The important features associated with plastic molding

The important features associated with plastic molding

Plastic molding, one of the most vital process required, is required to taken into utilize to shape plastic using a rigid frame or mould. Not to mention the way of using technique that allows for the creation of objects of all shapes and sizes with huge design flexibility for both simple and highly complex designs.

It starts with advanced techniques and placing liquid polymer into a hollow mould so that the polymer can take its shape – mainly with different ranges of pressure and heat required. You will get access to different plastic molding techniques that include rotational molding, injection molding, blow molding and compression molding to name just a few.

Plastic design

Plastic design process is not an easy part of the entire process. It is complicated and need assistance from top engineers and expert – who work in a planned way by focusing on various important things. Professionals who are working for plastic designs also remove uneven wall thickness by digging out material of triangle shape space and adding radius to compensate removed wall to reach even wall thickness.

Parts undercut are important that can’t be released from mold because of the undercut. You have to simply add a hole on top of undercut area. In order to make the plastic design process easier, they work on parts fitment. Original design is vertical tab that insert into plastic parts. Experts change tab into horizontal direction to ensure strong and unmovable fitment. They also provide you functional accuracy as injection molded parts can reach high accuracy

Injection molding machine

Use of injection molding machine is also important that depends on mold overall size, location ring, sprue bush, and ejection connector tap size with machine and a lot more. Waterline layout and nipple size, cavity layout, runner layout and weight, Mold steel type and hardness are some added features associated with it.

The most detailed mold test report is another important feature associated with plastic molding that assures easy and fast setting in mass production at client site.

Reaching the right and reputed plastic mold factory is important where you will get complete solutions for this process that is a popular manufacturing option – responsible for many car parts, containers, signs and other high volume items.

POM Material Injection Molding

POM Material Injection Molding

Polyoxymethylene (POM) is a thermoplastic material also known as acetal. POM-H (polyoxymethylene homopolymer), POM-K (polyoxymethylene copolymer) is a high density, high crystallinity thermoplastic engineering plastic with good physical, mechanical and chemical properties, especially with excellent friction resistance.

POM is a crystalline plastic with a sharp melting point. Once the melting point is reached, the melt viscosity drops rapidly. Decomposition occurs when the
temperature exceeds a certain limit or the melt is heated for too long.

Copper is a POM degradation catalyst. Copper should be avoided where it is in contact with the POM melt.

 1. Plastic processing

POM has a small water absorption, generally 0.2%-0.5%. Under normal circumstances, POM can be processed without drying, but it must be dried for wet
materials. The drying temperature is above 80℃ and the time is more than 2 hours. The specific conditions should be based on the supplier’s data.

The proportion of recycled materials used is generally not more than 20-30%. However, depending on the type of product and the end use, it can sometimes be up to 100%.

2. The selection of plastic machine

In addition to the requirement that the screw has no stagnant area, the POM has no special requirements for the injection molding machine, and generally
can be injection molded.

3. Mold and gate design

The common mold temperature is controlled to 80-90℃, the runner diameter is 3-6 mm, the gate length is 0.5 mm. The gate size depends on the thickness
of the wall, and the circular gate diameter should be at least 0.5-0.6 times the thickness of the product. The width of the rectangular gate is usually 2 times
or more of the thickness, the depth is 0.6 times the wall thickness, and the draft angle is between 40′-1º30′.

Exhaust system

POM-H thickness 0.01-0.02mm width 3mm

POM-K thickness 0.04mm width 3mm

4. Melting temperature

POM-H can be set to 215℃ (190℃ – 230℃)

POM-K can be set to 205℃ (190℃ – 210℃)

5. Injection speed

Medium speed. If too slow, it produces ripples. If too fast, it is easy to produce grain and shear overheating.

6. Back pressure

The lower the better, generally no more than 200bar

7. Stay time in barrel

POM-H can be held at 215℃ for 35 minutes

POM-K can stay in 205℃ for 20 minutes without decomposition.

POM-K can be retained for 7 minutes at 240℃. If the machine is shut down, the barrel temperature should be lowered to 150℃. If you want to stop for a
long time, you must clean the machine and turn off the heater.

8. After machine stops

The cleaning barrel must use PE or PP. Turn off the heating and push the screw in the front position. The barrel and screw must be kept clean. Impurities or dirt can change the thermal stability of the POM (especially POM-H).

9. Post processing

For very warm parts and high quality requirements, heat treatment is required.

The annealing treatment effect can be carried out by immersing the product in a hydrochloric acid solution having a concentration of 30% for 30 minutes,
and then visually discriminating whether cracks have residual stress.

