The Affect of Clamp Type on the Effectiveness of Venting…

I just received a question which highlights the difference between cylinder and toggle clamping systems…

We have a mold in our plant with vents problems (not enough) We have problems with our plastic parts due gas residues on them when we run it in a electric machine (toggle system) and when we run it in a hydraulic machine clamping cylinder) runs without any problem. Can you explain me what is the difference between this two types of clamping systems? Can the vents be affected with the toggle system?
My Response
Your first assumption is most likely correct…
The hydraulic clamp system on your machine uses a large diameter hydraulic cylinder in the center of the movable platen to apply tonnage to the mold. Since the clamping force is centered on the platen… deflection occurs on the perimeter. This deflection reduces the tonnage appied to the perimeter of the mold resulting in improved venting. Adversely, toggle clamps tend to provide a more evenly distributed force to the platen.
Additional Thoughts
Before you make the assumption that the machine is the only cause, keep a few more aspects in mind… 1) The clamp force might be more accurate on the newer machine. 2) If the mold is too small for the electric molding machine (uses less than 2/3 of the platen) then you can cause platen concavity resulting in additional force applied to the perimeter of the mold. 3) The newer machine may also provide a faster injection speed which would also affect the mold venting.

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