injection mold

injection mold

 

Your guide to injection molding

Injection molding is a manufacturing process for producing parts by injecting molten material into a mould. This process is used for mass-production of plastic and metal parts that requirer good tolerances.  The plastic injection molding process is just a way to produce plastic pieces in large volumes. The injection moulding process can manufacture a vast selection of products. These products vary greatly in their size, sophistication, and even use. Usually, injection molded parts can be used straight out of the mold and require little to no post-processing. However, secondary processes such as printing laser marking, CNC drilling,  ultrasonic welding, and assembling are not uncommon in a moulding factory.

Injection moulding is one of the most widely used manufacturing processes for the manufacture of plastic parts.  Polymer granules in the injection molding machine are melted, then injected under pressure into a mold, where the liquid plastic solidifies. The material used in injection molding are mainly thermoplastic polymers which might be coloured or filled with different additives. The injection molding process requires an injection molding machine, raw plastic material, and a mold.

 

 

Injection moulding can use many different materials, including metals, glasses, elastomers, and most often thermoplastic and thermosetting polymers. Parts to be injection moulded need to be designed for the moulding process; also the type of material needs to be considered. The fabrication of the mould, and the moulding machine also needs to be considered in the part design process.  There is a lot to consider when designing a plastic part, so if you need any assistance or help, I can help you by reviewing the Plastic part design and tool design.

 

 

Details on injection molding equipment.

The crucial actions within the injection molding process include: opening and clamped the mold, ejecting the parts from the mould, the injection of the plastic, melting the plastic granules and in the melting of the material for the next shot within the barrel of the machine. There are many injection moulding machine manufacturers that make molding machines of all different size and configurations. I assist businesses in specifying their equipment requirements and then sourcing suitable suppliers.

 

 

Besides the moulding machine itself, there is a lot of different types of ancillary equipment that can be used for injection moulding. A standard piece of ancillary equipment would be a water temperature controllers which is used to control the temperature of the water and pumped it around the mould.  These temperature controllers are usually located beside the moulding press and are piped directly into the mould. If the mould needs to be kept at a temperature higher than 90 degrees then an oil temperature controller is usually used. These units pump oil around the mould maintaining the mould temperature above 100 degrees.

There are also different methods of removing the plastic part from the tool face by using a robot. These robots can be mount on top of the moulding press over the mould, or they can be mounted beside the press and enter the open mould from the side.  Parts can then be placed on a conveyor belt or onto an assembly tray. These robots typically have their own control system and receive and give signals to and from the moulding machine via a euro map interface.

There are also a number of material handling systems that conveyed material from silos or bins to the moulding machine. These conveying systems are usually a vacuum system so that pallets of plastic material can be sucked along pipes directly to a hopper mounted on top of the moulding machine. There are also many types of mixing blending and metering equipment used to give a consistent blend of material.

In most large mould factories, you will find a central water chilling system, that keeps the water temperature consistent and pumps this water around the factory to machines and molds. This is of vital importance to the processing of plastics so that the process can run consistently.

There is a vast number of artillery equipment suppliers; however, most businesses will usually decide to go with a famous or well-known brand within their particular location, this is mainly due to the backup service that their agent can provide. However, this convenience comes at a cost, and the agent will have his agent fee and service fee that significantly increases the overall cost of buying the piece of equipment. Most businesses are reluctant to shop around due to the fear of equipment breakdown issues, and it is just more convenient to use a local service agent.

 

 

Specifying your equipment needs can take time. Why not let me help you get this job done. I can specify your equipment requirements, then source suitable suppliers and request quotations. I will also review these quotation options with you then draw up service contracts with the manufacture and local service companies on your behalf.

 

Design consideration of an injection mold.

The mold is usually machined from aluminium or steel. A sprue is an area which guides molten plastic out of the nozzle of the injection molding machine and into the entry point for the feed system within the mold. There are two main classes of runners (cold and hot) that can be used in a mold. Complexity in tool design can be incorporated into many elements of the tool design, like surface finishing, tolerance conditions, external or internal threads, or undercuts which all increase the tooling cost.  If you would like any advice or to review your tool design, I would be happy to talk with you about this.

