Thermoforming Engineering & Type

Thermoforming has benefited from applications of engineering technology, although the basic forming process is very similar to what was invented many years ago. Microprocessor and computer controls on more modern machinery allow for greatly increased process control and repeatability of same-job setups from one production run with the ability to save oven heater and process timing settings between jobs. The ability to place formed sheet into an inline trim station for more precise trim registration has been hugely improved due to the common use of electric servo motors for chain indexing versus air cylinders, gear racks, and clutches on older machines. Electric servo motors are also used on some modern and more sophisticated forming machines for actuation of the machine platens where form and trim tooling are mounted, rather than air cylinders which have traditionally been the industry standard, giving more precise control over closing and opening speeds and timing of the tooling. Quartz and radiant-panel oven heaters generally provide more precise and thorough sheet heating over older cal-rod type heaters, and better allow for zoning of ovens into areas of adjustable heat..
A new technology, ToolVu, has been developed to provide real-time feedback on thermoformer machines. This stand-alone system connects directly to the thermoformer and utilizes multiple sensors to record production-run data in real time including air pressure, temperature, tool strain gauge and other specifications. The system sends out multiple warnings and alerts whenever pre-set production parameters are compromised during a run. This reduces machine down time, lowers startup time and decreases startup scrap.
An integral part of the thermoforming process is the tooling, which is specific to each part that is to be produced. Thin-gauge thermoforming as described above is almost always performed on in-line machines and typically requires molds, plug assists, pressure boxes and all mounting plates as well as the trim tooling and stacker parts that pertain to the job. Thick or heavy-gauge thermoforming also requires tooling specific to each part, but because the part size can be very large, the molds can be cast aluminum or some other composite material as well as machined aluminum as in thin gauge. Typically, thick-gauge parts must be trimmed on CNC routers or hand trimmed using saws or hand routers. Even the most sophisticated thermoforming machine is limited to the quality of the tooling. Some large thermoforming manufacturers choose to have design and tool making facilities in house while others will rely on outside tool-making shops to build the tooling.

