What is the stop pin?

stop pins for plastic injection mold

The function of the stop pin

1.Reduce the contact surface betwwen ejector plates and clamping plates,it is easy to control the flatness of ejector plates by adjusting the thickness of stop pins.

2.Buffer against ejector plates

The material of stop pin

S45C,hardness HRC40°~45°

Position of stop pin

1.An STP must be installed under the RP to prevent deformation caused by large stress,see pic 1#

2. Avoid to interfere with other mold components,such as support,EGP,KO .etc. see pic 2#

The quantity of stop pins

The quantity of stop pin designing

Note:For a large size plastic injection mold, Stop pin is needed to increase the supporting points of the ejector backing plate, so as to prevent ejector plates from deformation


Headset band

Product: Headset band

Material: PC

No. of Cavity: 1X1

Product Characteristics: Simple shape, complex structure, with minimized parting line.

1.First of all, perform slope analysis. The following figure shows that the plastic injection mold has 4 undercuts.

2.The following figure shows that the mold has another 3 undercuts. That’s 7 undercuts in total

3.According to thickness analysis, the basic wall thickness of the product is 2.3mm.

4.It is determined that 2 sliders are placed at undercut 1 and undercut 6 respectively (slider 1 and slider2).

5.Undercut 2 and undercut 5 are located inside the product, so inner sliders are applied, which will work with the mold base and the 1 more plate for 2-stage ejection.

6.It is determined that undercut 4 and undercut 7 will be released through the application of slider 5 and slider 6.

7.There is no undercut at the location of slider 7, but the slider is applied to meet the requirements for minimized parting line.

8.Undercut 3 adopts the lifter design for release. Since it is surrounded by sliders, undercut 3 is subject a weak clamping force, so ejection will be performed by the lifter.

Through an overall review of the mold, we can come to the conclusion that this a very simple product with a very complex structure. In total, 7 sliders and a lifter are employed.