Moldeo por inyección de acetal

Moldeo por inyección de acetal

Acetal injection molding o Moldeo por inyección de POM parts manufacturered from Polyoxymethylene (POM), a highly processed thermoplastic material. POM can take a homopolymer or copolymer acetal form. Homopolymer acetal exhibits high strength because of its crystalline structure. However, it can be problematic as a result of the highly specific melting point. Copolymer acetal is easier to mold due to the larger processing window. It is less mechanically strong than the previous material as its crystalline structure is less ordered.

Some renowned suppliers offer copolymer acetals. While DuPont, a well-reputed material provider offers only Delrin®, a homopolymer with enhanced properties. Delrin® grades are categorized according to their strength, stiffness, viscosity, and resistance. It is compatible with both injection molding and CNC machining. Acetal mold products/parts are vitally used in automotive, medical as well as fluid handling sectors.

This article primarily focuses on acetal plastic injection molding, POM properties, benefits, and design guidelines for fabricating parts from POM. Moreover, we will provide an Injection Molding Design Guide, certain suggestions, and recommendations for optimal outcomes for your acetal injection molding project.

Acetal injection molding

What Is Acetal?

Acetal, which is also known as polyoxymethylene (POM), is a tough and high-performance thermoplastic. It’s a semi-crystalline material, commonly used for engineering applications. Acetal polymers are formed by the linking of long chains of the molecular formula CH2O. Some copolymer monomers are also incorporated to provide additional functionality. Depending on the structure, acetal can be a homopolymer or copolymer in nature depending upon the structure.

The best-known homopolymer acetal is DuPont™ Delrin®. Acetal plastics have a high strength and stiffness which make them ideal for applications that require high strength but low flexing. These plastics also possess low friction and high wear rates. Low water absorbency makes acetal possess excellent resistance to dimensional changes. For these reasons, acetal is used in place of metals for many uses.

Acetal/POM Material Properties

Table: Properties of various acetal grades

Propiedad Delrin® 100 BK602 Duracon® M90-44 Celcon® M90 Kepital® F20-03 Hostaform® C9021
Physical
Densidad (g/cm³) 1.42 1.41 1.41 1.41 1.41
Shrinkage Rate (%) 1.9–2.2 2.1–2.3 1.9–2.2 2.0 1.8–2.0
Rockwell Hardness 120 R 80 M NA NA NA
Mechanical
Resistencia a la tracción (MPa) 72 62 66 65 64
Elongation at Yield (%) 23 35 10 10 9
Módulo de flexión (GPa) 2.9 2.5 2.55 2.55 NA
Resistencia a la flexión (MPa) NA 87 NA 87 NA
Moldeo por inyección
Drying Temperature (°C) 80–100 NA 80–100 80–100 120–140
Drying Time (hrs) 2–4 NA 3 3–4 3–4
Melt Temperature (°C) 215 200 205 180–210 190–210
Mold Temperature (°C) 80–100 80 90 60–80 85

The table above presents the POM trade names mentioned above together with their properties. Homopolymer Delrin® 100 has the highest tensile strength because of a higher degree of crystallinity in the polymer. POM is characterized by very good tensile and flexural strength but by a high rate of shrinkage. Depending on the application requirements certain POM grades may contain fillers to improve strength, corrosion, or UV resistance.

Pros of POM Injection Molding

Acetal has high performance with desirable engineering characteristics. The material offers high fatigue and creep strengths when subjected to stress. High mechanical strength makes it optimal for different precision-demanding sectors, like aerospace, and automotive. Low friction helps POM to have a very small level of wearing over a long period. Moreover, acetal does not rust/corrode and can also work at high temperatures.

Resistencia a la fatiga

Acetal injection molding parts has good performance characteristics when it is subjected to repetitive stress cycles. It is most appropriate in situations where the load bearing is constant such as gears. Thus, homopolymer POM provides better fatigue strength than copolymers do. These peculiar features make it possible to have long-term dependability in conditions of high stress. Strength in fatigue makes POM suitable for use in applications where mechanical parts are desired.

Creep Resistance

POM molded part exhibits dimensional stability when subjected to mechanical loads in the long term. It has a very low tendency to undergo permanent deformation, even when it is subjected to constant stress. This characteristic makes POM suitable for use in load-bearing applications. The material’s lack of creep also makes it ideal for structural applications. This is a very reliable area of the performance under pressure of POM.

High Strength

POM injection molding parts provides the best tensile and flexural characteristics. The material provides the rigidity required in high-performance mechanical parts. Homopolymer versions of POM show even greater strength as compared with the copolymers. Some common uses include conveyors and safety-related components. POM mechanical characteristics are quite versatile to allow various applications.

Low Friction

Low friction of POM decreases wear and tear in the sliding members. The material is well-suitable for use in areas where there a little movement variation involved. It requires minimal maintenance because of its natural tendency to reduce friction: This ability of POM to resist abrasion keeps the molding parts ‘ life quite long. Therefore, it is often applied where low friction is a necessity.

Food Safety

Advanced POM food-grade material meets safety standards applicable to food contact products. POM can also be used by manufacturers of food processing machinery and equipment. It has complied with the FDA, USDA, and all legal and regulatory requirements of strict safety. Due to its non-toxicity POM is well-suited to employ in these sectors. acetal injection molding part is widely used in food processing equipment for its reliability and dependability.

Estabilidad dimensional

Acetal injection molding products comprise accurate dimensions once they have cooled from the molding processes. During molding its shrinkage rate is relatively high but afterward, it remains almost uniform. Dimensional stability is important in sectors such as automotive and electronics. POM injection molding parts remain dimensionally stable during mechanical application and pressure. This characteristic is a prerequisite for precision components.