Plastic Processing Type

Type:injection moulding, plastics extrusion, stretch-blow molding, thermoforming, compression molding, calendering, transfer molding, laminating, fiberglass molding, pultrusion, filament winding, vacuum forming, rotational molding
Injection moulding
Injection moulding BrE or Injection molding AmE, is a manufacturing process for producing parts by injecting molten material into a mould. Injection moulding can be performed with a host of materials mainly including metals, (for which the process is called die-casting), glasses, elastomers, confections, and most commonly thermoplastic and thermosetting polymers. Material for the part is fed into a heated barrel, mixed (Using a helical shaped screw), and injected (Forced) into a mould cavity, where it cools and hardens to the configuration of the cavity:240 After a product is designed, usually by an industrial designer or an engineer, moulds are made by a mould-maker (or toolmaker) from metal, usually either steel or aluminium, and precision-machined to form the features of the desired part. Injection moulding is widely used for manufacturing a variety of parts, from the smallest components to entire body panels of cars. Advances in 3D printing technology, using photopolymers which do not melt during the injection moulding of some lower temperature thermoplastics, can be used for some simple injection moulds.
Parts to be injection moulded must be very carefully designed to facilitate the moulding process; the material used for the part, the desired shape and features of the part, the material of the mould, and the properties of the moulding machine must all be taken into account. The versatility of injection moulding is facilitated by this breadth of design considerations and possibilities.
Plastics extrusion
Plastics extrusion is a high-volume manufacturing process in which raw plastic is melted and formed into a continuous profile. Extrusion produces items such as pipe/tubing, weatherstripping, fencing, deck railings, window frames, plastic films and sheeting, thermoplastic coatings, and wire insulation.
This process starts by feeding plastic material (pellets, granules, flakes or powders) from a hopper into the barrel of the extruder. The material is gradually melted by the mechanical energy generated by turning screws and by heaters arranged along the barrel. The molten polymer is then forced into a die, which shapes the polymer into a shape that hardens during cooling.
Stretch-blow molding
Blow molding ( BrE molding ) is a manufacturing process by which hollow plastic parts are formed: It is also used for forming glass bottles. In general, there are three main types of blow molding: extrusion blow molding, injection blow molding, and injection stretch blow molding. The blow molding process begins with melting down the plastic and forming it into a parison or in the case of injection and injection stretch blow moulding (ISB) a preform. The parison is a tube-like piece of plastic with a hole in one end through which compressed air can pass.
The parison is then clamped into a mold and air is blown into it. The air pressure then pushes the plastic out to match the mold. Once the plastic has cooled and hardened the mold opens up and the part is ejected . The cost of blow moulded parts is higher than that of injection – moulded parts but lower than rotational moulded parts
Thermoforming is a manufacturing process where a plastic sheet is heated to a pliable forming temperature, formed to a specific shape in a mold, and trimmed to create a usable product. The sheet, or “film” when referring to thinner gauges and certain material types, is heated in an oven to a high-enough temperature that permits it to be stretched into or onto a mold and cooled to a finished shape. Its simplified version is vacuum forming.
Compression molding
Compression Molding is a method of molding in which the moulding material, generally preheated, is first placed in an open, heated mould 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.
Calendering is a finishing process used on cloth, paper, or plastic film. A calender is employed, usually to smooth, coat, or thin a material.
With textiles, fabric is passed under rollers at high temperatures and pressures. Calendering is used on fabrics such as moire to produce its watered effect and also on cambric and some types of sateens.
In preparation for calendering, the fabric is folded lengthwise with the front side, or face, inside, and stitched together along the edges.The fabric can be folded together at full width, however this is not done as often as it is more difficult.
The fabric is then run through rollers that polish the surface and make the fabric smoother and more lustrous. High temperatures and pressure are used as well. Fabrics that go through the calendering process feel thin, glossy and papery.
Transfer molding
Transfer molding (BrE moulding) is a manufacturing process where casting material is forced into a mold. Transfer molding is different from compression molding in that the mold is enclosed rather than open to the fill plunger resulting in higher dimensional tolerances and less environmental impact. Compared to injection molding, transfer molding uses higher pressures to uniformly fill the mold cavity. This allows thicker reinforcing fiber matrices to be more completely saturated by resin. Furthermore, unlike injection molding the transfer mold casting material may start the process as a solid. This can reduce equipment costs and time dependency. The transfer process may have a slower fill rate than an equivalent injection molding processes.
Lamination is the technique of manufacturing a material in multiple layers, so that the composite material achieves improved strength, stability, sound insulation, appearance or other properties from the use of differing materials. A laminate is a permanently assembled object by heat, pressure, welding, or adhesives.
Fiberglass molding
Fiberglass molding is a process in which fiberglass reinforced resin plastics are formed into useful shapes.
The process usually involves first making a mold and then using the mold to make the fiberglass component.
Pultrusion is a continuous process for manufacture of composite materials with constant cross-section. The term is a portmanteau word, combining “pull” and “extrusion”. As opposed to extrusion, which pushes the material, pultrusion works by pulling the material.
Filament winding
Filament winding is a fabrication technique mainly used for manufacturing open (cylinders) or closed end structures (pressure vessels or tanks). This process involves winding filaments under tension over a rotating mandrel. The mandrel rotates around the spindle (Axis 1 or X: Spindle) while a delivery eye on a carriage (Axis 2 or Y: Horizontal) traverses horizontally in line with the axis of the rotating mandrel, laying down fibers in the desired pattern or angle. The most common filaments are glass or carbon and are impregnated in a bath with resin as they are wound onto the mandrel. Once the mandrel is completely covered to the desired thickness, the resin is cured. Depending on the resin system and its cure characteristics, often the rotating mandrel is placed in an oven or placed under radiant heaters until the part is cured. Once the resin has cured, the mandrel is removed or extracted, leaving the hollow final product. For some products such as gas bottles, the ‘mandrel’ is a permanent part of the finished product forming a liner to prevent gas leakage or as a barrier to protect the composite from the fluid to be stored.
Vacuum forming
Vacuum forming is a simplified version of thermoforming, where a sheet of plastic is heated to a forming temperature, stretched onto a single-surface mold, and forced against the mold by a vacuum. This process can be used to form plastic into permanent objects such as turnpike signs and protective covers. Normally draft angles are present in the design of the mold (a recommended minimum of 3°) to ease removal of the formed plastic part from the mold.
Rotational molding
Rotational Molding (BrE moulding) involves a heated hollow mold which is filled with a charge or shot weight of material. It is then slowly rotated (usually around two perpendicular axes), causing the softened material to disperse and stick to the walls of the mold. In order to maintain even thickness throughout the part, the mold continues to rotate at all times during the heating phase and to avoid sagging or deformation also during the cooling phase. The process was applied to plastics in the 1940s but in the early years was little used because it was a slow process restricted to a small number of plastics. Over the past two decades, improvements in process control and developments with plastic powders have resulted in a significant increase in usage.

