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acetal-plastic-screws-nuts
22 Sep
0 33 Post by

POLYOXYMETHYLENE

Acetal is an engineering thermoplastic. It is also known as polyoxymethylene or POM. POM is used in precision parts that require high stiffness, low friction, and dimensional stability. POM is known for its high strength from -40 degrees C to 80 degrees C. Natural POM is an opaque white material. However, it can easily be dyed to almost any color. It has a high crystalline composition. And is available as a homopolymer and a copolymer. Different chemical companies sell POM under different names, including Delrin®by DuPont and Celcon® by Celanese. However, it is not UV resistant and additives are required to make it useful in the sun’s rays.

ACETAL COPOLYMER VERSUS ACETAL HOMOPOLYMER

Acetal copolymer and homopolymer are two types of POM. Although these are very similar, they are not exactly the same material. The difference is in the structure of each. Acetal homopolymers have chains made of one monomer, while acetal copolymers have chains made of two different monomers. For many applications, either will perform well as most properties are within 10% of each other. However, there are important differences.

CHARACTERISTICS OF POM (ACETAL)

Both homopolymer and copolymer POM has the following characteristics:

  • Creep resistant
  • Excellent mechanical stability
  • Good electrical insulating and dielectric properties
  • Strong, rigid, and tough
  • Excellent moisture resistance, low water absorption
  • Low coefficient of friction, high lubricity
  • Chemically resistant. Mostly unaffected by solvents and fuels.
  • Low thermal expansion
  • High stiffness and hardness, therefore a good alternative to metals
  • FDA approved
  • Easily machined and molded
  • Easy to color


    Negatives
  • Acetal cannot be painted.
  • Flammable and heat sensitive
  • Does not adhere well to other objects due to high lubricity
  • Does not perform well in Chlorine and thus is not for swimming pool use.


    Acetal Copolymer
  • Acetal copolymer is a semi-crystalline thermoplastic. Importantly, the copolymer has the advantage of reduced centerline porosity. In addition,  the copolymer has better chemical properties. It has good pH resistance from pH 4-9. It is hydrolysis resistant up to 60 degrees Celsius. The continuous service temperature in the air is 90 degrees Celsius. And the acetal copolymer exhibits higher out-gassing. It is available in natural and black. In addition, the copolymer is a little cheaper.

ACETAL HOMOPOLYMER

Acetal homopolymer is a crystalline thermoplastic. Thus, it is the ideal material to replace metal parts. However, the negative side of the homopolymer is that it exhibits centerline porosity. Generally, the homopolymer has better mechanical properties:

  • 15% higher stiffness and strength.
  • 10% better creep resistance
  • Higher Rockwell hardness rating
  • Natural grade is FDA, NSF, and USDA compliant
  • Higher tensile strength
  • Significant impact resistance

Why Use Delrin® (Acetal Homopolymer) To Replace Metals

Delrin®has high tensile strength as well as low friction, and high wear resistance. In addition, it has low creep, is resistant to warping, and is overall tough and durable. Delrin® has low moisture absorption and is chemically resistant to hydrocarbons, solvents, and neutral chemicals.

While acetal copolymers exhibit some of these characteristics, it is the unique combination of properties that makes the acetal homopolymer the right plastic to replace metals in some applications.

This is not to say that Delrin® is as strong as metals. It is not. However, Delrin keeps on performing in applications such as pump and valve components where parts are exposed to moist or wet environments. Metals may fail while Delrin® keeps on performing.

APPLICATIONS

Typical applications for POM include high-performance parts such as gears, safety restraints, bearings, bushings rollers, fittings, and electrical insulator parts. Many parts such as screws, hex nuts, and washers, hex bolts and many other parts are made of. Also, it is used to make consumer products such as eyeglass frames, ski bindings, guns, and knife handles. Additionally, Delrin® is used widely in the consumer electronics industry. And it is preferred by the automotive industry for use on car interiors because of its impact strength.

Parts, Prints, or Problems. Contact us at Craftech Industries, Inc.

