Braiders Rock Solid Equipment - By Fred Noer in the Wiring Harness News (May/June 01)

Nothing gives a nicer appearance to a wiring harness than braiding. The uniform pattern of the threads or wires cannot help but add higher quality and attractiveness to a finished product, which may be enhanced with braids in various colors or textures.

 

Whether done to meet a job specification or sold as a value-added option, braiding has increased 500 percent in the wiring harness industry since the mid-1960s, according to Jack Dennehy, owner of Composite & Wire Machinery (CWM) in North Kingstown, R.I. He knows wiring harness braiding well, having sold braiding machines the past 34 years.

 

Because of the appearance and protection features of braided harnesses, Dennehy urges wiring harness assembly businesses not doing braiding to consider adding braiding to their operations. Also, assemblers subcontracting the work may want to evaluate the merits of bringing it in-house."People have told me that it doesn't pay to have harnesses braided elsewhere," Dennehy said. "With the time delays and the freight charges, it ends up costing them money. You can use a braider one week and then have it out of action six weeks, but it's still a good investment. Braiders can be paid off in a short time when they're in use."

 

Providing a harness made can have market penetration by offering braiding, in-plant braiding can be evaluated in terms of control, convenience and cost. Tighter controls on quality can be achieved by having the work done by company employees. Adding braiding as part of a plant's production schedule means greater convenience and eliminates the steps of shipping and receiving harnesses from a braiding specialty firm before final delivery. Braiding cost reductions may be realized by avoiding the mark-up of outsourcing.

 

One of the primary considerations in doing braiding is the equipment. Dennehy knows all about it, since he worked 21 years at New England Butt Co. (NEBC), an East Coast company that began manufacturing braiders in 1847 and dominated the U.S. braider market for decades. When the firm was acquired in 1987 by Wardwell Braiding Machine Co. in Central Falls, R.I., he worked there a short period before starting CWM 13 years ago. His company specializes in selling rebuilt NEBC machines, and 45 percent of CWM's business is in the wiring harness industry.

 

Regardless of manufacturer, a braider is a rock-solid piece of equipment, both in design and construction. "The last major redesign of the machine was in 1950 when existing parts were retooled, milled and machined to bring them up to standards of just using as-cast components," Dennehy said. "But the movement of the carrier to produce a braid has been the same over-and-under construction since the 1800s when braiders were built for making shoelaces, for instance. It's a slow process, but there's no other way to do it.

 

"Braiding machines don't wear out," he said. "There are machines from the 1960s and '70s still running, and the main heart of the machine is not worn at all. With lubrication, machines can last 20 to 35 years. There is no loosening of standards. They will produce a good braid until they are worn out. Once a machine starts jamming, then it's time for a rebuild."

 

He acknowledged some braiders use smaller gear teeth, but they wear more quickly. German and Spanish machines contain plastic and nylon parts, but their faster wear does not compare favorably to all-metal machines built in the United States and other countries.

 

New machines are manufactured in the United States by just one company – Wardwell. It continues to make the maypole-style braider popularized by NEBC. That style is used for braiding wiring harnesses. The other style of braider is the rotary, which is for insulating wires such sparkplug wire and cable TV conduit. Because of its purpose, a rotary braider operates three times faster than a maypole.

 

Since braiders last so long, a large market developed for selling rebuilt and reconditioned machines, in which Dennehy's company specializes. With a rebuilt machine consisting of mostly new parts, it can run as well as a new one. One advantage of a rebuilt machine is that it can be built and delivered more quickly than a new unit, 1-2 weeks as opposed to 3-4 weeks.

 

One method of sizing a braiding machine is according to the number of carriers, each of which contains a bobbin of braiding material. According to Dennehy, 90 percent of harness braiding is done on four sizes of machines with 16, 24, 32 and 48 carriers, respectively. Large harnesses, for such military aircraft as F-16 jets and Osprey tilt-rotor planes, are done on 64, 72 and even 144-carrier braiders.

 

Generally speaking, a 16-carrier machine is used to cover one wire or a harness up to 3/8 inch in diameter. For a harness between 3/8 and 5/8 inch, a 24-carrier braider is required. From 5/8 to 1 inch, 32-carriers are necessary. A 48-carrier machine is used on a harness between one inch and 1_ inches.

 

"Most job shops have at least one of each of the four different size machines," Dennehy said. "Which machine to use depends on the branches of a harness. A quarter-inch breakout branch could be done on a 16-carrier braider, while a larger machine would be needed for the rest of the harness."Braiding quality is determined by coverage and flexibility. Usually, achieving good coverage is not difficult, since a larger harness could be put through a smaller machine and result in the proper coverage. However, flexibility would suffer.

 

Perfect harness flexibility is attained when the braiding material is laid on the harness at a 45-degree angle. Braiding at that angle also has the best appearance. Since perfection often is not reached, as long as the angle is 40-60 degrees the harness is adequately flexible. When the braid angle is 70-90 degrees, unacceptable harness stiffness occurs.

 

Carrier number also affects overall machine size. On a 16-carrier braider, the head is 18 inches, while on a 24-carrier unit the head is 20-22 inches. A 30-inch head is on a 32-carrier machine, and 48-carrier braider has a 42-46-inch head.