7 fillers to enhance the performance of virgin PTFE sealing

PTFE (Polytetrafluoroethylene) has become a commonly used material in sealing applications where other materials do not meet temperature, chemical compatibility, friction, or wear requirements. Many users are unaware that “fillers” may be added to PTFE in order to enhance certain characteristics not found in virgin PTFE. Virgin PTFE possesses “creep” behavior that may reduce effectiveness in mechanical applications.ptfe
Significant deformation of virgin PTFE may occur over time even at room temperatures. The use of fillers improves the physical attributes of virgin PTFE, including creep and wear resistance. Which filler to use certainly depends on the application. Some of the common fillers include:
1,Glass is the most common filler for PTFE. Widely used in hydraulic piston rings, glass gives good wear resistance, low creep, and good compressive strength. Glass also has excellent chemical compatibility. The percentage of glass varies between 5 percent and 40 percent. The major disadvantage is that glass-filled PTFE compounds are abrasive to mating surfaces, especially in rotary applications.
2,Molybdenum disulfide (MoS2) improves wear resistance and further lowers the coefficient of friction. “Moly” is typically combined with other fillers (such as glass and bronze).
3,Carbon imparts excellent compression (low deformation under load) and wear resistance, good thermal conductivity, and low permeability. Carbon-filled PTFE compounds are not as abrasive as glass-filled compounds, but they are still more abrasive than polymer-filled compounds. The percentage of carbon added varies between 5 percent and 15 percent. Carbon-filled compounds have excellent wear and friction properties when combined with graphite. Carbon fiber lends better creep resistance than carbon powder, but fiber is more expensive.
4,Graphite is a crystal modification of high-purity carbon. Its flaky structure imparts excellent lubricity and decreased wear. Percentages of this filler vary between 5 percent and 15 percent. Graphite is often combined with other fillers (especially carbon and glass).
5,Bronze lends excellent wear resistance and thermal conductivity. Bronze-filled materials have higher friction than other filled PTFE compounds, but that can be improved by adding moly or graphite. Bearing and piston ring applications often use compounds containing 55 percent bronze – 5 percent moly. Bronze-filled compounds have poorer chemical resistance than other PTFE compounds. Bronze, when used as a filler, is added in percentages of weight between 40 percent and 60 percent.
6,Ekonol is thermally stable aromatic polyester. When blended with PTFE, it produces a composite material with excellent high temperature and wear resistance. Ekonol will not wear mating metal surfaces, making it good for rotary applications. Ekonol-filled materials are also good for food service.
7,Polyimide is another type of polymeric filler, which offers superior wear and abrasion resistance. Polyimide-filled PTFE compounds have about the lowest friction properties of all filled PTFE materials, so they provide great performance in non-lubricated (dry) applications. They will not abrade mating surfaces (even soft materials such as brass, stainless steel, aluminum, and plastic). Polyimide is one of the most expensive PTFE fillers, however.