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Categories: Fasteners, Material, Plastic Material
06 Sep
0 55 Post by

HOW IT ALL STARTED

Legos first entered our house about 4 years ago. It started with a present for the first birthday party that my son was invited too.  Afterwards it was only a matter of time before I gave in to my son’s pleas for a Lego set of his very own.  So I admit that, over the years, I have enabled my son’s Lego addiction.  Yes, you read that right, addiction.  A set of Legos with a remote control train set was my most recent enabling gift this past Christmas. 

SO LEGOS MADE FROM FROM WHAT POLYMER?

Eventtually during one of my many attempts to tidy the “Lego Room,” I made a note to myself to find out which plastic material the Lego company uses.  Since I work in the plastics industry, I was naturally curious.  There are so many different sized bricks and colors, supporting parts, doors, windows, and figures in a variety of themes-a myriad of pieces beyond belief.  So I thought the design and manufacturing process must be impressive to say the least.  Here’s a brief rundown on the history of Legos and how they’re made. 

THE HISTORY OF LEGOS

A carpenter from Billund, Denmark named Ole Kirk Christiansen started making wooden toys in his workshop in 1932.  His company came to be called “Lego” in 1934 from the Danish phrase “leg godt”, meaning “play well.” In 1947, the company expanded to producing plastic toys.  An early version of the now famous interlocking bricks started to be produced in 1949. 

By 1954, Christiansen’s son, Godtfred saw the immense potential in Lego bricks to become a system for creative play.  (I’d say hit a home run on that one. )  The modern brick design was developed in 1958 to address limited locking ability and versatility.  But it took another 5 years to find the right material which was ABS.  In 1958, the modern Lego brick was patented.

ACRYLONITRILE BUTADIENE STYRENE OR ABS

Basically ABS or acrylonitrile butadiene styrene is the plastic used in the most modern Lego elements.  This is just one of the materials we are familiar with at Craftech, since we machine parts out of ABS bar stock and injection mold the resin form.  The butadiene component (a derivative of natural rubber) is largely responsible for the strength and impact resistance of this plastic. 

The modern formula for ABS was developed as part of the war effort in the mid-1940s.  Bayer AG, a German chemical company, had long been the exclusive supplier to the LEGO group.  It spun off most of its plastics business in 2004 into the newly-formed Lanxess AG.  Virtually all plastic used by LEGO is a proprietary version of Lanxess’ Novodur ABS, Makrolon polycarbonate (for transparent elements) and Macrolex dyes for coloring.   Delrin or nylon variants are used to make cloth and string elements.

HOW LEGOS ARE MADE

Legos are injection molded.  Basically silos of material are available with pipes that feed plastic granules to the molding machines.  Each silo holds up to 33 tons of granules.  The molding process is almost completely automated. The molding machines heat up the granules to a temperature of about 450°F (230°C).  The plastic is then fed into molds.  The machine applies hundreds of tons of pressure to make sure the bricks are shaped with perfect accuracy.  After that they are cooled and ejected, which takes about 10 seconds.  Finished pieces go down conveyor belts into boxes. 

PACKAGING

When the boxes are full, a radio signal is sent by the molding machine to robot trucks that patrol the hall.  The robot trucks are guided by grooves in the floor.  After that the boxes are brought to an assembly hall where a giant printer stamps decorative details on faces, control panels, numbers, and words.  Finally the last step is to put the right components together to make a LEGO set.  Boxes, called “cassettes,” roll on conveyor belts underneath the bins that hold each type of piece.  And the right number of pieces is automatically released into each cassette.  Afterwards the package operators close the boxes and add additional pieces and building instructions. 

CONCLUSION

So now I feel a little more enlightened about this product and what it takes to get it on the shelf.  After all I may have this product in my house for a few more years, since son #2 has already been hard at work adding to his brothers’ masterpieces.

Are your children in love with Legos?  Tell me your Lego story in the comments section below. 

Problems, Prints, Parts?