Analysis of uneven color of injection molded products

Analysis of uneven color of injection molded products

The reasons and solutions for the uneven color of injection molded products:

1. The colorant is poorly diffused, and this often causes a pattern to appear near the gate.

2. The plastic or colorant has poor thermal stability. To stabilize the color tone of the part, it is necessary to strictly fix the production conditions, especially the material temperature, the amount of material and the production cycle.

3. For crystalline plastics, try to make the cooling speed of each part of the parts consistent. For parts with large difference in wall thickness, coloring agent can be used to mask the chromatic aberration. For the parts with uniform wall thickness, the temperature and mold temperature should be fixed. .

4. The shape and gate form of the part, the position has an influence on the filling condition of the plastic, so that some parts of the part have chromatic aberration and should be modified if necessary.

Analysis of the causes of color and gloss defects of injection molded products

Under normal circumstances, the gloss of the surface of an injection molded part is mainly determined by the type of plastic, the colorant and the finish of the mold surface. However, due to some other reasons, the surface color and gloss defects of the product and the dark color of the surface are often caused. The reasons for this and the solution are as follows:

1. The mold has poor finish, the surface of the cavity has rust, etc., and the mold is poorly exhausted.

2. The casting system of the mold is defective. The cold material well should be enlarged, the flow channel should be enlarged, the main flow channel should be polished, the runner and the gate should be polished.

3. The material temperature and the mold temperature are low, and the local heating method of the gate can be used if necessary.

4. The processing pressure is too low, the speed is too slow, the injection time is insufficient, and the back pressure is insufficient, resulting in poor compactness and darkening of the surface.

5. The plastic should be fully plasticized, but the degradation of the material should be prevented, the heat should be stable, and the cooling should be sufficient, especially thick-walled.

6. Prevent cold material from entering the part, and if necessary, use a self-locking spring or lower the nozzle temperature.

7. Excessive recycled materials are used, plastic or colorant is of poor quality, mixed with water vapor or other impurities, and the quality of the lubricant used is poor.

8. The clamping force should be sufficient.

Injection Mold Maker for Making Injection Molding Process Easier

Injection Mold Maker for Making Injection Molding Process Easier

Are you looking for high-grade and advanced injection mold machines or complete solutions for injection molds?

Such questions are very common in manufacturing units – mainly those where molding is an important work to give the right shape and design to any machinery, tool or equipment. A selected injection mold maker brings to you a gamut of solutions that are working dedicatedly to bring to you complete solutions. There is no denying the fact that injection mold is so expensive – not only in cost, but also in time. An injection mold maker takes the responsibility of doing everything from very beginning to end.

They provide you complete solutions and injection mold machine – related to mold overall size, location ring, sprue bush, ejection connector tap size with machine and solutions for parts related to gate, parting line and ejection. You will get mold related to waterline layout and nipple size along with cavity layout, runner layout and weight along with mold steel type and hardness.

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Not to mention CAE analysis and know problem a bit early in some case, where CAE is necessary to prevent problems in advanced instead of after mold construction.

You will also get detailed mold test report that assures easy and fast setting in mass production at client site.

Reaching the right company or a selected injection mold maker is important. Online search is one of the time-saving and convenient way to help you in reaching the right one. Among some of the top companies, you will find name of Jazz Mold comes on the top. You have to contact as per your requirement and leave rest of the work on experts working here.

Reach right plastic mold factory to get services and processes

Reach right plastic mold factory to get services and processes

Plastic molds are important industrial products in order to shape and mold plastic before it results to a more viable and feasible product in the market. It commonly undergoes injection molding in various forms but the most popular technique is forcing a plastic liquid into a metal mold. The molding is made through the use of molten plastic that cools while it is inside the mold.

Plastic molds are used in order to lessen down the costs related to various manufacturing processes. This technology is favored because of the quick turnaround time in the procedure. A variation known as reaction injection molding is also used for fiberglass, epoxy and polymer plastic. Here are ideas on the services, processes and equipment design employed in the manufacture of these products.

Plastic molding services result from rotational molding, blow molding, thermoforming and compression molding. Other services include mold prototyping, insert molding, micro-molding, two- shot injection molding, machining and hot stamping. These services have characteristics that make them distinct from one another.

For instance, machining is that phase where the molds are removed through drilling, milling or turning. Micro-molding is known to use special and mini molding machines in order to produce small parts out of the process. The parts produced out of these services are commonly less than two grams in weight. In a two- shot injection, a plastic product is produced from two sets of raw materials through the use of only one operation.

Plastic molding processes

Plastic molds cannot be completed without undergoing some processes. First on the list is the development of a three-dimensional or 3D CAD model. The making of a computer model is that point when a manufacturer may ask a consumer for concepts and prototypes to see if they are good enough for the production of plastics.