Basic Types of Plastic Pipes

Solid wall pipe
Extruded pipes consisting of one layer of a homogeneous matrix of thermoplastic material which is ready for use in a pipeline.
Structured wall pipe
Structured-wall pipes and fittings are products which have an optimized design with regard to material usage to achieve the physical, mechanical and performance requirements.
Structured Wall Pipes are tailor made solutions of piping systems, for a variety of applications and in most cases developed in cooperation with users.
Barrier pipe
Pipe incorporating a flexible metallic layer as the middle of three bonded layers. Barrier pipe is used, for example, to provide additional protection for the contents passing through the pipe (particularly drinking water) from aggressive chemicals or other pollution when laid in ground contaminated by previous use.
Most plastic pipe systems are made from thermoplastic materials. The production method involves melting the material, shaping and then cooling. Pipes are normally produced by extrusion.
Pipe Extrusion
Pipes made from PVC, PE and PP and other thermoplastics are usually manufactured by extrusion. This process starts by feeding plastic material (pellets, granules, flakes or powders) from a hopper into the barrel of the extruder.
The material is gradually melted by the mechanical energy generated by turning screws and by heaters arranged along the barrel.
The molten polymer is then forced into a die, which shapes the polymer into a pipe that hardens during cooling.
A great advantage of extrusion is that pipes can be made to any length. Due to its flexibility, pipes can be made at long lengths even coiling on a reel. Another advantage is the extrusion of pipes with integrated coupler including rubber seal.
Pipes can be connected in a variety of ways to form reliable and leak-free pipe systems. They can be connected by either a push fit joint with rubber seal or by a solvent cement system or by welding.
Straight pipes are mostly connected by pushing the plain end of one pipe into the socketed end of another. This technology is mainly used by PVC and PP piping systems. A variety of fittings are available to make branches or bends or to connect the pipe to other materials.
PE pipes for water pressure and gas distribution can also be connected by welding systems. Two pocesses are mostly used: Butt welding to connect pipe to pipe ends, and electro welding of fittings containing a heating wire to allow melting of materials together. A variety of fittings are available. Welding systems have proven to be very reliable.
Injection Moulding
Fittings such as joints, elbows or T-pieces are usually produced by injection-moulding.
In injection-moulding, the plastic material is fed from a hopper into the melting section of the injection-moulding machine. After melting, the material is transported forward by the screw and homogenised before being injected into the mould to form the shape of the desired product. In the cooling step, the plastic solidifies. Then the mould is opened and the product is ejected.
Blow Moulding
In the blow moulding process, the plastic is melted and extruded into a hollow tube that is then captured by closing it into a cooled metal mould. Air is then blown into the tube – inflating it into the desired shape. After the plastic has cooled sufficiently, the mould is then opened and the part is ejected.
Inspection chambers, manholes, septic and storage tanks are some of the products manufactured by this technique. Typically, these products are much lighter and easier to handle than non plastic materials.
Rotational Moulding
The rotational moulding process is a high temperature, low pressure plastic forming method that uses biaxial rotation to produce hollow, one piece parts. In the plastic pipe industry, it is typically used to make large inspection chambers, water and septic tanks from polyethylene (PE) or polypropylene (PP).

