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Medical Device Injection Mold Components Thermoformer For Machine

Categories Plastic Molded Parts
Brand Name: Alpha
Model Number: Alpha-PL-127
Certification: CE, ISO9001
Place of Origin: Suzhou Jiangsu China (Mainland)
MOQ: 1000pcs/run
Price: quote as per drawing
Payment Terms: L/C, T/T,
Supply Ability: 100000pcs/month
Delivery Time: 10 working days
Packaging Details: 150pcs/carton
Material: ABS/PP/PC/HDPE/HIPS/HDPS/PVS/PMMA/PA/NYLON/POM
Finish: Texture/Sandy/MT/YS/SPI/EDM finish/smooth/glossy
Color: Pantone/RAL and other custom colors
Drawing Forma: STEP/STP/IGS/X-T/STL/CAD/PDF/DWG and Other
Tolerance: 0.02mm -0.05mm
Mold Life: 500000 shots
MOQ: 1-5000pcs/run
Property: UV stable
Customized: Avialable
Application: Led lighting
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Medical Device Injection Mold Components Thermoformer For Machine

Medical Device Injection Mold Components Thermoformer For Machine



Molding Cycle Time

The sequence of events during the manufacturing is called the cycle. It begins when the mold closes and the polymer is injected into the mold cavity. When the cavity fills, the mold maintains a holding pressure to account for material shrinkage.

Then, the screw turns, and the next shot moves to the front of the screw. This causes the screw to react, and, once cooled, the mold opens and the plastic part removed.

A formula can be used to determine the cycle time of injection molding. The time it takes to make a part using injection molding is calculated as:

Total time = 2M + T + C + E

Where:
(2M) = Twice the Mold Open/Close Time
(T) = Injection Time (S/F)
(C) = Cooling Time
(E) = Ejection Time (E)
(S) = Mold Size (in3)
(F) = Flow Rate (in3/min)

The mold closing and ejection times of injection molded parts can last from less than a second to a few minutes, depending on the size of the mold and machine. The cooling time, which dominates the process, depends on the maximum thickness of the part.


About Injection Molding


Injection molding is the most common modern method of manufacturing plastic parts. It is used to create a variety of parts with different shapes and sizes, and it is ideal for producing high volumes of the same plastic part. Injection molding is widely used for manufacturing a variety of parts, from the smallest medical device component to entire body panels of cars. A manufacturing process for producing plastic parts from both thermoplastic and thermosetting materials, injection molding can create parts with complex geometries that many other processes cannot.


The first step of getting a plastic part injection molded is to have a computer-aided design (CAD) model of the part produced by a design engineer. The three-dimensional (3D) CAD model then goes to an injection molding company where a mold maker (or toolmaker) will make the mold (tool) that will be fitted into an injection molding machine to make the parts.

Molds are precision-machined usually from steel or aluminum, and can become quite complex depending on the design of the part. Plastic materials shrink at different rates when they cool, so the mold has to be constructed with consideration for the shrinkage rate of the material being used for the parts. In other words, a formula is applied in the construction of the mold to slightly increase the size so that when the plastic shrinkage occurs, the part will be to the dimensional specifications of the CAD model.

The Process

Plastic injection molding is a manufacturing process where resin in a barrel is heated to a molten state, then shot into a mold to form a part in the shape of the mold. The resin begins as plastic pellets, which are gravity fed into the injection molding machine through a funnel-shaped hopper. The pellets are fed from the hopper into a heated chamber called the barrel where they are melted, compressed, and injected into the mold’s runner system by a reciprocating screw.

As the granules are slowly moved forward by a screw-type plunger, the melted plastic is forced through a nozzle that seats against the mold sprue bushing, allowing it to enter the mold cavity through a gate and runner system. The injection molded part remains at a set temperature so the plastic can solidify almost as soon as the mold is filled.

The part cools and hardens to the shape of the mold cavity. Then the two halves of the mold (cavity or “A” side and core or “B” side) open up and ejector pins push the part out of the mold where it falls into a bin. Then the mold halves close back together and the process begins again for the next part.


Plastic Injection Molds

Steel injection mold


Injection molds, or mold tooling, are the formed halves that come together in the injection molding machine to be filled with molten plastic and produce the plastic parts in their image. The cavity side, or “A” side, is typically the half which will form the “best” surface of the part, and the core side, or “B” side, will typically show the visual imperfections caused by ejector pins because the parts get ejected from this half.

Injection molds are manufactured by machining or by Electrical Discharge Machining (EDM). Standard machining was the traditional method of building injection molds with a knee mill. Technology advanced the process, and Computer Numerical Control (CNC) machining became the predominant method of making complex molds, with more accurate details, and in less time than the traditional method.