Resistencia a la corrosión

POM is relatively immune to most chemical agents such as fuels and solvents. It is best used in places that may come into contact with chemicals. For example, cylindrical storage tanks. However, the material is affected by strong acids and bases. POM stands up well to chemical attack and, therefore is the right material for use in fluid management. It also has good and stable chemical resistance as well as a long service life in harsh conditions.

Resistencia al calor

POM is capable of enduring usage in areas that have high temperatures, up to 105°C. Homopolymer grades withstand higher heat bursts than copolymers do. The intended property is crucial for those components that are exposed to varying temperature conditions. This characteristic makes POM suitable for use in industries because of its tolerance to high temperatures. The right choice of materials used means the ability to withstand thermal climates. To plástico de alta temperatura pgae to know more high temperature materials.

POM plastic molding services

Key Considerations in POM Injection Molding Design

Injection molding acetal prefers the use of stainless steel molds. The material being used has a corrosive effect. Therefore the molds used must be strong and resistant. High shrinkage calls for a keen mold design to achieve precise parts. POM is widely applied in automotive, industrial, and medical parts. So, molding must be done in the right manner and in this case, it is going to ensure that the degree of precision and quality output is going to be high. It is important to take into account some features when designing for POM injection molding.

Wall thickness should be in the range of 0.030 and 0.125 inches. By maintaining thickness variation to the minimum, it is possible to achieve a uniform thickness of the part. The management of tolerances is crucial because the company’s rate of shrinkage is high, and this is evident from the case of POM. Radii should be minimized particularly in the regions that experience maximum stress. Draft angles ranging from 0.5 to 1 degree are ideal because their ejection is smooth.

Espesor de la pared

The thickness of the wall has a direct influence on the quality of injection-molded POM parts. Thicker sections may also make the piece warp or shrink in some ways or the other and this may not be desirable. This way the overall structure is improved and one maintains consistent thickness. However, extremely thin walls though difficult must fall within certain limits. Wall thickness plays a vital role in structural applications and if well done, helps reliably to withstand high pressures.

Tolerancias

POM exhibits high shrinkage which can become a challenge when working on POM molding parts that have to be within close tolerance. In particular, thicker walls are found to increase the probability of tolerance deviation. Designing to ensure equal measurements is not a bad idea as this will ensure that dimensions are consistent. There is always a way of properly molding and this would ensure that tolerances are within the acceptable limits. Problems due to dimensional changes are well managed by planning and control.

Radii

Radii in part designs help to minimize stress concentration in the use of the part. Sharp corners are always a problem because they are the points that can cause a structure to be less durable. By including radii these high-stress areas are minimised hence increasing the life of the part. Radii must be equal to or greater than 0.25 times the nominal thickness of the pipe wall. Smaller radii reduce stress; however, larger radii, up to 75% offer better stress distribution.

Ángulo de inclinación

It is possible to achieve high POM part ejection with minimal draft angles. POM has a low friction, it also has the possibility of having draft angles of 0.5 degrees. It is conceivable that for parts such as gears, zero drafts may not be essential to satisfy design specifications. Drafts help to avoid the difficulty of the separation of parts from molds with minimal or no harm. Good draft design enables efficient production and better quality of the part to be produced.

POM Material Processing Challenges

What makes POM difficult to process? Well, certain determinants decide its optimal functioning. As POM has a slight or low tolerance to high thermal conditions. Several factors are taken into consideration by mold operators during injection molding. Such factors are heat control, moisture level, molding parameters, and shrinkage. These elements are important to achieve successful production of high-quality POM injection molding parts.

Calor

One of the most critical aspects to be managed in POM injection molding is heat. When heated at a temperature higher than 210°C, the material undergoes thermal degradation. This breakdown results in the formation of by-products that are corrosive and end up affecting the injection mold. Mold temperature should be between 60-100°C for the best outcome. Further, the short heating cycles are also beneficial because they do not stress the material too much. With the increase in temperature, it should be accompanied by a decrease in residence time to achieve quality.

Humedad

The moisture absorption of POM is quite low and it lies between 0.2 to 0.5%. However, it is advised that POM resin should be dried before processing to get the best results. The drying time is normally between 3 to 4 hours, depending on the POM grade. This is important so that moisture levels are low during molding to decrease the occurrence of defects. Careful preparation avoids problems related to moisture during the injections.

Molding Parameters

The right molding parameter must maintained for POM injection molding. The successful injection pressure identified is between 70 to 120 MPa to ensure good repeatability of the experiment. A medium to high injection speed is also desirable to achieve a smooth production of the part. Molded part control requires proper parameter control to ensure that the molded parts meet specific specifications. By closely tracking these parameters it is possible to enhance the quality of the final product.

Contracción

Shrinkage is a usual problem with POM materials including Delrin®. Shrinkage rates are usually between 2 to 3.5 percent in the cooling stage of the cycle. The majority of shrinkage happens when the part is still in the mold, and the rest are during post-ejection. Non-reinforced homopolymer POM exhibits greater shrinkage than copolymer materials. These shrinkage rates must be considered in mold design to meet the desired dimensions.

POM INJECTION MOLDING

Disadvantages of Acetal Injection Molding

Although acetal molding offers several benefits. It also has its limitations and drawbacks. In addition, acetal molds come with many challenges. These limitations must be carefully considered during the molding process for companies to achieve good-quality end-use products.

