Punching Innovations

New technology can make punching operations more efficient by eliminating waste

January 1, 2011

Sheet metal fabricators need to look for cost savings in every aspect of business including scrap reduction and energy savings.

Parts smaller than 20 by 20 in. are deposited through a drop chute, and a conveyor will separate the parts into containers.

As sheet metal shops examine new ways to reduce costs, recently released new technology can save money in ways that previously were not possible. Skeleton removal and energy savings may not have the cachet that hits per minute (HPM) or a deep throat depth carries, but in today’s manufacturing, every little bit helps.

Eliminating Skeletons

Modern punching machines are highly sophisticated, fast, dependable, and often automated. However, there are a few things that can slow them down.

For example, when parts become caught in the skeleton, process speed and reliability are negatively affected. Also, unloading the skeleton is a separate work step requiring either the machine operator to move the unwieldy leftovers into a container, or using automation, which requires time and an outlay of capital.

Skeleton-free processing is a feature now available on some new punching centers developed by fabrication equipment manufacturer TRUMPF.

“Skeleton-free processing was developed to help improve sheet utilization,” explained TRUMPF’s TruPunch and TruMatic Product Manager Mike Kroll. “With the ability to punch up the sheet skeleton and separate it from finished parts, some scrap buyers will pay more for smaller scrap than larger, full-size frames.”

Software controls skeleton-free processing, which differentiates between parts and scrap and separates each into its proper containers. The tool used for skeleton-free processing is the same standard cutoff tool used for conventional processing.

“Skeleton-free processing breaks all the rules of conventional nesting techniques,” said Kroll. “Web widths used to maintain sheet stability are eliminated. Skeleton-free processing increases the average sheet nest by 10 percent, and smaller parts will have better nesting capabilities, allowing for better sheet utilization.”

Parts are processed in sequence and then freely punched prior to discharge or removal. Parts or scrap is rotated using a separating tool with a bilevel stripper and discharged from the machine.

Finished parts smaller than 20 by 20 in. can be deposited through a drop chute and a conveyor will separate the parts into containers. Larger parts can be removed using a vacuum suction system and deposited and stacked on an unload platform.

The sheet skeleton is then cut into pieces smaller than 20 by 20 in., deposited through a drop chute, and transferred to a container.

“One hundred percent of the sheet skeleton is deposited into the scrap container,” said Kroll.

According to Kroll, the processing time per sheet also remains the same.

“Anytime material has to be handled, it adds costs to a part,” said Kroll. “The sheet skeleton is part of that process, so if the sheet skeleton can be removed automatically without manual intervention, it will always be a less expensive way to process parts.”

In addition, skeleton-free processing saves space and makes additional equipment for cutting scrap unnecessary.

Saving Energy in Punching

Today's punch presses can reduce the amount of energy required for an operations without sacrificing machine productivity or efficiency.

Sheet metal fabricators need to look for cost savings in every aspect of business — process improvements, material costs, labor costs, and even energy costs. 

According to LVD Strippit Vice President of Marketing John Quigley, his company has been implementing power optimization technology for a number of years, and the new punch press energy reduction system (ERS) is the latest innovation designed to attack rising energy costs.

“The energy reduction system was developed to reduce the amount of energy required to operate punch presses without sacrificing machine productivity or efficiency,” said Quigley. “There is a worldwide interest in combating rising energy costs, and the energy reduction system contributes to lowering electric consumption in the sheet metal fabrication process.”

This new technology has been added to the company’s newest hydraulic turret punch press model, the Strippit VX-Series, which, according to the company, has one of the highest hit rates in the industry, yet uses less electricity than previous-generation machines.  

Talking specifically about the VX machines, Quigley said the ERS lowers energy consumption in several ways:

1. A frequency drive has been added to the pump. When oil flow is unnecessary, the frequency drive reduces the pump rotation to a minimum to eliminate unnecessary use of power.
2. A low/high-pressure system has been added. Only the required pressure necessary for the process is used, and the machine can switch automatically between the high and low pressures.
3. Accumulators are used to smooth out the request for peak power. This solves the previous problem of generating peak pressure or power when it is not needed.

The low/high-pressure system, which is part of the hydraulic press drive unit, uses a two-stage accumulator. High pressure, and the accompanying normal electricity consumption, is used only during the motion of the ram where the tool is penetrating the material being punched.  During the approach and retract motions, the system automatically and instantaneously converts to low pressure, or low energy consumption. 

“This feature significantly reduces energy consumption during a high percentage of the ram’s movement in the punching process,” said Quigley.

The second component of the ERS is the special frequency drive contained in the hydraulic unit. 

“During low-pressure conditions, when no hydraulic oil flow is required, the frequency drive on the hydraulic pump automatically reduces the pump rotation to a minimum to eliminate the unnecessary consumption of electric power,” said Quigley. “On average, this contributes to around 15 percent lower energy usage than previous LVD Strippit punch press models.”

This ERS is an automatic feature of the punch press, and according to Quigley, it does not delay the operation of the machine or require operator intervention.

“The system simply works in the background, automatically optimizing power consumption,” he said. “There also is no tradeoff in productivity for energy saving with ERS. If the machine is idle or in low energy consumption mode, it is immediately ready for production.”

For more information, visit www.lvdgroup.com and www.us.trumpf.com.