 

Plastic part design for injection molding

Plastic parts need to be engineered and designed by a knowledgeable industrial designer or plastics engineer. It is advisable to make use of a uniformed wall thickness trough out the part (if at all possible) and avoid thick sections within your design. If you can not keep the part wall thickness uniform, ensure the transition between the wall thickness is gradual. A uniform wall thickness of between 1.0 mm and 3 mm is usually suitable for most materials. The thicker walls of the plastic part, the more material will be used. Also, the longer the cycle time will be and the greater the cost per part.

 

Cost of injection molding.

Nearly every plastic part around you has been fabricated using injection molding: for example car parts, electronics enclosures, as well as appliances for the kitchen. Injection molding is extremely popular, due to its relatively inexpensive cost per unit part when manufacturing high volumes. Injection molding provides high repeatability and greater design flexibility. The principal restrictions on Injection Molding usually return to economics, due to the increased initial investment that mold building demands.

Before you attempt to have, parts made via injection molding consider a couple of points: Initial investment: The building of an injection mold calls for a sizable initial expenditure. But not all molds are the same and not all toolmakers offer good value. When trying to compare tool quality between mold makers it can be challenging if they are quoting to make different types of molds. This is why it is important to fully specify what type of tool you require what material you wanted to use, and what standard parts you want and spares and reports you need. In that way individual toolmakers can quote you for that specific tool, you are then in a position to compare and contrast tool quality versus price.

I can help you with fully specifying your tooling requirements, also as well as approaching toolmakers and request quotation on your behalf. By using my sourcing service, you will find the best tool value.

 

Once the mold build costs has been paid the cost per unit part with injection molding is relatively low. The unit price of parts also has a tendency to drop drastically as more parts are created. However, what you need to look at is the lifetime of the tool, and the part unit price. For simplicity, if we say the unit price is one euro and a life cycle of the mould is a guarantee, Then we will spend 1 million euro’s before we need to have a new mould made.  The mold may only cost 30,000. However, we will be spending over a million euros for the parts Produced from this mould. So as we can see over the long term, the part cost greatly outweighs the initial tooling cost. So even though one euro unit price does not seem like a lot It does mount up over the lifetime of the mold . It is usually worth investing a little bit more time and money in designing the mould.  So as to ensure you are using better materials in the mold so that the mold can achieve faster cycle times and a reduction in unit cost.

I provide a service where I reviewed the tool design and optimise your tool design for you, as that you can achieve faster cycle times. I also offer a sourcing service where I will approach moulders on your behalf for unit price quotations. I specify the equipment needs the machinery needed, material needs and determine the expected cycle time. By using my sourcing and specifying service, I’m able to approach a range of suitable suppliers on your behalf, and in so doing saving you time and money.

 

injection mold

The injection mold design must accommodate any complex features in the plastic part, like undercuts or threads, this will call for extra mold fabrication. Undercuts in the plastic part design requires an experienced mold designer to try and avoid or reduce the tooling costs. Parts with undercuts (including threads or perhaps even the hook of a snap-fit ) may not be manufacturable with a straight-pull mold. Another primary tool design consideration is the cooling circuit. The coolant in the mold absorbs heat out of the mould (that includes absorbed heat from the plastic). A tool that can run at a cycle time of 30 seconds will produce twice as many parts as the same mold running at a cycle time of 30 seconds. The speed at which a mould can be run at really comes down to how efficiently the mould can be cooled. Cooling channel design and how far the cooling channel is kept far away from the surface of the part will effect the cooling time of the mould. However, with cooling channels that are kept closer to the part surface the cooling time of the mould can be significantly reduced. However there Are limitations to this Asda mould structure most force be insured, drilling water channels in the steel of the mould can weaken the tool. so optimal design of the cooling channel so that it can efficiently cool the tool while also not weakling not causing the tool to be weakened .  A cooling system follows the contours of te part is called conformal cooling, and while it takes longer to design and is usually more expensive to manufacture, it does produce shorter cooling times within the mould. By achieving faster cycle time you should be able to achieve lower unit part price and over the life of the mold potential save a lot of money.

