Injection Molding Clamping
During the injection molding cycle, the mold is open and closed by a clamping mechanism. (RDC 9/5/2011)
“Presses are rated by tonnage, which expresses the amount of clamping force that the machine can exert. This force keeps the mold closed during the injection process. Tonnage can vary from less than 5 tons to 6000 tons, with the higher figures used in comparatively few manufacturing operations. The total clamp force needed is determined by the projected area of the part being molded. This projected area is multiplied by a clamp force of from 2 to 8 tons for each square inch of the projected areas. As a rule of thumb, 4 or 5 tons/in2 can be used for most products. If the plastic material is very stiff, it will require more injection pressure to fill the mold, thus more clamp tonnage to hold the mold closed. The required force can also be determined by the material used and the size of the part, larger parts require higher clamping force” (Wikipedia, Injection Molding, 9/5/2011)
“The toggle-type mold clamping apparatus connects a movable platen supporting a movable mold and a crosshead advanced and retracted by a drive unit with a toggle link mechanism, has the function of increasing the pressing force of the crosshead and transmitting it to the movable platen, generating a predetermined mold clamping force based on the extension of the tie bars in a state in which the toggle link mechanism is almost fully extended. In the mold closing operation, high-velocity mold closure is usually performed from a mold open position and, if the mold reaches a low-velocity low-pressure changeover position, the operation mode is switched to low-velocity low-pressure mold closing. The low-velocity low-pressure mold closure becomes the mold protection zone, from which a molded product that is not properly ejected is detected as a foreign object. If the mold reaches a preset high-pressure changeover position, the operation mode is switched to perform high-pressure mold clamping.” [Kato and Hakoda, US Patent 7,892,463 (2/22/2011)
Recent US Patents
11/1/2011
8,047,826
Mold fixing system
Kimura of Pascal Engineering, Japan, attached magnets to clamp plates for fixing a mold to the clamp plate. (RDC 11/4/2011)
2/22/2011
7,892,463
Mold clamping force correction method for mold clamping apparatus
Kato and Hakoda of Nissei Plastic, Japan, monitors and controls mold clamping forces during injection molding using sensors and softgware using deviations form a standard work load. (RDC 9/3/2011)