Molds & Dies

ASTM Molds & Dies (click to enlarge)

The mold must produce an imperfection free sample of uniform specified thickness.

The die must cut a specimen for testing that will be the specified shape within dimensional tolerances (including thickness) as indicated for the test in question.

Dies can be supplied with mallet handle for fast, easy hand stamping of test specimens using a maul, or for use in clicker presses. Special press adaptors can be produced upon request.

ASTM Molds and Dies

Tensile Test Dies

Other dies, in other dimensions and meeting different standards, are also available.

Model	Type	Catalog #
ASTM D-412	A-Clicker	CAD412
ASTM D-412	B-Clicker	CBD412
ASTM D-412	C-Clicker	CCD412
ASTM D-412	D-Clicker	CDD412
ASTM D-412	E-Clicker	CED412
ASTM D-412	F-Clicker	CFD412
ASTM D-412	A-Mallet	CMAD412
ASTM D-412	B-Mallet	CMBD412
ASTM D-412	C-Mallet	CMCD412
ASTM D-412	D-Mallet	CMDD412
ASTM D-412	E-Mallet	CMED412
ASTM D-412	F-Mallet	CMFD412
Gage length marker	1 in.	CGLM1
Gage length marker	2 in.	CGLM2

The inside surface is perpendicular to the cutting edge and polished, insuring cutting of a test specimen of uniform standard thickness. Dies are designed to be resharpened.

ASTM D-412 popular sizes C and D are standard, with A, B. E, and F also available upon request.

Rotary type cutters are designed for use in standard drill press chucks. Cutters can be supplied to standard dimensions as indicated by ASTM D-412.

Tear Test Dies

Other dies, in other dimensions and meeting different standards, are also available.

Model	Type	Catalog #
ASTM D-624	A-Clicker	CAD624
ASTM D-624	B-Clicker	CBD624
ASTM D-624	C-Clicker	CCD624
ASTM D-624	A-Mallet	CAD624
ASTM D-624	B-Mallet	CBD412
ASTM D-624	C-Mallet	CCD412

Tear Test Dies possess the same physical features as the Tensile Test Die, including the mallet handle/clicker press option.

Test Molds for Rubber Specimens

ASTM D-395 Compression Set Molds

ASTM D395 Mold and Constant Deflection Fixture (click image to enlarge)

Model	Catalog #
Four cavity TYPE1	CSCM11
Nine cavity TYPE1	CSCM21
Sixteen cavity TYPE1	CSCM41
Four cavity TYPE2	CSCM12
Nine cavity TYPE2	CSCM22
Sixteen cavity TYPE2	CSCM42
Method A Constant Load Device	CCLDA
Method B Constant Deflection Fixture	CCDFB
Additional Spacers (quantity 12)	CAS12

Various Molds

X-Flow Mold (click image to enlarge)

Model	Catalog #
ASTM D-429 Four cavity adhesion - Method A	CASTM429A
ASTM D-429 Four cavity adhesion - Method B	CASTM429B
ASTM D-3123 Spiral flow mold for plastics	CASTM3123
X Type rubber flow mold for compound evaluation	CXRFM
ASTM D-2138 Static adhesion Eight cavity, four cord test samples	CASTM2138
ASTM D-2138 Static adhesion Sixteen cavity, eight cord test samples	CASTM21388

Molds for Physical Testing Samples to ASTM D-3182

	Metric: mm L x W x D	English: inches L x W x D
Single-cavity CSCM1	Cavity: 152 x 152 x 20	6 x 6 x .077
	Overall: 190 x 190	7.5 x 7.5
Two-cavity CSCM2	Cavity: 152 x 152 x 20	6 x 6 x .077
	Overall: 190 x 380	7.5 x 15
Four-cavity CSCM4	Cavity: 152 x 152 x 20	6 x 6 x .077
	Overall: 380 x 380	15 x 15

