![]() The designer knew that the exposed length of the core pins would get extremely hot, even with a water-wash around their shaft. I once saw a medical mold that had extremely small-diameter core pins-so small that even tiny bubblers made of stainless-steel surgical tubing could not be inserted into them. ![]() Regardless of the type of material a core pin is made of, the smaller the diameter and the longer the exposed length, the more difficult it will be to keep cool. While a stainless pin is resistant to corrosion, it can also require an increase in the mold’s cycle time. But compared with copper pins and carbon-steel pins, stainless steel has considerably lower thermal conductivity. These are also a very good choice for core pins in many applications-particularly those for the medical industry. At least one mold-component supplier offers core pins made of 420 stainless steel with a through hardness of 50 to 52 Rc. However, since copper-alloy pins are much softer (90 to 98 Rockwell B) than steel pins, their face can deform if there is excessive force applied. You might also be surprised with the measurements you get from a domestic supplier that purchases its pins offshore.įIG 2 Copper-alloy core pins can provide faster cycle times. If you buy molds offshore, you might be very concerned about the measurements you get. ![]() It is always a good idea to check the diameter of any pin to four decimal places, and occasionally check the Rockwell hardness on the diameter and in the center of the face. Additionally, since we are only human, you will find discrepancies between what is specified in a supplier’s catalog, its website, and the actual product itself. I found one supplier that says its core pins are through-hard but specify a surface hardness of 62 to 65 Rc, and a core hardness of 50 to 52 Rc. In the event of future wear or corrosion, the ejector pin can then be replaced with a core pin, which has a tolerance of +0.0003 to +0.0008 in.īe very careful when selecting the type of pin to use. You might consider using one of these through-hardened ejector pins for a core pin application because the tolerance on the diameter of an ejector pin is about -0.0003 to -0.0005 in. However, some ejector pins are available in a through-hardened condition, typically 58 to 62 Rc, but can also be found with a lower hardness of 50 to 55 Rc.
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