Hannover Messe Hall 14, as L35
Stepper motor linear actuators are on the rise, especially if they can eliminate the elaborate pneumatic cylinder. at koco Motion their share of total sales has increased disproportionately in recent years. Reason enough to take a look behind the scenes of the extensive portfolio, which is available in standard and customized versions - the latter with an upward trend.
Statement by CEO Olaf Kämmerling
The reasons for using linear actuators are obvious: While the pneumatic cylinder requires a compressor and the required peripherals to generate the compressed air, the linear actuator needs electrical energy to move. At standstill, the holding current is then usually lowered, which saves energy. In addition, all intermediate positions of the maximum stroke can be approached directly. As a result, the changeover times can be significantly reduced because the linear actuator can be used very flexibly. End position damping can be easily achieved by setting acceleration and deceleration ramps, while additional compressed air volume reduction elements may be required for compressed air actuated linear drives.
Precise positioning, fast movement, long life
Based in Dauchingen, Koco Motion systems house offers a variety of linear actuators for use in a wide range of applications requiring a combination of precise positioning, fast movement and long life.
While the portfolio includes numerous standard versions, the overall range of customized solutions increases to an enormous number of variants. For example, adapted spindle, motor and cable lengths, the design of the spindle ends, individual spindle pitches, connectors, winding resistances as well as step angles or special nut and slot geometries are required.
Customer-specific stepper motor is increasingly in demand
"Customer-specific designs are increasingly in demand with us," says Olaf Kämmerling, Managing Director of Koco Motion GmbH. "This brings us to countless combinations that make it really hard for the user to choose the solution that suits him best. Therefore, we advise our customers to contact us with their requirements. We have the know-how to help him find the optimal solution for his application from the possibilities available to us ".
The linear actuators have a global home. The drives are manufactured by the company Dings' in China or as "Mdrive" or "Lexium Mdrive" by Schneider Electric Motion in the USA. The third basic drive comes from the collaboration of Koco Motion and the Liechtensteiner Ingenieurbüro Adlos incurred Modular system "Kannmotion". In Dauchingen then all the threads come together and the customer is advised by competent drive specialists.
Based on the stepper motor technology, the linear actuators are offered in the two technologies "permanent magnet" (PM) and "hybrid".
PM stepper motor linear actuator for small dimensions
The rotor in the PM motor consists of a radially magnetized permanent magnet. Therefore, only limited numbers of magnetic poles can be made, resulting in a larger step angle. This technology is inexpensive and can also be realized for smaller dimensions.
The PM stepper motor linear actuators have a round shape and are available in three sizes with the diameters 20, 25 and 36 mm. The resolution of the linear motion varies from 6,5 to 333 μm / step at a maximum thrust of 115 N - depending on the drive size, spindle pitch and step resolution.
Hybrid stepper motor linear actuator for high numbers of poles
The hybrid stepper motor combines two drive technologies in one: it is a symbiosis of reluctance and permanent magnet motor. Toothed metal caps are attached to the axial permanent magnets. The offset by half the tooth width ensures that the north and south poles alternate. This technique allows high pole numbers and thus very small step angles.
The hybrid stepper motor linear actuators are available in the sizes NEMA 8, 11, 14, 17, 23, 24 and 34. Depending on the step angle and spindle pitch, the resolution of the linear motion varies from 1,5 to 127 μm / step with a max. Push / pull force of up to 2400 N.
"Based on the above data, we determine the motor size and the spindle pitch and the spindle nut design. Other important aspects are the possible self-locking, the available space and the control of the drive. The answer to the question: 'What will be how, in what time, where, with what control parameters and how often?' Essentially, it returns all the information needed to select a drive, "says Olaf Kämmerling, explaining how to end the agony of choice.
Ball screw instead of trapezoidal spindle
If the standard trapezoidal spindle is not sufficient for the application, a ball screw can increase the performance even further. It can be used to implement even more precise positioning, a minimized backlash, lower friction, a particularly long service life and heavy loads. In addition, the large number of quality grades, grades, types, lengths, etc. meet most customer requirements.
Both technologies are available with winding connections for unipolar or bipolar control, whereby the bipolar controlled version is now common. The linear actuators are available either with hollow shaft nut and spindle (without or with internal anti-twist device) or with external spindle and nut. This results in four construction methods:
Four drive versions
In the external version, the linear movement is achieved by securing the nut against rotation on the spindle acting as a motor shaft. This is a very popular use case. In the carriage to be moved, the nut is attached and moved linearly by the rotational movement of the spindle. The carriage must be guided by the customer. In order to achieve a long service life and to reduce the frictional forces, it is important to adapt the guide exactly to the axis of rotation. The user himself has to take care of the anti-twist device, for example by attaching a guide rail. For longer spindles, the free end of the spindle may need to be counterbalanced.
In the non-captive variant, the nut is inserted in the hollow shaft of the engine. Their rotation causes a linear movement of the spindle. If the spindle is fixed here, the motor moves back and forth. If the motor is fixed, the mass sits at the end secured against rotation on the spindle.
The Captive C version (closed system) is suitable for harsh environmental conditions. Here, the linear motion is created by the already internally twist-proof push rod. The push rod has an internal thread and an anti-twist device and is guided in a specially shaped housing. If the rotor (spindle) rotates, a linear movement occurs over the screw drive and the push rod moves in and out. Since the anti-rotation is already integrated, the customer has the least design effort in this variant. The load is fixed at the end of the push rod.
The Captive K version differs from the Captive C version by the drive. The push rod is grooved at the front and thus guided against rotation. This design forms the drive together with the threaded spindle. If the rotor rotates, the push rod moves in or out. It should be noted here that the spindle on the back can extend depending on the stroke. The latest version is a very good alternative in many applications because of its smaller size compared to the Captive C version.
Great application potential stepper motor
"The possible applications for these linear actuators are so versatile that I can only name a few examples here," says Olaf Kämmerling. "They are used in the adjustment of filling machines for different product widths, for the adjustment of valves for flow control of filling products, in the closing technique of injection tools, for the positioning of products in three levels as on XYZ tables, as a drive for piston pumps, dosing units and grippers and in manipulators, belt stoppers, dosing and positioning units - wherever linear positioning takes place. "
In general, the applications do not differ due to the type of actuators used. Rather, their selection depends in part on the philosophy of the customer and the circumstances in the company or on factors such as price or available space.
Networking linear actuators for the future
If the linear actuator is used for positioning tasks, for example, the user increasingly wants to integrate it into their network. "For such applications, we can equip our drives with an integrated controller. Network capability is rarely desired for PM linear actuators. On the other hand, the requirement for the hybrid linear actuators is more on the wish list, "says the managing director.
The MDrive and Lexium MDrive drives with the well-known interfaces RS4.0 / Modbus, CANopen, Ethernet and Profinet are available for the factory of the future or industrial 485 applications. Or they can be completed via the Kannmotion control with an RS485 or a sequence program I / O control.
"Our technical consultants in the field and in-house help by telephone, in writing or with pleasure on site, to interpret the drives as a coherent concept. Cost and benefit orientation are always our priority ", concludes Olaf Kämmerling.