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Theories-opinions on hydraulic forces on side action cores?
I'm having a disagreement with a colleague about how to neutralize forces on cores. I don't believe there is such a thing as "neutralizing" the forces, but he believes that if the core enters a bore inside the mold (see image HOLE-SHUT-OFF.jpg) , there will be no hydraulic forces on the core. I believe this is only true if the hole is vented to atmosphere, in which case the axial forces on the core will be the same, but it's a moot point as it isn't possible in this mold, anyway. I maintain that when using an air cylinder to push the cores in, it is necessary to use locks and wedges (cams) to hold the cores in position, no matter what kind of "socket" or "hole" the core engages with, because the only escape route to atmospheric pressure is through the core print. I've been building molds for years, and I've never built one without some kind of provision for holding the cores in against the hydraulic pressures generated by injection of the plastic. The material is Nylon, 33% glass filled, the cores are approx 1" in diameter. Please see the pictures below. Any opinions?
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Re: Theories-opinions on hydraulic forces on side action cores?
the side action core looks like it has a step on it, correct? If so, it has molding surface area in which case you will need to lock it by a wedge or core lock cylinder (which are garbage) Even if there was no molding surface area and you were just molding a through hole, then it's still good practice to lock it some how, wedge preferred but you could maintain hydraulic pressure on the cylinder during injection.
I personally would never have a side action that wasn't locked somehow. Since the side action core seals against steel there is the chance that flash could get in between the two and blow it back
Re: Theories-opinions on hydraulic forces on side action cores?
It does have a step in it to create an edge-break around the hole in the molded part. My thinking is the same as yours; I have never even considered building a mold without locking the cores in.
I looked into the price of a locking hydraulic cylinder ($1500 and up), and you say you don't like them anyway.
Re: Theories-opinions on hydraulic forces on side action cores?
Quote:
Originally Posted by
Concepts_Design
the side action core looks like it has a step on it, correct? If so, it has molding surface area in which case you will need to lock it by a wedge or core lock cylinder (which are garbage) Even if there was no molding surface area and you were just molding a through hole, then it's still good practice to lock it some how, wedge preferred but you could maintain hydraulic pressure on the cylinder during injection.
I personally would never have a side action that wasn't locked somehow. Since the side action core seals against steel there is the chance that flash could get in between the two and blow it back
Old Thread I know.
Hard to find information on locking cylinder opinions
I'm just curious why you find locking cylinders to be garbage?
Thanks!