EDM is a process in which a shaped, copper or graphite electrode is slowly lowered onto the mold surface, which is immersed in paraffin oil. Electric voltage applied between the tool and the mold causes spark erosion of the mold surface in the inverse shape of the electrode. EDM has become widely used in mold making - many injection mold companies now have EDM in-house. The process allows the formation of molds which are difficult to machine, such as those with features such as ribs or square corners. It allows pre-hardened steel molds to be shaped without requiring heat treatment.

Compared to other plastic manufacturing processes such as CNC machining or 3D printing, injection molding has a high up-front investment because the tooling is expensive. However, for large production runs of thousands or even millions of identical parts, injection molding is typically less expensive in the long run, despite the high initial tooling investment, because of a lower piece price at high volumes. In addition, it is a much faster manufacturing process than the others mentioned.

Molds can be made of pre-hardened steel, steel that is hardened after the mold is produced, aluminum, and/or beryllium-copper alloy. The choice of mold material is determined in part by the number of parts to be produced.


Multiple-Cavity Molds (Family Molds)



Family molded parts

In addition to a single plastic part being produced in a molding cycle, the mold can also be designed to produce multiple numbers of the same part in a single shot. A tool with one impression is often called a single impression (cavity) mold, whereas a custom injection mold with two or more cavities of the same part is referred to as a multiple impression (cavity) mold. The number of impressions in the mold is often incorrectly referred to as cavitation. Some extremely high-volume molds – like those for bottle caps – can have over 128 cavities.

A multiple impression (cavity) mold may also be referred to as a “family” mold. However, a family mold is more accurately defined as one which can produce multiple, like-sized parts in the same quantity, color and material. Family molded parts are often part of an assembly, such as a mating top half and bottom half.

Overmolding


Example of Overmolding


Overmolding is a plastic injection molding process which is very useful for producing multi-material parts with some unique properties. For instance, this process can be used to add a second part, of a different material, for a handle or grip. Picture a power tool with a grip made out of a softer material than the body of the tool. Similarly, a game controller can be manufactured with different textures of plastics on the body of it.

Basically, a previously injection molded part of one material (the substrate) is re-inserted into an injection molding machine, and a different material (the overmold) is injected to form a new layer over the first part.

Some specialized injection molding machines have two or more injection units that can “overmold” in a single molding cycle. For example, “two-shot,” or “multi-shot” injection molds first mold a basic shape in a base color of plastic material, then the second material, of a different color, is injected into the remaining open spaces to produce a one-piece, multi-color plastic part.

Overmolding is not as straightforward as injection molding a part out of a single material, and it is not without its limitations. One consideration is that the two materials must be compatible, chemically and thermally. Since plastic materials have different melt temperatures, the substrate material must have a higher melt temperature than the overmolding material, otherwise the original part would melt and deform when the overmolding material is injected.

Insert Molding

Metal, ceramic or plastic pieces can be inserted into the molten thermoplastic to form multi-material, robust parts with additional functionality. For example, threaded metal inserts can be molded into the parts to allow them to be attached to other parts.

Insert molding can reduce cost by embedding secondary parts into the plastic injection molding process, as opposed to installing the parts after molding. By integrating the inserts at the time of molding, the parts become more robust compared to staking the pieces in post-molding. Of course, the insert pieces must be able to withstand the high temperature and pressure of the injection molding process.

Insert molding is naturally a more complex process that standard injection molding, so some injection molding companies are more experienced in the process than others. For low-volume production runs, a machine operator may load the inserts into the mold by hand, prior to the plastic injection cycle. For high-volume production runs, however, it is common to use automated machinery to place the inserts into the mold.

Process Efficiency

Optimizing the injection molding process is essential because it affects cost, quality, and productivity. Some of various optimization checks include:

• Optimize the holding time by conducting gate seal or gate freeze studies
• Conduct a cooling time study to optimize the cooling time for an injection molded part
• Pressure drop studies determine if the machine has enough pressure to move the screw at the set rate
• Perform viscosity curves to determine injection speeds
• Vary the melt temperatures and holding pressures to optimize the process window

Molding Trial

When an injection molding job is being set up for the first time and the shot size for that mold is unknown, a molding trial will be conducted to get everything “dialed in.” The mold technician will usually start with a small shot weight and fill the mold gradually until it is 95 to 99% full. Then a small amount of holding pressure is applied, and the holding time is increased until gate freeze off (solidification time) occurs on the injection molded part. Gate solidification is important because it determines cycle time, and cycle time is a crucial determinant in the efficiency, and therefore the economics, of the production process. If the parts have sink marks, the holding pressure will be increased until they are minimized and the part weight is achieved. Once the settings are settled in and the injection molding machine is making good parts, a setup sheet is produced for standardizing the process for future production runs.





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