injection molding

31
Aug

DIGI-REC 4.0 (optimización del impacto ambiental en inyección de plásticos)

Concluido el proyecto Europeo  DIGI REC 4.0, cuyo número de expediente es AEI-010500-2020-191, donde ZATEC ha participado junto con el Centro Español de Plásticos (CEP), ItanInnova y Citsalp,  exponemos a continuación un resumen y conclusiones del mismo.

PRESENTACIÓN 

Este proyecto tiene como objetivo principal maximizar la reciclabilidad de materiales plásticos empleados en procesos de moldeo por inyección, lo que implica maximizar la reducción de su impacto medioambiental, favoreciendo la circularidad del plástico y facilitando la producción energéticamente limpia. 

Los fabricantes de piezas de plástico normalmente utilizan material reciclado proveniente de sus propias piezas de rechazo y/o ramales, pero no conocen en qué proporción pueden mezclarlo con el material virgen sin comprometer (i) las características mecánicas del producto y (ii) la procesabilidad de la fabricación de las mismas. Un exceso de material reciclado puede suponer un empeoramiento en las características mecánicas del producto a fabricar y por otro lado puede generar problemas de procesabilidad en las máquinas de inyección que den lugar a defectos dimensionales o estéticos. Por miedo a ello, normalmente se emplea menos material reciclado del que sería posible. 

Por este motivo, el reto que ha sido abordado en este proyecto es la investigación experimental de la variación de propiedades de un material plástico con el reciclado, y la introducción y utilización de técnicas digitales que permitan conocer cuál es la cantidad máxima admisible de material reciclado que el producto y el proceso son capaces de admitir. 

OBJETIVOS 

los objetivos específicos de este proyecto son:

Establecimiento de procedimiento para la recuperación de desechos en planta y regranceado posterior para dosificación precisa de mezclas de material virgen con distintos porcentajes de material reciclado. 

Investigación de la procesabilidad de las diferentes mezclas realizadas para garantizar que la introducción de material reciclado es inyectable con las mismas garantías que el material virgen. 

Estudio de las propiedades mecánicas y físico-químicas del nuevo material obtenido, (material reciclado), para comparar con las del material virgen y análisis de los posibles cambios físicos en el material reciclado tales como transiciones térmicas y/o aparición de subproductos de oxidación (degradación). 

Ajuste de modelos para digitalización de los materiales reciclados, habilitando su uso en simulaciones del proceso de inyección con las diferentes mezclas de material reciclado en pieza de componente final. 

Creación de herramienta (basada en simulaciones de elementos finitos) con la que se pueda maximizar la cantidad de material reciclado garantizando la óptima procesabilidad en máquina de inyección 

Verificación en planta industrial de los porcentajes máximos de reciclado a conseguir. 

METODOLOGÍA 

Para ello, en el proyecto se ha seguido el plan de trabajo mostrado en la siguiente ilustración:

CONCLUSIONES 

Para el material seleccionado en este estudio (polipropileno con talco), inicialmente se preveía que podría existir una degradación evidente durante el reciclado que provocara una merma de propiedades, lo que conllevaría tener que alcanzar un compromiso entre la cantidad que se reintroduce, las propiedades que se obtienen y los cambios en el proceso de inyección que fuera necesario efectuar. 

Sin embargo, las investigaciones experimentales realizadas en el proyecto DIGI-REC han mostrado que, si se recicla en condiciones adecuadas, las propiedades del material permanecen muy estables. De hecho, el resultado fundamental ha sido que el material 100% reciclado prácticamente tiene las mismas propiedades que el virgen, con lo cual podría reintroducirse en cualquier porcentaje en el proceso de inyección. 

A la vista de este resultado se decidió ampliar la investigación y simular ciclos de reciclado para comprobar si se aprecia acumulación de degradación. Los resultados obtenidos en relación a las propiedades relacionadas con la procesabilidad (viscosidad, pvT, CTE, …), para hasta seis ciclos de regranceado, mostraron sólo ligeros cambios. El análisis de las propiedades mecánicas, en este caso realizadas hasta doce ciclos de reciclado, tampoco mostraron una merma apreciable. Esta investigación confirmó nuevamente la estabilidad de las propiedades de este material con el número de ciclos de reciclado. 

A pesar de la poca influencia encontrada en las propiedades de material, se completó el proceso inicialmente previsto de digitalización del material y la creación del gemelo digital del proceso de inyección de la pieza demostradora. Los ligeros cambios en propiedades como la viscosidad, pvT o CTE provocan según las simulaciones del proceso de inyección realizadas también pequeños cambios en la calidad estimada de la pieza. No obstante, a nivel metodológico se completó el estudio y el desarrollo de la herramienta para su aplicación a futuro a otros materiales que puedan ser más susceptibles a sufrir degradación durante el reciclado. 

