Stripper ring

Once the molded part has cooled sufficiently in the cavity, it has to be ejected. This is done mechanically by KO pins, KO sleeves, stripper plates, stripper rings or compressed air, used either singly or in combination. The most frequent problem in new molds is with ejection. Because there is no mathematical way of predicting the amount of ejection force needed, it is entirely a matter of experience. 

Figure 5.24 Plan and elevation of a t wo-plate mould with twin cavities. The plan shows the moulding projected area. Alternative methods for ejecting a cup moulding are shown the stripper ring and air vent are for very thin moulding.

Figure 4,50 shows apoitieoi of die same j Toduct (e.g., tiie rim of a pail). In Fig. 4.50A, the wall ends at the P/L, and the projection is within the stripper (ring). Because of the draft of the projection within the stripper, the product can be simply ejected from the core, since the cavity withdraws (opens) without catching the product. (Note Air pressure may be required to lift the product out of the stripper if the extension is long and could hold the product in the stripper.)... 

Slitter tooling refers to slitter knives (cutting tools), spacers (knife positioning), stripper rings (to support and strip slit material), and shims (to adjust an inaccurate spacer and knife setup) used on the slitter head arbors, as well as the separator plates on the recoiler, and separator disks and separator spacers used on overarm separator devices. 

In some machines, stripper rings double as pinch rolls to drive the material through the arbors. 

Correct use of stripper rings is a complex technology based on the two variables strip characteristics and slitter characteristics. Tooling vendors will be pleased to help the customer engineer the best stripper ring combination for their needs (Fig. 9). 

Figure 9 Typical arrangement for male and female rubber stripper rings.

Strip width out of tolerance Incorrect setup Incorrect stripper ring practice Loose arbor nut Out-of-square condition on arbor Arbor deflection... 

Knives chip Too much vertical overlap Incorrect horizontal clearance Incorrect passline Incorrect stripper ring practice Speed mismatch Incorrect knife grade selection... 

Wavy edges Poor quality master coil Incorrect horizontal clearance Incorrect vertical clearance Incorrect stripper ring practice... 

Hydraulic arbor lockup nuts have become a standard in the industry. Unfortunately, research on these nuts and their effect on tooling has been sparse. A test that we have done and recommend for every application where hydraulic nuts are used is as follows. After confirming arbor and slitter-head tolerance specifications by making a setup that is clean (shimless and without stripper rings), set the overlap to zero, and, with a dial caliper, check and record each male and female size from the outside face of the knives. Be sure to remove by carefully stoning any grinding burr from the knife faces. 

The quality of rubber rings continues to improve. The specifications for the use of rubber are no longer just a good guess. The basic rules for stripper rings are... 

Step II Stroke of the stripper rings 7 and 8, to get space for the elastic strip-off ... 

First, the molded part remains on the core after opening the mold. Then, stripper rings 7 and 8 are operated until enough space is created for the molded part to expand. In the next phase, the stripper ring 8 remains on place to allow the strip-over process. A so called 2-step ejector system, which is offered by many manufacturers... 

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