Strain Transmitter Offers Effective Mold Protection for High-Speed Injection Molding Machines

Kistler presents a new strain transmitter for measuring forces during mold movement and clamping forces of high-speed injection molding machines. This transmitter helps protect valuable injection molds and sensitive automation equipment from damage.

The new high-resolution, ultrasensitive, two-channel strain transmitter Type 4350A… measures dynamic and static forces on stationary or moving machine components such as toggle levers and back plates and is attached with four screws on a machined surface. In contrast to conventional piezoelectric transmitters, these new strain transmitters do not require a reset/operate signal and are therefore ideal for very fast mold movements without a retention period at the end of travel. With its two programmable, independent measuring ranges, it can measure both low forces during movement as well as high clamping forces after mold locking.

Background information: Mold protection for injection molding machines
State-of-the-art injection molding machines are equipped with both clamping force sensors and mold protection functionality. Mold protection during mold movement protects the mold from damage. This function enables machines to react quickly to foreign objects on the mold parting line, e.g. parts that have not been ejected. The clamping force is measured as soon as the two mold halves connect and is used for controlling the locking force. Typically, the forces applied during mold movement are smaller than the locking forces by a factor of between twenty and forty.

Both requirements are easily met by measuring the surface strain, for example on a toggle lever or on the back plate of the clamp unit. Extensions of machine structures are proportional to the applied forces but dependent on the structure’s rigidity, which means that the forces on the toggle are usually greater than those on the back plate.