What Is a Motor Shaft?
The main component in most rotating equipment is the motor shaft. A shaft is a mechanical section for rotating and converting torque. The size of the shaft significantly affects the torque in these devices. Therefore, precise modeling and prototyping of shafts are essential for all applications.
In addition to the need to mount the rotor and a variety of attachments, the model of the motor shaft is based on the cooling concept selection of the electric device. Especially with more electric motors and thus longer and larger motor shafts, a hollow shaft enables the new model cases to have both a lightweight construction and a cooling system.
In transmission, a few different performances are used to resume the transmission of torque from power to kinetic output and thus move the device. Based on the great rotation speed of over 20,000 rpm and the large torque, the motor shaft must bear a very high load. This requires high-strength parts that still have to meet the high requirements for lightweight modeling.
How Shafts in AC/DC Motors Function:
Shafts in a motor are cylindrical component that exits the motor & its housing. The purpose of the shafts is to convert the energy from the motor to the end-use application. The precision pins and shafts act as a function of speed versus torque.
When no load is applied to the shafts, it will run at its fastest speed for that voltage with almost zero torque. When enough load is applied to the shafts that it stops rotating completely & its speed becomes zero, it will generate maximums amounts of torques for that voltage & is said to be operating at stall torque.
DC motor is designed to run under low torques and is assumed to exhibit optimum performance when the shaft is operating at a medium between zero loads and stall torque. If more torque is required, a gear reducer is often combined with the motor to reduce the shaft speed and increase its torque.
Common Uses of AC/DC Motors:
AC/DC motor is used in a wide range of industries & applications depending on the type of AC or DC motor used. The Mentioned below are some of the most common types of AC/DC motors and their specific uses.
#1. Synchronous AC Motors
In asynchronous AC motors, the shafts speed is kept constants. This makes synchronous AC motors ideals for high-precision positioning equipment used in robotics and instrumentation.
#2. Induction AC Motors
Induction AC motors produce large amounts of torque and are therefore commonly used for their load capacity. You will often find induction AC motors used in home appliances as well as pumps, conveyor belts, compressors, and other manufacturing equipment.
#3. Brushed DC Motors
A brushed DC motor is preferred for cost-sensitives applications where the required control is relatively simple. They are commonly used in consumers applications as well as some basic industrial equipment.
#4. Brushless DC Motors
Brushless DC motors have higher initial costs than brushed DC motors; however, they meet those costs by exhibiting a longer life span for high usage applications.
A Brushless DC motor is often used in fans, pumps, compressors, & other applications where a high degree of reliability & durability is required.
Construction of a Motor Shaft:
Choosing the appropriate material can improve reliability. After considering the best material for the device and its shaft, you should think primarily about cost. The material used for atypical motors shaft is mild steel, but once higher strength is required, alloy steels such as chromium-vanadium, nickel, and nickel-chromium are used.
Most motor manufacturers apply SAE 1045 to either hot-rolled (HRS) or cold-rolled steel (CRS). C1045 is a medium carbon, the medium tensile steel that is supplied as forged or normalized. This steel exhibits suitable toughness, strength, and wear resistance. Go here to see the build process.
It is used for bolts, axles, crankshafts, forgets connecting rods, lights gears, torsions bars, guide rods, etc. Other substances includes sulfurized SAE 1137, SAE 1117, SAE 1144, cold-rolled SAE 1018, & hot-rolled SAE 1035.
A ground stock of any material is mounted on special CNC turning machines. In general, sulfurized and cold-rolled steels will increase prices by relatively 15% and perform better than HRS. Machining tests need to be implemented to control the additional cost.
Since all shaft-turning devices perform differently, there are no installed substance or machining maintenances. On cost-per-pound explanations, hot-rolled plain carbon steels are more cost-effective than the cold-rolled sulphurized type.
However, there is some drawback when we want to employ them. The size of the hot-rolled material must be larger than that of the cold-rolled form due to the lack of monitoring of the outer diameter (OD) in the rolling process.