Compression molding

Compression molding is a method of molding in which the molding material, generally preheated, is first placed in an open, heated mold cavity. The mold is closed with a top force or plug member, pressure is applied to force the material into contact with all mold areas, while heat and pressure are maintained until the molding material has cured. The process employs thermosetting resins in a partially cured stage, either in the form of granules, putty-like masses, or preforms. Compression molding is a high-volume, high-pressure method suitable for molding complex, high-strength fiberglass reinforcements. Advanced composite thermoplastics can also be compression molded with unidirectional tapes, woven fabrics, randomly orientated fiber mat or chopped strand. The advantage of compression molding is its ability to mold large, fairly intricate parts. Also, it is one of the lowest cost molding methods compared with other methods such as transfer molding and injection molding; moreover it wastes relatively little material, giving it an advantage when working with expensive compounds. However, compression molding often provides poor product consistency and difficulty in controlling flashing, and it is not suitable for some types of parts. Compression molding produces fewer knit lines and less fiber-length degradation than injection molding. Compression-molding is also suitable for ultra-large basic shape production in sizes beyond the capacity of extrusion techniques. Materials that are typically manufactured through compression molding include: Polyester fiberglass resin systems (SMC/BMC), Torlon PAI, Vespel PI, Meldin PI, Ryton PPS, and many grades of PEEK.

Compression molding was first developed to manufacture composite parts for metal replacement applications, compression molding is typically used to make larger flat or moderately curved parts. This method of molding is greatly used in manufacturing automotive parts such as hoods, fenders, scoops, spoilers, as well as smaller more intricate parts. The material to be molded is positioned in the mold cavity and the heated platens are closed by a hydraulic ram. Bulk molding compound (BMC) or sheet molding compound (SMC), are conformed to the mold form by the applied pressure and heated until the curing reaction occurs. SMC feed material usually is cut to conform to the surface area of the mold. The mold is then cooled and the part removed. Materials may be loaded into the mold either in the form of pellets or sheet, or the mold may be loaded from a plasticating extruder. Materials are heated above their melting points, formed and cooled. The more evenly the feed material is distributed over the mold surface, the less flow orientation occurs during the compression stage.

Thermoplastic matricies are common place in mass production industries eg. automotive applications where the leading technologies are Long Fibre reinforced Thermoplastics (LFT) and Glass fibre Mat reinforced Thermoplastics (GMT).

In compression molding there are six important considerations that an engineer should bear in mind^{[citation needed]}:

• Determining the proper amount of material.
• Determining the minimum amount of energy required to heat the material.
• Determining the minimum time required to heat the material.
• Determining the appropriate heating technique.
• Predicting the required force, to ensure that shot attains the proper shape.
• Designing the mold for rapid cooling after the material has been compressed into the mold.

Structural Plastic Injection Molding

Structural Foam Injection Molding Process

The Structural Foam Process is a low pressure injection molding process where an inert gas is introduced into melted polymer for the purpose of reducing density and hence weight of the finished product.

Structural foam molded products have cellular cores surrounded by rigid, integral skins. Foaming agent (NI, CO₂ or CBA) is introduced into the polymer melt stream, creating a homogenous mixture of polymer and gas.

The mixture is short-shot injected through nozzles into the mold in a volume that is less than the amount required to mold a solid part. Injection pressure and expansion of the polymer/gas mixture fills the mold.

A porous skin is formed when the melt contacts the cold surface of the mold. The expanding polymer/gas mixture forms the cellular core.

The expanding gas provides the final pack and hold pressure. Once the plastic gas mixture enters the mold cavity, the gas expands (i.e. foams), filling the cavity and forming cellular structures within the part. The finished part is typically 10 - 30% less weight than an equivalent solid part.