How ordinary items are made using plastic injection molding

Increasing use of thermoplastics in manufacturing took place during the middle of the past century, coming on especially strong during the war years, 1940-45, where many applications substituted the use of plastics for metal. Even in the sixties it was a booming and yet still infant, emerging technology. The 1967 movie, “The Graduate,” starring Dustin Hoffman and Anne Bancroft, made a powerful reference to the promise that plastics held in the American economy when, upon college graduation, the character Benjamin Braddock received a one-word piece of advice from a family friend. “Plastics,” he was told, as if this material was destined to be the next great breakthrough, which it was.
In today’s manufacturing environment, plastics are being used to make everything from automotive body parts to human body parts. Each application requires a special manufacturing process that can mold the part based on specifications. In a previous article on our blog, we break down the various types of plastic molding and their advantages.
Plastic injection molding is a process of forming this durable, resinous material into just about any form or fashion imaginable. The first injection molding machine was invented and patented by brothers John and Isaiah Hyatt in 1872. It resembled a large hypodermic needle, with a heated cylinder through which a large plunger forced the gooey mass into a mold. Today the process is more complicated, although the basic principle of plastic being injected into a waiting mold is still the same. One of the biggest advancements has come by way of the materials used, and there are now thousands of different formulations available for making ‘plastic.’
The first plastic injection molding process was used to produce hair combs, buttons and collar stays. Starting in the 1940s, when high demand existed for mass-produced products that were inexpensive to manufacture, the industry expanded exponentially. In 1946, at war’s end, came the invention of the first screw-type injection machine, which provided for more precise control of a consistent shot, thereby improving the quality of the products being made. Molds were being made for any variety of applications and what was once used to make buttons and combs was now being employed to produce a wide range of items for many industries, including:
Aerospace; Automotive; Consumer products;Construction;Medical;Packaging;Plumbing;Toys;
Raw materials used in the plastic injection molding process include thermoplastics, thermosets and elastomers. Also called polymers or resins, there are more than 20,000 unique formulations that can be injected into molds to produce parts with specific properties to be utilized for specific purposes. Examples of common thermosetting plastics include polymers such as epoxy and phenolic. Common thermoplastics are nylon, polyethylene and polystyrene.
Injection molding machines are fairly simple and straightforward, consisting of a hopper where raw material is placed, a heating cylinder and an injection plunger. Molds are typically made from steel or aluminum. Major advantages to using plastic injection molding for the manufacture of parts include:
Ability to complete high production rates; Repeatability of high tolerances; Low labor costs; Minimal scrap loss; Little need for finishing; Wide range of materials available for specific applications
Whether it’s a snowboard or a vinyl window being produced, injection molding is efficient and economical, especially if large numbers of items are being made. The only real disadvantage is initial start-up costs incidental to obtaining the necessary equipment and the time, expertise and resources required for mold design.
Injection molding is the most common plastic molding process and is used to create a huge variety of complex parts of different size and shape. Products can be produced of a highly complex geometry that other processes are unable to duplicate, and at a fraction of the cost. When one stops to think about the role plastics play in our everyday lives, it’s difficult to imagine a life without this ubiquitous substance. Plastics are now available that are actually stronger than steel, more durable than almost any substance on earth and relatively inexpensive to produce and reproduce a million times over and again.

How to Avoid Injection Molding Defects

When working with any manufacturing process, a number of defects unique to that process commonly occur. This is true across many processes and industries, including plastic injection molding and high volume injection molding.
Resin- and Additive-Caused Defects
Two common defects caused by issues with the resin or resin additives used during injection molding are delamination and discoloration.
Delamination:Delamination, when a finished part has a layer of flaky material at the surface, hurts both aesthetic of your part and its strength. Caused by moisture contamination of the resin pellets or by other contamination of the melted resin with a dissimilar resin, or by release agents in the mold, delamination is the result of the resin being prevented from bonding.
A number of methods, both simple and more complex, can be used to prevent delamination. If moisture is the issue, pre-drying the resin pellets or increasing mold temperature will help. If mold release agents are the cause, a mold redesign that places more focus on the ejection mechanism will help to eliminate mold release. If it is caused by cross-contaminated resins, that will need to be replaced with virgin material
Discoloration:Discoloration is simply when a finished part is a color different than intended. Caused most commonly by leftover pellets in the hopper, too hot of a barrel temperature or leftover resin in the feed zone, the problem can be addressed by thoroughly flushing the hopper and feed zone of a machine in between processes, thus preventing discoloration as a matter of course. Purging compound can also be effective to remove unwanted color or resin.
Process-Caused Defects
Despite continual advances in injection molding technology, process-derived injection molding defects still occur. Two of the most common are burn marks and flow marks.
Burn Marks:Burn marks are surface marks, sometimes advancing to degraded plastic, that are caused by either trapped air which becomes overheated or actual resin that overheats. There are three ways to avoid burn marks: decrease resin injection speeds, which will lower the probability of air becoming trapped; include or optimize venting and degassing systems; or reduce the mold and/or melt temperature.
Flow Marks:Flow marks are lined patterns, often wavy, or discoloration on a part surface. They are most commonly caused by resin cooling too quickly or improper gate location. In the best case scenario, flow marks can be eliminated by increasing injection speed and pressure, which will help to ensure uniform filling and cooling. In a worst case scenario, a mold redesign with an emphasis on avoiding sudden flow direction changes and gate location may be necessary.
Mold-Caused Defects
Flash and short shots are two of the more common injection molding defects caused by mold design or maintenance issues.
Flash:Sometimes known as burrs, flash is the occurrence of thin, wafer-like protrusions on a finished part caused when melted resin escapes the mold cavity. Most common along the parting line or up an ejector pin, flash can be caused by excessive injection speed or pressure, in which case the fix is a simple reduction. More often flash is due to poorly designed or severely degraded molds, in which case a redesign or retooling is required. Flash can also be caused by too high of a mold temperature and excessive barrel heat.
Short Shot:A short shot is literally when a shot of resin falls short of filling the mold. It can be caused by attempting to use the wrong resin type or by poor process settings, but is most commonly caused by gate blockages or too small of a gate diameter, a common problem due to too low pressure or not enough heat. If a higher melt index resin or increased melt temperature doesn’t solve a short shot problem, you may need to redesign the runner system to optimize flow.


