Producers of seals and other components employing Teflon (PTFE) quickly they wind up sweeping nearly all of their profits out with the machining chips when producing elements from typically compression molded rods and tubes. Polyurethane rod resins are costly and making parts from compression molded rods or even tubes often winds up yielding only 10-20% of the material acquired to the finished parts. Since PTFE, once sintered, can not be reground and re-used, 800-724 of the material cost end up in the waste. The solution is to utilize isostatic molding processes to make thin walled tubing.
Isostatic molding originated from the W.S. Shamban Company in the 1950s and 60-s. Formerly, when rocket nose cones heat shields were made of PTFE, a method was needed to smoothly reduce PTFE powder over the bullet shaped area of a nose cone. This is done by setting PTFE powder over a nose cone-shaped aluminum plug, then within the powder using an elastomeric kidney. The plug, powder and kidney were then placed in a pressure vessel and high pressure water pumped in to ultimately achieve the retention of the powder in to the preformed shape ready for oven sintering.
Being an interesting side note, as rockets became, and the nose cones became too big to fit into pressure vessels, the bladder-covered plugs with resin dust sandwiched inside were just lowered into the sea to the appropriate level to reach the appropriate retention pressure.
Modern isostatic molding machines have come a long ways from your rocket nose cone times. Now they use gas instead of water in cylindrical pres-sure vessels. Isostatic molding machines generally use a hydraulic pressure system serving a custom intensifier to end the pressure up from the regular 3000 psi hydraulic system elements to the higher pressures had a need to achieve excellent physical properties within the molded HDPE Sheet.
The greater designs employ interchangeable mandrels to really make the device adaptable to many sizes of tubing, and polyurethane end pieces and external diameter forms to move the hydraulic pressure from the urethane bladder to numerous different sizes of tubing. The smooth urethane functions as a substance itself to transfer the hydraulic pressure towards the powdered resin being squeezed. By using soft end bells, end belling common with earlier patterns is removed so that the total amount of the carved pipe is usable.
Minimum hydraulic controls are needed, and many the hydraulic components needed are available off-the-shelf. The exception will be the intensifier, which should generally be developed from scratch to ultimately achieve the necessary pressure increase and volume make-up requirements of this type of large, flexible hydraulic system.
The only real difficulty with isostatic molding is there are no products it is possible to only buy off the shelf. Each must be custom designed and tailored to meet the precise size ranges and substance retention parameters needed. This usually winds up meaning there is a considerable investment in design and hard-ware costs. In addition it requires a number of months to have a device made, fabricated installed and tested. Once that expenditure is made, though, the payback times are fairly short, frequently way less-than three years.
Having isostatic capability allows smaller seal, displaying and custom machined PTFE makers the power to contend with their larger competitors by substantially reducing their scrap prices and permitting them to competitively bid on high-volume applications Read This.
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