Advantages over alternative methods

• Part weight reduced 10% to 30%
• Density Reduction, hence resin savings
• Low cost N₂ or CO₂ - much less expensive than chemical blowing agents (CBA's)
• Large part molding with low clamp force requirements
• Mold Cavity Pressure; typically 200 - 600 psi ( 14 -41 Bar )
• Lower energy costs vs. other IM processes
• Lower cost aluminum molds vs. high pressure IM machines
• Faster cycles due to better heat transfer of aluminum
• Thick wall parts from 0.125" - 0.500" ( 3 - 12 mm )
• Stiffer parts at the same weight as IM as a result of cellular foam structure
• Complex parts without sink marks
• Higher impact strength than thinner wall IM
• Parts can be sawn, screwed, nailed or stapled like wood

THE ROTATIONAL MOLDING PROCESS

	Bi-Axial Rotation Rotational molding technology is expanding the capabilities of polymer product manufacturers by enabling them to create light-weight, seamless, stress-free parts of virtually any size in the most complex shapes. Rotationally molded products represent a wide range of materials, performance characteristics, colors, surface textures and finishes. The products can be custom-designed to meet precise market requirements more economically than by conventional injection or blow molding. Rotational molding is a three-stage, no-pressure, plastic molding process. During the heating stage, the mold slowly rotates in two planes (bi-axial rotation). Heat transfer causes the plastic charge inside the mold to melt and uniformly coat the interior of the mold. During the second stage, the mold moves to the cooling station,		3-Stage Process where it is cooled by air and/or water spray. In the final load/unload stage, the part is removed from the mold and a new charge of material is loaded into the mold. Ferry's innovative RotospeedTM machines enhance this process with design styles that vary the configuration of these three stages. A variety of sizes accommodate most processor needs. Ferry offers over 30 standard models of Rotospeedª rotational molding machines, with mold swings to 218" (5537 mm) and weight capacities to 10,000 pounds (4540 kg). Versatile, dynamic and market-responsive, Ferry Industries is committed to introducing new designs, product refinements, and effective integration of ancillary equipment to advance the technology and value of the Rotospeed product line.
	What you can make by rotational molding!
	This unique polymer molding process affords molders the ability to produce items ranging from small toy doll components to agricultural tanks that will hold up to 22,500 gallons (85,167 liters) of liquid. A variety of polymer materials can be used to provide specific characteristics to the products. By interjecting multiple-charges a foaming		agent can be added to provide insulating qualities. Close tolerances and tight radii can also be made to afford interchangeable and interlocking components. The world of rotational molding is the fastest growing segment of the polymer industry. We can help you grow too!
	FREQUENTLY ASKED QUESTIONS
	What do you need from me to recommend the best style and size of machine for my needs? We need the dimensions of your products, projected annual production and the type(s) of resin you plan to mold. Sketches help and any other details. What other equipment do I need to start producing? Typically a tow motor, semi-skilled operators, resin, secondary finishing equipment such as router, and of course, a building. What is the difference between an Independent-Arm and a Fixed-Arm Turret machine? With Fixed-arm turret machines, 3- or 4-arm, all the arms index at the same time. This means oven, cooling and servicing operation need to be accomplished within same time allotment. The Independent-arm machine, with 5 stations, allows one arm to index while the other arms may remain stationary, providing more process flexibility. What type of molds are used for rotational molding? The most common type of molds are cast aluminum, fabricated aluminum, fabricated steel and stainless steel. Other types are available such as machined and electro-formed. Here are links for some of the mold suppliers to rotational molders.		Cole Industries, Inc. Norstar Aluminum Molds, Inc. Johndel, Inc. What types of material are commonly used for rotational molding? Polyethylene (HDPE, LPDE and LLPDE), PVC, Fluorocarbons, Polypropylene, Nylon and Polycarbonate. Here are links to some of the material suppliers to rotational molders. A. Schulman ICO Polymers Nova Chemicals Total Petrochemicals Can you recommend some independent consultant to discuss our needs regarding rotational molding? Yes, here are some is a highly regarded and very knowledgeable independent consultants to the world-wide rotational molding community. Paul Nugent Einar Voldne Glenn Beall Are the molds under high-pressure and spin fast? No, rotational molding is a low/no pressure process where the molds are charged with resin, clamped shut and rotate in two axes at low speeds. Typically the major axis revolves four times to every one time of the minor axis. The speeds are slow enough that no centrifugal force is involved.

About Thermoforming

What is thermoforming?

What are the benefits of thermoforming?

When and where does thermoforming fit?

What kind of forming and trim tolerances can ATI hold for my parts?

In thermoforming, why can only one side of the part be controlled in the forming process?

