How to Clean Injection Molds

Injection molding is an industrial plastic-making process.

Injection molding is a production process in which plastics are heated until liquid and sprayed into a mold where they cool and are given the final shape of the manufactured product. As the project cools, it shrinks away from the mold walls, allowing it to be ejected. To keep this process working efficiently, molds need to be systematically and regularly cleaned. Although most molds are cleaned haphazardly and by hand, there are also a number of technological solutions available.

 

Instructions

1.                            Cleaning Molds by Hand

1

Disassemble the mold using a screwdriver to disconnect the parts. Separate the parts that are most susceptible to corrosion and contaminate build-up. These include the front and rear clamp plates, bubbler plates, bushings, water lines and wear plate grease grooves.

2

Spray the pieces of the mold with a cleaning spray, or place them in a solvent bath. More abrasive cleaning chemicals may work more quickly, but they will also cause wear and tear on the mold that can shorten its life.

3

Scrub the mold with a stiff brush to remove the contaminants, then wipe dry.

2.                            Cleaning With Dry Ice Pellets

4

Connect a dry-ice pellet blasting system to an air line near your mold. A double-line system introduces the pellets at the spray nozzle, while single-line systems introduce them at the hopper and offer a more powerful spray.

5

Disassemble the mold and strongly secure the parts to be cleaned. The force of the dry-ice pellet impacts can easily knock over unsecured parts, possibly damaging them.

6

Ensure the area is clear. These guns spray dry ice at 900 feet per second, which can cause severe injury.

7

Put on safety gear. This includes a face mask, gloves and an apron as well as ear protection that can block the 102-decibel noise produced by the sprayer.

8

Turn on the air line and squeeze the trigger to spray the parts. The dry ice will dissolve on impact, taking residue with it. This method, however, may not be very effective at rust removal.

3.                            Cleaning Molds Ultrasonically

9

Disassemble the mold and immerse the parts in a detergent solution. The exact type of detergent depends on what kind of contamination is to be removed. Heavily alkaline solutions like sodium hydroxide are very effective with most contaminants, but are dangerously caustic. Mildly acidic solutions are better for rust, but will turn steel gray.

10

Connect an ultrasonic generator to a shop power line. This generator transforms regular current into the very high frequencies necessary for ultrasonic cleaning.

11

Attach transducers to the bottom and sides of the tank. These transducers will vibrate at the high frequencies coming in from the generator, which produces tiny bubbles in the water that impact the mold pieces with force enough to strip away contaminants, while leaving the metal mold undamaged.

12

Set the timer on the generator, and walk away. The cleaning process will proceed on its own.

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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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Two Different Types of Injection Molding

Injection molding is a manufacturing process for producing high volumes of finished parts at a low cost per part. Various plastic or rubber parts are produced in a wide range of colors. The injection molding machine injects heated molding material to the part mold through input channels. The two principal types of injection molding machines use either a cold runner channel or a hot runner channel.

Cold Runner Machines

Cold channel injection molding machines cool the entry channel, or runner, after each part is molded and ejected. During each molding cycle a part is produced with material in the runner channel. After the part is ejected, the runner is waste material and must be separated from the molded part. Runner waste is reground and reused or thrown away. Disposed material affects part cost. Reground and reprocessed material may affect part quality. Changing part colors in a cold runner machine is fairly easy since each ejected parts carries the material with it. Cold runner machines offer the advantages of cheaper mold designs, lower maintenance costs and lower operator skills.

Hot Runner Machines

Hot runner injection machines keep the runner portion of the mold hot. This reduces or eliminates runner scrap material, which may reduce part costs. Hot runnermachines are more expensive than cold runner machines. Hot machines require more skilled operators and require costly maintenance. Changing colors in hot runner machines is difficult because material is hard to remove from the runners. Hot runner machines eliminate wasteful runner scrap and the need to separate them from molded parts.