Plastic Injection Molding Terms

Parting line – A line on a part formed when the two sides of the mold come together.
Polymer – A substance that has a molecular structure consisting chiefly or entirely of a large number of similar units bonded together, e.g., many synthetic organic materials used as plastics and resins.
Prototype tool – Also called a soft tool, a preliminary mold built to produce prototype parts and used to make adjustments to the final production tool.
Purging – The process of cleaning the injection machine of remnant color or materials prior to running a new part.
Runner system – The channel system that allows the flow of the melted material to fill the part cavities.
Short shot – A defect where the material does not fully fill the part cavity.
Shot – A complete cycle of the injection machine.
Shrinkage – The amount of volume reduction that takes place when a plastic material cools.
Sprue – The opening feed that conveys material from the nozzle to runner system in the mold.
Thermoplastic – A material that can be heated and cooled repeatedly without changing the material structure. Highly recyclable.
Thermoset – A material, which when heated, is pressed or molded into a shape. The heating process changes the structure of these materials, and for this reason they cannot by re-heated.
Undercut – Can be a design flaw that results in an indentation or protrusion that inhibits the ejection of the part from the mold. Other times undercuts are designed into a mold to ensure a part holds onto the correct side of the mold.
Vent – A channel from the mold cavity that allows gas and air to escape as resin is being injected into the cavity to prevent many types of defects from occurring.
Weld line – Also called a knit line, the juncture where two flow fronts meet and are unable to join together during the molding process. These lines usually occur around holes or obstructions and cause localized weak areas in the molded part.
Additives – These compounds are added to resins to improve the overall performance and appearance of finished products. A key trend in this area today is using additives that are made from organic materials such as eggshells, wood pulp, rice hulls or materials that improve the biodegradability of the plastic.
Blister – As the name says, this is a part defect which appears as a small bubble or blister on the surface of a part and it generally created by gas or air bubbles.
Cavity – The machined shape within a mold which created the form of the plastic part.
Colorant – A pigment system, usually in pelletized form, powder or liquid, which is mixed with resin to produce the desired color.
Core – A protrusion or set of matching protrusions, which form the inner surface of a plastic part. They are often considered they “male” side of the part.
Cycle – The overall time it takes for the plastic injection process to complete a finished part.
Degassing – Opening and closing of a mold to allow gas to escape. Trapped gas and/or air can cause parts defects such as blistering and bubbles.
Delamination – This defect appears as a flaky surface layer on the part and is often caused by contamination or moisture in the resin pellets.
EDM or electric discharge machining – A manufacturing process used to create molds, where the shape of the mold cavity is obtained by removing metal material using electrical discharges.
Ejection pin – Metal rods in the mold which push the parts from the mold.
Ejector return pins – Pins that push the ejectors back into position once the parts have been released.
Flash gate – An alternative to a fan gate, which conveys the melted resins into a thinner gate section creating a linear melt flow into the cavity.
Flash or burrs – A thin lip or protrusion beyond the body of the part that is generally caused by poor clamping force, improper mold design and/or mold damage.
Flow marks – A wavy pattern or discoloration caused by a slow injection speed which allows the material to cool too quickly.
Flow rate – The volume of material passing a fixed point per unit time.
Gate – The channel into which melted plastic flows into a mold.
Injection molding – A manufacturing process in which melted plastic is injected into a mold to form a part.
Masterbatch – A solid or liquid additive for plastic used for coloring plastics or imparting other properties to plastics.
Memory – The action of plastic returning to its previous size and form.
Mold – A hollow form that plastic is injected or inserted into to manufacture a plastic part.
Over molding – A two-shot process, in which two plastic substances, are injected into a mold sequentially, usually a harder base material with a coating of softer material.