Desde un punto de vista de la metodología desarrollada, la digitalización de los materiales reciclados y la generación de gemelos digitales del proceso, se prevé aporte notables beneficios para otros materiales que sufran mayor degradación, ya que permite aunar en una herramienta ágil los requerimientos de procesabilidad y calidad dimensional de la pieza para maximizar el porcentaje de material reciclado reintroducido. 

27
Jul

Considerations of design about injection molding

Many times we receive a drawing with demanding tolerances, a 3D design that turn on all alarms, for example  big accumulation of mass, with paralelism, perpendicularity or flatness in raw materials like polyamide with high percent of glass fiber. By this reason, we think it is necessary to bear in mind some considerations about design of  injection molding based on more than 25 years of knowledge, that probably it could be of help.

In ZATEC we can advise to customer collaborating in this first phase of design, checking the feasibility analysis to optimize the design of piece, according to adequate raw material depending onf inal application and our process of injection molding, to reduce the investment if it is possible. As you can read as follow, we have remarked some examples about it:

Thickness

although sometimes it is not possible to avoid changes of thickness, is very important to have homogeneus thickness without sudden cahnges always it will be possibe. An irregular thickness could generate problems like deformations due to differences of shrinkage in the mentioned thickness, or sink marks in the opposite face.

Sharp Edges,

the sharp edges are stress concentrations (Kc) weakening the piece. Although we can do radii in some areas could complicate the mold, also we improve the design considerably.  It is necessary to take acocunt the big accumulation of mass in the perimeter when we round this area. A good example is a plastic part like a box, and the barrel efect.

Nerves

If we want a rigid piece, it is better to add nerves like reinforcement than increase the thickness. It is very important to bear in mind the crosses of nerves due to possible accumulation of mass, that as you know, this accumulation can generate asthetic defects. In areas with flat surfaces, besides of mentioned nerves, it is necessary to take account the cooling in mold with variations of temperatute, location and size of injection gate(s) and the chosen of adequate engineering plastic based on final application.

Towers and spigots

It should be designed to avoid big accumulation of mass, bubbles… theredore the important consideration is the difference between exterior radius and inner radius.

considerations about design of injection molding

Threaded

if it is possible, avoid the thread’s pitch too thin.  In case of female thread, avoid the fillet ends up to final of piece by possible breaks. In case of  male threads demolded by sliders, can be stopped at height of union line, avoiding if it is possible the problem of wear. As we have mentioned, is important to avoid the sharpd edges with weak mechanical properties, by this reason a good option is to reduce them.

Parts with Inserts

The inserts must not weakening the around material, by this reason the optimum thickness of around material of insert, it must be verified. The shrinkage of plastic on the metal can generate an overflow. This overflow could be removed, doing a ribbed uniform and crossed in the insert part.  Based on our knowledge, it is recommended to heat the insert before injectioning.

If we can help you with a project of plastic part, based on our expertise of engineering plastics and injection molding, do not hesitate to contact us like company of technical plastic injection located in Muel, Zaragoza (Spain), where we can collaborate actively with our customers.

25
May

CREEP in thermoplastics

It is not the firs time in Zatec where we found this phenomenom known like Creep, a problem to bear in mind depending on some final applications. Like injection molding company of technical parts in engineering plastics located in Zaragoza(Spain), we help to our customers to chose the adequate raw material based on final requierements. As you can read as follows, we are going to explain you this problem of Creep.

Creep in plastic injection Sleeves

Sometimes, our plastic parts are subjected to constant strain during long time, and therefore, the deformation can increse up to break, even below the resistance of material.  Normally, we represent in a graph with deformation or strain based on time, according to tensile tests. A datum to bear in mind is the Young Modulus, very usefull for designers due to we can include this mentioned datum in ecuations of resistance materials or simulations about finite element method by computer to predict the behaviour during lifetime.

The raw material, composition and, obviously, the process of injection molding can influence in their properties, like creep. For example, some materials with glass fiber have a better behaviour for this phenomenom than other unreinforced materials, due to hardness. In fact, the most materials used in Zatec have a lot of content of glass fiber, but this tipe of reinforcement could generate a fragile fracture. By this reason, we must consider some extra additives like impact modifiers or conditioning the humidity in some higroscopyc poliamides, avoiding or minimizing the mentioned fracture, being ductile fracture instead of fragile fracture.

Creep

Creep in Brackets, Frames…

The failure in plastic part could be by excessive deformation and due to formation of cracks. Therefore we will have a non-functional piece.  The cracks can appear like an asnwer by applied stress, internal or external overcoming the intermolecular links like hydrogen or Van der Waals forces.

Some typical example is the break around of groves, where the final customer apply a force in screw due to tightening torque in the final assembly. Anyway the break could generates some time after.

