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World Class Die Maintenance
World Class Die Maintenance By: Jim Szumera - MACOR Published on: 06/9/2016
Building World Class Die Maintenance
Die maintenance is a service organization, much the same as an automobile dealership service department. Most dealerships cannot make the absorption rate to break even, so it is a necessary evil. Dealership service departments thrive on factory recalls. This is because they can bill back the hours to the manufacturers. It really cannot operate as a profit center, but in today’s economy it still must be world class. This is due mainly to the fact that they have to service what they sell and they are dealing directly with their customers on a personal level. Service is an integral part of any business, but because it cannot make a profit on its own, it usually is neglected and thus underperforms.
How does your shop measure up? First we would have to separate out the specialty or niche tooling that you may deal with. That is not to say it doesn’t the fit the mold. Specialty or niche tooling may require a unique approach to certain portions of die maintenance. For instance, a special grinding fixture may be needed to service and sharpen unique punches or forms. A special handling device or equipment may be required. Aside from the specialties, the desired results are almost always the same; reduced turnaround time to production; a better tool life cycle between maintenance, increased press uptime, improved first time set ups, and reduced overall costs. The ingredients we look at are equipment, procedures, drawings, spare parts, quality, ergonomics, and staffing.

A world class die maintenance operation has all the tools required at hand. This would include, but not limited to machine tools than can meet or exceed finish and tolerance requirements. Machine availability should never come into question. The equipment and machines should address every possible common operation needed to service the dies properly and expeditiously. Surface grinder, drill press, vertical mill, lathe, bead blaster, degreasing sink, hydraulic press make up the major portion of machine tool needs. Support equipment such as grinding fixtures, diamond dressers, radius dressers, Norbide dressers, grinding wheels, surface plates, V blocks, magnetic chucks, demagnetizer, etcher, hand held die grinders, bench grinders, belt sander, polishing lathe, lapping plate, laps, stones, pneumatic or cordless torque wrenches, shim fabricators is needed and should be placed conveniently and with purpose in the area. All pertinent die hardware, including springs, nitrogen cylinders, screws, shoulder screws, shoulder screw shims for lengthening and shortening, dowels, shim stock, markers, connectors, fittings, should be visible and readily available. Depending upon the size of the tooling and work area, these items should be organized and made visible and mobile. Looking for shims and making shims can increase actual maintenance time by as much as 50%. Shims should be ready made, organized and readily accessible.

Procedures or die maintenance work instructions should be formally integrated documents or simple task checklists can be a good substitute. In any case these should be accessible and visible in the work area. Tooling drawings and part print drawings, along with any associated quality documents must be readily accessible. This may require die books or a PC with read only and print capability. Effective wall charts work well. Most die service, diagnosis and repair is usually left up to the tool and die maker. The die is then released to production as he or she sees fit. There are no checks and balances at this point. The die should be checked and verified by a “die checker” as a final step. Remember, if you have 10 toolmakers you will get 10 different renditions of what a preventative maintenance should consist of. That is not to say that anyone is wrong, just different. That makes process improvement next to impossible.

Specific die components such as punches bushings, pilots, die sections and blocks, sensors and spring pins can be pre kitted and ready for change over, as opposed to disassembly, sharpen and reassemble. The expended details can be sharpened by a grinder hand at a later time. This will eliminate actual sharpening and handling by the die technician during maintenance and reduces the turnaround time tremendously. Utilizing spare parts in this manner speeds up the entire process. Many shops keep a tooling inventory for emergencies and tool breakage. This dollar investment should be utilized to cut costs, not increase costs.

Tool quality and inspection should also be at point of use. Drop indicators, surface gages, gage pins, surface texture gage, shim gages, angle gages, gage blocks, micrometers, calipers, spring tester, hardness tester, and comparator make up a partial list of the measurement and inspection tools needed and should also be readily available. Depending upon certain shop variables, a tooling inspection area could be set up separate but should always be convenient and accessible. The die maintenance inspection area should be capable of inspecting production parts as well as the tools, dies and punches. Granted, some items may require a CMM and it may not be practical in the die repair area. Measure, measure, measure, inspect! Anything that goes into a production tool needs to be verified, if only the criticals.

Ergonomics and Kaizen play an important role in reducing costs by simplifying the process, eliminating redundancy and making for a workplace that is enjoyable to be in. Pretty heavy stuff! The days of the cabinets, loose leaf binders and index cards is over. A visible, ergonomic and safe workplace that is well lit is the solid foundation that leads to sustainability.

