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2014年7月13日星期日

How to Clean Chromed Plastic on Vehicles


How to Clean Chromed Plastic on Vehicles

·                               Chromed plastic is found on many locations of a vehicle such as grills, door handles and body mouldings. It becomes water spotted, can be discolored from acid rain or covered in bug residue. Using a glass cleaner to remove these contaminants is the safest way to clean the plastic without harming the adjacent painted areas. This process can be repeated as needed. However, since the glass cleaner dries to a spotless finish, usually no further cleaning is necessary. 

Instructions

1
Mix a bucket of soapy water using dish detergent and water as if preparing to hand-wash a car. Use the mixture with a kitchen sponge to clean the moulding of all road film and grime. Dry when complete with a chamois or kitchen-type towel.
2
Apply glass cleaner such as Windex to a kitchen towel or directly onto chrome and scrub chromed area with the kitchen towel. Chrome does not scratch easily, so use moderate pressure to scrub stains.
3
Repeat as necessary. Due to the majority of stains, such as tree sap or acid rain spots, being water-based contaminants, a water-based cleaner such as Windex is the best for cleaning. Although glass cleaner should remove all stains, rubbing compound with a terry cloth rag and elbow grease may be used for removing more difficult stains such as dried bird droppings or bug residue.


2014年5月30日星期五

How to Generate Runner Sizes for Plastic Injection Mold Design


How to Generate Runner Sizes for Plastic Injection Mold Design

The runner feeds the molten plastic from an injection machine into the mold to form the desired plastic part. The length of the runner is completely dependent on the part design, so there are no specific rules regarding overall length. It is the diameter of the runner that impacts part quality and cost and therefore it should be sized with some care. Once the runner freezes, no more plastic can be injected into the part. The runner should be sized to make sure that part receives sufficient plastic without excessive fractional heating, while freezing quickly enough to minimize cycle time.

Instructions

1.                            Calculating Runner Diameter

1
Determine thickest cross-section of the desired part.
2
Where part design allows, locate runner nearest to the thickest cross section of the part. If the part is of a uniform thickness, locate the runner near the center or along the longest edge, as part design allows.
3
Runner diameter should be between 75% to 100% of the part thickness where the runner is located.
4
Based on your injection machine type, determine the acceptable pressure drop for an injection cycle.

2.                            Calculate Injection Pressure Drop

5
Calculate runner volume. V = pi x r^2 x L, where pi = 3.14159, r = runner radius and L = runner length.
6
Calculate volumetric flow rate (Q) based upon your pre-determined fill time. The fill time is a function of material type, part thickness, and desired cycle time. The molder must know this independent of this exercise. Q = V/t, where t = seconds of fill time.
7
Calculate shear rate (S). S = 4Q/(pi x r^3)
8
Calculate the pressure drop (P). P = (S x m x 2L)/r, where m = melt viscosity of the plastic. The melt viscosity is a function of S, melt temperature, and the material. The molder must know this independent of this exercise, although many plastic suppliers can help with this.
9
Compare pressure drop to predetermined acceptable pressure drop. If improvement is desired, change the runner diameter and repeat the exercise. Repeat calculation until an acceptable runner diameter is found.
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2014年5月29日星期四

The Plastic Manufacturing Process


The Plastic Manufacturing Process

1.                            Plastic Injection Molding Process


Injection molding is one of the main methods by which parts are manufactured from plastic. The first step in the injection molding process is to feed plastic pellets into the hopper, which then feeds the pellets into the barrel. The barrel is heated and contains a reciprocating screw or a ram injector. A reciprocating screw is typically found in machines that produce smaller parts. The reciprocating screw crushes the pellets, making it easier for the plastic to be liquefied. Toward the front of the barrel, the reciprocating screw propels the liquefied plastic forward, thereby injecting the plastic through a nozzle and into the empty mold. Unlike the barrel, the mold is kept cool to harden the plastic into the correct shape. The mold plates are held closed by a large plate (referred to as a movable platen). The movable platen is attached to a hydraulic piston, which puts pressure on the mold. Clamping the mold shut prevents plastic from leaking out, which would create deformities in the finished pieces.