Poor Weather Resistance

Acetal is highly vulnerable to degradation. Normally, in situations when it’s exposed to ultraviolet light or UV light. This is so because constant exposure to them can cause major color shifts and eventually affect their performance. UV deteriorates the aesthetic value and physically weakens the material. Moreover, UV radiation strips the structure of polymers away. Hence, there must be use of stabilizers to enhance acetal’s resistance to weathering. These stabilizers may not prevent the degradation fully over long periods outdoors thus hampering the use of acetal in exterior uses.

Fragilidad

In its solid state, Acetal is highly resistant and possesses high stiffness, but undergoes brittle failure under special circumstances. Temperature Low temperature affects the material characteristic of acetal and makes it prone to crack or fracture when experiencing an impact. However, this brittleness is a drawback in any applications where high-impact strength is desirable, particularly at low temperatures. There are significant challenges in designing products that are molded from acetal so that they can endure shock without fracturing.

Concerning the effects of the acetal molding process on the mechanical properties of parts, considerations should be taken into account.

Acetal Injection Mold Design

When designing an application using acetal material it is important to get the mold right because it determines the quality and stability of the end product. Here are some key design guidelines to follow:

  • Runner Diameter: The runner diameter is suggested to be between 3 and 6 mm to enable easy flow of the material during injection.
  • Gate Length: Ideally, the gate length should be some 0.5mm to provide proper regulation of the throughput of the material. It improves the uniformity of the mold so that no defects are formed when filling the mold with the material.
  • Round Gate Diameter: This should be between half and six times the thickness of the part being molded. By sizing the gates properly it eliminates cases like short shots and weld lines.
  • Rectangular Gate Width: By design, the width of the rectangular gates must measure at least twice the thickness of the product. This should ideally be about 0.6 times the wall thickness as far as the structural reinforcement of the vessel is concerned.
  • Draft Angle: A mold angle of 40 to 1 30 is proposed for straightforward removal of the molded part without any abrasion on the surface.

Pre-Drying Acetal Material

Even if it has a high moisture absorption value, the acetal part is suggested to be pre-dried before injection molding for the resin. Pre-drying also reduces the presence of some form of moisture that is destructive like the formation of voids or bubbles. The drying process should be at a temperature of 80–100°C and should take 2-4 hours. Correct drying is as important since it assists in retaining various characteristics of the materials besides facilitating guzzle-free molding.

Acetal Molding Temperature Control

When it comes to acetal injection molding it is very crucial to maintain both moisture and melt temperature for enhanced results. The mold temperature should be maintained between 75 and 120 centigrade and the melt temperature to be between 190 and 230 centigrade (374 and 446 Fahrenheit respectively). Parameters such as accurate temperature regulation also manage problems like distortion shrinkage or even poor surface finish. Accurate regulation of thermal conditions helps to cool uniformly and, therefore, minimize stresses when improving the dimensional characteristics of the final product.

Injection Pressure

Each material requires a specific injection pressure that needs to be attained to provide the specific part quality. The pressure range is in the range of 40–130 MPa depending on the melt flow rate of acetal and the thickness and sizes of the runner gate and part. When pressure is low, the mold can be filled inadequately, and if pressure is high, then there is likely to be flash or other defects. The optimum pressure is important for the creation of appropriate part formation and the exclusion of defects.

Injection Molding Speed

The injection speed is also another that greatly influences the process of acetal molding. Depending on puddle formation, mold injection speed ranges from moderate to fast to avoid defect creation as the mold is filled. In case of slow speed, the flow marks or surface imperfections are seen on the surface. On the other hand, high speed may lead to what is called jetting or shear overheating which is bad for the strength and surface finish of most parts. Through modification of the injection speed, one can be able to eliminate the molding defects as well as enhance the molding productivity.

These considerations allow manufacturers to enhance the efficiency of their acetal injection molded parts by controlling parameters, and issues incurred. To make the best use of the positive attributes of acetal while avoiding its drawbacks, certain aspects of mold design, material handling as well as the process must be finely tuned.

Conclusión

Acetal or polyoxymethylene is a type of injection-molded semi-crystalline thermoplastic. This material is commonly used in mechanical parts such as bushings, bearings, gears, and sprockets.

Compared to metals and other plastics acetal has a low friction coefficient and high rigidity. These features greatly improve its wear properties, and thus the resultant products are long-lasting.

Altogether these characteristics make acetal a material of choice for many engineering applications. The proper processing and design of the equipment improve their efficiency and durability in different industries.

Introducing acetal into production processes may result in higher efficiency and lower frequency of maintenance of mechanical equipment.

 

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Espesor de pared del moldeo por inyección, su importancia y factores que lo afectan

moldeo por inyección de pared gruesa

El moldeo por inyección es un método general que se utiliza normalmente en la industria manufacturera. En este método, el material se introduce a alta presión en la cavidad de una matriz. Normalmente, durante la etapa de diseño, el espesor de la pared de una pieza es uno de los factores más importantes a tener en cuenta. Por ello, en este artículo, analizaremos el espesor de la pared, su relación con el moldeo por inyección y su relación con la calidad de la pieza y la capacidad de fabricación.

¿Cómo definirías el espesor de la pared del moldeo por inyección?

