In metal stamping, heavy-duty steel belt conveyors are a staple owing to their durability and efficiency in handling scrap material. Conveyer solutions reduce labor costs, improve shop floor safety and, ultimately, increase overall productivity in stamping operations.
“A conveyor system reduces labor costs by automating the removal process, reducing labor requirements,” says Dustin Krueger, director of engineering, Jorgensen Conveyor and Filtration Solutions. “It can also lower the amount of scrap bin dumps needed. Shop floor safety is increased by reducing the number of times an employee needs to handle the components. If the shop is using a central system, it can reduce the need to physically handle components to almost nothing.”
For most stampers, running 24/7 is almost a given in today’s manufacturing environment with its tight deadlines. Consistency is the name of the game when it comes to moving material, which can be even more challenging when the conveyor is operating under extreme conditions. It is essential, therefore, to maintain conveyors and keep up with repairs to avoid downtime due to breakdowns.
Design elements can be built into a steel belt conveyor system to improve material flow, prevent jams and increase conveyor life. Considerations need to be made for the various material types and payloads being transferred as the design is based on material geometry, weight, total volume of material and how the material is introduced onto the conveyor.
A well-fitting conveyor can manage a range of materials and challenging load conditions. They are often made with features such as enhanced durability at inclines and curves to reduce premature wear and maintenance requirements.
Out of a jam
Avoiding jams and overload conditions in the conveyor system requires keeping material from becoming caught in the conveyor belt or wedged between the belt and the frame. This is done by guiding the material away from the side wings and by utilizing wing guards.
“It starts by understanding the scrap size, volume and how the scrap is introduced onto the conveyor,” says Bob Anspaugh, conveyor sales engineer, Prab Inc. “Small, thin scrap can get caught in between the seams and it can also work itself over the side wings and get into the track. This can cause premature wear on the belt and the frame as well as maintenance issues. This can be greatly reduced in the design and quoting phase by adding wing guards and welding the seams on the belt.”
Krueger agrees. “Design elements are relatively easy to determine with customer-provided information. If stampings are small or thin enough, they can work their way into the natural gaps in the belt. Depending on the stamping size, we add belt armor, which reduces the natural gaps between a hinge steel belt, as well as welding the side wing to the apron plate to eliminate the natural gap at the edges of the apron plates.”
Other design options are clean-out areas (pullout trays) on the conveyor casing that allow any material that might stick to the belt to fall out, preventing material buildup in the casing, which minimizes the chance of jamming and increases conveyor life. Also, if applicable, the lowest incline angle possible should be used to carry out longer material. The longer the component, the lower the incline should be.
“To prevent jams,” Krueger says, “it is important that the conveyor is sized correctly for the application, cleat centers are spaced so there is no chance of pinching components and cleat heights are sized to guarantee carry out in transitions.” (Cleats keep material on the belt when traveling along inclines and declines.)
One other note: For dry material, having an oiling system on the belt side bars and rollers can increase the service life. To prevent oily material from sticking to the belt, pimpled or rigidized belt surfaces are used to break the surface tension and allow the material to be discharged.
A mighty fall
An important consideration for conveyor life is the drop height onto the belt, especially for heavy material. Repeated drops can have a significant impact, leading to reduced reliability and increased maintenance requirements. It can also cause the material to bounce on the belt, which can lead to it working its way into the side wings of the belt.
Solutions include slowing down the speed of the material to reduce the impact on the conveyor belt. Also, the chutes between the press and the conveyor can be designed to absorb some of the impact of the drop. Lastly, implementing impact plates, load shoes and load bars prevents the belt from being damaged by drops.
“Thick, heavy scrap that free falls prior to landing on the belt can damage the belt pans and hinges,” Anspaugh says. “We eliminate this by adding impact plates to the top surface of the belt and load shoes on the bottom surface of the belt. We also have a load bar on the inside of the frame that works with the load shoes to minimize belt deflection.”
Impact plates are welded to the top hinge of the belt and load shoes are welded to the bottom of the belt. A load bar is part of the frame that runs right below the hinge. When a heavy piece of scrap drops on the belt, the load shoe hits the load bar and the force is transferred to the frame rather than the belt.
Anspaugh adds that for magnetic conveyors, the impact from the scrap falling onto the slide surface should be minimized or it can permanently damage the conveyor slide surface.
“Once the scrap is laying on the conveyor,” he says, “it settles and does not move unless it’s going up an incline. As it goes up the incline, the flights on a steel belt or the magnets on a magnetic conveyor limit how far it can slide. Having the correct spacing between flights or magnets helps reduce rollback on the incline. Keeping the depth of burden as low as possible is important and can be achieved by increasing the belt speed. I always recommend customers running 24/7 go with our heavy-duty design that utilizes an abrasion resistant track and flanged belt rollers for better durability.”
Regardless of the conveyor purchased, “it must be interlocked with the press controls so that the conveyor starts when the press starts,” he notes. “Many times, this gets overlooked and creates issues with scrap falling onto a conveyor that is not running and it just piles up.”
Service upkeep
One of the most important aspects of any conveyor system is to have a regular preventative maintenance program, according to Anspaugh. He stresses the importance of having this service done at least every six months, depending on the number of shifts running at a plant.
And for any maintenance requirements, easy access is appreciated. Features for conveyors that make the equipment more serviceable include access panels in areas that may be susceptible to jams and removable guarding.
For example, Krueger notes that the areas for regular maintenance on belt tension and bearing lubrication are easily accessible at the head and tail sections of the conveyor.
For Prab, “On closed-frame designs, we laser cut an opening in the frame and put a plate over the opening,” Anspaugh says. “This allows the maintenance team to easily remove the plate to gain access to the inside of the frame and in between the belt. Our open-frame conveyors are designed with our 6-in.- and 9-in.-pitch steel belt conveyors. This design has removable panels the entire length of the conveyor on both sides and is much easier to maintain.”
Latest advancements
Some newer developments for conveyor systems include state-of-the-art controls and sensor technologies to optimize the performance of the conveyor.
“All of the materials are getting harder and cuts are getting faster,” Krueger says. “Machines like to monitor the health of the conveyors as far as if a jam is involved or if the belt is rotating. We monitor conveyor health via sensors and logging fault conditions with our patented jam manager technology in our variable-frequency drives. We also use sensors for monitoring bin levels or bin placement. The conveyor system can be integrated into additional automated processes as well, such as packaging and heat treating.”
Today’s stampers can gain more insight into their scrap removal processes by taking advantage of these newer technology features. Along with keeping up with maintenance issues, this leads to improved operations and overall efficiency enhancements.