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Categories: Plastic Material
09 Aug
0 178 Post by

You have a plastic part in your hand. How do you determine what plastic it is made of? Here are four good places to start:

  • Plastic Resin Identification Codes
  • Burn Test
  • Floats or Sinks in Water
  • Unique Appearance

PLASTIC RESIN IDENTIFICATION CODES

The plastics identification codes were developed in 1988 by the SPI Society of Plastic Industries. These codes are intended to be recycling codes. #1 is polyethylene terephthalate (PETE, PET), and #2 is high-density polyethylene (HDPE). #3 polyvinyl chloride (PVC), #4 low-density polyethylene (LDPE), #5 Polypropylene (PP) #6 Polystyrene (PS) while #7 Misc. includes polycarbonate (PC), nylon, ABS, acrylic, and polylactic acid (PLA).

Indeed knowing what object you have is an important clue to knowing what plastic it is made from. For example, if you are holding a milk jug the material is probably high-density polyethylene. But a plastic container that once held laundry soap and most colored containers are also made of HDPE. Often trash bags are made from low-density polyethylene.

However if the object has a code molded into it or written on its label, you will know what plastic it is made of for sure. For example, the objects below are coded number five, so we know they are made from polypropylene. And of course, a Styrofoam cup will usually have a 6 on the bottom of it.

THE BURN TEST

The burn test is another way to get information about what plastic a part is made of. It is important however that this test be performed in an industrial setting with the correct equipment as some burning plastics can release carcinogens. Also, molten plastics are very hot, and some will drip. Heat the plastic with a lighter until it burns using the proper ventilation equipment.

MaterialOdorColor of
Flame		DipsFloats in Water
ABSacrid. black
smoke w soot		orangenono
PETE, (PET)light smokeyellowyesyes
PTFEburnt hair——-nono
Nylonburnt wool or
hair		blue, yellow
tipped		yesno
Polycarbonatefaint, sweet
aroma, black
smoke w soot		orangeyesno
Polyethylenecandle waxblue, yellow
tipped		yesyes
Polypropylenesweet odorblue, yellow
tipped		noyes
Polystyrenegas odor,
(naptha)		yellow, black
smoke		yesno
PVChydrochloric
acid		yellow w green
spurts		nono
Polyestershydrochloric
acid		yellownono

FLOATS OR SINKS IN WATER

Plastics all have a particular density. Not all plastics float on water. If the density of the material is greater than water, it will sink. If it is less dense, it will float. We have all read about the amount of plastic waste floating in the earth’s oceans. The Great Pacific Garbage Patch in the north-central Pacific Ocean is the largest accumulation in the world. So it must be made of plastics that float on water. Sadly, not one square mile of the surface ocean is free from plastic waste.

PLASTICS THAT FLOAT

There are three plastics that float on water. And all have a density of less than that of water. These are HDPE, LDPE, and PP. See the chart below. Since plastics can vary in density when they are manufactured, there is a range of values indicated for each plastic.

Density Table (G/mL)

Water 1.00
(1) PETE (PET) 1.38-1.39
(2) HDPE 0.95-0.96
(3) PVC 1.16-1.35
(4) LDPE 0.92-0.94
(5) PP 0.90-0.91
(6) PS 1.05-1.07
(7) Others. Nylon 1.14, polycarbonate 1.2, acrylic 1.15, etc.

PLASTICS THAT SINK

To understand what plastic the object you are holding is made from knowing if it will sink in water is auseful. So higher-density plastics such as PET (polyethylene terephthalate), PVC (polyvinyl chloride), and PS (polystyrene), do sink. PETE (or PET) is used to make single-use plastic drink bottles. Since the density of PETE is 1.38-1.39 many of those bottles we use and do not recycle may wind up sinking to the bottom of the oceans.

PVC is made into sheeting, rope, blood bags, and medical tubing as well as siding and flooring to name just a few of its uses. After polyethylene, PVC is the most widely used plastic in the world. And PVC also sinks. Finally, polystyrene is made into hot cups and clam shells for hamburgers and other food we eat on the go. With a density of 1.05 to 1.07, PS will also sink.

NYLON

Most nylon produced is used to make clothing and carpet although all clothing and carpet are not necessarily made of nylon. But with a density of 1.14, it will sink. Additionally, if the smell the material gives off in the burn test is that of burnt wool, if the flame is blue with a yellow tip, if the molten plastic drips, and it does not continue to burn when the flame source is removed, what you have is pretty sure to be nylon.