Machines for injection molding, blow molding and thermoplastic injection are a few examples of plastic mold factory equipment designs. The basic outputs from these machines include insulated runners as well as CAM, encapsulating, stack and insert molds. This important aspect in manufacturing plastic molds is the fabrication of machineries to create the output. Barrels, liners, component and feeders are also created out of the equipment design. Along the process, special forms of equipment for different plastic mold services are formed.

Plastic molding, one of the most vital process required, is required to taken into utilize to shape plastic using a rigid frame or mould. Not to mention the way of using technique that allows for the creation of objects of all shapes and sizes with huge design flexibility for both simple and highly complex designs.

Reaching the right and reputed plastic mold factory is important where you will gt complete solutions for this process that is a popular manufacturing option – responsible for many car parts, containers, signs and other high volume items. There are a number of added features and benefits associated with it that will surely persuade you to reach the right factory that is involved in offering you complete and comprehensive solutions.

Warpage analysis of thin-wall injection molded parts

Warpage analysis of thin-wall injection molded parts

Warpage deformation refers to the distortion of the shape of the injection molded article and the warpage, which deviates from the shape accuracy requirement of the workpiece. It is one of the most difficult product defects that are common in injection mold design and injection production.

With the development of the plastics industry, especially the development of the electronic industry, the requirements for the appearance and performance of plastic products are getting higher and higher. Such as notebooks and mobile phones, warping deformation has been one of the important indicators to assess product quality. It is hoped that the cause of warpage of plastic parts can be predicted in the design stage, in order to optimize the design, reduce the warpage of the product, and meet the precision requirements of product design.

1. Causes of warpage deformation

Warpage deformation is caused by uneven stress and shrinkage during the injection process. Poor mold release, insufficient cooling, shape and strength of the parts unsuitable, mold design and poor process parameters setting make the plastic parts loose shape.

  • The mold temperature is not uniform, and the internal temperature of the plastic parts is not uniform.
  • The difference in wall thickness of the plastic part and uneven cooling result in a difference in shrinkage.
  • The plastic part has a thick condensing pressure difference and a cooling speed difference.
  • When the plastic parts are ejected, the temperature is too high or the ejection force is uneven.
  • Plastic parts are improperly shaped and have a curved or asymmetrical shape.
  • The mold has poor precision and the positioning is unreliable, which makes the plastic parts easy to warp and deform.
  • The position of the gate is improper, the injection process parameters are not good, the shrinkage direction is obvious, and the shrinkage is uneven.
  • The difference in molecular chain orientation between the flow direction and the flow direction is different, resulting in different shrinkage rates.
  • The wall thickness of the convex and concave molds is asymmetrically cooled, the cooling time is insufficient, and the cooling is improper after demolding.

2. Influence of mold structure on warpage deformation of injection molded parts

In terms of mold design, there are three main factors affecting the warping deformation of plastic parts, namely the filling system, the cooling system and the ejection system.

  • Gate design

The injection mold gate is a key part of the entire casting system. Its position, form and number of gates directly affect the filling state of the melt in the mold cavity, resulting in plastic curing, shrinkage and internal stress variations. Common types of gates include edge gate, point gate, sub gate, direct gate, fan gate, and film gate.

The gate location should be chosen to minimize the flow of plastic. The longer the flow distance, the greater the flow difference between the inner fluid layer and the outer freezing layer, so that the greater the internal stress caused by the flow and the feeding between the frozen layer and the central fluid layer, the plastic deformation also increases;

On the contrary, the shorter the flow distance, the shorter the flow time from the gate to the flow end of the workpiece, the thickness of the frozen layer is reduced when the mold is filled, the internal stress is lowered, and the warpage deformation is also reduced.

For example, if a thin-walled large plastic part is used with only one center gate or side gate, since the radial shrinkage rate is greater than the circumferential shrinkage rate, the molded plastic part will have a large distortion; if multiple points are used instead, it can effectively prevent warpage and deformation.

When using point gate molding, also due to the anisotropy of plastic shrinkage, the position and number of gates have a great influence on the degree of deformation of the plastic parts.

The test of the number of different box-shaped plastic parts in different gates:

Using 15% glass fiber reinforced PA66, the weight 1450g plastic parts, there are many reinforcing ribs along the flow direction of the surrounding wall. Use basically the same process parameters. Gate method: (a) direct sprue, (b) 5 to 4 gates, (c) 9 to 8 gates. According to the test results, the gate number according to (b) has the best effect and meets the design requirements. The gate designed according to (c) is worse than the direct sprue, and the amount of warpage deformation exceeds the design requirement of 3.6~5.2mm.

