Face Time - Maximizing under-press conveyor life.
Maximizing under-press conveyor life
December 2019 - “There are critical elements necessary in the design phase that will reduce the impact of force from scrap—ensuring good material flow, reducing downtime and maintenance, and helping to keep operators focused on press output,” says Bob Anspaugh, conveyor sales engineer for PRAB Inc.
Q: Why use a steel belt for metal stamping scrap?
A: As press technology has expanded to meet the changing demands of customers in the automotive, aerospace, defense and construction equipment sectors, the reliability and robust nature of the steel belt conveyor design remains one of the most efficient methods for the transfer of flat scrap from metal stamping operations.
Q: Are all under-press steel belt conveyors the same? Why does the design matter?
A: The design of the steel belt conveyor for a given application is a critical component to maximizing asset utilization and decreasing costs by avoiding conveyor wear and unplanned downtime. The increased demands on stampers to achieve tighter tolerances using a wider range of materials, coupled with 24/7 run times, means that equipment purchases normally made as second nature now need to be evaluated for dependability and longevity under extreme operating conditions.
Q: How does the force from falling scrap affect the life of the conveyor?
A: The structural and functional design of a press is focused on the operating process and the quality of the output. How and where the scrap is collected and disposed of is typically not part of the design process. This reality can pose challenges when stamping operations purchase conveyors for moving their scrap.
Stamping scrap can fall from 36 inches up to more than 10 feet when it is discharged from the press. The impact of this drop can be significant on the conveyor belt, reducing the reliability and increasing the need for maintenance.
To understand the implications of the scrap falling on the conveyor belt, we can use a typical formula for impact of the force of a falling object. While there are other application-specific variables that can be added to this calculation, the basic equation helps to see the exponential impact of force.
An example, as a result of one specific calculation, was finding that the impact of a piece of scrap weighing 1.2 pounds had 460 pounds of force on the conveyor belt. Ouch! In this case, the conveyor belt was assumed to deflect 1⁄8 inch under impact. Repetitive high-force impacts of this type explain the potential for premature conveyor failure.
To illustrate the impact of force, consider the effect of an air bag in an automobile. In a crash test simulation without an air bag, a crash dummy hits the windshield with high force. The addition of the air bag reduces the effects of the force because the air bag lengthens the stopping time and distance and absorbs a portion of the generated force.
Q: What design solutions are available?
A: Engineers and plant managers looking to get the most out of their conveyors can work to reduce the effects of impact force on the conveyor. One approach is to slow the scrap down with a chute. The other method is to design the belt so it is more resistant to the impact from the scrap. There are several additional solutions that can be put in place to get the most life out of the conveyor, and they should be discussed in the design phase, before build and installation.
Q: What should I know from the supplier when looking for the right solution?
A: Understanding the impact of force from metal scrap falling from a press onto a steel belt conveyor is important to know during the design and quotation phase of a new conveyor purchase. There are some core design elements that can be built into a specific steel belt conveyor that will not only reduce the effects of force but also improve material flow. Both elements will reduce unplanned downtime and maintenance costs and will help keep your focus on press output. MM
Bob Anspaugh is conveyor sales engineer for PRAB Inc., Kalamazoo, Michigan, with more than 12 years of experience in automation technologies. PRAB engineers and manufacturers metal scrap handling conveyors, metal chip processing, fluid filtration and wastewater treatment systems