So the cooling Circuit design within the mould is crucial for the efficiency and the cycle time of the mould. I would recommend when getting a mold made that you specify what cycle time you want to achieve, As the cycle time has a significant effect on the costing of the part unit price.  

Another consideration in tool design is the incorporation of inserts within the mold; this helps to facilitate maintenance of the mould by building the mold in pieces, called inserts. Some molds can be manufactured from a simple plate of steal where the core and cavity is machined out of individual plates. However, if for any reason the plates gat damaged or wear, it usually would mean the mould will have to be remade. However with the bolster insert method where an individual or wear parts within the mould are individually machined as an insert, The parts can be easily replaced, and spare parts can be kept so that there is limit down time for repaire. This is generally taught of as a better mould however, it does mean more design and generally costs more. This is why it is important to specify exactly how you want your mould made so when you are comparing to tooling quotes you are essentially comparing apples to apples. As a consultant in this area, I offer a tool specification service. Where I fully define your tooling requirements so that you can approach different toolmakers and request similar quotation types.

After an injection mold cycle (which usually is 5 to 45 seconds ) the molten plastic freezes, leaving a solid plastic from the sprue, gates, runners and section cavities. The ejector bar of the molding machine then pushes the ejector plate forward within the mold and then the mold ejector pins push onto the molded part. After the run is done, parts are boxed and shipped or assembled onsite then shipped out.

 

 

Benefit of injection molding.

The primary benefit of injection molding would be in its capacity to scale up production relatively simply. Compared to conventional manufacturing processes such as CNC machining which cut off material from a block of material. The waste plastic from injection molding manufacturing usually comes from three areas: the sprue, the runners, and the gate locations; however, this material can generally be recycled.

The main disadvantage of injection molding is longer lead times than different manufacturing technologies. The average turn around for injection molding fluctuates between 6 to 12 weeks with 6 to 8 weeks to fabricate the mold, also 2 to 4 more weeks for shipping and production.  

 

Rapid production of plastic parts

Online you will find many companies promoting themselves as rapid prototypers or rapid production of plastic parts; these are great places to go if you require small volumes anything up to 1000 or 2000 parts. These companies essentially CNC a block of aluminium for the core and cavity side; usually, they don’t incorporate cooling channels. The core and cavity inserts are then put into a standard mold base, and parts are molded, usually at longer than standard cycle time, due to the lack of cooling within the core and cavity inserts.

The tools are usually good for a few thousand parts; however, the problem with this is if you need to go to larger volumes the mold will have to be redesigned and made from harder, stronger metal. Cooling channels will need to be incorporated into the tool; cycle times will be reduced so parts will need to be ejected from the tool quicker, the draft angle on the tool may need to be increased so your initial part design will need to be changed.

The new tool may need to have to change the gate location, draft angle, ejection area, split line. All these changes can have a significant effect on your part assembly and visual aesthetics of your part. So while these one-stop-shop rapid tooling online businesses do offer a great initial low-volume , low cost production option. It would be help if you weighed up the long-term costs and time investment when considering going into larger volume production. As you will probable need to redesign your part and mold when looking at larger volume production.

It may be better to have a one of a two-cavity tool designed from tool steel first. This tool can be used for initial low volume runs. Then if the market demands, you can simply take that tool design and replicated or go for a larger cavity tool with the same part design.

 

Injection molding Materials

Since 1995, the entire quantity of available materials for injection moulding has grown at a rate of 750 a year; yet there were approximately 18,000 materials available when the trend began — available material including metals or combinations of previously developed materials. Product designers can decide on the correct material from a huge selection of material to choose from. The main selection criteria for most application is the materials’ durability and functional demands aswell as the price of the material. Additionally, each material contains different parameters for moulding that must be taken into consideration.