TEFLON (PTFE)

Teflon (PTFE) is a polymer known for its chemical resistance and ability to withstand high heat applications. It also has a characteristic appearance. It is generally very white in color and has a waxy feel. Additionally Teflon is notably soft, so much so that you can use your thumbnail to make an indent in it.

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Categories: Material, Plastic Industry
29 Jun
0 174 Post by

Resin Identification Codes or RIC were first introduced in 1988 as the “Voluntary Plastic Container Coding System” by The Society of the Plastics Industry (now called the Plastics Industry Association). The intent was to make it easier to identify what plastic objects were made of. Thus the codes made it easier to know whether to either recycle or dispose of them.

However, since 2008 the codes have been administered by ASTM International, an international organization of standards. After that the original coding system became ASTM D7611-Standard Practise for Coding Plastic Manufactured Articles for Resin Identification. In 2013 the graphic for the various codes was changed from a number surrounded by a triangle of three chasing arrows to a number surrounded by a triangle.

Meaning Of Resin Identification Codes

The resin numbers go from 1-7 with 1 being the easiest to recycle and 7 the least. So 1 and 2 can usually be recycled while 6 and 7 are usually disposed of. And for 3, 4 and 5… well that depends. Thus while an RIC code on a plastic object may mean it can be recycled, it does not necessarily means that nor does the absence of the code indicate it cannot be recycled.

Meaning of Resin Manufacturing Codes

The uses in this paragraph are original manufacture uses.

  1. Polyethylene terephthalate (PETE, PET): Soft drink bottles, tote bags, polyester fibers, thermoformed sheet, carpets, and furniture. Additionally, cold drink cups, peanut butter and salad dressing containers, and water bottles.
  2. High density polyethylene (HDPE, PE-HD): Juice and clear bottles, grocery bags, milk jugs, playground equipment, plastic lumber, trash can liners, butter and yogurt containers.
  3. Polyvinyl chloride (PVC): Pipes, siding, fencing, non-food bottles such as detergent containers. Also cooking oil bottles, toys, plastic floors, lawn chairs, clear wrap for food, bottles for window cleaner.
  4. Low density polyethylene (LDPE, PE-LD): Six pack rings, tubing, plastic bags, containers, and squeeze bottles as well as bread and frozen food bags.
  5. Polypropylene (PP): Auto parts and industrial fibers. Plates, bowls and cutlery, food containers. Also syrup and catsup bottles.
  6. Polystyrene (PS): Coffee cups and lids, as well as clamshell containers, egg cartons as well as packaging peanuts and other packaging materials.
  7. Other or O: Includes acrylic, nylon, polycarbonate, polylactic acid (PLA), and multiple combinations of different plastics. Bottles, safety glasses, food packaging, plastic lumber, headlight lenses.

Recycling

According to the United Nations Environment Program less than 10% of the plastic waste generated worldwide has ever been recycled.

  1. PET, PETE: These are recyclable and should be washed and dried before being put in your recycling bin. This plastic is turned into flakes and used to spin carpet fiber, fiberfill and tote bags.
  2. HDPE is very resistant to deterioration. These items should also be rinsed and dried before disposal. It is recycled into among other things plastic fencing, picnic tables and lawn chairs.
  3. PVC can break down into dangerous chemicals like vinyl chloride. It is reprocessed into items like traffic cones, garden hoses and floor mats.
  4. LDPE is considered a safe plastic for human food use and does not leach any chemicals. It is reprocessed into trash can liners, composite lumber and piping.
  5. PP is safe to be reused. All items should be rinsed and dried before putting them in your recycling bin. PP can be re-manufactured into brooms, bike racks, ice scrapers and bins.
  6. PS is lightweight and does not break down easily. Because of its light weight it takes a very large amount to recycle the plastic. Thus it is not economical for reprocessors to accept.
  7. As described above this is a group of plastics that are less used and therefore are not generally recycled.
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Categories: Material, Plastic Industry
29 Jun
0 271 Post by
Can a simple wax worm cause the decomposition of polyethylene? Over three trillion single-use plastic bags are produced every year.
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Categories: Plastic News
06 Jun
0 117 Post by

WHAT IS AN INJECTION MOLD?