Manufacturers of electric motors should evaluate whether hot-rolled bar stock with larger size and the lower-material cost is more or less expensive than cold-rolled bar stock. The lack of residual stress, hard and soft spots, voids, and other matter is typical with hot-rolled materials, making it more problematic to machining.
With some high-strength steels, the hardest side is just the outer layers, so when shafts are used, there is less strength. Conducting the test will help you select the best substance among CRS, HRS, Sulfurized, & Non-Sulfurized materials.
Industrials Electromechanicals Repairs Services (or IER Services) was introduced in 2011 to supply effective, fast repair services for all types of electromechanical equipment, including DC and AC motors, variable frequency drives, pumps, dynamic balancing, and much more.
They also support shaft alignment services. They not only provide their clients with quality Motor Shaft Fixings, but they also offer specialized Electric Motors Shafts for use in other Valves, Pumps, Motors, & Hydraulics.
Materials Available in Motor Shaft Manufacturing:
- Alloy Steel
- Beryllium Copper
- Carbon Steel
Electric Motor Shaft Manufacturing:
As discussed earlier, most motor manufacturers apply SAE 1045 to either cold-rolled (CRS) or hot-rolled steel (HRS). Hot rolled carbon steel material is cheaper than cold rolled, at a cost per pound. But the rolling process has some tradeoffs, such as size considerations.
Manufacturers of electrical equipment estimate whether low-material-cost and sizable hot-rolled bar stocks are more or less expensive than cold-rolled bar stocks. Hot-rolled material, by the nature of its characteristics, lacks soft and hard spots, voids, residual stresses, and other materials, making it more problematics for machining.
Mains drawbacks with some high-strength steels are that the hardest sections are just the outer layers, so once the shaft is down, the system will miss out on strength. Machine tests need to be done to select the best one from various materials. Due to difficulties with HRS, some motor manufacturers will use sulfurized CRS.
Importance of Motor Shaft Alignment:
There are three types of motor shafts misalignment:
#1. Angular Misalignment Occurs
Angular misalignment occurs when the motor is installed at an angle to the equipment being driven. If the centers of the driven tool and motor shaft were to be extended, they would actually cross each other rathers thanks run or superimpose along a standard centerline.
The “space” the space difference between coupling faces or the slope difference of the motor shaft can be in the vertical direction, the horizontal direction, or both when compared with the slope of the fixed machine shaft. Angular misalignment can cause serious damage, especially to powered equipment and motors.
Parallel misalignment occurs when two shaft centerlines are in a parallel configuration but are not in the same line. There are two forms of parallel misalignment because shafts can be offset vertically located at different heights, horizontally displaced left or right, or both.
Combination misalignment occurs when the motor shaft suffers from both parallel misalignment and angular misalignment simultaneously. This is the most traditional misalignments situation encountered in the system.
#2. Motor Shaft Misalignment of Couplings
Large motors are usually connected directly to their load with flexible or rigid couplings. Flexible couplings tolerate a small amount of misalignment, while rigid types do not compensate for motor-to-driven-instrument misalignment.
Flexible couplings can also reduce vibration transferred from one section of equipment to another, and some powered equipment can protect the shaft from stray electrical currents. Even flexible couplings require some alignment considerations presented in the instruction sheet for them.
It is a mistake to rely on flexions of the coupling for additional misalignment since flexing of the shaft & the coupling will put a load on the driven equipment and motor bearings. These loads can cause shaft breakage or breakage, premature bearing, seal or coupling failure, and additional axial and radial vibrations. Secondary effects include loosening of foundation bolts & broken or loose coupling bolts. Performances lives are reduced when shafts are misaligned.
It is practically difficult to achieve proper alignment without employing an alignment tool such as a laser alignment device or a dial indicator. The appropriate motor shaft alignment procedure is primarily to monitor the driven equipment since moving a pump, for example, would entail thrusting on the mounted piping.
The next tip is setting up the couplings on the powered equipment. The motor should then be moved to the appropriate alignment and connected to the coupling. After the equipment has been exposed for a long time to be temperature-stable, we should turn it off and control the alignment immediately. Alternatively, we can control the relative positions modifications of the machines with laser systems equipped to perform the task.
