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A good rule of thumb is to have at least 1 ½ times the diameter of the bolt in the platen. Anything less than this could pull the threads out of the platen. The greater the amount of thread in the platen, the better. But don't bottom out. Depending on the grade of bolt you use, the torque will vary. You can call the service department on the brand of machine you use; they will tell you the recommended amount of torque for that platen.
For 120- to 1800-lb molds, we use 80 to 120 lb of torque; for anything heavier than 1800 lb we add extra clamps to ensure the placement is secure. We are currently trying a new clamping system for our molds called Enerpac QMC-Systems. This system will operate on machines up to 300 tons, which might be a more suitable answer to your problems. It's faster and should end the headaches of stripped
platens.
-P. Beard, Nyloncraft, Bowling Green, KY, (270) 782-6224.
I am a captive molder running injection machines from 100 to 500 tons. We have had tools "fall" out of a press before so we take this issue very seriously. We set the torque at whatever value is listed for that bolt size by SAE standards. Always use four clamps per side and increase the number of clamps as the tool weight increases.
You can take a dial indicator reading to see the rise or fall of a tool as it unclamps and clamps, If the moving platen side moves as much as the leader pin clearance when the mold faces kiss, rehang your tool. You can check this alignment over time to see if the mounted mold is moving and add clamps as necessary.
Managers who haven't been hands-on molders tend to view clamp bolts like rocks-they never change. Remember that a bolt works because it stretches, and it will fail if overstretched (over torque) or stretched repeatedly. We have replaced all of our clamp bolts and engraved a replacement date on each of them. Bolts and clamps are cheaper than
accidents.
-S. Sjoquist, Imation Corp., Wahpeton, ND, (701) 642-8711, sasjoquist@imation.com
It depends on the bolt diameter and the size of the clamp more than anything else. I have asked service engineers from two machine manufacturers and they've said that 100 ft-lb of torque is plenty for 5/8-11 and 16-mm size bolts.
I recommend four clamps per mold half, and it's better to use more clamps on bigger molds than to tighten the bolts
more
-B. Tutmark, GM Nameplate, Beaverton, OR, (503) 646-0444, bradt@gmnameplate.com
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