2.                            Plastic Extrusion Molding Process


Extrusion molding is another method of manufacturing plastic components. Extrusion molding is very similar to injection molding and is used to make pipes, tubes, straws, hoses and other hollow pieces. Plastic resin is fed into a barrel where it is liquefied. A rotating screw propels the liquefied plastic into a mold, which contains a tube-shaped orifice. The size and shape of the tube determines the size and shape of the plastic piece. The liquefied plastic then cools and is fed through an extruder, which flattens the plastic and forms the piece into its final shape.

Issues That Arise in the Plastic Manufacturing Process

A number of complications can arise during the plastic manufacturing process, including burned parts, deformities, surface imperfections and brittle parts. Parts become burned when the molds are not kept cool or if the melting temperature in the barrel is too high. Additionally, if the reciprocating screw becomes jammed or is not rotating fast enough, liquefied resin will remain in the barrel too long and become scorched. Surface imperfections and deformities occur when the surface temperature of the mold is uneven, if the molds are not clamped tightly enough or if the melting temperature is too high. Brittle pieces are formed when not enough liquefied resin is injected into the mold or if the plastic hardens before the mold can be filled. Regular testing and calibration of injection and extrusion molding machines is critical to ensure that the process runs smoothly.
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Using a Valve Gate for Injection Molding


How to Use a Valve Gate for Injection Molding

A hot runner system with a valve gate can lower the production cost of molded plastic parts.
A hot runner system offers some significant advantages in injection molding. A key component of such a system is the valve gate. The valve gate shuts off the flow of molten plastic to the mold at a specific time right at the part surface. This allows a part to be molded without a sprue or runner remaining on the part. Eliminating the sprue or runner improves the appearance of the part, may shorten cycle times, eliminates the need for a runner removal operation and eliminates the waste associated with a discarded runner or sprue.

How to use a Valve Gate in Molding

1
Size and select a valve gate in tandem with the hot runner system. The hot runner system provider will aid in the selection process. In many cases, the mold maker will coordinate this effort. The material to be molded and the overall part design will be the fundamental keys to sizing a valve gate.
2
Install the mold with a hot runner system and the valve gate in an injection press. The electronic controls for the valve gate will need to be tied to the press timer that times the injection cycle. Additionally, valve gates are often pneumatically or hydraulically actuated. Ensure that proper controls are set up to actuate the valve.
3
Determine the time in the injection cycle when the gate should be closed. This will be a function of the rate of material flow and the size of the part. Once the mold has been sufficiently filled by molten plastic to produce acceptable quality, there is no need for additional plastic to be injected. This is when the gate can be closed and the melt procedure for the next cycle can begin.
4
Set the actuator on the valve gate to shut when the injection timer reaches the time determined in the previous step.
5
Set the actuator on the valve gate to open when the injection timer is reset at the beginning of the next cycle.
6
Commence operating the injection press as per normal operating conditions.

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2014年5月27日星期二

How to Find Quafiyied Plastic Injection Molding Companies


How to Find Qualified Plastic Injection Molding Companies

Selecting the best plastic injection molding company from the suppliers out there can be a difficult task. Let's take a look at how to find the best molding company for you budget by following these steps.