Moldeo por inyección Espesor de pared El espesor de pared es una medida del espesor de las paredes de la pieza moldeada producida con la ayuda de un proceso de moldeo por inyección. Es la cantidad, en milímetros, desde una de las superficies más externas de la pieza hasta la otra superficie más externa. Además, el espesor de pared es quizás el más importante, ya que determina la capacidad de la pieza moldeada para resistir los mecanismos de falla. Estos pueden incluir fluencia, pandeo, deformación y defectos cosméticos. El espesor de pared siempre debe diseñarse para adaptarse a ciertas condiciones, es decir, el material, el funcionamiento de la pieza, el diseño y el equipo de moldeo utilizado. Por lo tanto, seleccionar el espesor apropiado para las paredes es fundamental para entregar las piezas deseadas.

Espesor de la pared del moldeo por inyección

¿Cuál es la importancia de un espesor de pared uniforme?

Un espesor de pared uniforme es muy importante cuando se trata de alta calidad. Ayuda a proporcionar piezas moldeadas por inyección libres de defectos y estructuralmente sólidas y también aumenta la integridad estructural. Además de esto, ayuda a mejorar la eficiencia y optimizar el uso del material. Entonces, analicemos más sobre la importancia del espesor de pared uniforme.

1. Impacto en la calidad de las piezas

En primer lugar, un espesor de pared uniforme permite una refrigeración uniforme y también evita tensiones internas y deformaciones. Además, ayuda a mantener unas dimensiones precisas, por lo que se pueden evitar imperfecciones en la superficie, es decir, hundimientos y deformaciones. Además, aumenta tanto la funcionalidad como la estética de la pieza final.

2. Reducción de defectos

En segundo lugar, si el espesor de la pared es uniforme, se reducen en última instancia las deformaciones y las marcas de hundimiento. Se promueve un enfriamiento uniforme y se reducen las tensiones internas, por lo que, en última instancia, obtenemos piezas más resistentes y duraderas con menos puntos débiles.

3. Integridad estructural

El espesor uniforme de la pared proporciona una distribución equilibrada de la carga para mejorar la resistencia y la durabilidad. Además, mejora las propiedades mecánicas de los productos, es decir, la resistencia a la tracción y la resistencia al impacto, para proporcionar un rendimiento confiable.

4. Mayor eficiencia en la fabricación

También facilita el diseño de moldes y los procesos de moldeo por inyección, reduce los tiempos de ciclo y los costos de producción, además de promover un enfriamiento más rápido y mejor y optimizar el proceso de producción.

Consideraciones sobre los materiales en el moldeo por inyección

Las siguientes son las consideraciones materiales para el espesor de la pared de fundición por inyección.

  1. Tipo: Ejemplos: termoplásticos, incluidos ABS y PC; termoestables como resinas epoxi; elastómeros como caucho de silicona; y TPE.
  2. Fluir: El llenado del molde depende de la viscosidad, donde el producto debe ser fino, se requiere material de alta fluidez y donde se requiere espesor, el material de baja fluidez es el más apropiado.
  3. Contracción: Con los metales, se reducen de tamaño desde un estado fundido y exhiben un estado sólido o un estado de fundición; esto se considera en el diseño de un molde para hacer el tamaño correcto de una pieza.
  4. Fuerza y flexibilidad: Los factores adicionales incluyen la rigidez y la resistencia, ya que éstas determinan el espesor de la pared durante la construcción para una perspectiva estructural confiable.
  5. Resistencia: Resistencia al calor y a los productos químicos para promover una larga vida útil en cualquier tipo de condición de operación.
  6. Acabado superficial: Las características de un material de moldeo influyen en el acabado de la superficie y el aspecto de la pieza moldeada para aumentar su estética y suavidad.
  7. Costo e impacto ambiental: Estos incluyen el costo unitario del material, su capacidad de reciclaje y su conformidad con los estándares sustentables.

Entonces, la siguiente tabla describe los rangos adecuados que puede soportar el material respectivo; a continuación se muestra una pieza de moldeo por inyección de pared gruesa que fabricamos en material de PC, obtenga más información sobre Moldeo por inyección de PC.

Moldeo por inyección de paredes gruesas

 

Material Rango típico de espesor de pared:
ABS 1,0–3,0 mm
Policarbonato (PC) 1,0–3,0 mm
Polipropileno (PP) 0,8 – 2,5 mm
Polietileno (PE) 1,0–3,0 mm
Nailon (PA) 1,0–3,0 mm
Acetal (POM) 0,8–3,0 mm
Tereftalato de polietileno (PET) 1,0–3,0 mm
Cloruro de polivinilo (PVC) 1,0–3,0 mm
Acrílico (PMMA) 1,0–3,0 mm
Acetato de vinilo de polietileno (EVA) 1,0–3,0 mm
Elastómeros termoplásticos (TPE) 1,0–3,0 mm
Resina epoxídica 1,0 – 5,0 mm
Silicona 1,5 – 6,0 mm

Pautas para el diseño del espesor de pared en el moldeo por inyección

A continuación se muestra una breve tabla que nos ayudará a diseñar un espesor de pared óptimo en el moldeo por inyección.

 

Pauta Descripción
Reglas generales ● Mantener un espesor uniforme para evitar defectos.

● Garantiza transiciones suaves y gruesas.
Espesor mínimo de pared ● Depende del flujo del material; los materiales de alto flujo pueden tener un espesor de entre 0,5 y 1,5 mm.

● Asegúrese de que el espesor mínimo sea para mayor resistencia.

● Permitir el llenado completo del molde.
Espesor máximo de pared ● Las paredes más gruesas (>4 mm) aumentan el enfriamiento y el tiempo del ciclo.

● Optimizar para reducir costos y peso.

● Las paredes más gruesas corren el riesgo de dejar marcas y huecos.
Requisitos estructurales/funcionales ● Paredes más gruesas para piezas sometidas a altas tensiones.