How thick of materials do we work with?

What type of plastics can you thermoform?

What kind of cosmetic features can be achieved with thermoforming?

What is twin-sheet forming and what kind of parts does it allow ATI to form?

What kinds of thermoforming molds are there?

• Machined aluminum molds
• Cast aluminum molds
• Composite molds

What is thermoforming?
Thermoforming is a generic term for the process of producing plastic parts from a flat sheet of plastic under temperature and pressure. In the highest expression of the technology, thermoforming offers close tolerances, tight specifications, and sharp detail. When combined with advanced finishing techniques, high-technology thermoforming results in products comparable to those formed by injection molding. All of us are exposed to many thermoformed plastics in our daily lives. They have replaced many parts previously manufactured from wood, paper, glass, and metal.

What are the benefits of thermoforming?
Thermoforming is efficient and very cost-effective for the production of many plastic parts depending on their size, shape, and quantity. Initial project costs are usually much lower, and lead times to tooling and production are generally much shorter than other processes. Modifications to design often times may be achieved. Temporary tooling offers an inexpensive short-term test for design issues and product market acceptance.

When and where does thermoforming fit?
Large panels, housings, enclosures, and similar parts are especially well-suited to the thermoforming process. Tooling costs for these parts is considerably less than injection molding, which may have cost-prohibitive tooling costs. Parts with features mostly confined to one side of the part are best suited to thermoforming, but features on the uncontrolled side of the part may be addressed by trimming or fabrication and assembly.

What kind of forming and trim tolerances can ATI hold for my parts?
The following table list our standard tolerances:

Typical Thermoform & Pressure Form Tolerances
Download a PDF of this file.

Formed Features

Formed Features	Pressure-forming	Vacuum forming
Less than 6"	+/-.010"	+/-.015
6" to 12"	+/-.020"	+/-.025"
12" to 18"	+/-.025"	+/-.030"
Above 18", add	+/-.002" per inch

CNC Trimmed Features

Machined features from a formed surface	+/-.015
"Hole to Hole"	+/-.010
Hole Diameter	+/-.005

In thermoforming, why can only one side of the part be controlled in the forming process?
The side of the plastic formed against the mold can be controlled with close tolerances. The side away from the mold cannot be controlled although it can be predicted what will occur on the uncontrolled side. Tolerance requirements on the uncontrolled side are addressed by trimming or fabrication and assembly.

How thick of materials do we work with?
We typically deal with materials ranging in thickness from .040" to .500".

What type of plastics can you thermoform?
Plastics that lend themselves best to thermoforming are: acrylonitrile-butadiene-styrene copolymer (ABS), high-impact polystyrene (HIPS), high density polyethylene (HDPE), high molecular weight polyethylene (HMWPE), polypropylene (PP), polyvinyl chloride (PVC), polymethyl methacrylate (or "acrylic") (PMMA), and polyethylene terephthalate modified with CHDM (PETG).

What kind of cosmetic features can be achieved with thermoforming?
Sharp, crisp detail with close tolerances can be achieved. Undercuts, formed-in texture, formed-in logos, formed-in hardware, and custom colors are just a few of the many features that can be accomplished with thermoforming. This subject is covered in more detail on our design considerations page.

What is twin-sheet forming and what kind of parts does it allow ATI to form?
Twin-sheet forming is accomplished by simultaneously forming two separate sheets in their respective separate molds to create hollow and double-walled parts comparable to roto-molded parts but with much more detail and better cosmetics.

What other tooling is required in the thermoforming process?
A vacuum fixture is required when a part must be CNC trimmed. Vacuum fixtures are constructed by taking a reverse impression of the part and mounting this impression into a vacuum box. The trim fixture then holds, under vacuum pressure, each part being CNC trimmed to ensure consistent results. Other tooling specifically required in the forming, trimming, fabrication, and assembly of each part is designed by ATI engineers and constructed by the ATI tooling department.

What kinds of thermoforming molds are there?