Instructions


1
First, in order to begin evaluating plastic injection molding companies, it is important to know what you need them to mold for you. Specifically, you will need to have a fully defined 3D Model and engineering drawing of the plastic component you wish to have molded. Be sure to fully specify draft angles and surface textures in drawing.
It is important to also specify things like maximum allowable flash.
2
Next, it is critical to realize that for most companies seeking an injection molding supplier, for right or wrong, the largest factor tends to be cost. Going oversees to places like China or Korea usually results in a lower piece cost than staying in the United States. However, this savings in cost per molded part can be offset by delays in getting the product to market.
Based on the project your company is working on, determine if there are absolute restrictions on price as this will be important to know.
3
Next, when evaluating a potential injection molding company, it is very important to learn about the history of the company and their capabilities. How long have they been in business and what industries do they typically mold parts for?
If you have a part that requires extremely tight tolerances, an injection molding company in the health or aeronautics industry may work out better than a company that molds toys.
4
After you learn about the background of the company, investigate their capabilities. What type of molding capabilities do they have? Do they have any specialties such as 2-shot molding or insert molding?
What type of presses do they use and how old are they? Are they able to handle the volumes or quantities that you require?
As alluded to earlier, lower molded component cost does not always translate to an overall savings. Depending on the quality control of the molder, their quality may be sub par resulting in delays in the schedule or worse...returned product from the customer.
Take some time to understand how the plastic injection molding company monitors and ensures quality. Do they do control charting? Are they ISO certified? Ask to see examples of quality records/documentation for some of their recent projects.
If some unacceptable product is found during an audit, what is their corrective action plan? Do they quarantine the last X hours of product?
5
Lastly, the location of the supplier can also be very important. Where are they located and how will this impact your working relationship? Having an injection molding supplier "right in your backyard" so to speak is great as it allows you to make day trips to the supplier when issues arise. Contrast this to going overseas to an Asian supplier where it will cost thousands of dollars per person per trip to visit.
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2014年5月26日星期一

How to Texture Injection Molds


How to Texture Injection Molds

Injection molds receive a finish to eliminate the machining marks from the mold. High-speed machines typically do this polishing. In some cases, a textured finish is desired. A chemical etch procedure creates the texture based on a pattern. This process usually is manual.

Mold Texturing

1
Create a design of the desired texture as a photocopy or digital file.
2
Transfer the design to a negative. This can be easily done with a scanner. Most scanners have the capability to scan to a negative output file. Or, if the file is already digital, many photo editing software packages have the option to convert a file to a negative.
3
Transfer the negative to a flexible elastomeric material with the desired texture. This is not a do-it-yourself activity for the average person. In general, commercial equipment, often a laser engraver, is required to complete this step. A commercial provider of this type of service should be considered.
4
Placing the textured elastomeric material on the mold surface and add the chemicals to etch the mold. The exact chemical used depends on the specific metal of the mold. It is generally one of the stronger acids.
5
Completely wash the mold of all chemical residues.

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Minimize Sink Marks in Injection Molding


How to Minimize Sink Marks in Injection Molding

Sink marks are caused when a plastic part is not thoroughly packed out. This results from less plastic entering the mold than the volume of the mold was designed to hold. As the plastic cools, it shrinks. When insufficient plastic is injected into the mold, the thicker cross sections will sink as there is not enough plastic there to completely hold the desired structure. The three main reasons for this are poor gating location, poor processing conditions and insufficient gate or runner diameter.

Instructions

1.                            Poor Gating Location

1
Thin sections of plastic will freeze off before thick sections. Determine if the part has uniform wall thickness.
2
If the wall sections are uniform and the gate is relatively central to the part, move on to the next possibility.
3
If the wall sections are not uniform, make sure that the part is gated into the thickest section. This allows the thicker sections to fill with material before the thin sections freeze off and starve them.

2.                            Poor Processing Conditions

4
Running a mold too cold or molding a part with too short of a cycle time can cause a part to be insufficiently packed. First, weigh five parts produced at the current molding conditions and determine the average part weight.
5
Increase the cycle time by 10% and produce five additional parts.
6
Weigh the parts, and determine if there is a noticeable increase in the average part weight.
7
If there is an increase in weight, return to step two and repeat the experiment. Continue repeating until there is no significant change in part weight.
8
If after step two there is no change in part weight on the first attempt, repeat the series of experiments with a different process variable, such as mold temperature. Increase mold temperature by 10 degrees Fahrenheit and repeat the test.

3.                            Insufficient Gate or Runner Size

9
Insufficient gate and runner diameters may allow the runner to freeze before sufficient plastic is injected into the mold. To check for this, first determine the designed volume of the part.
10
Determine the specific gravity of the plastic resin that is being used. The material supplier can give that information if it is not readily known.
11
Calculate the designed part weight. The part weight in pounds is found by multiplying the part volume in cubic inches x specific gravity x .0361. Weigh a set of five parts and determine the actual average weight of the part.
12
If the part weight is below the calculated part weight, increase the gate or runner diameter by one standard size. Mold new parts and weigh.
13
Repeat the process as needed. Once the actual part weight reaches the calculated weight, optimal gate and runner size have likely been

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Advantages of Injection Molding


Advantages of Injection Molding

Injection molding is a method of creating plastic products. Most plastic products are made using injection molding. This process is attractive to manufacturers because of multiple advantages it provides over other plastic molding methods. Overall, injection molding is simpler, more reliable, more versatile and more efficient than most other types of injection molding.