● Espesor específico para aislamiento térmico y eléctrico.

● Equilibre el grosor para lograr flexibilidad y resistencia.
Diseño para la fabricación ● Asegúrese de la compatibilidad del diseño y el flujo de materiales.

● Incluye corrientes de aire de 1 a 2 grados para una fácil expulsión.

● Refuerza paredes delgadas sin añadir volumen.
Simulación y pruebas ● Utilice CAE para predecir y solucionar problemas.

● Probar prototipos para validar el diseño.

Herramientas y recursos para optimizar el espesor de las paredes

Aquí hay algunas herramientas y recursos que pueden ayudarle a aumentar la eficacia del espesor de la pared del moldeo por inyección.

Herramientas de software para simulación

Se utiliza de forma eficaz en el moldeo por inyección para determinar un espesor de pared adecuado. Desempeña un papel muy importante en la determinación del espesor de pared. Estas herramientas proporcionan información sobre cómo se transportará el material y su comportamiento en el proceso de moldeo por inyección. De este modo, los diseñadores pueden prevenir o resolver algunos de los desafíos que pueden surgir durante el proceso de moldeo propiamente dicho. Entre los beneficios y características clave se incluyen:

  1. Análisis de flujo: Imita el proceso de entrada del material fundido en el molde y muestra las partes en las que el material podría no fluir correctamente o donde se están creando trampas de aire.
  2. Análisis de enfriamiento: Utiliza modelos informáticos para predecir patrones de enfriamiento y permitir que el enfriamiento se produzca a un ritmo uniforme. De este modo, ayuda a eliminar problemas como deformaciones y marcas de hundimiento.
  3. Análisis de estrés: Comprueba las tensiones en la pieza para confirmar el espesor de la pared. Comprueba si es óptimo y si el nivel de tensión es suficiente para la aplicación prevista, pero no demasiado alto.
  4. Algoritmos de optimización: Proponer cambios que se deben realizar en el espesor de la pared y otras características de diseño, ya que pueden afectar la capacidad de producción de la pieza y la eficiencia de su funcionamiento.

Algunos de los programas de simulación más conocidos para el moldeo por inyección son Auto Desk Mold Flow, Solid Work Plastics y Moldex3D. Todos ellos ayudan a los diseñadores a diseñar secciones para optimizar las soluciones sin defectos.

2. Opciones de creación de prototipos

Existen varios tipos de prototipado posibles, lo que significa que los diseñadores pueden realizar ajustes físicos y de forma real importantes en comparación con los modelos simulados. Además de esto, estas opciones tienen como objetivo fabricar la pieza, por lo que estos métodos de prototipado incluyen:

  • Impresión 3D (fabricación aditiva): Permite desarrollar prototipos a mayor velocidad manteniendo diferentes espesores de paredes laterales. La ventaja más evidente es que es económico probar rápidamente varios diseños. Además de esto, pueden ser prototipos de forma o de función.
  • Mecanizado CNC: Ofrece prototipos contemplativos en los que se han utilizado materiales de producción para que el resultado sea casi perfecto. Este método permite identificar las características de la pieza mecánica y su comportamiento en condiciones reales de funcionamiento.
  • Herramientas blandas: Se caracteriza por el uso de matrices de conformación de baja resistencia y corta duración para producir menos piezas en comparación con la fundición a presión. Por lo tanto, este enfoque es ventajoso para la evaluación del proceso de moldeo, así como para la identificación del espesor de pared. También ayuda a la estandarización de todo el tipo de molde.

¿Qué factores afectan el espesor de la pared del moldeo por inyección?

Existen múltiples factores que pueden afectar el espesor de la pared en el moldeo por inyección. Analicemos estos factores en detalle:

1. Propiedades del material

Estas propiedades pueden incluir:

  • Viscosidad: Si hablamos de materiales de baja viscosidad, estos fluyen fácilmente en secciones delgadas y permiten paredes más delgadas. Mientras que los materiales de alta viscosidad pueden necesitar paredes más gruesas para realizar el llenado completo del molde,
  • Contracción: Los materiales con un alto valor de contracción pueden necesitar paredes más gruesas, por lo que pueden tener en cuenta los cambios dimensionales durante el enfriamiento.
  • Fuerza y flexibilidad: Las propiedades mecánicas, es decir, la resistencia a la tracción y la flexibilidad, determinan el espesor de la pared para un rendimiento óptimo.

2. Requisitos de diseño

Los siguientes requisitos de diseño pueden afectar el espesor de la pared.

  • Requisitos funcionales: Todo depende de la pieza que necesites fabricar. Si es una pieza estructural, entonces las paredes deben ser más gruesas para que puedan ser rígidas. Por otro lado, la parte cosmética necesitará paredes más delgadas para que puedan lograr el mejor aspecto.
  • Consideraciones estéticas: Las paredes delgadas pueden brindar una apariencia elegante. Por otro lado, las paredes más gruesas son lo suficientemente fuertes y pueden evitar defectos, es decir, hundimientos o deformaciones.
  • La complejidad del diseño: Las geometrías complejas pueden requerir distintos espesores de pared, por lo que se puede garantizar que todas las características se formen correctamente y que la pieza se pueda extraer fácilmente del molde.