Machined Aluminum Molds
Machined aluminum molds are typically built for shallow parts with small draw ratios. ATI uses 6061-T6 aluminum for the construction of these molds, which can be held to very close tolerances. These molds are then mounted on a temperature control base to control the mold temperature during the forming process. Male or female molds and vacuum-form or pressure-form molds can be machined aluminum molds. They can be textured and may offer features such as loose cores, pneumatic cores, and inserts.

Cast Aluminum Molds
Cast aluminum molds are cast at a foundry from a pattern machined by ATI from a composite material. The temperature controls are cast into the back and sides of the molds at the foundry. Cast aluminum molds typically are built for parts with large draw ratios and may be male or female and vacuum-form or pressure-form. Features such as texture, loose and pneumatic cores, and inserts are available.

Composite Molds
For prototyping and short production runs, cost-efficient composite materials are used for mold construction. These molds produce parts that are to be evaluated for fit, form, and function and may be modified to evaluate possible design changes. These molds are for vacuum-forming only and are not temperature controlled. These molds have a limited life.

Thermoforming

Vacuum forming is accomplished by taking a flat piece of plastic, heating it until it softens, then using a vacuum to pull it onto a contoured surface where it is held until it cools and hardens. Tooling costs for this process are the lowest of any plastic molding process.

Pressure forming is vacuum forming that uses air pressure to assist the vacuum. This results in much better definition on the part surface.

Twin sheet forming is two pressure or vacuum forming operations occurring simultaneously, which are joined to produce an integrally welded hollow part.

Process Characteristics
Part Cost - moderate to high Tool Cost - low Production Rate - low Capable of producing very large parts Parts are molded without stress, so they are very stable
Examples

Blow Molding

Blow Molding

Blow Molding is a highly developed molding technology developed back in the late 1800's to produce celluloid baby rattles. It is best suited for basically hollow parts (such as plastic bottles) with uniform wall thicknesses, where the outside shape is a major consideration.

The first polyethylene bottle was manufactured using the blow molding process in December of 1942. This was the real beginning of a huge industry which currently produces 30 to 40 billion plastic bottles per year in the U.S. alone.

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The Basic Process

1. A thermoplastic resin is heated to a molten state
2. It is then extruded through a die head to form a hollow tube called a parison.
3. The parison is dropped between two mold halves, which close around it.

4. The parison is inflated.

5. The plastic solidifies as it is cooled inside the mold.

6. The mold opens and the finished component is removed.

Variations

There are basically four types of blow molding used in the production of plastic bottles, jugs and jars. These four types are:

1. Extrusion blow molding
2. Injection blow molding
3. Stretch blow molding
4. Reheat and blow molding.

Extrusion blow molding is perhaps the simplest type of blow molding. A hot tube of plastic material is dropped from an extruder and captured in a water cooled mold. Once the molds are closed, air is injected through the top or the neck of the container; just as if one were blowing up a balloon. When the hot plastic material is blown up and touches the walls of the mold the material "freezes" and the container now maintains its rigid shape.

Injection blow molding is part injection molding and part blow molding. With injection blow molding, the hot plastic material is first injected into a cavity where it encircles the blow stem, which is used to create the neck and establish the gram weight. The injected material is then carried to the next station on the machine, where it is blown up into the finished container as in the extrusion blow molding process above. Injection blow molding is generally suitable for smaller containers and absolutely no handleware.

Extrusion blow molding allows for a wide variety of container shapes, sizes and neck openings, as well as the production of handleware. Extrusion blown containers can also have their gram weights adjusted through an extremely wide range, whereas injection blown containers usually have a set gram weight which cannot be changed unless a whole new set of blow stems are built. Extrusion blow molds are generally much less expensive than injection blow molds and can be produced in a much shorter period of time.

Stretch blow molding is perhaps best known for producing P.E.T. bottles commonly used for water, juice and a variety of other products. There are two processes for stretch blow molded P.E.T. containers. In one process, the machinery involved injection molds a preform, which is then transferred within the machine to another station where it is blown and then ejected from the machine. This type of machinery is generally called injection stretch blow molding (ISBM) and usually requires large runs to justify the very large expense for the injection molds to create the preform and then the blow molds to finish the blowing of the container. This process is used for extremely high volume (multi-million) runs of items such as wide mouth peanut butter jars, narrow mouth water bottles, liquor bottles etc.