The multi-gate can shorten the flow ratio (L/t) of the plastic, thereby making the density and shrinkage of the melt in the mold more uniform. At the same time, the plastic part can fill the cavity under a small injection pressure, reduce the molecular orientation tendency of the plastic, reduce the internal stress, and reduce the deformation of the plastic part.

  • Cooling system design

During the injection process, the unevenness of the cooling rate of the plastic part will also form the unevenness of the shrinkage of the plastic part, and the difference in the shrinkage causes the bending generated plastic part to warp.

For example, if the temperature difference of the mold cavity and the core of the large flat plastic part is large, the melt of the cold mold cavity surface will cool down quickly, and the material close to the surface of the core will continue to shrink. The shrinkage will not continue Evenly and warp the plastic parts. Therefore, the cooling system design of the injection mold should strictly control the temperature balance of the core and the cavity.

For precision flat plastic shell parts, the material with large shrinkage and easy deformation is tested. The production test shows that the temperature difference should not exceed 5°C.

After the distance from the pipe wall to the surface of the cavity is determined, the distance between the cooling water holes should be as small as possible. If necessary, the arrangement of uneven water density should be adopted, that is, the cooling water holes are densely packed at a high temperature, and the material temperature is low. The cooling water hole rows are sparse to maintain the cooling rate substantially the same. At the same time, since the temperature of the cooling medium rises as the length of the cooling water channel increases, the length of the water passage of the cooling circuit should not be too long.

  • Ejection mechanism design

The design of the ejection mechanism also directly affects the deformation of the plastic part. If the ejector mechanism is unbalanced, the deformation of the ejection force is caused to deform the plastic part. Therefore, it is necessary to balance the demolding resistance when designing the ejection mechanism. The cross-sectional area of the ram should not be too small to prevent the deformation of the plastic part per unit area due to excessive force.

The ejector should be placed as close as possible to the part with large draft. For precision flat plastic case parts, add as many ejector pins as possible to reduce the deformation of the plastic parts, and a composite release mechanism combining the ejector release and the pusher plate release.

When using soft plastic to produce large-scale deep-cavity thin-walled plastic parts, the mold release resistance is large and the material is soft. If the mechanical ejection method is completely adopted, the plastic parts will be deformed. Combined or gas (liquid) pressure combined with mechanical ejection will be more effective.

3. filling speed, pressure and warping deformation

The molten plastic is filled into the mold cavity under the action of the injection pressure and cooled and solidified in the cavity. In this process, the temperature, pressure and speed are coupled to each other, which has a great influence on the quality of the plastic parts.

Higher pressures and flow rates produce high shear stresses, causing differences in molecular orientation parallel to the flow direction and perpendicular to the flow direction, resulting in greater internal stresses in the plastic part. The influence of temperature on warpage deformation is mainly reflected in the following aspects:

The temperature difference between the inner and outer surfaces of the plastic part causes thermal stress and thermal deformation;

The temperature difference between different areas of the plastic part causes uneven shrinkage;

Different temperature conditions can affect the shrinkage of plastic parts.

Therefore, strict control of appropriate injection process parameters is an important means to reduce warpage.

4. The shrinkage and warping deformation of the parts

The direct cause of the warpage of the injection molded part is the uneven shrinkage of the plastic part. For warpage deformation analysis, shrinkage itself is not important, what is important is the difference in shrinkage. In the injection molding process, the melt is bent in the flow direction due to the arrangement of the polymer molecules in the flow direction during the injection filling stage, and the shrinkage ratio of the plastic in the flow direction is larger than that in the vertical direction, so that the injection molded part is warped.

Generally, uniform shrinkage only causes changes in the volume of the plastic part, and only uneven shrinkage will cause warping deformation. The difference in shrinkage between the flow direction and the vertical direction of the crystalline plastic is larger than that of the amorphous plastic, and the shrinkage ratio is also larger than that of the amorphous plastic. Therefore, the tendency of the crystalline plastic part to warp deformation is much larger than that of the amorphous plastic.

5. Residual thermal stress and warpage

In the injection molding process, residual thermal stress is an important factor causing warpage deformation. Since the influence of residual thermal stress on the warpage deformation of the workpiece is very complicated, the mold design is usually analyzed and predicted by injection molding CAE software.

6, summary

There are many factors affecting the warpage of precision flat and thin plastic parts. The structure of the mold, the thermophysical properties of the plastic material and the process parameters of the injection molding process all have different effects on the warpage of the part. Therefore, the experimental research on the mechanism of warpage deformation of the workpiece must focus on a number of factors.