3. Capacidades de fabricación

  • Diseño y construcción de moldes: Los moldes de alta precisión pueden manipular paredes más delgadas con facilidad, y los moldes más simples necesitan paredes más gruesas para un llenado adecuado, por lo que pueden garantizar la calidad de la pieza.
  • Presión y velocidad de inyección: Las máquinas con alta capacidad pueden lograr paredes más delgadas y ofrecen mayor presión y velocidad.
  • Tasas de enfriamiento: El enfriamiento uniforme es muy importante, ya que las paredes más gruesas necesitan tiempos de enfriamiento más largos. Esto afecta directamente el tiempo de ciclo y la eficiencia de producción. Por lo tanto, los sistemas de enfriamiento avanzados ayudan a crear paredes más delgadas y también mantendrán la calidad.

Conclusión

En resumen, el espesor de pared del moldeo por inyección proporciona piezas de alta calidad, bien formadas y rentables. Por lo tanto, es esencial considerar cuidadosamente las propiedades del material y los requisitos de diseño para ayudar a los diseñadores a mantener un equilibrio. Este equilibrio aumentará el rendimiento y la capacidad de fabricación de la pieza. Además, puede utilizar diferentes opciones de creación de prototipos y software de simulación avanzado para refinar todo el proceso. Estas herramientas también producirán diseños con defectos mínimos. Además, los avances en materiales, tecnología de simulación, monitoreo en tiempo real y prácticas sostenibles harán mejoras en el moldeo por inyección. Por lo tanto, puede optimizar el espesor de pared de manera más precisa y eficiente.

moldeo por inyección de gran volumen

Preguntas frecuentes

¿Qué factores influyen en la elección del material en el moldeo por inyección?

El tipo de material se decide en función de propiedades como la resistencia a la tracción y la elasticidad, la microscopía electrónica, el calor y la resistencia química. Además de esto, también depende de la apariencia y la suavidad del material, su costo y su capacidad de reciclaje.

¿Cuáles son algunos defectos comunes en el moldeo por inyección y cómo se pueden prevenir?

Algunos de los defectos más frecuentes son las marcas de hundimiento, que se originan por diferentes velocidades de enfriamiento; la deformación, resultante de la tensión interna; y la rebaba, que es una acumulación excesiva de material en moldeo por inyección Líneas de separación. Estos problemas pueden evitarse normalmente mediante el cumplimiento de los mejores procedimientos de diseño y la regulación de los grados de calor, presión y otras condiciones que podrían afectar al producto.

¿Cómo puede el software de simulación beneficiar los procesos de moldeo por inyección?

La simulación asistida por computadora permite a los diseñadores e ingenieros modelar y analizar los diseños de moldes, la elección de materiales y los factores de proceso en un entorno virtual. Con la ayuda de este software, se pueden predecir los patrones de movimiento de materiales, las velocidades de enfriamiento y otros factores antes de diseñar los moldes físicos para su uso. Esto ayuda a mejorar la calidad y la capacidad de fabricación de la pieza.

¿Cuáles son las ventajas de utilizar aditivos o cargas en los materiales de moldeo por inyección?

Los aditivos y rellenos pueden mejorar las características de los materiales, como la resistencia, la rigidez, la resistencia a las llamas y la resistencia al impacto. También pueden mejorar la procesabilidad y reducir el costo del material al agregar un mayor volumen de otro material más asequible a la resina. Sin embargo, se debe hacer un gran esfuerzo para lograr compatibilidad, dispersión uniforme e interferencias mínimas en los demás componentes.

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Proceso de moldeo por inyección de termoplásticos

moldeo por inyección de HDPE

Thermoplastic injection molding has become the most applicable plastic manufacturing process. It is renowned for producing products of high standard quality in minimal turnaround and large quantities. The increasing need for high quality plastic products in different sectors has boosted the application of thermoplastic materials.

These materials are based on polymer resins, and when heated, they turn into a homogeneous liquid that becomes solid when cooled. Injection molding employs thermoplastics and thermosetting plastics or even elastomeric materials to form high-performance moldable parts or products. Newer technologies in injection molding thermoplastic and better molds have enabled the reduction of costs, better looks, and better manufacturing prospects.

Why Are Thermoplastics Materials Used in Injection Molding?

 

Thermoplastics are used in injection molding since they melt at high temperatures and crystallize at low temperatures. This property makes them ideal for being recycled and formed into different forms and structures. They are the most preferred materials in industries due to their flexibility and versatility of use.

thermoplastic injection molding

How To Produce Injection Molded Thermoplastic Products?

Thermoplastic injection molding is one of the most fundamental processes in contemporary production. It entails the creation of a variety of plastic products through the employment of thermoplastic polymers.

Step 1. Appropriate Material Selection

The material type used determines the final product’s functionality, appearance, and durability. Select materials by considering their mechanical properties, heat stability, and specific use.

Step 2. Material Preparation

This process entails drying raw plastic pellets to eliminate moisture. Because moisture content significantly impacts and is destructive to the melting process and the molded part. These prepared pellets are then fed into the hopper of the injection molding thermoplastic machine through a conveyor belt.

Step 3. Melting

The plastic pellets are melted in a barrel which entails a reciprocating screw. These pellets then take the form of molten lava or red hot liquid. During this phase, temperature controls are crucial to obtain the right consistency and the flow of the molten plastic to the required standard.

Step 4. Injection

As the name suggests, the molten plastic is injected into the mold cavity by applying highly controlled injection pressure. The precise control over this process determines the part’s exact specifications and finishes. The resulting parts are then cooled down and solidified at optimal conditions.

Step 5. Ejection

The required part is then taken out from the mold by using ejector pins after the solidification. This process must be timed and controlled so that it does not harm the part and that it is released properly.