An injection mold is a tool that when all the parts are assembled fits into an injection molding machine to manufacture identical plastic parts. Injection molds start with a drawing of the part required for the required application. Then an engineer with knowledge of the injection mold-making process creates a drawing of all the parts of the mold.

Making an injection mold takes a great deal of skill and some very expensive machinery. They are generally made out of tool steel by CNC machines. They are the negatives of the actual part required. There is also a runner system that allows the hot plastic to fill all the mold cavities in addition to channels that help cool or heat the mold thus controlling its temperature. About 10% of a typical injection molding cycle is dedicated to actually injecting the molten plastic. The remaining percentage is dedicated to cooling and solidification, packing, and holding.

The simplest injection mold is a straight-pull injection mold consisting of two halves. The “A” side and the “B” side. The front side or A side faces the cavity and is referred to as the cavity. The B side faces the cavity and is known as the core mold. However, not all injection molds follow this simple pattern.

PARTS OF AN INJECTION MOLD

The engineer designing the mold will decide if it requires an insert tool or a free-standing mold.

To make a free-standing injection mold manufacturers buy pre-made mold bases from one of several worldwide companies such as Misumi, DME or Hasco.

An injection mold will include cooling lines, a runner system, a sprue, cavities, and gates. Injection molds also have threaded holes for eye bolts that are used in mounting the mold in a molding machine. Additionally, they have guide pins for lining the mold up on a workbench so that alignment of the A and B sides is not necessary once the mold is in the machine.

EJECTING A PART

Once a part solidifies, it is ejected from the mold with an ejection pin, pins, and sleeves or using any one of the other methods including ejector plates, air ejection, and more.

EDM (ELECTRONIC DISCHARGE MACHINE)

But some parts have a cavity that cannot be readily milled. In this case, an electrode made out of graphite or copper tungsten is turned on a CNC machine and then placed in the bath of an EDM (electronic discharge machine.) The EDM will erode the steel to form a cavity exactly the shape of the electrode. There are two types of EDM: sinker and wire. A sinker EDM is designed to make a cavity while the wire EDM uses a fine brass wire to cut simple or compound shapes.

THE RUNNER SYSTEM

The runner system allows the liquid plastic to flow into the cavities. There are three main sections to the runner system of an injection mold: the sprue, the runner, and the gate.

A sprue is hooked up to the nozzle of the molding machine barrel. The molten plastic is delivered by the reciprocating screw to the nozzle and thus through the sprue. Then the material flows into the runners. Finally, the molten plastic will fill each cavity through the gate. Gas may be released through a vent. A vent can be used to release gasses.

INJECTION MOLDING MACHINE

An injection molding machine is made up of a loader, a reciprocating screw, the barrel, the nozzle, and a platen. During this process, polymer granules are first put into a dryer to remove moisture. Then the granules are moved into the barrel where they are heated to the melting point of the plastic being used. A large reciprocating screw runs through the barrel and moves the plastic along until it reaches the nozzle. It is injected through the nozzle into the mold which is installed on the platen. After the plastic cools, the mold opens, and the plastic parts are knocked out by ejector pins. The cycle is usually repeated every 60-90 seconds.

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Categories: Injection Molding
07 Jan
0 140 Post by
PEEK or polyetheretherketone is a high-performance, engineered plastic. It is one of the materials of choice medical implants such as spinal replacement disks as well as trauma fixation. Trauma fixation is the repair of broken bones or any bodily injury that can result from force or violence applied to the human body.
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Categories: Fasteners, Material, Medical Industry
carbon-fiber-plastic
11 Mar
0 265 Post by
The use of carbon reinforced fibers in plastic materials has a long history.  As early as 1879, Thomas Edison was experimenting with carbon fibers made from cotton threads and bamboo slivers.  In fact, the first incandescent light bulb heated by electricity contained carbon fibers.
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Categories: Material, Plastic Material, Plastic News
01 Feb
0 208 Post by
Carbon Fiber Reinforced Plastics (CFRP) have long been used in high-performance race cars. However, the cost, as well as the manufacturing time of components, has made CFRP prohibitive for consumer applications. But that is changing.
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Categories: Material
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