Rib is a frequently used feature in plastic injection molded parts design for the purpose to enhance the strength of the plastic parts, typical rib design see below figure.

The thickness and location is essential of the rib design. Usually, ribs should be designed with a thickness of 1/2 of the wall thickness to avoid a thick section at the base of the wall, which would cause sink marks on the part surface. Ribs are usually spaced at a distance at least twice the wall thickness to allow enough steel between the ribs for adequate cooling.

The injection molding machine outputs cannot be set, but the inputs can be each time you set the injection mold. Some of these set points, like mold temperature and barrel temperatures can be set. Of course this depends on which factors are the most critical to the injection molding process. If you had ability to perform a simple screening DOE before you put a specific injection mold into production, Minitab can pare to out the most significant inputs. If nothing else, these would be the ones to monitor. However, you'd likely want to capture fill time, cushion, screw recovery (loading time) and cycle time (especially if the machine is not run automatically.

Bottom line, if you have unlimited funds to purchase advanced monitoring systems and have employees that know how to operate them properly and analyze the data they produce, then by all means use them. But if you are dependent on your machine operators to produce good product, you must give them simple tools that they can understand and use while they are right at the injection molding machine. And they can monitor virtually every shot in real time, so if something does drift, or a machine or mold issue does arise, they can notify appropriate engineering personnel immediately.

Proper location of the gate point will be directly affect the quality of the injection molded parts gate location selection should follow the following principles:

1. Gate location should be chosen in parting surface, so that it would be easier for machining and maintenance.
2. The runner should be designed even, mold flow distance and sectional size in balance can achieved stable molding quality.
3. Gating location should be on the thick-wall area so it ensure the cavity can be filled completed.
4. The mold flow should not be right on the inserts or lifter, high pushing pressure of melt flow would probably deform the inserts.
5. Try to avoid weld marks or weld lines created in the critical surface, changing location of gating and try to make the weld line on uncritical surface.
6. Consider the venting when design the gating, make sure the end of the mold flow have good venting.
7. Gates should be easily removed and gate mark should not affect the appearance of the molded parts.