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b. If the mold is equipped with knockout extensions, the ejector bars should be flush or slightly recessed from the face of the moving platen when the machine ejector (aka butterfly) plate is fully retracted. IN SET-UP MODE: 23. Advance the moving platen until it is 4 to 6 in. away from the back of the mold. WITH THE PUMP MOTOR OFF: 24. Slide the knockout bars forward and thread them into the back of the mold. 25. Tighten the knockout bars with a pipe wrench or other suitable tool. IN SET-UP MODE: 26. Advance the moving platen up against the back of the mold. a. Look and listen for the knockout rods binding or bending. 27. Lower the chain hoist slightly to remove any tension. 28. Set the die height to the pre-established clamp pressure. a. If the clamp pressure has not been established yet, use a high pressure value for large molds or large parts, and a medium pressure value for small molds or small parts. WITH THE PUMP MOTOR OFF: 29. Attach the clamps on the moving-platen side (see steps 19 a-e) 30. Torque the clamp bolts on both the fixed and moving platens to the appropriate value (see Table 2). a. "Click-type" torque wrenches help ensure all of the clamps have the same amount of torque. If all the clamps are not torqued evenly, the one(s) with the lower torque value may come lose. 31. Remove the safety strap(s) and eyebolt(s). 32. Move the hoist out of the molding area. IN SET-UP MODE: 33. Open the mold and advance the ejector plate, if needed, to gain access to the back of the knockout rods. WITH THE PUMP MOTOR OFF: 34. Install the hex nuts or socket-head cap screws on the end of the knockout rods with a ratcheting socket wrench or other suitable tool until they are tight. 19. Attach the clamps on the fixed-platen side to prevent the mold from rotating or the locating ring from disengaging from the alignment hole, but do not yet fully tighten the bolts to the specified torque value. a. Grade 8 bolts should engage the relatively soft die-cast platens by a minimum of 1.5 times their diameter to prevent stripping the threads. Two times their diam- eter is preferred (see Table 1). b. Ideally, the mold clamp should be square with the mold and the toe of the clamp be fully engaged in the slot. c. The clamp bolt should be as close to the mold as possible. You want the pressure of the bolt acting on the toe—not the heel (see Fig. 1). d. If the bolt is closer to the heel end than the toe end, switch to a longer clamp. e. It is acceptable for the clamp to be parallel with the platen, but it is preferred that the heel end of the clamp be slightly farther from the platen than the toe end. This puts the front edge of the toe in contact with the face of the clamp slot (Fig. 2). Failure to do either of these two steps may result in the mold dropping out of the machine. f. Forged, closed-toe clamps with "no-turn" washers are preferred. 20. Use only hardened-steel washers designed to distribute the load on the clamp. Soft "hardware-store" washers will deform and come loose. IN SET-UP MODE: 21. Retract the moving platen enough to install the ejector bars—typically 8 to 12 in. WITH THE PUMP MOTOR OFF: 22. Put ejector bars in the holes matching the pattern on the mold. a. Make sure ejector bars are the correct length, the same length, that they are straight, and the threads are in good condition. Bad OK Good FIG 2 Ideally, the tip of the mold clamp should touch the face of the clamp slot at about a 1° angle. TABLE 2 Mold Fastening Torque For Lubricated Grade 8 Bolts Bolt Size & Pitch, in. Torque, ft-lb ½ -13 75 5/8 - 11 150 ¾ - 10 270 1 – 8 560 X° Y° 54 JUNE 2017 Plastics Technology PTonline.com T ips & Technique s