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Frequently Asked Questions

honing head

Picture by Britton harper of Winona Van Norman, CC BY-SA 3.0, Link

Will honing out a Barrel affect the performance of an Extruder or Injection Moulder?

Barrels hardly ever wear evenly, and therefore a worn barrel needs to be honed to the size of the most-worn section. The maximum amount that a barrel can be honed is dependent on a number of factors including the wall thickness of the barrel, the extrusion pressure generated, the material being processed and the geometric properties (compression ratios etc.) of the screw. All these factors must be considered before a barrel is honed, but in many cases the performance of the barrel and screw can be increased. It is critical that the barrel and screw are assessed and refurbished as a unit.

Used Extruder Barrel

Can a previously Nitrided Barrel be honed?

Yes. Nitrided Barrels are made from steel with a specific alloying of of chromium, aluminium and nickel. The nitriding process creates a layer of hardened material between 0.2 and 0.8mm thick on the surface of the material. Below this layer, the material remains mostly unaffected. The honing process removes the hardened layer, and allows another nitriding cycle to be applied to material.

Grinding a Refurbished Screw

The screw for my machine has broken right through. Can MMTS join an Extruder or Injection Moulder Screw?

Yes. In many cases, a screw will break at the smallest diameter, and the remainder of the screw will still be in good condition. We may be able to repair these screws so that you can put them back into service for a fraction of the cost of a new one. We typically make mechanical joins to ensure durability and reliability, although all screws should be replaced as good practice. It is also possible for us to join twin screws, but these repairs should be regarded as a interim measure which allows the plant to run while new screws are manufactured.

Screw Tip Set with Check Ring

What is a check-ring?

A check-ring is a hollow cylindrical device that is usually part of a tip assembly for an injection moulder screw. The check ring slides forwards during the charging stroke of the screw, allowing the melt to flow into the barrel ahead of the tip assembly. When the screw moves forward to inject the melt into the mould cavity, the check ring seals against the seating washer and prevents the melt from flowing back down the screw. This allows more consistent injection volume and allows the pressure in the mould (cushion) to be held for a period while the melt cools in the mould.

Injection Molder Tie Bars

Pitcture by Glenn McKechnie / CC BY-SA

The tie bar in my injection moulder has broken right through. Can MMTS join and refurbish my tie bar?

Yes. In many cases, a tie bar will break at the smallest diameter or at the threaded end of the tie bar nut, and the remainder of the tie bar will still be in good condition. We are able to repair these tie bars so that you can put them back into service for a fraction of the cost of a new one. The joins are stress relieved and heat treated to ensure durability and reliability. If required, we can manufacture anew tie bar or refurbish it by grinding, chroming and grinding it to OEM specification.

Bundels of plastic for Recycling

I want to start Recycling plastic. Can MMTS help me get going?

Yes. We are able to provide you with a turnkey plastic recycling line that will take post-consumer plastic items like bottles, crates and film and turn it into pellets for onward sale to plastic conversion company.

All we need is for you to estimate what volume and type of plastic that will be recycled each month so that we can configure and size the line appropriately. Then you can produce a business plan and obtain financing. Give us a call and we can discuss your requirements.


PET (PETE) Recycling Symbol

Anton poliakov / CC BY-SA

What is polyethylenetherephthalate? (PET or PETE)

polyethylene terephthalate (sometimes written poly(ethylene terephthalate)), commonly abbreviated PET, PETE, is a thermoplastic polymer resin of the polyester family and is used in synthetic fibres; beverage, food and other liquid containers; thermoforming applications; and engineering resins often in combination with glass fibre. Source

HDPE Recycling Symbol

Anton poliakov / CC BY-SA

What is high Density polyethylene? (HD-PE)

high-density polyethylene (HDPE) or polyethylene high-density (PEHD) is a polyethylene thermoplastic made from petroleum. It takes 1.75 kilograms of petroleum (in terms of energy and raw materials) to make one kilogram of HDPE. HDPE is commonly recycled, and has the number "2" as its recycling symbol. In 2007, the global HDPE market reached a volume of more than 30 million tons. Source

PVC Recycling Symbol

User:Tomia / CC BY-SA

What is Polyvinyl Cholride? (PVC)

polyvinyl chloride, commonly abbreviated PVC, is the third most widely used thermoplastic polymer after polyethylene and polypropylene. Around the world, over 50% of PVC manufactured is used in construction. As a building material, PVC is cheap, durable, and easy to assemble. The PVC world market grew with an average rate of approximately 5% in the last year and will probably reach a volume of 40 million tons by the year 2016.

