The Impact of Hydraulics on Tool Design

Hydraulic cylinders are used for a variety of purposes in injection molding tooling: slides, core pulls, ejection, reverse ejection, gas-assist overflows, gas-assist valve pins, valve gates, locks, unscrewing molds, etc. If you’ve worked with them, you know all about oil leaks and the headaches they create. So my preference is to avoid hydraulics whenever possible. That said, I will recommend hydraulic cylinders in situations where I feel they will perform better than mechanical features.   In any situation where hydraulic cylinders are used, it’s important to have a better understanding of set/pull pressures and speeds. The set/pull pressure and speed can directly affect downtime with leaks and repairs. Pressure and speed can be both friend and foe. Time is money, so speed is your friend from that perspective. But it’s your foe if it causes an impact with a mechanical feature that you can hear when it is set or pulled. This will result in stress, wear, and at some point broken components in T-slot couplers or threaded rod ends.   There are a few options to protect your components from the negative impacts of speed. Cushions can be added in the cylinder. On the pull direction, it’s better to have your cylinder bottom out instead of your component. On set position your component needs to be home, so you typically do not want your cylinder bottoming out, but there’s a solution to this that I’ll get to later. So you need to determine how speed will impact your component and potential failures.  Hydraulic pressures can also h