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The first production meeting with my new employer went something like this: “We want you to establish a PM program that is based on maximum cycle counts for all our molds.” Then, before I could launch into an explanation of how best to determine maximum cycle counts, I was hit with the follow-up: “So, how many cycles do you think our molds can safely run before we need to clean them?” Leaving my crystal ball at home and unable to get my x-ray vision working, there was no way to answer this question with any real accuracy. Unfortunately, this is not what they wanted to hear. The group of PhDs surrounding the table looked on with minor disgust, assuming this should be an easy question for a mold guy to answer. They also were disappointed because they would not be able to leave the meeting with a solid scheduling plan for production that would help molds run better and eliminate some apparent mold damage issues they had suffered in the past from molds being over-run. Generic Numbers Residue type, powder, flakes, gummy (tar like) or oily consistency Vent locations, depth and finish Vent dump size, location and configuration (ring, channel, blind pockets, etc.) Static vs. dynamic (moving tooling) vents Tooling plating type and condition Inaccessible internal bushing and other actuating components Internal condensation level and mold plate steel type O-rings and other internal water seal leakage history Specific hot or cold runner issues In Real Life Let me clarify. Molders are customer-driven—as they need to be—when it comes down to running a mold to complete an order. If a couple of more hours, shifts, days and in extreme cases—weeks are required to get an order completed, the mold will run—or lock up trying. So why bother setting max cycle counts if they are not adhered to? Although we may not always be able to clean every mold every time it needs it, it is critical with some molds simply because of the damage that can occur when max counts are ignored. When steel is gone—it’s gone. So the challenge in the shop is to know max counts for molds along with a safe range where molds should be pulled if possible, but if in danger of missing production schedules, may be run longer without undue damage. Molds that require short production runs also are in danger of premature tooling wear if the tool room doesn’t track total mold cycles for a series of short orders. It is easy, without a tracking system, to damage tooling simply because cycle counts get lost in the day-to-day affairs of pulling and setting lots of molds. Overrun molds also create situations that require more abrasive cleaning methods, which in itself can be hard on tooling and drastically reduce usable life, as noted in the following case. An Expensive Lesson Once the vent dumps are full, and having nowhere to go now, the residue was forced past the flats, between the core and sleeve where the resulting sliding action of the core and sleeve during ejection turned the typical red powery residue in to a black gummy substance that quickly wore down the parting line of the softer, and expensive, core. This resulted in flash on the bottom of the part. The mold builder would not let our tool room increase the size of the dump (his reasoning becomes clear) maintaining it would compromise the ability of the sleeve/core alignment during part fill and ejection. Run It Anyway Through ongoing diligent inspections during repairs, we found that even a few hours over the maximum cycle count caused excess and measurable wear, and from that point on this mold had a mandatory max count of 150,000 cycles, no exceptions. We also found that if the mold ran over its cycle limit, the cores required scotchbriting to remove the excess ground in residue. If this was performed incorrectly—a repair tech could easily round-over the sharp, leading edge of the sealing diameter of the parting line, which in turn would cause flash, setting up yet another toolroom versus process debate over the actual root cause of the flash. But cleaned during the safe range of cycle counts, the residue was quickly and easily removed via ultrasonics, creating no additional wear whatsoever. A hard lesson indeed, but a common problem that portrays the importance of setting accurate numbers for maximum cycle counts on molds that from time to time—get overrun. On the other end, there are many molds that can easily run over 250,000 cycles, that need to have this number validated. One mold was a 48-cavity jump thread cap mold that we started out at 250,000 cycles and found—after steady count increases of 100,000 per run—that we could actually run the mold to 1,500,000 before it needed cleaning! The fill configuration and resultant residue in this mold was contained in non-critical static vent dumps that posed no threat to moving tooling or shut-offs. For non-tooling trained administrators, it is sometimes difficult to understand why molds that run similar resins have such different reactions to extended cycle counts. This is why the effects of process variations need to be monitored and understood so we can maximize runtime without additional component wear. Basic Production Data Required What press did it run in? Who started it? What configuration is the mold running? Date and time the mold was stopped. Who stopped it? Why was it stopped (scheduled or unscheduled stop reason)? How many cycles did the mold run? And also very helpful when evaluating mold residue/wear levels: Was the run interrupted by stops for changeovers, unscheduled breakdowns or weekend downtime? Were repeated ejector counts required to release the parts from the mold? Was the mold properly and regularly serviced in the press during the run? Was the cycle time and processing parameters consistent with past runs? Are any part defects related to flash in a vented area?
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