High Pressure

Plastic injection molding operates at a very high pressure, meaning that the melted plastic is pressed harder against the mold than in other molding processes. This provides the advantage of a greater amount of detail in the design of the piece being molded, included complex geometry or detailed features.
Speed
The injection molding process is also very fast compared to other molding processes. A full injection molding process takes very little time, which allows for far more products to be generated from the same mold. Therefore, you get a lot more mileage out of a single mold. Injection molding is highly efficient.
Automation
Injection molding is a highly automated process. Most injection molding is done by machines that a single operator can run. Therefore, very little overhead will have to go into paying the labor force in a plastic injection molding process.
Monomer-Free
Injection molding is a monomer-free process. Monomers are a type of plastic that create a lot of fumes, which many people have a negative physical reaction to. Therefore, any molding process that employs monomers require a good deal of ventilation. If you use injection molding, you will not have to worry about these problems.
Multiple Plastic Types
When you use injection molding, you have the option of molding two different types of plastic at once. This process is called co-injection molding. Therefore, you do not have to worry about access to a particular type of plastic.
Thermoplastics
Injection molding makes use of thermoplastics. Thermoplastics can be injected into the mold, then the excess can be remelted and used again. Therefore, injection molding can save you on materials. Thermoplastics can also come in a wide variety of densities or strengths.
Fillers
Injection molding provides you with the option of using fillers in your molds. Fillers are used to reduce the density of the plastic as it is molded as well as provide greater strength to the product once it is molded. This is another method of reducing the total cost of the process.

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2014年5月25日星期日

What’s hot runner mold?


What’s hot runner mold?

  It use an assembly of heated components in plastic injection molds that inject plastic into the cavities of the mold. There are two general types of runnerless molds  - the insulated system and the hot runner system. Hot runners mold retain the advantages of the insulated 
  runner system over conventional cold runner system and eliminate a number of the disadvantages. Hot runner system is one of the more important enhancements you can incorporate into a mold to improve molded part quality, reduce production times and remain price competitive
  Injection Mold with Hot runner Solution will use reliable hot runner system and mold design tools. Our engineering department work harder and quicker than any other supplier to offer you new design ideas and mold concepts using any kind of hot runner system.with long history of experience and reliability for plastic injection molding and hot runner mold manufacturing,  we can deliver the best solutions. 
  Although there are many hot runner manufactures , a few major components is same:
  1. Hot runner plate (MANIFOLD)
  2. Nozzle
3. Temperature Controller
  4. Auxiliary parts

  Advantage of hot-runner mold in injection molding industry  
 Why some many customer select hot runner to make injection mold .This is mainly due to such injection mold has following salient feature:
  Less plastic raw materials: in the age of expensive oil and raw materials . hot runner technology is the effective way to reduce the materials cost.
  Quickly cycle time for injection molding, Due to no cooling time constrains runner system.
  Plastic can be more uniform state injection into each cavity, the result is consistent quality
  parts. Such injection molding components of good quality and low residual stress after ejection part distortion. reduce product costs, improve product quality

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Types of Plastic Injection Molds


Types of Plastic Injection Molds

Plastic injection molds create objects when melted plastic is forced into mold cavities. They often are used in mass-manufacturing operations to create products such as toys, kitchen utensils, bottle caps and cell phone stands. You can spot items constructed using an injection mold by the "flash lines" of extra plastic around the seams. Here are four major types of injection molds commonly used.

