Product History: More About DriTran

The Past
In the third century B.C., Archimedes developed a crude bilge pump resembling the modern screw. ships made by securing a spiraling tube to a central shaft. By continuously rotating the shaft it forced water to enter the tube, enabling sailors to draw water out of their ships.

Early screws were made in a similar manner by wrapping and securing a wire around a bar. By forging a softer material around the "screw", a "nut" was created. When rotated, the nut rode up or down the wires of the screw. Similarly, by holding the nut from turning and rotating the screw, the nut would travel along the screw.

Scientifically speaking, Archimedes' device, as well as a nut and a screw, convert torque input into thrust output, just like today's linear drive systems.
The earliest screw nut combinations were manufactured with primitive methods and no standards. Following the wire wrap method was a technique of cutting threads into a solid bar using a single point cutting tool. Screws and nuts were usually used in matched sets, since the absence of accurate cutting methods rendered unmatched combinations non-functional. While not interchangeable, these matched sets were eventually dubbed power screws, since they were very durable and could be used to hold or move considerable loads. The first known standardization of power threads were developed in the mid 1800's by Sir Joseph Whitworth. The standards defined many sizes of threads and detailed diameter and pitch tolerances. As a result, an improved method of cold forging steel into threads, known as thread rolling, was soon developed. Heavy rolling of modern screws by industrial machines, however, did not begin until the late 1950's. These improved rolling methods are capable of meeting modern thread standards such as the Unified Screw Thread standards, and the fastener and power thread standards defined by the International Standards Organization.

Due to its many advantages, thread rolling is the preferred method in todays in manufacturing. Yielding strong and accurate threads, it is efficiently used from the mass production of acme screws to the tight tolerances of modern ball screws.

Ball screw drives came into existence in the 1800's. They use a series of ball bearings placed between the threads of the screw and nut. Rotating the screw transfers movement to the nut through the low friction rolling of the balls. While very efficient, these early devices could not carry significant loads. They did, however, achieve wide spread use in the 1940's as improved steering mechanisms for the automobile industry.

DriTran drive systems are the evolutionary result of ball screw drives that were designed into many types of industrial equipment. These ball bearing based devices began being exposed to increasingly extreme environmental conditions, causing many of them to suffer sudden catastrophic failures. Such machine failures can be very disruptive to assembly line environments, costing manufacturers thousands of dollars a minute. In an effort to reduce machine downtime, application engineers at several locations began removing the ball bearings from damaged ball screw systems, placing the screw inside the nut housing, then filling the thread path with an epoxy. Once cured, the configuration allowed a machine to perform production tasks at reduced speeds, while a replacement drive system was in transit. This epoxy concept quickly led to the design and development of the DriTran epoxy composite drive nut in the early 1980's.

TranTek Drive Systems, Inc. was awarded patents for the epoxy composite casting method, casting apparatus and for the mechanical use of DriTran epoxy composite nuts. It was discovered that mating an epoxy composite drive nut to a screw with many thread starts and a large lead yielded a drive system that is ideal for industrial applications.

The Moment of Truth
DriTran epoxy composite nuts with high lead screws proved to be reliable and cost effective replacements for ball screw drives in a variety of applications. Improvements, in the form of excellent wear characteristics and extraordinary strength, result from the substantial amount of load surface area between the epoxy composite nut and the drive screw. Initial DriTran drive systems were retrofitted into competitor's press loading shuttles in place of ball screw/rack and pinion speed multiplying systems. For instance, A "Big Three" fabrication plant had been changing out ball screws in a particularly overworked press-to-press transfer system on a weekly basis. TranTek convinced them to evaluate a DriTran epoxy composite nut drive system in that very machine. After three months, because the drive was still operating so well, the plant manager began replacing more of the same type systems. Three years later, the first drive was still functioning perfectly, and TranTek drives could be found throughout the facility.

The Present
TranTek continues to design and sell DriTran epoxy composite nut high lead screw drive systems to first and second-tier suppliers for automotive manufacturing facilities serving Daimler-Chrysler, Ford, and General Motors, as well as for assembly equipment at furniture manufacturers and flying cut-off saws in lumber mills. Having completed over 3000 custom drive systems, TranTek has developed a comprehensive set of standard drives that can easily be integrated into your next automation design.

The Future
Manufacturing of both durable and non-durable goods continues to grow at a steady rate in the United States. As companies automate, the market for material transfer systems increases. Life expectancy of these systems is increasing as well, and drive systems such as ball screws, rack and pinions and belt drives must be increasingly durable. Since TranTek drives with DriTran epoxy composite nuts and high lead screws have superior wear characteristics and increased life expectancy as compared to these other drives, they are increasingly becoming the drive system of choice. Limited mostly by the creativity of today's engineers, their many uses are only now beginning to reveal themselves.