 

A braider is positioned on legs and a plate on the floor. The base-plate sizes are: 16-carrier, 24 inches square; 24-carrier, 30 inches square; 32-carrier, 32x38 inches; and 48-carrier, 42 inches square. A 16-carrier braider can weigh up to 500 pounds, and a 24-carrier machine can top out at 700 pounds. Weight of a 32-carrier braider is 800 pounds, and 48-carrier machine exceeds 1,000 pounds.

 

Overall machine height averages 70 inches. That is with a harness receiving wheel or capstan on top measuring 18 or 24 inches in diameter.

 

The carriers contain the braiding material. Often it is made with PVC covered nylon or polyester and specified by color, temperature sensitivity and abrasion resistance. Brand-name materials include Kevlar, Fiberglas, Peek, Nomex, Trevira and Vectran. "A braider does not care what kind of material is being processed," Dennehy said. "Changing the springs for the different types is all that's required."

 

Even Nextel, a ceramic fiber with resistance to high temperatures, is used. Dennehy said braiding with Nextel is difficult because it flakes. "Before the machine design was changed from vertical to horizontal, the residue fell into the machine's oil and gears, but now it falls on the floor," he said. Due to Nextel's abrasiveness, carrier guides have to be switched to carbide from chrome, which works fine for other materials.

 

To prevent static in radios and other electrical components, wire is used in braiding. Copper can be used either bare or plated with nickel, silver or tin. Wire also can be aluminum, bronze, stainless steel, nickel 200, Inconel and Monel.

Most of the heavy equipment cover materials are .028 inch thick, and some may be .040 thick. Others are measured in denier. For example, Nomex is 840 denier.

 

Fabric braiding of wire harnesses first was done for military applications in the mid-1960s, Dennehy related. "The braid not only provided abrasion resistance, but nobody could tamper with a harness without somebody else's knowledge," he said. "In the 1970s harness braiding slid over to the civilian side when Caterpillar and others started using braid instead of tape on off the road vehicles. It just went from there into, forklifts, aerial ladders and even garbage trucks. It grew so that any type of construction machine had braiding. The PVC material is used the most because it provides good performance but is not overly expensive."

 

Power for operating the machine is provided by a fixed-speed or variable-speed motor, which is a fractional horsepower type. The 16-carrier braider is powered by a 1/3 h.p. motor, and a 24-carrier machine has a 1/2 h.p. motor. A 3/4 h.p. motor powers a 32-carrier machine, and a 1 h.p. motor is on a 48-carrier braider. A 110-volt motor is standard, but a230-volt, three-phase motor is available.

 

A fixed-speed motor requires an operator to shut it off completely when a harness breakout is encountered during braiding. A variable-speed motor, found on 75 percent of braiders, allows an operator to simply slow the machine when it has to braid around a breakout. Although machine speeds to establish per-foot or per inch braiding rates are available, determining braiding production time depends on operator expertise.

 

To buy a new machine with 16 carriers, the cost is approximately $6,250. A rebuilt unit is approximately 25 percent less at $5,000. The price of a new 24-carrier machine is $8,125 ($6,500 rebuilt), 32-carrier braider $10,000 ($8,000 rebuilt) and 48-carrier machine $13,125 ($10,500 rebuilt). Up to $2,200 can be spent on options for a new or rebuilt braider. Options include such items as a foot switch, different capstan, fittings, double-wheel gantry system and grease kit. The latter provides for greasing a machine every 40 hours of operation as opposed to every day with oil.

 

Considerable money may be saved by buying used braiders, but they are scarce, according to Dennehy. "You're not going to find used machines unless companies go out of business," he said, "but that hasn't happened in the last four or five years.

 

"Most wiring harness shops buy machines that come from a company they already know, so they have a good idea the machine is OK," Dennehy said. "There are very few used braiding machines around. I would say 90 percent of my customers don't bother with buying used. They buy reconditioned or rebuilt machines."

Nonetheless, should a company consider buying a used braider, Dennehy urged careful inspection of the machine. Such functions as motor and clutch performance should be checked. If a problem is discovered, what repair will be necessary – a minor fix or complete teardown?

 

Whether a company starts with a new or rebuilt machine, it should last the same amount of time, according to Dennehy. "If a machine is maintained and lubricated properly, it should last a long time," he said. "Harness shops usually have just one shift, so a braiding machine is not going to be run three shifts over 24 hours a day, seven days a week. The life of the machine should be 20 years."

 

Parts of the machine need to be lubricated once a week or every 40 hours. The track should be oiled lightly every day so the carriers operate smoothly. The carriers do wear out after 3-5 years, but most shops have two sets of carriers for each machine. The same carriers work on different size machines.

 

When a machine is rebuilt, Dennehy stated that new gears, belts, pulleys, gear reducers, switches, bearings, carriers, clutches and other parts are installed in addition to a new motor. The cost is approximately 50 percent of a new machine. If the track plate has to be replaced, the cost increases approximately 20 percent.

 

Although a braider may sound complex due to its many parts, operation is simple. Minimum skill and good manual dexterity are required by an operator to send a harness through a machine. "Running a braider is strictly a manual operation," Dennehy said. "There's no way to automate braiding."

 

Training a person to operate, adjust and maintain a braider requires approximately six hours. "People often have a lot of reservations initially, but after training they are totally confident," he said. "A person can be trained in a day, but it takes longer to pick up speed and learn how to do a back braid and how to handle the harness when the machine is stopped."

Dennehy noted that a braiding machine is noisy. He recommended isolating braiders in a room away from other plant operations. A braider operator must wear ear protection.