Step 5. Post-Processing

This phase is typically used to cut to shape parts into desired shapes. The parts can be painted, anodized, trimmed, polished, etc, depending on the required functionality and aesthetics.

What are the Critical Parts of a Thermoplastic Injection Molding Machine?

A thermoplastic injection molding machine is made of several parts. Some commonest parts include;

Clamping Unit

The clamping unit tightly holds the two parts of the mold to ensure that they do not open during the injection. It has to apply enough force to resist the force exerted by the molten plastic being injected to ensure that the mold does not open and the part is well formed.

Injection Unit

The injection unit, which is said to be the heart of the machine, is in charge of heating the plastic material and injecting it into the mold cavity. It has a heated barrel with a screw that moves back and forth to force the plastic through a nozzle into the mold and maintain a steady supply of material.

Dwelling and Cooling System

Once the molten plastic has been injected into the mold, the dwelling and cooling system keeps pressure to guarantee that the plastic occupies all the mold cavities and solidifies into the right shape. Cooling is a very important process in the reduction of the cycle time as well as enhancing the quality of the final product.

Ejection Process

After the plastic has been set, the ejection process starts. The mold is opened, and the ejector pins, which are provided on the side of the mold, throw out the finished part from the mold cavity. This process must be done carefully and at the right time so that the part is not damaged and the removal is done well.

Mold Tool

The mold tool is a negative one and is made from steel or aluminum and forms the final product. It defines the surface finish and size of the product. The tool has two halves that are connected at the center and which are injected apart from each other.

termoplástico moldeado por inyección

Material Types Are Used in Thermoplastic Injection Molding?

The are many type of thermoplastic injection molding materials used to create molding products include;

ABS (Acrilonitrilo butadieno estireno) is characterized by high impact strength, high rigidity, and low shrinkage. This makes it ideal for automotive components, consumer electronics, and toys where durability and mechanical stress resistance are of paramount importance. Read more about Moldeo por inyección de ABS.

Poliamida (nailon) has high strength, thermal stability, and wear resistance. These attributes make it ideal for use in automotive parts, mechanical products, and other consumer products that require strength and performance. Read more about Moldeo por inyección de nailon.

Cloruro de polivinilo (PVC) has the advantages of high strength, good chemical resistance, and fire resistance. Some of the uses are plumbing pipes, medical tubing, and outdoor furniture, which makes it a material that can be used in many fields.

Tereftalato de polietileno (PET) is valued for its transparency, mechanical properties and food contact approval. This material is used in beverage bottles, packaging materials, and synthetic fabrics because of its strength and clarity.

PMMA or Acrylic offers sound light transmission and is not affected by weathering or UV radiation. These features make it suitable for signs, lamps, and windows where transparency and strength are desirable. Read more about Moldeo por inyección de PMMA.

Poliestireno (PS) is a lightweight material, relatively cheap, and often used in disposable cutlery, CD cases, and insulating materials because it is easy to shape and relatively cheap. Read more about Moldeo por inyección de PS.

Poliuretano termoplástico (TPU) is characterized by high elasticity, oil resistance, and abrasion resistance. It is applied in the production of soles and insoles of shoes, flexible medical tubes, seals and gaskets of automobiles, etc. Read more about Moldeo por inyección de TPU.

Polioximetileno (POM) has high rigidity, low wear rate, and good resistance to shrinkage and swelling. It is suitable for applications that call for strength and accuracy, like gears and bearings, electrical parts, and consumer products. Read more about Moldeo por inyección de POM.

Polybutylene Terephthalate (PBT) has good electrical properties, heat and chemical resistance. It is widely applied in electrical parts, automotive parts, and under-hood parts because of its high strength and heat resistance.

Poliestireno de alto impacto (HIPS) is characterized by high impact strength and good processability. It is used in model making, sign writing, and in the housing of consumer electronic products where strength and stability are required.

Elastómeros termoplásticos or TPE are materials that have characteristics of both thermoplastics and rubber and are flexible and elastic. They are applied to sealing and gasket applications, soft feel parts in household goods, and handles. Read  more about Moldeo por inyección de TPE.

Polyphenylene Oxide (PPO) is well known for its heat resistance, low thermal expansion coefficient and electrical insulation. It is applied in automotive parts, electrical parts, and appliances that need to be hard-wearing and heat-resistant.

LCP is characterized by high mechanical strength, high-temperature stability, and good chemical resistance. It is applied in high-voltage electrical contacts, microwave oven parts, and other critical uses.

Polieterimida (PEI) has high heat, strength, and flame resistance. It is used in aerospace parts, medical equipment, and other places where high stress is experienced.

Polyether ether ketone (PEEK) is characterized by high-temperature stability, chemical inactivity, and mechanical characteristics. It is applied in aerospace parts, automotive applications, and medical applications where strength and toughness are needed. Read more about Moldeo por inyección de PEEK.

Sulfuro de polifenileno (PPS) has high heat resistance, chemical resistance, and low thermal shrinkage. It is used in automotive, electrical and electronics and in coatings that require chemical and heat stability. Read more about Moldeo por inyección de PPS.

Styrene Acrylonitrile (SAN) is preferred for its clarity, stiffness and resistance to chemicals. These properties make it suitable for use in food containers since fats and oils are some of the things that the containers should be able to withstand. SAN is also often applied in kitchenware because of its high heat resistance and in bathroom fittings because of chemical resistance.

Acetal (Polyoxymethylene, POM) is highly stiff, self-lubricating, and has good dimensional stability. Acetal is also used in electrical insulators and consumer goods. Some common examples include; zippers and window latches, where strength and wear resistance are required.