Due to thermal growth, devices aligned in the “cold” pre-operating state are nearly out of alignment when the working temperature is attained. Many equipment manufacturers publish thermal offset values, so alignment technicians can modify them to account for thermal development during the initial alignment process.
#3. Suggested Actions of Motor Shaft Misalignment
- Here, some suggested actions for motor shaft misalignment are presented:
- Check shaft alignment of all production-critical equipment annually.
- Check newly installed equipment for alignment variations due to solidification of the foundation after 3 to 6 months of work.
- Control vibration rising vibrational tendencies as the main signs of misalignment. Misalignment can be caused by insufficient bolt tightening, settling of the foundation, or output shaft faults.
- Apply predictive maintenances methods, including frequency spectrum analysis & vibration testing, to distinguish between shaft misalignment, bearing wear, or electrically generated vibration.
What Are Electric Motor Shaft Circulating Currents?
Motor shaft circulating currents arise due to “asymmetry” in the magnetic paths in the rotor and stator iron. As the rotor rotates through the stator and once the stator’s magnetic field moves, small differences in the magnetic “reluctance” of the main components generate small voltages between sections of the shaft.
As you can understand from the above discussions, the circulating currents are the results of the electrical modeling of an electric motor. This is why some the constructor will design the motors with an insulated bearing housing; Bearing, or enable.
These special designs are produced in bearings to impede closed paths for transmitting currents in the grounded motor structure. These currents will jump through the ball-bearing space or break intermittently into sleeve-bearing oil films. This results in a race in ball bearings or electrocution on the very polished surface of the balls, which causes initial failure and fatigue.
It must be recognized that motor shaft circulating currents may also be caused by external supplies such as welding, etc., to magnetize the shaft (i.e., magnet). There are also static charges which can result in shaft transmitting current problems.
As the shaft is electrically charged, it then discharges into the bearings causing damage. It is also worths considering that shafts circulating currents are becoming more commons in small horsepower electrical equipment due to the popularity of variable frequency controllers.
A variety of devices are now being employed, such as the AEGIS shaft grounding ring, which is manufactured and modeled to help the motor protect itself and divert circulating currents.
Characteristics of a Motor Shaft:
According to the demands of the users, the motor shaft can be made as a hollow shaft as well as a solid shaft.
- The lightweight design can be used employing the tube and as a manufactured version.
- A combination of different materials is possibles.
- Motors shafts are ready for installation or as a semi-finished component close to the final contour.
- Low weight conservation of resources and high transmission efficiency
- Splines can be changed according to customers’ requirements.
Shaft Manufacturer in Our Workshops:
Here at Mawdsley, we can machine a wide variety of motor shafts to complement our machine repair service. With our experience in high-class naval equipment, we understand the importance of producing high-quality and closely endurable parts.
With our own machining facilities, we can respond quickly when needed and manufacture on an immediate basis. All our shafts are machined and final inspected by our own engineers to ensure compliance with the required specifications.
#1. Electric Motor Drive Shaft Replacement
The driveshaft can be damaged by improper use, overload, wear, or lack of care and maintenance. Usually, we see many types of damages, such as bad-bearing magazines, bad threads, keyways, and damaged threads. In some cases, the shafts can be repaired; however, in many circumstances, it is necessary to replace the entire shafts.
#2. AC Motor Shafts
Depending on applications, these shafts are generally steel or stainless steel. These have various machined diameters that can be finished with keyways, grooves, or threads. For motors with a low vibration target, bearing magazines may be the final basis after the rotor is built.
#3. DC Motor Shaft
These are similar to AC motor shafts in terms of machining required. However, the DC motor is more complicated to manufacture due to the fitting of the commutator.
It often has to be disconnected from the armature winding and removed before the shaft can be pressed. In some circumstances, the armature will need to be reminded after the shaft and commutator have been rebuilt.
If the shaft has a bearing journal, fan seating or drive connection diameters, these can be retrieved without removing the shaft from the assembly.
The shaft is machined to allow plating to be added, which is done by a specialist company. Once complete, the shaft is machined to finalize the correct size.