Art Hedrick Art Hedrick

Avoiding the 7 Deadly Sins of Stamping: Part 2—Out-of-Sequence Timing

March 29, 2024

In Part 1 of this series, I discussed the importance of knowing and understanding how a fundamental understanding of material behavior affects the decision-making process and how taking action without it is the first deadly sin of stamping. In Part 3, in the June/July 2024 issue, I will finish discussing timing of a stamping die and delve into the different operations. I also will present some tips on resolving pilot release or feeding problems.

I’m reasonably confident that most of you reading this column have heard the simple phrase “timing is everything.” Many of the problems that I have consulted on were resolved by analyzing and correcting poor timing of the dies, feeder and press. Out-of-sequence timing is the second deadly sin of stamping.

Although timing is not the only consideration for a successful stamping operation, it is a critical one. Metal formers must pay close attention to timing fundamentals for the die, feed equipment and press.

When I conduct a die-troubleshooting or die-maintenance conference, I introduce a very fundamental timing process. Although using this process certainly will not solve all problems, it serves as a good place to start before performing any work on the tool:

  1. Locate the part or strip.
  2. Secure the part or strip.
  3. Perform the work. 

These steps may seem obvious, but, in my consultation work, I have encountered problems many times that stemmed from not following these steps.

Keep in mind that these steps must always be performed in the correct order as written above. For example, if you try to bend the part without first properly locating it in the press, the bend likely will be in the wrong position and the part geometry will not be correct. If you locate the part and then attempt to bend it without securing it, it likely will move during the bending process, resulting in an improper or mislocated bend. If you secure the part to the die with a high-pressure pad and then try to locate it and move it with a pilot or gauge, it likely will not move. The worst-case scenario: performing bending, flanging, drawing or cutting, and then attempting to hold the part down with the pressure pad, and then attempting to locate the part after all of the work has been performed. This completely reverses the process shown above. Not good. 

Let’s take a detailied look at each of these steps.

Locate the Part

You can locate the part or strip accurately within the die in numerous ways. Gauge pins, pilots and internal blocks that match the 3D forms on the part often are used to properly locate the part. It is important to understand that, although feeding equipment such as coil feeders and transfer systems serve to move the part from station to station, typically they are not intended to locate the part precisely. Their basic function: get the part within proximity so that the gauge pins, pilots or forms can locate precisely the part. In short, the feeder system does not locate the part; the die does.

That being said, it is logical that the first things that must engage with the part or strip are the pilot pins, gauges and other part-location mechanisms. For this reason, pilot pins and gauges must extend above any pressure pads or plates.

Pressure pad and pilot gauge timingBecause it is critical that the parts be allowed to move freely in the die so that the gauge pins, pilots or locators can easily locate them, the device that moves the part from station to station must release it before the gauge pins or pilots engage. This basic principle applies not only to progressive dies, but to transfer systems as well. In progressive dies, this timing between the feeder and the tooling is commonly referred to as pilot release or feed release. When a transfer system is used, such as a two- or three-axis layout utilizing transfer rails and part pick-up fingers, the transfer fingers/grippers must release the part before locating it, or they must be designed to allow the part to move freely within the fingers, enabling the pilots, gauges or locators to precisely locate the part. 

Secure the Part

Pressure pads, draw pads, stripper plates and various other pressure-related components function to hold or secure carrier strips and parts so that work can be performed. These pads or plates are flat or contoured, and typically are equipped with pressure components such as coil springs, nitrogen-gas cylinders or urethane springs. These pressure components supply the force necessary to hold the material or part during forming and cutting operations. They also serve to secure the part tightly to the die.

This helps the part to remain flat in areas where part flatness is critical while items such as forming and cutting punches are removed from the part or strip. Once the part has been secured, it becomes very difficult to move. If the pressure pad engages the part before a pilot has the opportunity to locate it, the hole into which the pilot enters likely will be out of position. The pilot or gauge pin will deform the pilot hole, or potentially bend or break it. Not only does this result in nonconforming parts, but also could cause serious die damage. Pressure pads and strippers should engage only after the part has been precisely located but before work is performed. 

Perform the Work

Once the part has been properly located and held in place using pressure pads or plates, work such as trimming, punching, lancing and notching, bending, flanging, hemming, embossing, drawing, and coining can be performed. Keep in mind that attempting to perform any cutting or forming operations before properly locating and securing the part/strip likely will result in nonconforming parts and possible die damage.

Data and understanding are the key.

Until next time … Best of luck! Art MF

Industry-Related Terms: Bending, Coining, Die, Draw, Drawing, Forming, Gauge, Notching, Stripper, Strips, Transfer
View Glossary of Metalforming Terms


See also: Dieology

Technologies: Tooling


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