Ethylene Vinyl Acetate (EVA) is known for its flexibility, high-impact strength, and clarity. It is a rubber like material that can be molded and recycled and is used in foam products used in sports equipment padding, footwear such as soles and insoles, and flexible packaging films.

Polyurethane (PU) is a flexible polymer that is applied to foam furniture and car seats because of its comfort and sturdiness. Also, PU is used in wheels and tires of industrial and recreational vehicles and automotive interior parts such as dashboards.

PPSU is highly heat resistant, very tough, and can withstand steam sterilization, which makes it suitable for challenging conditions. PPSU is widely used in medical instruments that are often sterilized, aircraft interiors that are exposed to high temperatures and stress, and plumbing where heat and mechanical stress are essential. Read more about Moldeo por inyección de PPSU.

Polyethylene Naphthalate (PEN) is a variant of PET but has better barrier properties, heat and chemical resistance. PEN is applied in packaging materials that need to be very strong and have good barrier properties and in electronics where parts need to be dimensionally stable and electrical insulating.

Polybutylene’s peculiar characteristics, like heat and pressure resistance, make it ideal for use in piping systems in hot and cold water distribution and under-floor heating systems where high temperature and pressure are required.

Polymethylpentene (PMP) is a rather special type of thermoplastic due to its transparency and heat resistance. PMP is used in laboratory equipment where chemical resistance and clarity are required and in microwave cookware because of its heat resistance and quality food preparation.

Polysulfone (PSU) is characterized by high heat resistance, strength, and transparency. These characteristics make it ideal for use in medical devices, especially those that are reusable and need to be sterilized, water filtration systems because of their stability and strength, and electrical parts where insulation and heat resistance are important.

Injection Molding Nylon

Thermoset Vs Thermoplastic Injection Molding: Key Differences

Moldeo por inyección de termoplásticos

This thermoplastic molding technique uses materials such as; polyethylene and nylon that can be reheated and recycled for second use. It is perfect for producing numerous components that require flexibility, impact strength, or clarity.

Thermoset Injection Molding

This method uses materials such as epoxy and polyester, which undergo a chemical reaction when exposed to heat and harden to a specific form. They cannot be reshaped once they have cooled down. It is used where high strength, heat or chemical resistance is required, but unlike thermoplastics, they cannot be recycled

Therefore, the major distinction is that thermoplastics can be recycled through melting and thermosets are permanently molded and cannot be remolded, providing different strength as per the requirement.

Industrial Applications of Thermoplastic Injection molding

Industria del automóvil: Thermoplastic injection molding is widely applied for fabricating interior to exterior components of automobiles like dashboard parts, bumpers, and door panels of cars. It is also useful for creating under-the-hood parts such as fluid reservoirs and housings because of its strength and accuracy.

Industria médica: In the medicare sector, thermoplastic injection molding is very significant in the manufacturing of disposable syringes, surgical instruments, and enclosures for medical devices. Due to its precision in developing complex patterns, it is essential to develop parts utilized in diagnostic tools and prosthetics.

Electrónica de consumo: In electronics, this molding process is used in the production of enclosures of smart phones, remote controls, and computer parts, among others. It is also used in the fabrication of battery casings and connectors because of its strength and versatility of shape.

Construction Industry: In construction, thermoplastic injection molding is applied in the production of pipe fittings, plumbing parts, and electrical enclosures because of the strength and durability of the material. It is also applied in the production of insulating materials and window frames due to its strength and heat resistance.

Toys and Recreation: This molding process is used in creating action figures, puzzles, and boards games that have designs that are complex. It is also used in the manufacture of outdoor items such as garden implements and children’s play equipment since it can yield strong and safe products.

Household Products: Thermoplastic injection molding is vital in the production of kitchen appliances, containers, and utensils because of the heat and chemical resistance. It is also used in making storage bins and cleaning tools due to its strength and simplicity.

Thermoplastic Injection Molding: Common Defects & Remedies

Below are typical challenges encountered during the process and strategies to address them effectively:

Insufficient Filling: This is so when the mold is not fully filled. To address this, one may increase injection speed or pressure, check the temperature of the material, or increase the size of the gate.

Flash Formation: This is a condition where there is the formation of a thin layer of plastic on the edge of the part after it has been molded. This can be solved by either lowering the injection pressure or clamping force or by checking the mold for any damages.

Warping: If the part distorts during cooling, then consider uniform cooling temperature, cycle time to optimal state.

Sink Marks: These are small contours on the part’s surface and normally occur in varying sizes. To prevent these, increase the cooling time or reduce the holding pressure.

Burn Marks: These occur when a material is overheated or air is trapped and may cause black or brown discoloration on the part surface. This can be overcome by reducing the melt and mold temperature and, at the same time, increasing the injection speed so as to avoid overheating or the formation of air pockets.

Such changes should enhance the quality and productivity of the injection molding process.

Resumen

Thermoplastic injection molding remains one of the most significant pillars of innovation that offers flexibility and effectiveness in developing quality products. It is used in automotive and medical industries, consumer electronics and many more industries proving its versatility and efficiency.

Companies like Sincer Tech are the best examples of plastic injection molding services that provide full-service solutions with a focus on quality and accuracy. Our company specializes in overmolding and insert molding and uses a variety of materials to guarantee that each product is of the highest quality.

They offer a wide range of thermoplastics, and their experience in prototype molding and mass production makes them among the best. Whether it is a prototype or a mass production project, Sincere Techs’ dedication to the advancement of technology and the production of high-quality products is evident in all of their work.

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