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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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Producing Quality Parts on Older Machines
Producing Quality Parts on Older Machines By: Jim Szumera - MACOR Published on: 05/20/2015
Tips and Tricks to Producing Quality Parts in Older Machines
Oftentimes I fall into the blame game. Is it the press? Is it the die? I have had new dies installed into presses only to make several hundred hits before the punches would shear. I have had draw dies set up resulting in cracked cups, wrinkling on one side only, galled and sheared. The initial tendency is to address the problem as a tooling issue; after all, it was the tool that failed. If the tool is machined and set up correctly, it can never be a tooling issue. The root cause often lies elsewhere. If a tool fails shortly after set up, one needs to look closely at the press variables. These can be alignment, wear, parallelism, speed, stroke, timing or lubrication. One of the most critical performance criteria is press alignment. Older presses, through neglect, age, off center loads, constant area loads and the floor foundation itself all contribute to miss alignment. Several simple checks should be made to determine the press accuracy and alignment. First, the surface of the bolster and ram need to be checked for flatness. After years of pounding, the ram and the bolster may have an area of impression. A good rule of thumb is .001 per linear foot. Any more than that is trouble. The bolster may have to be reground if it shows excessive depressions. The ram also may have areas of depression. Resurfacing the ram may be too costly and time consuming. To compensate for the ram I may elect to “soft mount” the upper shoe using a hard urethane sheet between the ram and the upper shoe. This acts as a “filler” and will compress slightly on the down stroke. Another method is to mount a pre hardened 4140 plate to the ram, provided you still have adequate shut height. Basically we are installing a new surface to the ram. All high volume heavier material stamping dies should be designed using a 4140 steel die shoe to begin with. The higher strength material will prolong the surface life of the ram and bolster. Using 4140 for the die shoe, in many cases, will allow the elimination of back up plates. That savings will more than offset the increased cost of the shoe. The lower shoe must be supported all the way through the bolster, wherever there are large cutout areas. I have actually encountered a lower die shoe so flexed that the shims behind the bushings slipped under the die block. In another case, slugs actually slipped under the bushings. The die shoes also need to be checked for excessive bending and corrected as necessary. If you are stamping thin materials, you may not experience these types of issues. Short of rebuilding the press, I will modify the tool to improve alignment and prevent shearing, galling or breakage. If I am dealing with older presses I may design my tooling with guided strippers and no press fits. On draw dies, I will allow the draw punches to float and find their own center. This will always make for a better looking even draw. In some applications, involving high speed dies, I will not bolt down the lower shoe. It is allowed to float. Any modifications to mounting methods should be done in a safe and protected manner.

We have listed several ways to help correct the press inaccuracies such as installing pre-heat treated plates to the upper ram, regrinding the bolster, supporting the lower shoe, and various tooling corrections. Other issues that can cause die failures are crank and pitman timing on double crank machines, galling of the press slides and gibs, short guide pins that exit the bushings on the upstroke. This usually results in deflection and “bounce” on the down stroke. The crank assemblies can be out of timing with respect to each other. Another critical component are the isolation units under the press feet. Are they worn or collapsed? The floor foundation is another factor. Does the entire press flex on the down stroke, given the weakness of the floor foundation. I have had instances where the floor was cracked between the press legs and actually flexed. In the idle state, the press checked out fine. Another issue that rears its head slowly is with open back incline presses or OBI type. These presses can "yawn" or open more in the front over time. It may be necessary to actually shim the front of the bolster to compensate. In any case, if you have evidence of press degradation you must set up a plan to address these issues. The plan may include increasing inventory, outsourcing, or running in optional available machines giving time to rework the press, and planning for new presses in the future. You cannot keep running presses in poor condition and expect quality parts every time. Post your ideas.
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QDC The Whole Story
QDC The Whole Story By: Jim Szumera - MACOR Published on: 02/24/2015
QDC (SMED) Quick Die Change
Do you still feel like you’re hemorrhaging money?
QDC is only one piece of the puzzle.
The quick die change movement is getting long in the tooth and little misleading when it is focused only on the storage, retrieval, movement and installation of the die in the press. Although this is an excellent first step, it represents only a piece of the puzzle. I like to look at quick die change as part of a larger process. That process is called production readiness. It makes no sense to invest in equipment and procedure to remove and install dies into the press without addressing upstream and downstream activities and tasks. For instance, what is the value of reducing die set up time from 1 hour to 15 minutes, when it takes an hour to get a quality verification to run production. What is the process for production approval? Are gages readily available? What type of gage is being used? Who has floor authority to run jobs on deviation? What about the turn around time in die maintenance? Have the bottlenecks been eliminated? Is there redundancy? Are the tools properly supported? Can you create tooling kits and modules to facilitate changeovers? Is the documentation forthcoming, available and up to date?

I like to set up a Value Stream Map of the entire process, beginning with the die maintenance area. For example, I have witnessed die technicians walking a 500 yards or more to complete the task of punch sharpening. The dies are disassembled in an area apart from where the maintenance is actually performed. Adding to that problem, the punches are sharpened individually in different machine set ups. Basically, the technician dissembles the die, then travels back to his bench area to retrieve tools required for the removal of components. Then he travels to the grinding area to sharpen the components.
Kaizen Events can reveal and correct many of these issues, resulting in optimum production readiness. Die maintenance creates many bottlenecks to the overall performance objectives of the company. If you would like more information please contact me at
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