The reheat and blow molding process (RHB) is a type of stretch blow process. In this process, a preform is injection molded by an outside vendor. There are a number of companies who produce these "stock" preforms on a commercial basis. Factories buy the preforms and put them into a relatively simple machine which reheats it so that it can be blown. The value of this process is primarily that the blowing company does not have to purchase the injection molding equipment to blow a particular container, so long as a preform is available from a stock preform manufacturer. This process also allows access to a large catalog of existing preforms. Therefore, the major expense is now for the blow molds, which are much less expensive than the injection molds required for preforms.

There are, however, some drawbacks to this process. If you are unable to find a stock preform which will blow the container you want, you must either purchase injection molds and have your own private mold preforms injection molded, or you will have to forego this process. For either type of stretch blow molding, handleware is not a possibility at this stage of development. The stretch blow molding process does offer the ability to produce fairly lightweight containers with very high impact resistance and, in some cases, superior chemical resistance.

Whether using the injection stretch blow molding process or the reheat and blow process, an important part of the process is the mechanical stretching of the preform during the molding process. The preform is stretched with a "stretch rod." This stretching helps to increase the impact resistance of the container and also helps to produce a very thin walled container.

Materials -

The extrusion blow molding process allows for the production of bottles in a wide variety of materials, including but not limited to: HDPE, LDPE, PP, PVC, BAREX®, P.E.T., K Resin, P.E.T.G., and Polycarbonate. As noted above, a wide variety of shapes (including handleware), sizes and necks are available. Injection blow molding allows for the production of bottles in a variety of materials, including but not limited to: HDPE, LDPE, PP, PVC, BAREX®, P.E.T., and Polycarbonate.

Besides the P.E.T. noted above for stretch blow molding, a number of other materials have been stretch blown, including polypropylene. As time goes on and technology moves forward, more materials will lend themselves to stretch blow molding as their molecular structures are altered to suit this process.

Blow Molding Machine Manufacturers -

For shuttle extrusion type machines Bekum, Battenfeld/Fischer, and Hayssen are probably the best known in the United States. For injection blow molding machines JOMAR is a well known brand. For stretch blow and reheat and blow type machines there are Sidel, Nissei and other machines produced by Johnson Controls and others. For wheel machines you might wish to contact Johnson Controls or Wilmington Machinery.

Extrusion process

Introduction

Extruded products constitute more than 50 % of the market for aluminium products in Europe of which the building industry consumes the majority. Aluminium extrusions are used in commercial and domestic buildings for window and door frame systems, prefabricated houses/building structures, roofing and exterior cladding, curtain walling, shop fronts, etc. Furthermore, extrusions are also used in transport for airframes, road and rail vehicles and in marine applications.

The term extrusion is usually applied to both the process, and the product obtained, when a hot cylindrical billet of aluminium is pushed through a shaped die (forward or direct extrusion, see Figure 1). The resulting section can be used in long lengths or cut into short parts for use in structures, vehicles or components. Also, extrusions are used for the starting stock for drawn rod, cold extruded and forged products. While the majority of the many hundreds of extrusion presses used throughout the world are covered by the simple description given above it should be noted that some presses accommodate rectangular shaped billets for the purpose of producing extrusions with wide section sizes. Other presses are designed to push the die into the billet. This latter modification is usually termed "indirect" extrusion.

Figure 1: Scheme of direct extrusion

The versatility of the process in terms of both The versatility of the process in terms of both alloys available and shapes possible makes it one of the most valued assets in helping the aluminium producer supply users with solutions to their design requirements.

The extrusion process
The fundamental features of the process are as follows: A heated billet cut from DC cast log (or for small diameters from larger extruded bar) is located in a heated container, usually around 450 °C - 500 °C. At these temperatures the flow stress of the aluminium alloys is very low and by applying pressure by means of a ram to one end of the billet the metal flows through the steel die, located at the other end of the container to produce a section, the cross sectional shape of which is defined by the shape of the die (Figure 2).