Cold Runner Molds
Cold runner molds are the most common type of plastic injection molds. These molds use a sprue and runner to inject plastic into each cavity. However, the sprue and runner harden along with the part once it solidifies. Workers then cut these pieces off and recycle them. This can create a problem with waste, which may make them less economical to use.
Two-Plate Cold Runner Molds
Two-plate cold runner molds are so named because they feature two plates that fit together. There is only one parting plane, and that is where the runner must be located. This is the simplest type of cold runner mold.
Three-Plate Cold Runner Molds
Three-plate cold runner molds have three pieces, which means there are a pair of parting planes. The three pieces are the runner plate, the moveable plate and the floating plate. The runner plate contains the sprue and half the runner. The moveable plate contains the part's ejector system and half the part's geometry. The floating plate contains the other halves of the runner and geometry. The system can be located at either parting plane, and the piece can be gated anywhere on the surface to provide flexibility.
Hot Runner Molds
Hot runner molds deliver plastic in a different way. While cold runner plastic injectors cool along with the part, the runners in hot runner molds are situated inside the mold and kept at a temperature higher than the plastic's melting point. This means the sprue and runner never have the chance to harden. This also reduces the amount of wasted plastic. However, hot runner plastic injection molds require more skill and maintenance and have a higher baseline cost. However, they often pay for themselves based upon the material savings.
c
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2014年5月22日星期四

What Is Injection Molding Used for?


What Is Injection Molding Used for?


Injection molding is used for manufacturing plastic, rubber and metal. Materials are fed through a heated barrel in the machine and forced into a mold where it will cool and take its shape. An injection molding machine can stamp out metal car shell parts, rubber valve steam seals, and even plastic toys for kids.

 

Plastic


Injection molds uses plastic to make toys for children, milk containers and movie cases. It also makes other plastic products such as combs, kitchen utensils and dust pans.

Rubber

Injection molds make many rubber automobile parts. It makes valve steam seals and oil seals for the engine. It also makes earplugs, rubber hoses and telecommunications items.

Metal

Injection molds can stamp out small to large items. It can stamp out automobile parts from spark plugs and floor pans to ball bearings. It also can stamp out items like TV hangers and knitting needles.
 
 
 
 
 

2014年5月21日星期三

injection molding (2)

injection molding

 

Injection molding is a plastic manufacturing process whereby granules of plastic are heated until they melt and are then forced into a specially designed mold. Once in the mold the plastic is allowed to cool and hardens into the form of the mold. Injection molding is widely used in industry to produce plastic artifacts like computer casings, toys and cookware.

Barrel

·                                 The key part of an injection molding tool is the barrel. This is a metal cylinder that houses the reciprocating screw. The plastic granules are emptied into the barrel via the hopper and while in the barrel a combination of heat from the heaters and friction from the reciprocating screw liquidizes the plastic pellets. At the end of the barrel is an injection nozzle, through which the molten plastic is injected into the mold.

Reciprocating Screw

·                                 The reciprocating screw sits inside the barrel of the injection molding device. This tool rotates and forces the plastic pellets through the barrel and into the mold. In appearance, the reciprocating screw is roughly cylindrical, tapering slightly to a point at one end. Its outer surface is shaped into a screw thread.

Hopper

·                                 The hopper is a tool used to store the plastic granules before they enter the barrel. It consists of a large funnel into which the plastic granules are deposited before they enter the barrel.

Heater

·                                 The heaters sit around the barrel and raise the temperature of the plastic granules to the point at which they melt. This enables the molten plastic to be injected into the mold. The heaters sit wrapped around the cylinder and are powered by electricity.

Mold

·                                 The mold and the corresponding mold cavity determine the final shape of the injection molded artifact. There are certain limitations on the design of the mold and the design of the molded artifacts caused by the necessity of being able to remove the artifact once it has solidified.

Mobile Platen

·                                 The platen is a mobile flat plate that is used to push the mold and the mold cavity together. This ensures that the molten plastic migrates to every part of the mold and mold cavity. The platen is held in place against the mold by a clamp.

Clamp

·                                 The purpose of the clamp is to hold the mold and the platen as close together as possible while the molten plastic is setting into the final shape of the injection molded artifact. The clamp is often adjustable so the pressure on the platen can be increased to ensure that the molten plastic has reached every part of the mold cavity.

c

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