Overmolded material is often rubber or thermoplastic. Overmolding can be used as a double injection molding process, often resulting in either a chemically bonded part of the materials being mechanically interlocked. The types of products that are overmolded include scissors and medical products such as cannulas, needles, tubing, and catheters.

1. The melt pressure at the front end of the barrel is too high, the material temperature is high, the viscosity is decreased, the flow of the melt in the screw groove and the leakage flow between the barrel and the screw gap are increased, which will reduce the plasticizing efficiency (plasticization per unit time).

Overmolding creates a powerful molecular bond by optimizing the co-polymerization of the two substrates (one of which is usually hard while the other is soft). The ability to create a molded unit from two different types of materials in one process is the biggest advantage of the overmolding process.

Insert Molded Solution: An alternative design was formulated which separated the extension lumens into a circular pattern, allowing for more space between the mandrels and preventing them from touching during molding. This was a success and today our solution is still utilized where there are more than 3 lumens in a catheter assembly.

The injection molding process starts by introducing thermoplastic resin into a hopper. The resin then undergoes heating, reaching temperatures ranging from 300° to 650° Fahrenheit, causing it to melt. Once in a molten state, it is then pressurized and injected into a sturdy steel mold.

Our Innovation: Our proposed solution involved placing stainless steel wire mandrels through individual extension lumens, then positioning them into separate passageways in a multi-lumen extrusion. This assembly was then placed in a mold and polyurethane was insert molded in the shape of a manifold. Afterward the mandrels were removed, leaving unobstructed passageways in the plastic manifold connecting the extension lumens to the multi-lumen extrusion.

2. The gas in the melt can be “extruded” to reduce the air bubbles on the surface of the product, internal bubbles, and improve gloss uniformity. Slow down the screw retreat speed, fully plasticize the melt in the barrel, increase the mixing uniformity of the toner, color masterbatch and melt material, and avoid the color mixing phenomenon of the product.

Molding inserts are the established, or pre-formed, parts that the thermoplastic resin will mold around during the insert molding process. These require special attention, as not all parts may be suitable, so they have to meet strict temperature and pressure resistance requirements.

1. It can compact the melt in the barrel, increase the density, and improve the stability of the amount of shot and the weight and size of the product.

3. The back pressure is too high, the screw is slowed down, and the pre-plasticizing time is long, which will increase the cycle time, resulting in a decrease in production efficiency.

5. It can raise the temperature of the melt, improve the plasticization quality of the melt, improve the fluidity of the melt during filling, and there is no cold rubber on the surface of the product.

3. the surface of the product will appear shrinkage, air flower, cold material, uneven gloss and other undesirable phenomena.

Unique Challenge: In 1983, a Baxter engineer approached Aberdeen Technologies with a revolutionary product idea to create a multi-lumen heart catheter using insert molding. At the time this had never been done before. All catheters were assembled using a pre-molded manifold and then gluing the extension lumens in place. This slow and inefficient process resulted in high rejection rates and hazardous adhesives for the medical industry

Insert molding is a manufacturing technique that involves encasing an established part, typically metal, with thermoplastic resin to create a single, integrated unit. Examples of insert molded applications include electrical wire harnesses, multi-lumen catheters, knife blades, and screwdrivers.

Back pressure, also known as plasticizing pressure, is controlled by adjusting the oil return throttle valve of the injection cylinder. The back of the injection cylinder of the pre-plasticized screw injection molding machine is equipped with a back pressure valve to adjust the speed of the injection cylinder when the screw rotates backward, so that the cylinder maintains a certain pressure (as shown in the figure above); the screw backward speed of the whole motor (Resistance) is controlled by an AC servo valve.

4. appropriate increase of back pressure, can improve the shrinkage of the surface of the product and the rubber around the product.

Inserts typically have to have undercuts or bosses in order to provide better retention strength with the molded plastic.

In both Insert Molding and Overmolding, molds play a pivotal role. Mold components, including mold cavity design, pins, and alignment tools, guide the plastic during the manufacturing process. Selecting the right mold design is essential to ensure the desired outcome in terms of product quality and structural integrity.

The molds used in insert molding, over-molding, and injection molding are made up of steel plates, water lines, and ejection pins, with other components as needed. A simple open-shut mold is a mold that can be pulled apart without any slides or other components getting in the way.

