Internal threaded mold

Product Details:

Product name: Internal threaded mold

Industries: Industry

Mold base: LKM

Steel: P20

Plastic: PA66

Cavity no.: 1x2

Dimensions: 400x500x360mm

Mold life: 300,000 shots

Lead time: 6 weeks


Internal threaded mold, cold runner, LKM standard, P20, 0.3 million shots guarantee.

Internal threaded mold making is very popular in all industries, it usually need hydraulic cylinder or motor for mold release. An internal thread form is basically an undercut that does not allow free ejection from the mold.

Low production prototype molds can be unscrewed by hand, but most molding is done automatically. Parts that have a suitable thread form and low modulus of elasticity, can be stripped off the threaded cores, because the undercut shape and flexibility allows this to happen. A collapsible threaded core can be used to mold internal thread forms and freely eject small to medium size parts. The majority of all thread forms (especially medium to large) are unscrewed before ejection takes place.

There are many different designs and methods for unscrewing style molds. How complicated the design becomes is dependent upon:

  • 1. The thread form shape, number of cavities, and mold life.
  • 2. The core and drive design used.
  • 3. The power required.


The drawing represents one type of unscrewing mold. This design can be used for one or more cavities. Additional racks and pinions could be added for more cavities if press size and capacity were big enough. The power to drive the rack can be from an air or hydraulic cylinder, (as shown here) a motor driven gear train, or a rack and pinion gear train driven by the mold and press opening and closing.

The closed mold has the rack in its retracted position and the pinion gear forward, so that the threaded core is in its molding position. After molding and cooling, the mold opens completely, parts stay on the ejection mold half. Then the piston is timed to push the rack forward, causing the pinion gears and shafts to rotate counter clockwise. The pinion shaft will screw into the lower thread bushing, while the threaded core on top of the shaft will unscrew out of the part, ejecting it from the mold.

The collapsible core shown can be used to mold internal threads, protrusions, dimples, interrupted threads, and cut outs. Molding can be economically done on high or low volume requirements. Up to 80% full threads or undercuts can be molded. Threads do not have to run to the top of the mold as with unscrewing molds. The collapsing core also permits threads to stop at any point along the molded length. A longer threaded area can be formed, without adding to cycle time or requiring long rack and pinion mechanisms. Sizes vary from as small as 13mm.


After molding, the ejection half of the mold base travels back to its full open position. The press ejector rod is actuated and forces the ejector assembly forward, along with the stripper plate, collapsible threaded core, and molded part. As the ejector assembly and collapsible core move forward, the center pin pulls out of the inside of the core, (since it is fixed) and allows the core to collapse. In case the core should stick, the positive collapsible sleeve insures the core will collapse. A limit switch is activated and the air cylinder extends the ejector plate, forcing the part to be ejected off the collapsed core.


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