What is “milk run” maintenance? It is basically a phrase to describe the regular maintenance of the tools and dies used to produce parts needed. To keep inventory levels in check and pipeline activity at an even keel, they usually are done on a weekly or biweekly basis.
You should be able to count on a die that has been maintained to go in and make good parts.
5 Sharp Tips for Maintaining Optimal Die Performance …
A few practices may help streamline the process of readying your steady revenue generators—stamping dies!
- Have Spares on Hand. On high runners—dies made to last for high-volume, long runs—you should have a predetermined number of ready-to-plug-in spares. (Hopefully you considered these during the quoting process and then finalized how many you would need during the design phase.)
- Sharpen Consumables Constantly. Consumables (cutting components, mainly) usually are sharpened, shimmed, and put back into the tool each cycle. On larger, more complex tools, it is possible to run into a lead-time crunch while you are performing maintenance between runs. When this is the case, take a cue from the pressroom single-minute exchange of die (SMED) team and perform some of the work ahead of time.
One way you can do this is to create a dedicated, compartmentalized drawer—one for upper details, one for lower—that contains every component requiring maintenance at every interval. Each compartment would contain a sharpened detail with proper edge conditioning and shim size.
This is also a great way to train apprentices and junior diemakers. While the die is running in the press, they could perform the initial grinding on these tools. Theoretically, the same shim would be selected, and the same amount of material should be removed each time. Then the apprentices and junior diemakers can work with the veteran diemaker on edge conditioning and finalizing the kit. This way, when the tool comes into the shop, press downtime is reduced to a clean-inspect-swap, details-and-go situation.
- Save the Last Part, Last Strip. It is best to have the last part and last strip available for inspection when the tool goes in for maintenance. These can be very handy when determining if any extra actions may be needed during the procedure. Occasionally, material properties at the edge of spec or cutting lubricant that was not applied to the strip properly during the last run—or a host of other reasons—can cause wear or galling that is not addressed by the standard operating procedures (SOP). (This is why the word theoretically is added regarding the standard material removal amount!)
- Circulate Inspection Report. You can take step three even further by providing the last inspection report to the diemaker when the die goes into the shop. These documents usually monitor critical-to-quality (CTQ) specs and dimensions that need to be controlled for internal purposes. For example, the part may need to fit into a fixture properly in a downstream assembly operation. This is not meant to create a knee-jerk reaction in the die shop. A dimensional problem during the last run may have been human-induced or some sort of random occurrence.