Therefore, we can say like final conclusion, the creep is a combination of several factors that we must analyze before in the design phase to avoid the break by Creep.

26
May

Flame retardant plastics

Somtimes, we have received some quotations where a customer needs a flame retardant plastics, and/or with determinated homologated brand, due to several reasons. Nevertheless It is necessary to take account the type of flame retardant as you can see below, based on depeding on thickness.

Battery Case with flame retardant_Zatec

An example, one request for quotation where we must us the homologated raw material “x”. But if we inject this thermoplastic we cannot meet the customer’s requirements due to the part had about 1,5 mm of thickness and the mentioned raw material was flame retardant grade V0 based on a test piece of about 3 mm of thickness. By these reasons, we consider necessary to talk about this additive used in several sectors like electronic, electrical or household appliances. We are talking about the flame retardant plastics.

According to UL94 classification (Underwriters Laboratory in EEUU, with their known yellow datasheets)  and based on test where the test tube is burned in vertical by flame analyzing up to the fire is self-extinguishingTherefore the different grades of flame retardant are as follow:

  • V2, the combustion of sample is stopped in 30 seconds and there are dropping of particles in flames
  • V1, the combustion of sample is stopped in 30 seconds but there are not dropping of particles in flames.
  • V0, the combustion is stopped in 10 seconds and there are not dropping of burning particles, like previous case.

There are other nomenclatures such as 5VA, 5VB with vertical test tube, too. In these cases a burn can produce a hole or not. These cases are not so common than three mentioned nomenclatures before. The lower UL94 classification is for HB grade, where the sample is placed in horizontal.  It is known like self-extinguished although this type burn like wood (to understand the simile).

Below you can see a good video from youtube (source:Filoalfa 3D)  with different behaviours in final parts (ABS in this case), alhtought obviously there are more flame retardant engineering plastics like Polyamide (PA),Polycarbonate (PC)…

The flame retardant agentes more common to get some grades that we are talking about it are: antimony trioxide,  red phosphor (common for dark colors), halogens (fluor, chlorine, bromine, iodine, astatine)… for example. But, sometime these elements can produce harmful smoke for human beings during combustion. By this reason each time is more usual to use flame retardants halogens free, from biological raw materials sustainably manufactured, decreasing the fossil resources besides of carbon emissions to atmosphere.

If you need technical support  to chose the adequate enginnering plastic based on your application, we are glad to help you working together from initial design (bearing in mind our injection molding process) up to serial plastic part

20
Apr

Plastic Injection, situation in automotive about COVID-19

Unfortunately, today is very difficult to talk without saying the word of COVID-19. Despiste of this, laying aside the santitary situation, where we do not pretend deepen now(although we understand this is the most important), but obviously we must to take a conscience of near future based on this eventually moment, due to automotive market has changed dramatically in few time, affecting to all supply chain, since OEM to final Tier-n company.

Sector Automoción

Sector Automoción-imagen de intermpresas.net

This year 2020 it already was complicated and strange. Zatec like injection molding company of technical parts in engineering plastics for automotive(mainly), we are seeing each day too many bad news about the stop in the manufacture industry in Spain, there is much uncertainty about the come back to the work in OEMs companies without a clear date. Anyway in ZATEC we will try to be optimistic, because we are looking to return with relative normality and with more force than before based on adequate safety measures, analyzing the current situation:

The pause in the production of several OEMs at national level(we can say global, in multinational companies), affecting to Tier1 companies, where the common is to cancel or postponed the ongoing orders, and therefore this situation generates more uncertainty increasing the “snow ball” kwnown like crisis, rolling down to the next companie in the supply chain. Logically, to avoid the quick spread of virus.

Almost all Tier1 companies have stopped their manufacturing process, many of them wihout previous advise, therefore there are several parts in transit wihout possibility to download up to new message or several orders in injection machines, but these parts cannot be sent. This is more stock, which we do not know what will be the date of delivery.

Talking about stocks, car dealers will decrease their sales. The reason is simple, the people will spend less money or spend the money in other things based on Maslow’s pyramide.  Besides there is the battle betwwen electrical car versus Diesel cars, but this is not the adequate moment to open other debate.

All of this mix implies as follows, if the company does not invoice or the payment terms with their customers are very stifling, the companies will be problems with cash flow. Therefore this is an important value to take in count at this moment, and it would be necessary an action from government to promote this sector or others. As you know, everything is connected. By this reason, this mentioned action from government must be available first for Little and Medium companies, preserving the business fabric. The last crisis began wiht a financial collapse but now we think there is still margin to act.

Anyway, we already working thinking  to return with a relative normal activity based on preventive safety plan. This is an oportunity to improve in all departments, adapting our work according to new situation.

We want to communicate you, the technical and sales areas continue at your disposal with a know-how of more than 25 years of expertise in injection molding, collaborating with customers since deign phase to serial plastic part.

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