PNEUMATIC PRESS COMBINATION SHORTENS LEAD TIMES
To meet tighter quality demands and shorter deliveries, John Bornhorst of AIRAM Press explains how this in-motion die-equipped pneumatic press eliminates secondary operations and reduces material handling up to 40 percent when fabricating parts for metal buildings, roofing, grain bins and elevators, as well as truck, automotive, appliance and HVAC applications.
Posted: October 29, 2011
To meet tighter quality demands and shorter deliveries, this in-motion die-equipped pneumatic press eliminates secondary operations and reduces material handling up to 40 percent when fabricating parts for metal buildings, roofing, grain bins and elevators, as well as truck, automotive, appliance and HVAC applications.
As recession survivors shake off the dust of the past two years, some industry experts say a growing trend has OEMs asking suppliers for stricter quality standards and shorter lead times. Flexibility will also be an important commodity for manufacturers that want to grow their profits. In-motion die technology, an application developed for pneumatic presses by AIRAM Press Co. Ltd. (Covington, OH), allows fabricators to support these production goals by eliminating secondary processes and reducing material handling and overall labor expenses.
During the last five years, this air press technology has been quietly stealing the show with its ability to tackle workloads normally reserved for mechanical and hydraulic presses at nearly half the capital equipment cost. When installed on a pneumatic press, the in-die motion application also gives fabricators the versatility to move from general stamping operations to rollforming or plastic extrusion.
The green pneumatic press, generally described as a four-post or two-post precision die set with nominal tonnage rated at 100 psi input pressure, uses air pressure on the downstroke and mechanical springs for the upstroke of the press ram. On the downstroke, the air tube/elastomeric actuator is filled with air at the signal from the control system, forcing the air tube to expand and apply pressure to perform the required work.
Unlike a mechanical press, which only develops full tonnage about 1/8 in off the bottom, full tonnage on the pneumatic machine is available through the entire stroke. The stroke can be controlled so it cycles down to strike material as quickly or as slowly as the application requires.
In a stamping operation, the machine’s small footprint (3 tons to 210 tons) lends itself to anchoring a manufacturing or finishing line. Prior to or following blanking, embossing, forming or coining, the in-motion die technology allows the die to literally travel with the material so that it can be punched or cut-off without stopping the operation.
For jobs with requirements of 200 tons or less, the pneumatic press is able to reduce traversing distance between the die and tool without reducing strokes per minute or line speed processing 30 to 35 parts per minute. In a comparable operation, the mechanical press is limited to approximately 12 parts per minute with production on a hydraulic press limited to 3 to 5 parts per minute.
Rollforming lines typically dictate flying cutoff or punching of the material following the rollforming operation. Because hydraulic and mechanical presses slow at the bottom of the stroke, flying cutoff operations take longer when compared to the air press, which can move in and out of the material three times faster. In a heavy duty rollforming line, the in-motion die-equipped air press can cut material 1.75 in thick by 6 in wide and 20 in long to length, moving in and out of the material in less than 50 seconds.
With rollforming, keeping the line moving is especially critical since stopping the operation can mark the material and potentially scrap the part. In plastic extrusion or ejection molding operations, the in-die motion-equipped air press can cut cardboard for packaging applications or angle board parts at 47 ft per minute in 5 in lengths.
In addition to tonnage requirements, fabricators can evaluate whether an in-die motion-equipped air press is right for them by considering factors that include:
- Amount of mass to be moved
- Production time
- Material column strength
- Floor space
- Type of parts
- Cellular or line manufacturing versus stand alone production
- Line speed
Fabricators also need to consider the type of mechanism they will need to accelerate the die during the in-motion process. There are three alternatives to consider. First, in-die motion can be servo-driven. For materials with little to no column strength, such as cardboard or light aluminum, servo actuation is recommended. The most costly of the three choices, the servo is also the most accurate, able to meet tolerances within a few thousandths of an inch.
Second, in-die motion can be air cylinder actuated. Accelerating and decelerating the die with an air cylinder is a reliable, low cost method. While not quite as accurate as the servo mechanism, the air cylinder with a uniform air supply is a low maintenance option. Since the air cylinder is moving the die and not the part itself, the buckle strength of the material is not a factor.
Third, a spring component can also allow processed material to accelerate the die with or without the air press by allowing the die to return to the home position. The spring method is also a cost effective, low maintenance option that is reliable and experiences little down time. This method uses the momentum of the part as it comes out of forming to accelerate the die when the punch or blade comes into contact with the material. The spring returns the die to home position as soon as the punch leaves the material.
The in-motion die-equipped pneumatic press is especially suited to fabrication of parts for metal buildings, roofing, grain bins and elevators as well as truck, automotive, appliance and HVAC applications. Processing advantages can also be achieved with cardboard and plastic applications for the shipping and packaging markets using the air press with in-motion die technology.
In addition to the wide range of components a fabricator can produce with the press, the ability of the in-die motion technology to eliminate secondary operations and reduce material handling by up to 40 percent are key factors for companies looking to make quality parts faster.