This process not only lowers assembly and labor expenses but also grants manufacturers greater design flexibility without requiring any sacrifices in the structural integrity of the part. Insert molding is revered as one of the best methods to manufacture lightweight and compact parts that are reliable, durable, and fully functional.

Aberdeen Technologies’ Reputation: Today, Aberdeen Technologies continues to be a leader in complex insert molding parts, such as helping develop devices with smaller footprints and ever-thinning lumen diameters. This pioneering work on multi-lumen heart catheters stands as a testament to our commitment to innovation in insert molding and patient safety.

Generally, this manufacturing process is carried out on a machine specially designed and built to carry out a double injection in a single cycle. The first stage involves injecting one type of plastic into a mold. On completion of this insert molding process, the machine rotates the plastic mold automatically before injecting another type of plastic into the mold. This is what is known as overmolding.

Initial Complication: The greatest challenge was ensuring the channels were not touching one another, which would result in leakage between the passageways when fluids were introduced into the assembly during a surgical procedure. The first design featured a flat "Y" shaped manifold. Unfortunately, keeping the mandrels from crossing paths during injection molding proved incredibly difficult. Even minor shifts caused channels to touch, compromising the integrity of the final product.

The adjustment of the injection back pressure should be based on the properties of the raw materials, the drying conditions, the product structure and the quality conditions. The back pressure is generally adjusted at 3-15kg/cm3. When the surface of the product has air, mixed color, shrinkage, and product size and weight change, the back pressure can be increased. When the nozzle leaks, flows, melts overheating, product discoloration, and screw charge too slowly, consider reducing the back pressure.

5. In the process of beer plasticization, the back pressure is often too large, and the nozzle leaks, which wastes the raw materials and causes the heating ring near the nozzle to burn out.

Overmolding, is an effective manufacturing approach employed by industries to manufacture complicated components that are too complicated and uneconomical to produce using a single molding process.

During the melting and plasticizing process of the plastic, the melt is continuously moved to the front end of the barrel (measuring chamber), and more and more, gradually forming a pressure to push the screw backward. In order to prevent the screw from retreating too fast, and to ensure that the melt is evenly compacted, it is necessary to provide a reverse pressure to the screw. This reverse pressure, which prevents the screw from retreating, is called back pressure.

While Insert Molding and Overmolding share the fundamental concept of molding plastic around existing components, they differ in the number of steps involved and the nature of the resulting product. Insert molding is often a single-shot process, whereas Overmolding is a two-shot process.

2. For plastics with poor thermal stability (such as: PVC, POM, etc.) or colorants, the thermal decomposition of the melt due to the increase in temperature of the melt and the increase of the heating time in the cylinder, or the degree of discoloration of the colorant increases, the surface color of the product / Gloss deteriorates.

Thermoplastic and thermoset resin are the two main types of plastic used for the injection molding process. Thermoplastic can be reheated multiple times while thermoset cannot. For example, a milk jug is a thermoplastic, while a tire is a thermoset.

More recently, some 3D printing technologies have been used to overmold objects of two or sometimes more materials. One material is commonly known as the substrate. The substrate is either partially or fully covered by a second material referred to as the overmolded material. The substrate material can be anything from metal to plastic or glass.

Injection Molding involves heating thermoplastic resin to a molten state and injecting it into a steel mold. There are two ways to accomplish this, insert molding and overmolding.

Overmolding differs from insert molding as it involves the use of two separate materials to produce a single molded product. Overmolding is still a part of the injection molding family and deals delicately with the molding insert. A common use case for this specific type of molding is cable overmolding or micro molding.

4. The back pressure is high, the melt pressure is high, and the nozzle is prone to melt the glue after the glue is injected. When the glue is injected next time, the cold material in the nozzle flow channel will block the cold spot in the nozzle or the product.

3. Slow down the screw retreat speed, fully plasticize the melt in the barrel, increase the mixing uniformity of the toner, color masterbatch and melt material, and avoid the color mixing phenomenon of the product.

1. When the back pressure is too low, the screw retreats too fast, and the density of the melt flowing into the front end of the barrel is small (relatively loose), and more air is trapped.

Another consideration is if the mold can close off to the insert so that there isn't any blow-by, meaning the plastic will blow past the insert during manufacturing, causing a flange or additional plastic that will need to be trimmed off.