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Upon review, the company has instituted very effective procedures for cleaning all of the material delivery, storage, and drying systems. I observed the entire cleaning process and realized they forgot to clean the feedthroat shut-off. Believe it or not, most companies do not give proper attention to the slide just below the hopper. In this case, they actually remove the hopper from the slide and vacuum the feedthroat, but they neglect the small fines that become trapped between the surfaces of the feedthroat shut-off.

The important lesson is to ensure that you look at any problem as objectively as possible and to see if there is a new cause to your problem that you may not have previously thought about.

-Andy

The theoretical necessary contact force is based on multiplying the cross sectional area of the sprue bushing or nozzle opening (whichever is largest) by the injection pressure (in plastic pressure).

In most cases, the only critical force acting upon the nozzle is the pressurized plastic. Mold deflection will push on the nozzle, but it actually helps to create the seal between the nozzle and the sprue bushing while the actual plastic pressure pushes the nozzle away from the sprue bushing.

-Andy

Failure to properly level a molding machine can result in premature wear, equipment damage, and even clamp failure. Any twist or non-levelness of the clamp system results in non-linear movement of the platen and uneven forces applied to the tie bars, bushings, and parting lines. The most wear points are premature wear of bushings, wear plates, and feet. When processing, you may notice uneven clamping and uneven flash. If there is twist, excessive wear of leader pins and parting line seals may occur… and the molding machine might even ‘walk’ or move on the plant floor.

For more on leveling, please feel free to read:

-Andy

The most common method of measuring this is to follow the procedures of measuring parallelism as discussed in the previous post on measuring platen parallelism. The difference between the parallelism before and after clamping will give you important information regarding the change under strain. For instance, if the platens are parallel before clamping, but they are out of parallelism after clamping, the change indicates the amount of additional strain in a particular tie bar

When possible, you should try to measure the stretch using a ultrasonic strain gauges. These use sensors at each end of the tie bar which measure the actual stretch of the tie bar during mold clamping. This is much more accurate since it can measure the actual stretch of each tie bar.

-Andy