It can be made softer and more flexible by the addition of plasticizers, the most widely-used being phthalates. In this form, it is used in clothing and upholstery, and to make flexible hoses and tubing, flooring, to roofing membranes, and electrical cable insulation. It is also commonly used in figurines and in inflatable products such as waterbeds, pool toys, and inflatable structures. Source

LDPE Recycling Symbol

Anton poliakov / CC BY-SA

What is Low Density polyethylene? (LDPE)

Low-density polyethylene (LDPE) is a thermoplastic made from petroleum. It was the first grade of polyethylene, produced in 1933 by Imperial Chemical Industries (ICI) using a high pressure process via free radical polymerisation. Its manufacture employs the same method today. LDPE is commonly recycled, and has the number "4" as its recycling symbol. Source

PP Recycling Symbol

Anton Poliakov / CC BY-SA

What is Polypropylene? (PP)

Polypropylene or Polypropene (PP) is a thermoplastic polymer, made by the chemical industry and used in a wide variety of applications, including packaging, textiles (e.g. ropes, thermal underwear and carpets), stationery, plastic parts and reusable containers of various types, laboratory equipment, loudspeakers, automotive components, and polymer banknotes. An addition polymer made from the monomer propylene, it is rugged and unusually resistant to many chemical solvents, bases and acids.

PS Recycling Logo

Anton poliakov / CC BY-SA

What is Polystyrene? (PS)

Polystyrene, sometimes abbreviated PS, is an aromatic polymer made from the aromatic monomer styrene, a liquid hydrocarbon that is commercially manufactured from petroleum by the chemical industry. polystyrene is one of the most widely used kinds of plastic.

Polystyrene is a thermoplastic substance, which is in solid (glassy) state at room temperature, but flows if heated above its glass transition temperature (for molding or extrusion), and becoming solid again when cooling off. pure solid polystyrene is a colourless, hard plastic with limited flexibility. It can be cast into molds with fine detail. polystyrene can be transparent or can be made to take on various colours.

Solid polystyrene is used in disposable cutlery, plastic models, CD and DVD cases, and smoke detector housings. products made from foamed polystyrene are nearly ubiquitous, for example packing materials, insulation, and foam drink cups.

Polystyrene can be recycled, and has the number "6" as its recycling symbol. Unrecycled polystyrene, which does not biodegrade, is often abundant in the outdoor environment, particularly along shores and waterways, and is a form of pollution. Source

1-hexene, an example of an alpha-olefin

Polimerek / Public domain

What is polybutylene terephthalate? (PBT)

Polybutylene terephthalate (PBT) is a thermoplastic engineering polymer that is used as an insulator in the electrical and electronics industries. It is a thermoplastic (semi-)crystalline polymer, and a type of polyester. PBT is resistant to solvents, shrinks very little during forming, is mechanically strong, heat-resistant up to 150&176;C (or 200&176;C with glass-fibre reinforcement) and can be treated with flame retardants to make it noncombustible. It was developed by Britain's Imperial Chemical Industries (ICI).
PBT is closely related to other thermoplastic polyesters. Compared to PET (polyethylene terephthalate), PBT has slightly lower strength and rigidity, slightly better impact resistance, and a slightly lower glass transition temperature. PBT and PET are sensitive to hot water above 60&176;C (140&176;F). PBT and PET need UV protection if used outdoors, and most grades of these polyesters are flammable, although additives can be used to improve both UV and flammability properties. Source

1-hexene, an example of an alpha-olefin

Gmrozz / CC BY-SA

What is a polymer?

A polymer is a substance or material consisting of very large molecules, or macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic and natural polymers play essential and ubiquitous roles in everyday life. polymers range from familiar synthetic plastics such as polystyrene to natural biopolymers such as DNA and proteins. polymers, both natural and synthetic, are created via polymerization of many small molecules, known as monomers. Their consequently large molecular mass, relative to small molecule compounds, produces unique physical properties including toughness, high elasticity, viscoelasticity, and a tendency to form amorphous and semicrystalline structures rather than crystals. Source

1-Hexene, an example of an alpha-olefin

H Padleckas / Public domain

What is a polyolefin?