Material selection can be a difficult and daunting task as there are so many materials to choose from, and each material is having its own unique benefits our properties. A big factor in selecting a material for a particular application is the type of material that is currently being used for similar products, the mechanical properties of the material and the costs involved. Their selection the material selection process is a process of elimination and narrowing down where we first look at the overarching requirements of the material. For example, whether it needs to be clear flexible, tough, transparent, UV protection etc. All these considerations need to be assessed to be able to narrow down the selection of materials.

I provide a material selection service where I consider what your requirements are for the product then translate that into material specifications and then through a large database of materials I narrow down the list of materials Where I can look at cost and processing considerations to be able to narrow it further down to three or four options. With the material narrowed down to a few, it is then easier for us to be able to test for the best material option for the particular application.

 

Prototyping

Before considering to create an injection molded part, it may be advisable to create a prototype part first. There are many solutions for prototyping: 3D printing (using SLS, SLA or Material Jetting) CNC machining plastic and rapid tooling for low-run injection molding. All these procedures can produce realistic prototypes such as function and form that strongly resemble the visual appeal of an injection moulded part.  There are many companies out there offering 3D services and depending on your specific part design requirements, different types of prototyping will be suitable. I offer is resin casting service where I 3D print of your part then I make a silicon mould of your part. From this mould I can produce relatively low cost parts with a variety of materials. 

 

Other plastic production processes.

plastic injection moulding is not the only way of making plastic parts , there are there are other ways to manufacture plastic parts that may be suitable for your application . before you consider manufacturing your parts with injection moulding it would be worth considering order cheaper options .  below is a list of butter process is that can be used to manufacture plastic parts . if you need any advice or assistance on this you can contact me.

  1. This is a process somewhat similar to injection moulding except it is used to manufacture hollow components . A tube of plastic is extruded vertically down this is usually called a paracin . the person is extruded over a mandrel which is a metal part that air can be blown through . Asda when do tube is extruded to their correct lent AMOLED is closed around the Paris and and mandril one small disclosed here is blown into the mandril Which blows out di The Paris and into the shape of the mould . the mould is usually made from aluminium material and cooled with water . tableau moulding machine will cost Trim and cut any excess material this is how your milk bottles are made and many other lightwise consumer bottles .
  2. Compression moulding , this is a process that has become popular in recent years however it is a relatively old process . it is essentially where material is hand laid into the mould the mall is closed And mould is he said . the cycle times in the process are usually quite long in the order of several minutes in recent times it has been used to mould large parts for the automotive industry specially in car panels and larger component parts made from a composite material. however, this is a relatively inexpensive way of manufacturing large parts and the tooling costs are not as high as with injection moulding .
  3. Rotational moulding this is a process where a mould is filled with polymer powder the mould is then clamped up and rotate it 360 degrees within an furnace . the mall rotates and heat up so that the plastic is molten and rotates around the tool and sticks to the tool surface. the mould is then taken out of the furnace and allowed to . This process is generally used for ticker Wold parts with not so much detail in them. large Rd barriers would use this process.
  4. Thermoforming – this is a process where a tin sheet of plastic somewhere between one and three millimetres in thickness Is he said usually buy an electric heating element when the plastic becomes somewhat soft the mould is pushed up into the soft film and a vacuum is applied underneath the mould which sucks the plastic filament onto the mould. food curtains and packaging items are generally vacuum-formed like this. Tooling is usually made from aluminium and air-cooled, does the tooling is not so expensive.

these are just some of the other processes that can be used to manufacture plastic parts injection moulding is a very technical process. it needs experts in this type of manufacturing business for it to be competitive .in the market, therefore, a very scientific and systematic study should first be made before endeavouring to go on on a manufacturer your parts fire injection moulding if you need any assistance or help please feel free to reach out, www.pro-plastics.com  

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