Figure 2: Extrusion principle

All aluminium alloys can be extruded but some are less suitable than others, requiring higher pressures, allowing only low extrusion speeds and/or having less than acceptable surface finish and section complexity. The term 'extrudability' is used to embrace all of these issues with pure aluminium at one end of the scale and the strong aluminium/zinc/magnesium/copper alloys at the other end. The biggest share of the extrusion market is taken by the 6000, AlMgSi series. This group of alloys have an attractive combination of properties, relevant to both use and production and they have been subject to a great deal of R & D in many countries. The result is a set of materials ranging in strength from 150 Mpa to 350 Mpa, all with good toughness and formability. They can be extruded with ease and their overall 'extrudability'is good but those containing the lower limits of magnesium and silicon e.g. 6060 and 6063 extrude at very high speeds - up to 100 m/min with good surface finish, anodising capability and maximum complexity of section shape combined with minimum section thickness

Press load capacities range from a few hundred tonnes to as high as 20,000 tonnes although the majority range between 1,000 and 3,000 tonnes. Billet sizes cover the range from 50 mm diameter to 500 mm with length usually about 2-4 times the diameter and while most presses have cylindrical containers a few have rectangular ones for the production of wide shallow sections.

The ease with which aluminium alloys can be extruded to complex shapes makes valid the claim that it allows the designer to "put metal exactly where it is needed", a requirement of particular importance with a relatively expensive material. Furthermore, this flexibility in design makes it easy, in most cases, to overcome the fact that aluminium and its alloys have only 1/3 the modulus of elasticity of steel (Figure 3). Since stiffness is dependent not only on modulus but also on section geometry it is possible, by deepening an aluminium beam by around 1,5 times the steel component it is intended to replace, to match the stiffness of the steel at half the weight. Also, at little added die cost, features can be introduced into the section shape which increase torsional stiffness and provide grooves for say fluid removal, service cables, anti-slip ridges etc. Such features in a steel beam would require joining and machining, thus adding to the cost and narrowing the gap between initial steel and aluminium costs.

Figure 3: Designing extrusions with improved stiffness

Source: European Aluminium Association

Basics of Injection Molding

Making thermoplastics and shaping them into various useful objects is an amazing science. Among the many processes used in shaping plastic resins, injection molding is the most commonly used.

Injection molding is the primary method in producing parts, using large machines called injection-molding machines, from thermoplastic materials. The process of injection molding is an economical and rapid way of producing varieties of plastic materials in a high quality precision manner.

The process of injection molding was first used in the early 1920s for producing cellulose-plastic toothbrushes, combs and other small industrial items. Since then, the basic process and principles of injection molding has not changed drastically. Due to the developments of different kinds of plastics and state-of-the-art injection molding machines, the process of injection molding have become a common method in producing objects for many markets and industries.

There are several steps in the injection molding process:

1) Plastic pellet or granules are heated until melted (The heat depends on the kind of plastic used, but typically ranges from 350 – 550 degrees Fahrenheit).

2) The melted plastics are then placed under high pressure into an unyielding mold (usually using metal, steel or aluminum).

3) The plastic is cooled down to re-solidify, producing the desired dimensions and shapes of the plastic.

Injection-molded parts vary in sizes. It can be as small as an object hardly visible to the naked eye or as huge as the exterior of a car’s body panel.

Since these plastic molds are processed in high intensities of heat and pressure, the results are guaranteed to be heavy-duty construction materials. For this reason, any item produced from injection molding machines can be expensive.

If you need only a few items, injection molding is not a practical option. This is because large quantities of plastics are needed to pay off the costs and allow for economical finished products. Plastic injection molding may cost anywhere from a few hundred dollars to thousands of dollars, depending on the size of the molds.

Plastic molds are made with high precision. For this reason, new injection molding machines are designed to control temperature and pressure strictly. In addition, plastic materials are made with high-class specifications. Because of these improvements, a single injection-molding machine can produce thousands of the same objects, which are identical in quality, appearance, integrity and performance.

By using the process of injection molding, you will be able to produce durable products that provide quality, usability and consistency… anytime.