The right staffing of the die maintenance area can be a difficult task. Finding qualified people who can hit the ground running is not easy, if not impossible. Utilizing existing personnel as die technicians is the new future of tooling maintenance. Not only does this approach boost moral, but makes good business sense and cuts cost at the same time. The candidates should be somewhat familiar with your current press operations, know how to use calipers and micrometers, and read tooling and part print drawings. This is all that is needed. You probably have the right people working in the plant right now and just need to leverage this talent differently. Tool and Die makers are not needed in this function, if you have everything in place. You are more than half way there!

The type of production stampings one makes is not an excuse for being world class. World class is really a simple idea with good execution. A world class die maintenance function should not make shims, sharpen dies, look for tools, or go somewhere else for something. It is not a place with poor lighting where you put a couple of machines, a ball peen hammer and some sand paper and expect results. It is an area staffed with the right people, the right tools, the right space, and the authority to make decisions and run itself.
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Eliminate Screw Failure
Eliminate Screw Failure By: Jim Szumera - MACOR Published on: 02/20/2016
We have all experienced screw and bolt failure in our careers to varying degrees. In some instances we were lucky. The damage was minimal. In other cases, not so lucky. The die crashed and resulted in broken details, strippers and punches. All things considered and assuming we have executed best practices in utilizing correct tap drill sizes, proper torgue and application, the screws still fail. Three vital, less known criteria to eliminate screw failure is as follows:

1. Only use quality name brand fasteners certified to meet or exceed specification, such as Unbrako, Holo-Krome and others. Do not purchase counterfeit screws and bolts. By counterfeit, I mean sub-standard material, heat treatment and machining. This problem proliferated from cost and resulted in poor quality imports from Asia, and Europe. It became widespread and was used in everything from bridge building and construction to high speed stamping dies. It became such a systemic problem that Congress passed the Fastener Quality Act of 1999.

2. In die applications the class of fit is critical. Many die builders go oversize on the tap drill size to facilitate CNC, tap life, and expedience in screw removal. While this may be good for die building economics, it spells disaster when trying to run these dies. Screws come loose and cause all kinds of havoc. Using a slightly smaller tap drill, or preferably fine thread usually works well. This is especially critical when fastening upper dynamic components, such as punches into hardened retainers and back up plates. Many die shops engineer punch removal in the press.

3. The last little known item is proper through hole preparation. Here we are referencing the inside clearance hole. It must have a chamfer to allow for the radius at the screw head. Often this step is overlooked in the die building process because it may not be called out on the prints or due to bad practice or negligence. This causes the screw to fail at the head. This may not develop into a failure mode if the counter bored hole is in soft steel. The screw will actually form the soft steel slightly when tightened. Check out the Parameters for Eliminating Screw Failure file in the Technical Data Tab.
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What Size Pilot?
What Size Pilot? By: Jim Szumera - MACOR Published on: 09/7/2015
What size pilot?
I have been involved with hundreds and hundreds of tools, dealing with every conceivable type of stamped part imaginable from .001 Kapton film to stamping 1/8 inch thick lawnmower decks, from .010 beryllium copper connectors to a 3/8 inch thick trailer hitch. In every case the pilots were .0002-.001 smaller than the pierce punch. Almost in every instance, the tools stamping the thicker materials had broken pilots, made miss hits and caused die damage. In a lot of cases the pilots had to be removed in order for the die to run. Not good. Many good die designers live in a false world of precision. They adhere to the notion that the pilots should be .0002- .001 smaller than the pierce punch and that is how to hold part tolerance. Not necessarily true. The pilots only purpose is to register the strip in its advanced position and help hold the strip straight. The station tooling should be so engineered to locate and form or blank. The exception would be a washer that has a center hole and must hole true position. The blank punch may have a center pilot installed in it. The pilot diameter is really a function of the metal thickness being stamped and its relationship to the pierce punch. Given strip growth stress and deformation, as a rule, if the stamped material is .025 or thinner I make the pilots .001 smaller that the pierce. I may use .0005 for material .015 or thinner. Material .025-.050 requires a pilot .001-.002 smaller. Material thickness .050-.090 require pilots .002-.004 smaller. Material above .090 thickness require pilots .004-.006 smaller. These sizes apply to all progressive dies. If the pilots are made too close in diameter to the pierce, progressive dies never run successfully. The dies will miss hit constantly, gall, break pilots and cause lower damage to the holes and bushings.
Having the right size pilot contributes to a smoother running tool without affecting tolerance. As a general guideline it is also recommended to spring load the pilots. This prevents further unnecessary die damage.
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