Changing Injection Molding Technology

Until recently, all injection molding machines were hydraulic devices. Newer machines are operated by an all-electric process or a hybrid combination of both technologies. Each injection molding process has an advantage. Hydraulic injectors offer high injection rates. Electric injection machines produce precision parts accurately and consistently. Hybrid machines are best suited to part positioning accuracy and repetitive parts. In a paper presented in May of 2008 to the Energy Technology Conference at New Orleans, Amit Kanungo and Eric Swan, senior engineers for RLW Analytics stated, "though it is a challenge to choose a right machine for molder's processing needs, by most accounts in the near future, all-electric machines will dominate the injection molding industry in the U.S."

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Research and Forecast of Injection Molding Machine Industry in China, 2014-2018

The injection molding machine belongs to the plastic machinery type that has the largest output and application volume in China, as well as being the main force of China's plastic machinery export. In 2013, the export volume of injection molding machines was 22,946 sets with the export amount of USD 932 million; in 2012, the export volume was 24,830 sets, so the export volume in 2013 declined, but the export value in 2013 increased 3.78%, which fully shows that the average price of export products of China's injection molding machines is gradually growing. With the increasing demand for plastics, plastic machinery industry has huge market potential. From the global perspective, the top three plastic machinery types are injection molding machine, extruder/extruder production line and blowing molding machine, which account for more than 80% in the plastic machinery total output value. Among them, injection molding machine accounts more than 50% of the total output value of these three main types of plastic machines. 

In 2013, the output of China's injection molding machines was about 82,000 sets, rising by 4.21% compared with 2012. On the whole, the growth of China's injection molding machine industry gradually slowed during the year of 2007 to 2013, but the output was still rising. During 2007 to 2013, the average growth rate of output of China's injection molding machines was 4.77%. 

As this report estimates, the market supply volume of China's injection molding machines will reach 86,175 sets by 2014, 89,612 sets by 2015 and about 101,095 sets by 2018

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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

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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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

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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Profession Tool Shop in China

Free Technology Co.,Ltd(www.freetech-mould.com)

was established in 1993, being specialized in mould design and manufacture. At present, Free tech is located in Shajing,Bao‘an, Shenzhen, has a factory of 8,000 square feet and more than 300 employees, including 20 engineers,we use UG,Pro-E,AutoCAD,Matercam and Catia as our CAD software,and mould managment system, passed ISO9001:2000 quanlity assurance system in 2005.

The company owns a wide range of advanced equipments, for example: Fanuk high speed CNC from Japan,3200mm CNC milling center, 3500mm (CNC) EDM machine, precision wire-cutter,1200mm hole-drilling machine,1600-ton plastic injection molding machine, Japanese automatic 3D scanner,Mitutoyo coordinate measure mahine,Mitutoyo projector,etc.....

For over 20 years,Free tech has made varieties of moulds for famous companies. They included automobiles for HONDA、TOYOTA、Nissan, Ford, air conditioner for DAIKIN, electrical tools for Panasonic,washing machine for HITACHI, TV for 3 Bird,monitor for DELL,Acer,etc,80% of moulds are exported to USA, UK,France,Germany,Sweden,Spain and Japan etc.....

Our company have insisted on management theory of “Customer Centered, Based on practice, Develops on quality & reputation”. We supply our customer high quality mould with reasonable price. We are looking forward to your visiting our company and cooperating with you sincerely.

Free technology is a professional mold manufacturer specializing in mold research and development.Over the past 20 years, our business has spreaded into the following fields: --Part Research & Design --Plastic Mold Manufacture & Injection Process --double color mould machining --Precision Component Machining --Die Casting Mold Manufacture--Rubber & Silicone Part--blow mold and metal part Our products has been distributed into USA, UK, Ukraine, UAE,Canada, Russia, Italy, New Zealand, Japan,Australia and so on.....

Free-tech mold has gained good feedback from our customers,and has established a customer base. However, one of our business strategy is to develop new customers and to give our best servivce to more companies. If you have any inquiry on molds or parts, please feel free to contact us , we will make your design into the perfect actual products. You are welcome to visit our plant to get more information about us.