Balanced multi-cavity injection molding of ridged-wall plastic products

A method of balancing a multi-cavity mold for injection molding a plurality of ridged-wall plastic products, wherein each of at least two mold cavities defines a product comprising a plurality of longitudinal folds of alternating ridges and furrows, each fold including a first side strip laterally extending from the top of a said ridge to the bottom of a said furrow;

• and a second side strip laterally extending from the bottom of the said furrow to the top of a said ridge next to the said ridge;
• wherein the first side strip has a different lateral orientation than the second side strip;
• and wherein the first side strip has a greater wall thickness than the second side strip, the method comprising the steps of:
• (a) providing mold parts defining therebetween said at least two cavities for forming said ridged-wall plastic products, wherein each cavity defines a plurality of flow channels in which injected plastic material flows within the cavity and in which flow channels the first side strips are formed;
• (b) injecting plastic material at a given injection pressure approximately simultaneously into said at least two mold cavities in order to form the products with the injected plastic material;
• (c) measuring the relative extent to which said at least two mold cavities are filled with the injected plastic material;
• and
• (d) when said at least two mold cavities are not filled to the same degree approximately simultaneously, adjusting the relative dimensions of the flow channels for forming the first side strips in said at least two mold cavities to be such that when plastic material is injected in accordance with step (b) injected plastic material flows within said at least two cavities at respective flow rates that cause said at least two mold cavities to be filled to the same degree approximately simultaneously with the injected plastic material.