How to Avoid Ejector Pin Marks on Medical Ejector Pin Mold Parts
Ejector pins are a vital part of injection molding that designers cannot overlook. The type of molded plastic, mold draft angle and shape complexity all contribute to determining the appropriate pin size, location and quantity.
Custom manufacturer of clevis, cotter, dowel, hitch and locating pins. Products are available in chromium, zinc and black oxide finishes. Offers prototype and low to high production volume. Serves automotive, electrical and plumbing industries.
1. Material
Ejector pins are a vital component of injection molding. They remove finished plastic pieces from the metal molds Medical ejector pin mould parts supplier manufacturer after cooling. However, they can leave marks on the molded part if not properly used or placed. These marks appear as glossy or whitish-looking dents that are often located at the areas where a pin contacts the plastic. These ejector pin markings can affect the appearance and functionality of a molded product. To avoid them, a few tips are worth keeping in mind.
The size of the ejector pin and its placement are important factors in reducing blemishes. For instance, installing larger diameter pins distributes the pushing force over a larger area, thus minimizing resistance and reducing ejector pin mark formation. It also helps to reduce the number of undercuts, which are protrusions that prevent direct ejection from the mold.
Another way to reduce ejector pin marks is to use a draft angle, which is a slant in shape and applied on both sides of the mold. This slight distortion in the mold reduces friction during the ejection process and prevents the part from cracking.
The type of resin is also an important factor to consider. Some resins are stickier and thicker than others, which means they require more force to be ejected from the mold. For this reason, it is advisable to use larger diameter ejector pins for these types of materials.
2. Design
Ejector pins are the unsung heroes of precision and efficiency in the molding industry. But their precise placement, type and size depend on a variety of factors. Some resins are stickier or thicker and require more force to be released from the mold. The shape of the part also affects whether certain areas will cling to the pins and create cosmetic defects. In addition, the pins must have a flat area to push against and should not be subject to slants or curves, which can also cause them to puncture or mar the surface of the molded plastic.
Ejector Pins are usually located in the B-side of the metal mold, which is the half that stays when the molding machine opens. They extend into the mold to push out finished products and then retract so the mold can close again and be refilled. They occasionally leave marks on the finished product, which can be difficult to remove from the plastic.
There are several types of ejector pins, including straight, shoulder, and blade pins. Straight ejector pins have a simple cylindrical design and are commonly applied for parts with simpler geometries. Shoulder ejector pins have a larger diameter at the shoulders and a smaller one at the tip and are suitable for ejection from deep and narrow cavities. Blade ejector pins have a flat and wide surface at the tip and are suitable for ejection of parts with uneven geometry.
3. Size
Ejector pins are a crucial part of the injection mold. Injection molders need to choose the right pin type, size and placement for their specific applications. A number of factors impact this decision, Medical ejector pin mould parts including part size, draft angle, shape complexity and vertical wall height. Injection molders also need to consider the type of plastic being molded.
High-performance ejector pins are often made of hardened steel. They are usually through-hardened, with a surface hardness of 60 HRC and higher. This hardness is ideal for handling tough materials. They are also designed for high heat and thermal shock. In addition, they can be used for a wide range of temperatures, which makes them an excellent choice for most plastics.
Another option for ejector pins is to use cold-work steel. These pins are typically through-hardened, with a surface nitrided to improve their wear resistance. Cold-work ejector pins are less expensive than their through-hardened counterparts. They are also suitable for a wide range of temperatures and are often a good choice for high-output or low requirements molds.
Another popular option for ejector pins is copper alloys. These are a good choice for low-temperature work and can be produced with either beryllium-copper or beryllium-free grades for medical use. They are not as strong as high-performance ejector pins, but they are still good for most applications.
4. Finish
Ejector pins with a high surface hardness and corrosion resistance are an ideal choice for medical and other cleanroom applications. One type of stainless steel pin, called a DLC (diamond-like carbon) pin, can be run without lubrication, which reduces cleaning time and the risk of contamination. This type of pin is typically made from cold-work steel and through-hardened to around 60 HRC.
Another type of ejector pin is the plated pin, which has a layer of nickel or chrome that helps resist wear and corrosion. It also provides a high level of conductivity, which improves the efficiency of injection molding.
The surface finish of the pin can also affect its performance. Polishing the contact surface or incorporating a demold slope can facilitate smoother ejection, reducing the stress on the pins and the likelihood of breakage.
A manufacturer of ejector pins and mold parts for the plastic injection, injection molding and mold-making industries. Its products include clevis, dowel, cotter, hitch and locating pins, plus shoulder bushings and retainer locks. It offers black oxide, chromium, nickel, cadmium and silver plated finishes. It also provides CAD or fixture design and CNC machining services. The company serves the automotive and medical industries. It is ISO 9001:2000 certified. It also offers a range of secondary services, including surface grinding and refinishing. It works with nylon, acetal, polyethylene and styrene.