Cable ties are bands or straps made from the polymeric materials referred to as polyamides. The cable tie’s length or surface has hooking mechanisms, which allow for locking when binding items together. The ties come varying colors and sizes and they have a clasp at one end, near a thin strap with a pointed and ribbed end?
The cables function as fasteners for bundling items together, especially electrical wires and cables. Cable ties are usually low cost and easy to use, and for that reason, they find use in an extensive range of applications. ?
Cable Tie Raw Materials- Types of Nylon
Cable ties were first commercially produced in 1938. The first cable tie material of choice was nylon synthetic polymer, its physical properties stacked favorably against others. The nylon polymer has high strength and reliable temperature resistance. That makes it easy for the material it finds use in engineered work – therefore, it falls into the group of polymers referred to as engineering thermoplastics
Nylon materials comprise of a group of resins, that contain the amide group -CONH-. During polymerization, small amide monomers are linked together to form a long polymer chain called polyamides.
Nylon has remarkable properties, including strength, stiffness, toughness and high service temperature. Nylon zip ties are popular because they are highly resistant to the effects, and have a desirable friction coefficient, and perfect abrasion. The material is also resistant to lubricants, chemicals and other fuels. However, nylon is not immune to more strong acids, phenols, and other oxidizing properties.
Other concerns include the material’s susceptibility to environmental conditions. It is for that reason that
Cable ties have to be moisturized to for optimal performance. All Nylon cable ties need to be stored in cool, dry places, away from direct sunlight. Taking measures such as these will help to extend the cable tie performance levels and durability,
General-purpose nylon can work in most applications at stable temperatures of upto 185 F. On the other hand Nylon 6/6, a sturdy nylon grade that is most preferred for the cable tie manufacturing, meets the UL 94V-2 flammability. The materials can work well in temperatures ranging from -40 F – 185 F.?
Nylon 66 is a raw material comprising of two monomers each with six carbon atoms, plus Adipic acid and hexamethylenediamine. Nylon 66 is is a material that combines Propylene, Benzene with Adipic Acid and HMD. These raw materials are often known as Feedstocks.
Another form, Heat Stabilized 6/6 can be used in a high temperature of up to 250 F. In the same temperature; general- nylon will depreciate in the physical properties as well wear out due to the high temperatures. The Nylon cable together with the special heat stabilizers have more heat endurance. These stabilized nylons are well designed and targeted for continuous exposure to the high-temperature range of 185 F. The materials meet the UL criterion for electrical use.
UV Stabilized 6/6 Nylon can work well in continuous or even in extended exposure. Such nylon cable ties are weather resistant, additional ultraviolet light. The grade is usually produced when the stabilizers in the nylon resin are incorporated. The Stabilized UV nylon cable ties are normally available only in the black color.
The Injection Molding Process
Cable Ties are made through the injection molding process. The standard cable ties use Nylon 66 as the raw material. In the process, nylon 66 pellets are loaded into the injection molding machine and usually heated to a molten state. After they are molten the Nylon 66 materials through pressure, are wwell injected into steel molds with numerous cavities shaped in the form of Cable Ties.
Individual plastic molds are grouped side by side to create a batch of cable ties in a single stroke of molten injection. It doesn’t take long before finished Cable Ties are removed from the steel molds, conditioned and packaged ready for shipment. Cable ties are usually made in batches of varying numbers informed by size. If the cable ties are small size, there will be many ties in one batch.
Cable Tie Manufacturers like to label each mold with some identification mark at the point of production. The label could either be a number, a letter or the company logo in some cases. These marks come in handy when the manufacturer starts doing quality control to remove defects or blocking or identify faults in the molding cavities.
During the production of long ties like the ones sized 370 x 4.8 millimeters, a few molds will be present in the molding cavities, thereby leading to the production of a few cable ties for every injection of plastic. If molding cavities labeled A-Z are used, ties consecutively marked A-Z are produced.
Usually, manufacturers create back-up molds to replace faulty ones identified during quality control.
The design and shape of a cable tie are dependent on the size and shape of the molding cavity used during the production process. Each manufacturer has different ways of achieving unique shapes, colors, and length of its cable ties. The manufacturing process also has to minimize microscopic markings during manufacturing. These could include striations, protrusions, and indents caused by fine irregularities in the molding cavities and the pins that used to remove the ties from the cavities.?
The Molding Machines
Injection molding machines can have a vertical or horizontal orientation. Many of the machines are horizontally oriented, even though some niche applications work with vertical machines to utilize gravity. In some vertical machines, manufacturers don’t have to face the molds. There are several ways of fastening the tools to the platens but mostly, manual clamps used. ?
The mold can use a cold runner system or a hot runner system to channel the plastic and fillers to the cavities. A cold runner uses A channel carved into the shape of the mold. The nylon in the cold runner cools and is ejected as a sprue. A hot runner is more intricate, using cartridge heaters to maintain a high temperature of the plastic in the cavities as the part cools.
The molding machines can be hydraulic, mechanical or electrical
Hydraulic presses were the first ones to be used. They are not as precise mechanical or electric molding machines.?
These machines use a toggle system for building up pressure on the clamps. This force is needed to keep the clamp side from opening due to the injection pressure.?
Electric injection molding machines reduce the energy consumption of the hydraulic machines. These machines are quieter and faster and are known to have higher accuracy. However, they are more expensive.
Why Special Machines Are Needed During Cable Tie production?
The nature of cable ties demand so
All multipurpose cable ties tend to be long, narrow and thin. They come in various lengths, widths, and varying strengths.
Successful molding is an involving process
When pouring the molten nylon 66 into the molding cavities, the machine must push the nylon material from top to bottom in a very short time, so that it doesn’t freeze midway.
Pressure is needed
When pushing the molten material into the molding cavities, the process requires a high injection speed and pressure. This force will naturally be-be transferred to the clamping unit on the machine. If the force is not enough, the mold can be blown open.
Cable tie molding cavities are long and narrow
The fact the molding cavities are long and narrow means that it would take a unique design of the toggles and the whole clamping structure to focus the force at the center of the moving platen. In case the toggles and the clamping units do not function as required to move the platen, the molds will have a problem caused by an uneven force.
Injection speed needs to be high
There are customized molding machines that can increase injection pressure and injection speed by raising pump and motor capacity. This helps to fill the cavity fast for successful molding. Nevertheless, with each injection and clamping, there will be a greater impact on the toggles and the same force will be transmitted to the clamping unit. If these components are not ready to absorb the pressure, they will quickly wear out.
Also, the reason why the injection molding needs special equipment is the fact that the process is mostly used in mass production. A single cable tie in itself is not worth the process. The energy needed in preparing the plastic and forcing it into the molding cavity as well as keep the mold clamped is so high. For that reason, it is cost effective to mold many of them in tandem.
The most special aspect of the cable tie injection machine is the molding tool. But there are usually problems around getting the molten plastic to all parts of the mold before the starts deteriorating. That can often be solved by gating. Some molding machines use hot runners that prevent the plastic from freezing or hardening while in the cavities.
To sum it up, nylon cable ties are made using a molding injection process. The process is intricate, and the machines are special, using either hot or cold runners. During the process, the material is kept at the right temperature and moisture content for optimal cable structures.