A polyolefin is a type of polymer produced from a simple olefin (also called an alkene with the general formula CnH2n) as a monomer. For example, polyethylene is the polyolefin produced by polymerizing the olefin ethylene. polypropylene is another common polyolefin which is made from the olefin propylene. Source

polyolefins are impossible to join by solvent cementing because they have excellent chemical resistance and can only be adhesively bonded after surface treatment because they have very low surface energies. They are also extremely inert chemically and exhibit decreased strength at lower temperatures.

polyolefin is used for blown film as well as rash guards or under garments for wetsuits. polyolefin eloastomer pOE is used as a main ingredient in the molded flexible foam technology such as in the fabrication of self skinned footwear (think Crocs shoes), seat cushions, arm rests and spa pillows etc. Source

Furface Finish

What is Surface Finish?

Roughness is a measure of the texture of a surface (the finish after a manufacturing process). It is quantified by the vertical deviations of a real surface from its ideal form. If these deviations are large, the surface is rough; if they are small the surface is smooth.

Roughness plays an important role in determining how a real object will interact with its environment. Rough surfaces usually wear more quickly and have higher friction coefficients than smooth surfaces (see tribology). Roughness is often a good predictor of the performance of a mechanical component, since irregularities in the surface may form nucleation sites for cracks or corrosion.

Although roughness is usually undesirable, it is difficult and expensive to control in manufacturing. Decreasing the roughness of a surface will usually increase exponentially its manufacturing costs. This often results in a trade-off between the manufacturing cost of a component and its performance in application. Source

Emok / Public domain

honed Barrel or Cylinder

What is honing?

honing is a manufacturing process that produces a precision surface on a workpiece by scrubbing an abrasive stone against it along a controlled path. honing is primarily used to improve the geometric form of a surface, but may also improve surface texture.

honing is classified as an abrasive machining manufacturing process. As with all abrasive machining processes, material is cut away from the workpiece using abrasive grains. In the case of honing, the grains are bound together with an adhesive to form a honing stone (or hone). Generally, honing grains are irregularly shaped and about 10 to 50 micrometers in diameter (300 to 1,500 mesh grit). Smaller grain sizes produce a smoother surface on the workpiece.

A honing stone is similar to a grinding wheel in many ways, but honing stones are usually more friable so that they conform to the shape of the workpiece as they wear in. To counteract their friability, honing stones may be treated with wax or sulfur to improve life; wax is usually preferred for environmental reasons.

Any abrasive material may be used to create a honing stone, but the most commonly used are corundum, silicon carbide, CBN or diamond. The choice of abrasive material is usually driven by the characteristics of the workpiece material. In most cases, corundum or silicon carbide are acceptable, but extremely hard workpiece materials must be honed using superabrasives. Source

Single Screw extruder Barrel

What is a Nitrided Barrel / Nitriding?

Nitriding is a process which introduces nitrogen into the surface of a material. It is used in metallurgy, for example, for case hardening treatment of predominantly steel but also for titanium, aluminium and molybdenum. Nitriding is widely used in automotive, mechanical and aeronautical engineering. Typical components receiving this metallurgical process are gears, crankshafts, camshafts, cam followers, valve parts, extruder screws, die-casting tools, forging dies, extrusion dies, injectors and plastic-mould tools.

All nitriding processes enrich the surface of a material with nitrogen. processes are named by the medium used to donate nitrogen. The three main methods used are gas nitriding, liquid or salt bath nitriding or ion (plasma) nitriding.

A nitrided barrel is usually made from a carbon steel with a combination of nickel, chromium and aluminium to produce an alloy that most readily accepts the nitriding process.

Bimetalillic Barrel and Screw

What is a Bimetallic Barrel?

A bimetallic barrel has a hardened alloy layer fused to the inner bore of the barrel. The hardened layer is intruduced into a barrel blank as a powder. The barrel is placed in a high temperature furnace that subjects the powder to temperature of more than 1100 deg C while spinning the barrel, which fuses them together. Barrel cooling is carefully controlled on removal from the furnace and this results in a super-hard, highly uniform lining in the bore. The inner layer is then precision honed and the resutling bore lining is at least 1.5mm thick.

