Power Transmission And Linear Motion Components: How Motors And More Can Benefit Production
Motors and power generation are the foundation on which manufacturing is built. Motors drive nearly all powered equipment, from turning fans and running conveyor belts to driving pumps and powering tools. Power transmission is a key factor when converting the power generated from a motor into usable work for manufacturing. In addition, most motors generate the rotary motion and power transmission drives that are used to convert rotary power into linear motion. In this manner, motors are flexible workhorses that can drive nearly any tool or manufacturing process.
The Basic Design Principles Of Linear Motion
The coupling between a motor and a shaft is the point where rotary engines can output linear motion. This conversion of energy is obtained, in the simplest form, of only a few components working in concert.
The groundwork consists of a rotary motor that spins a threaded shaft. A nut is connected to the threads of the shaft. As it rotates, the nut does not revolve. Rather, the rotary movement drives the nut along the length of the shaft. This movement is now linear motion, successfully converted from the spinning of a shaft. This is the simplest form of converting between different types of energy. The nut is now traveling in a straight line as opposed to in a circular fashion. By coupling the nut to a sliding tube or other aperture, the rotating motor can create linear motion.
The Acme Lead Screw
There are numerous applications and techniques that are more diverse than the above example. The lead screw operates on the sample principle, but in a different fashion. In this case, the nut is fixed in place and rotates along with the running motor. The threaded screw is instead pushed forward by the spinning nut. Still, a rotary motor is able to drive a shaft in a straight line.
Overall, the lead screw is still a simple and compact design. This setup unfortunately generates a good amount of friction and heat and so the efficiency of power transmission suffers. A typical lead screw only converts energy with an efficiency rating in the range of 20% to 70% at best. However, this loss in energy is offset by the simplicity of design, low cost, and ease in manufacturing.
Variations on this design also change the thread angles and orientations. However, in the end, they are a powerful tool to drive a shaft forward by using a rotating motor.
A More Complex Example – The Ball Screw
In order to address the friction and efficiency issues, the ball screw utilizes ball bearings to achieve the same power transmission to linear motion affect. The threaded shaft in this piece of equipment creates a spiral ‘raceway’ for ball bearings to travel. Acting like a precision screw, the shaft is propelled forward from the moving ball bearings. By utilizing these moving balls, friction is reduced tremendously and an efficiency rating of nearly 90% is achieved. On the downside, however, this setup requires especially clean threads that are free of debris and obstructions for effective operation.
The end result of this configuration is a powerful tool for machining, precision manufacturing equipment, and in computer numerical control manufacturing systems. Ball screws are more expensive and complicated due to their design, but the increased efficiency can offset this cost by requiring a less powerful motor since less energy is lost during Metric bushing. A protective bellows, made from rubber or even leather, keeps the shaft and ball system relatively clean and free from obstructions.
Bearings And Linear Motion
The bearings used in the many different types of power transmission systems provide for free and easy motion of moving parts to reduce friction, energy loss, and wear and tear. In the broadest sense, they come in two configurations, plane and rolling element.
A rolling element bearing is similar to the common conception of bearings. An outer sleeve or ring is filled with rows of balls in cages. Moving parts glide over the ball bearings in order to achieve smooth operation and high precision. Typical applications include appliances, precision instrumentation, robotic assemblies, and even in cabinetry. A variation includes rollers instead of balls to achieve the same effect but with a larger surface of contact to handle heavier loads.
Plane bearings work without the use of rolling devices and instead consist of a bearing surface, like a shaft rotating in a plain sleeve. These are inexpensive and are able to handle a heavy load distributed over a large surface area at the cost of precision.