By Jason Holbrook
Regional Sales Manager,
Absolute Haitian Corp.
Injection molding machinery suppliers often receive requests for quotes asking for pricing based on the tonnage of the machine only. When asked for more details, the buyer might respond, “I just need a 1,000-ton quote.” Better to consider the molding machine as two separate pieces — the clamp unit and the injection unit — and dig into the details to help ensure you purchase the best configuration for your needs.
Start with the Clamp
The clamp has tons to consider. Yes, that pun was intended. Beyond just clamp tonnage, other important factors are tie-bar spacing, minimum mold height, maximum mold height, stroke and daylight.
Let's look at the types of clamp design. The toggle clamp is a time-tested design that has been around for decades, as has the clamp design based on a hydraulic ram. Over the last 20 years, the industry developed the two-platen machine, which for practical purposes has replaced the hydraulic ram. Last is the C-frame clamp design typically employed by vertical machines; it has more recently been seen in horizontal machines but only those offered by one supplier. The most common clamp designs are toggle and the two-platen.
Tonnage is presented by manufacturers in three ways: kilonewtons, metric tons and U.S. tons. Asian suppliers typically refer to kilonewtons, whereas European suppliers will discuss metric tons and U.S. suppliers and customers talk about U.S. tons. A metric ton is basically a 10th of a kilonewton. A U.S. ton is going to be 10 percent more than a metric ton.
An important factor to consider is tie-bar spacing. Today’s molders are trying to put big molds into clamps. Don’t forget about minimum mold height, maximum mold height, stroke and daylight to ensure the largest mold you plan to run will fit comfortably in the machine.