a fourth sometimes being a complete mold rebuild. Those usually practiced are Wipe-down, General, and Major Disassembly.
Accurate and efficient troubleshooting of past and current defects is based on a repair technician’s ability to understand and relate existing processing and production conditions (as revealed by tooling wear marks and residue characteristics) to historical data. Issues should be segregated (long gates, specific flash etc.), analyzed, and then corrected one at a time.
4. CORRECTIVE ACTION
Effective, efficient, reliable, and professionally implemented corrective actions depend on a repair technician’s shop culture, experience, tools, and skill level. As problems are addressed and resolved, the stages of troubleshooting and corrective action work hand in hand until all issues have been resolved or a next action determined.
At this stage, put away all measuring instruments and hand tools and focus on how best to clean the tool. The type, frequency, and method of cleaning molds should be based on cycles, hours, or production in conjunction with mold-specific factors (resin, residue, vent location and capacity, tooling concerns, etc.) that will dictate the cleaning level and process.
Accurate mold and tooling component assembly is a critical step in mold repair—and is the origin of many preventable, unscheduled mold stops (breakdowns). Poor workmanship and mistakes are usually a result of too much speed, lack of focus or physical skills, and disorganized work habits. If several repair techs are involved in the assembly of a mold, communication breakdowns between them can require the mold to be disassembled yet again to correct an oversight or install something that was forgotten.
7. FINAL CHECK
Before any mold is released for production (“blue-tagged”), it is imperative to put the mold through a series of final-check bench procedures to verify “All Systems Go” and minimize any opportunities for the mold to be stopped and returned to the shop for something that should have been caught before it was released. Water leaks, heater problems, etc., can be avoided with a final-check procedure.
After a mold has been cleaned, repaired, changed over, and final-checked, it needs to be given a new status and moved to one of three areas—typically racked in holding/storage area, reset in the press, or staged as a back-up mold in a molding-cell operation. It could also go to an outside vender for rebuild or production. You should know where your molds are.
These mold repair stages are absolutely sequential and should not be mixed up or rearranged. Actions required and taken in each of the eight stages depend on the preceding stage. Accurate data from prior stages is needed to establish clear objectives in subsequent stages.
Working in a systemized, staged manner promotes a professional approach that rewards technicians with more efficient, effective, and consistent results—and, ultimately, higher profits for the company.
About the Author
Steven Johnson worked as a toolmaker for 26 years, rebuilding and repairing multicavity molds for Calmar Inc. and then as mold-maintenance engineer for Hospira Inc., a medical device manufacturer. Today, he is the maintenance systems manager for Progressive Components and has his own business, MoldTrax in Ashland, Ohio, which designs and sells software for managing mold maintenance (www.moldtrax.com). He can be reached at email@example.com or (419) 289-0281.
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