Ideal Cushioning uses unique measurement tech-nology and lab proven guidelines to increase throughput of air cylinders, and at the same reduce noise and wear on the cylinders.

Ideal Cushioning of Aluminum Air Cylinders Reduces Cycle Times Using pneumatics in wood processing increases performance

Bosch Rexroth Pneumatics has developed the concept and application of Ideal Cushioning for optimizing air cylinders to increase productivity. When using the Rexroth ISO 15552 pneumatic cylinder line, cushions can be adjusted “ideally” to achieve reduced cycle times, re-duced noise and vibration, and increased cylinder life. Ideal Cushioning means that there is no end of stroke bounce, i.e. the direction of travel of the piston is the same throughout the entire cushioning sequence, and that its velocity is exactly zero when it reaches the end of its travel. The steps include measuring piston velocity in both directions, which is made easy by an electronic Ve-locity Time Meter available from Bosch Rexroth. Speeds are then adjusted to conform to a maximum for a given pressure and cylinder load. Next the cushions are ad-justed properly through a series of specific lab proven steps to achieve the ideal performance described above.

Ideal Cushioning has been used successfully in sawmills and other wood industry applications to reduce cycle times of bin sorters, trim saws, waste gates, etc. A sawmill recently increased the speed of their bin sorter line 35% by applying Ideal Cushioning at their facility in the Northwest. An exact measurement of piston speed forms the basis for optimizing systems. The Velocity Time Meter (VTM) measuring device from Rexroth is the only one of its kind in the market to easily and precisely measure piston speed or cycle time. Connected to the VTM sensor on the cylinder, the displays will show the current piston speed in m/s or the cycle time in milliseconds. Typically, the piston velocity is adjusted to a specified standard using right angle flow controls located in the connection ports of the cylinder. Then recommended adjustments using cushioning screws are made and the result will be achieving “Ideal Pneumatic Cushioning” which means; increased piston speed, reduced stress and mini-mized downtime resulting in increased performance! The VTM is suitable for cylinders with magnetic pistons and can be used to adjust all ISO 15552 cylinders from Rexroth. The unique cushion design of Rexroth ISO 15552 cylinders enable end position Ideal Cushioning. The customer enjoys cost savings from reduced wear and impact on the cylinder and other equipment, in addition to the savings achieved from higher production output. When a cylinder is exchanged, exact calibration reduces start-up time and protects the machine from an overload.

Traditionally, manufacturers of equipment used in harsh sawmill applications have used pneumatic cyl-inders made of steel, believing that steel was necessary to tolerate the debris, temperature fluctuations, vibration and shock generated in tough applications such as trim saw line. Today, however, industry application engineers are realizing have been able to realize cost and performance advantages by switch-ing to aluminum pneumatic cylinders coupled with the concept of Ideal Cushioning. Lower overall component cost combined with greater productivity have won them over. The speed and productivity benefits come from aluminum’s lighter weight and the elimination of the end of stroke bounce. An OEM uses Ideal Cushioning to speed up their trim saw to 200 board feet per minute at 40 to 60 milli-seconds per stroke. The planer mill trim saw has eleven saws on one-foot centers and is used to trim planed boards to length prior to sorting. The machine processes 4 to 6 inch wide boards with thicknesses from 2 to 4 inches and in lengths from 6 to 10 feet. The boards are fed into lugs just before the trim saw, and then pass laterally via a chain conveyor through the machine. The saws are independently actuated in a quick down-and-up motion to trim the boards to the specified length. The extension and retraction of each saw is driven by Ideally Cushioned Rexroth 80mm bore ISO cylinders. The cylinders are con-trolled by a master PLC and use 80 psi to complete the down-and-up stroke. Originally they had been skeptical whether an aluminum cylinder could hold up, much less achieve higher speeds. Per the OEM: “We ultimately chose the Bosch Rexroth 523 cylinder because it proved to be the best performer,” he explains. “The heavy-duty aluminum, wall thickness, and forged housing of the cylinder held up impres-sively well during testing. Bosch Rexroth’s Ideal Cushioning successfully dampened the shock and pre-vented the rod ends of the cylinders from breaking. All of these benefits, including an overall weight reduction afforded by the aluminum, were remarkable given the unprecedented speed we demanded of the cylinder.” OEM’s often choose the Rexroth Series 581 ISO valve or the Rexroth Ceram™ ISO valve in combina-tion with the ISO 15552 cylinders. Both air valve lines have been proven in the wood industry for years and use standard ISO subbases with either NPT or ISO-G ports.

Rexroth ISO15552 aluminum air cylinders are available with ISO-G (BSPP) or NPT ports, and metric or UNF piston rod threads. Shown above are the Series TRB tie rod (replaces Series 523 gray), Series PRA profile, and Series 523 green profile (protected sensor).