Thursday, March 14, 2019

Why shimming dies has no place in your press brake operations

Stop wasting your time, money, and materials

Chances are, if you own a press brake eight feet or longer, your operators are shimming dies to achieve consistent bend angles. And chances are, if your operators are shimming dies, it's costing you time, money, materials, and contributing to premature wear on your equipment.


Shimming press brake dies: an overview

Although time consuming and costly, shimming is often used to compensate for deflection or inconsistencies in the ram and bed and how they react when they are put under load. Press brake deflection is when the ram and bed flex under load in the shape of an arc, causing what's known as the "canoe" effect on bent parts. Inconsistencies can appear in the form of "peaks" and "valleys" in the rams and bed of older machines after years of use.

When shimming, operators place thin pieces of paper or metal under the tooling in the areas where the tooling needs more height to close up the angle. In some ways, it’s a very effective method of compensation. Depending on the v-opening, a single sheet of paper can add as much as 1° to that area of the bend. A larger v-opening will need more shims, because the punch has to penetrate further into the v-opening to affect the bend angle. 

However, shimming press brake dies also comes with a hefty price. From a productivity standpoint, shimming should only be used as an absolute last resort. It’s an art form that requires a skilled and experienced operator, and most inexperienced operators will struggle to produce quality results by shimming press brake dies. In an industry where it is becoming increasingly difficult to find skilled operators, shimming adds a vulnerability to the quality and consistency of your manufacturing process and comes with extra hidden costs.


The hidden costs of shimming press brake dies

Materials – By nature, shimming press brake dies is a trial-and-error process that can quickly produce a lot of scrap material. While scrapping material is cost prohibitive enough on its own, the cost of scrapping material at the press brake can increase exponentially. Depending on your manufacturing process, the scrapped material has likely gone through various other value-added processes in your shop. This could be everything from shearing, punching, laser cutting, finishing, etc. When you scrap material at this stage in the manufacturing process, you don’t only lose that material and time lost at the press brake, but all the processes that came before it as well.

Premature wear on equipment – Shimming also promotes premature wear on expensive equipment. By adding unnecessary and frequently uneven load on your equipment, it can lead to more problems down the road. Excessive shimming on the same tooling dies can lead to premature wear on your dies, reducing their working height slowly over time. However, since tools are often changed fairly frequently, this usually isn’t a problem unless you consistently shim the same dies. However, if you are consistently shimming dies and your die holder is non-hardened, this can distribute wear across the length of your die holder unevenly and prematurely, which only increases the need for more shimming down the road. Eventually, it may be necessary to purchase a new die holder or remachine your existing die holder.

Non-value added time and lost revenue – The most costly result of shimming press brake dies is the inefficiency and lost productivity due to its time consuming trial-and-error nature. If shimming is a regular part of your set-up process, it could be accounting for up to 50 percent of your average non-value added time at the press brake, often taking 15 minutes or longer. Every minute spent shimming dies is a minute that could be spent running the press brake to produce profitable parts with a more efficient setup.

The other side of the coin when considering the amount of time consumed by shimming dies is your hourly burden rate. Press brake operators are often the most skilled and highest paid machine operators on the floor. But like any high skilled position, a craftsman is only as good as the tools in their toolbox. Wasting time shimming dies can severely limit the productivity potential of the most high skilled, high paid machine operators in a shop. 

Invest in a better solution

It’s hard to truly understand the cost shimming has for your business without looking at the numbers. However, it isn't uncommon for shimming to account for $20,000 in lost revenue per year. A good crowning system is the most efficient way to consistently produce accurate bend angles across the entire length of your parts. The right crowning system can significantly reduce your set-up time and scrapped materials. Not sure which crowning system is right for you? Read our "10 Things to Look for When Choosing a Crowning System" guide to help you make the right decision.

Why shimming dies has no place in your press brake operations

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