Universal plastic Recycling Symbol

Users Cbuckley, Jpowell on en.wikipedia / Public domain

What is plastic?

Plastic is the general common term for a wide range of synthetic or semisynthetic organic amorphous solid materials suitable for the manufacture of industrial products. plastics are typically polymers of high molecular weight, and may contain other substances to improve performance and/or reduce costs.

There are two types of plastics: thermoplastics and thermosets. Thermoplastics, if exposed to enough heat, will melt. Thermosets will keep their shape until they are charred and burnt. Some examples of thermoplastics are grocery bags, piano keys and some automobile parts. Examples of thermosets are children's dinner sets and circuit boards.

Common plastics and uses :

  • Polypropylene (PP) : Food containers, appliances, car fenders (bumpers).
  • Polystyrene (PS) : packaging foam, food containers, disposable cups, plates, cutlery, CD and cassette boxes.
  • High impact polystyrene (HIPS) : Fridge liners, food packaging, vending cups.
  • Acrylonitrile butadiene styrene (ABS) : Electronic equipment cases (e.g., computer monitors, printers, keyboards), drainage pipe.
  • Polyethylene terephthalate (PET) : Carbonated drinks bottles, jars, plastic film, microwavable packaging.
  • Polyester (PES) : Fibers, textiles.
  • Polyamides (PA) (Nylons) : Fibers, toothbrush bristles, fishing line, under-the-hood car engine mouldings.
  • Poly(vinyl chloride) (PVC) : plumbing pipes and guttering, shower curtains, window frames, flooring.
  • Polyurethanes (PU) : Cushioning foams, thermal insulation foams, surface coatings, printing rollers. (Currently 6th or 7th most commonly used plastic material, for instance the most commonly used plastic found in cars).
  • Polycarbonate (PC) : Compact discs, eyeglasses, riot shields, security windows, traffic lights, lenses.
  • Polyvinylidene chloride (PVDC) (Saran) : Food packaging.
  • Polyethylene (PE) : Wide range of inexpensive uses including supermarket bags, plastic bottles.
  • Polycarbonate/Acrylonitrile Butadiene Styrene (PC/ABS) : A blend of PC and ABS that creates a stronger plastic. Used in car interior and exterior parts, and mobile phone bodies.

Special-purpose plastics :

  • Polymethyl methacrylate (PMMA) : Contact lenses, glazing (best known in this form by its various trade names around the world; e.g., Perspex, Oroglas, Plexiglas), aglets, fluorescent light diffusers, rear light covers for vehicles.
  • Polytetrafluoroethylene (PTFE) (trade name Teflon) : heat-resistant, low-friction coatings, used in things like non-stick surfaces for frying pans, plumber's tape and water slides.
  • Polyetheretherketone (PEEK) (polyetherketone) : Strong, chemical- and heat-resistant thermoplastic, biocompatibility allows for use in medical implant applications, aerospace mouldings. One of the most expensive commercial polymers.
  • Polyetherimide (PEI) (Ultem) : A high temperature, chemically stable polymer that does not crystallize.
  • Phenolics (PF) or (phenol formaldehydes) : high modulus, relatively heat resistant, and excellent fire resistant polymer. Used for insulating parts in electrical fixtures, paper laminated products (e.g., Formica), thermally insulation foams. It is a thermosetting plastic, with the familiar trade name Bakelite, that can be moulded by heat and pressure when mixed with a filler-like wood flour or can be cast in its unfilled liquid form or cast as foam (e.g., Oasis). problems include the probability of mouldings naturally being dark colours (red, green, brown), and as thermoset difficult to recycle.
  • Urea-formaldehyde (UF) : One of the aminoplasts and used as a multi-colourable alternative to phenolics. Used as a wood adhesive (for plywood, chipboard, hardboard) and electrical switch housings.
  • Melamine formaldehyde (MF) : One of the aminoplasts, and used as a multi-colourable alternative to phenolics, for instance in mouldings (e.g., break-resistance alternatives to ceramic cups, plates and bowls for children) and the decor