Introduction to our new injection mold for threaded cable glands
We are happy to write today about our new injection mold, which we are producing now, for manufacturing of cable glands.The new mold is design to produce plastic cable glands with external metric thread M12.
These parts, that this tool will produced, are general-purpose cable glands (from CG – series of Fa. Sentera Controls) intended as a sealing device for electrical cables passing through an enclosure or panel. The cable gland ensures that the characteristics of the enclosure in which the cable enters can be maintained adequately. CG series can be used to maintain a maximum ingress protection of IP67. For optimal cable sealing, a TPV rubber ring is inserted. It features a thread of M12 x 1,5 and a clamping range of 3 - 6 mm.
The thread was formed with sliders in injection mold, which makes this tool slide injection mold. Accept the sliders the mold has lower and upper cores, which help the forming process.
The threads found on molded parts are a bit different from the ones made in a machine shop. As we know, all mold makers bear in mind, that the plastic threads have to be carefully considered. Let’s see why:
Originally, screw threads were invented for metal parts, though molded threads on plastic parts are now also common, as seen we seen them on every plastic bolt and cap. The challenge for the designer of plastic product with thread is: The product designer just has to consider thread size and pitch when designing the part to avoid threads that might strip more easily than metal counterparts might.
The thread made of plastic tend to strip more easily, especially on fine pitch threads or those the size of a pencil or smaller. That’s why the recommended internal threads should be no smaller 7.6mm in diameter, and recommends using the coarsest pitch possible (regardless of size) for your design.
Another consideration, which the mold maker should take into at least on external threads, is the position of parting line—the best place is lengthwise down the exact center of the thread, essentially cutting the mold into two equal halves. That is exactly the method, which we use for designing our mold.
Another consideration, which the mold maker has to take into, is the material selection for molded threads.
To keep production rolling along smoothly, any molded parts with internal threads should be made of ABS, POM (Delrin), or nylon. Avoid glass-filled and high-temp materials. No such limitation exists for external molded threads.
Aside from the issues discussed so far, success with plastic injection molding requires designers to follow the “best practice” rules:
• Draft angles of 1 degree or greater should be used to assure easy part ejection.
• Wall thicknesses should be fairly consistent, and sharp corners avoided.
In the production of threaded plastic parts, shape plays an important role. In our company, we understand this and strive to continuously develop and produce precise injection moulding tools for a wide variety of applications, types of plastics and series sizes.
The threads found on molded parts are a bit different from the ones made in a machine shop. As we know, all mold makers bear in mind, that the plastic threads have to be carefully considered. Let’s see why:
Originally, screw threads were invented for metal parts, though molded threads on plastic parts are now also common, as seen we seen them on every plastic bolt and cap. The challenge for the designer of plastic product with thread is: The product designer just has to consider thread size and pitch when designing the part to avoid threads that might strip more easily than metal counterparts might.
The thread made of plastic tend to strip more easily, especially on fine pitch threads or those the size of a pencil or smaller. That’s why the recommended internal threads should be no smaller 7.6mm in diameter, and recommends using the coarsest pitch possible (regardless of size) for your design.
Another consideration, which the mold maker should take into at least on external threads, is the position of parting line—the best place is lengthwise down the exact center of the thread, essentially cutting the mold into two equal halves. That is exactly the method, which we use for designing our mold.
Another consideration, which the mold maker has to take into, is the material selection for molded threads.
To keep production rolling along smoothly, any molded parts with internal threads should be made of ABS, POM (Delrin), or nylon. Avoid glass-filled and high-temp materials. No such limitation exists for external molded threads.
Aside from the issues discussed so far, success with plastic injection molding requires designers to follow the “best practice” rules:
• Draft angles of 1 degree or greater should be used to assure easy part ejection.
• Wall thicknesses should be fairly consistent, and sharp corners avoided.
In the production of threaded plastic parts, shape plays an important role. In our company, we understand this and strive to continuously develop and produce precise injection moulding tools for a wide variety of applications, types of plastics and series sizes.