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Techno Linear Motion Catalog 39 Technical Information Changes in speeds and loads which are common in machining and positioning applications, contribute to changes in the tuning of the system.  Although most of the dynamic impact of changes are absorbed in the mechanical reduction unit (ball screw, gear train), there is enough transmitted to the motor to create a slight disturbance.  This causes an “untuning” of the system.  Lighter than normal loads can cause a system to approach an underdamped state, while heavier loads can cause a system to approach an overdamped state.  To account for this, the Techno Servo Controller PID chip has been designed to provide critical to slightly overdamped tuning, so that an underdamped system is avoided. PLC’s are another common control type in industry.  They are advancing very rapidly, and are becoming smaller, less expensive, and easier to use.  The primary function is to logically link and control I/O.  This can be very useful for repetitive operations that can be actuated by solenoids or other digital devices, as found in  pneumatic  applications.    However,  only  more  advanced  and  expensive  PLC’s  have  developed  to  the point where they can effectively control complex motor functions.  If an application requires extensive logical operations in conjunction with motor automation, then a motor controller can be operated in conjunction with a PLC by means of the proper handshaking and data exchange.  If an application requires moderate logical  operations  along  with  motor  automation,  then  a  Techno  controller  with  I/O  capabilities  may  well serve the entire application. 8)    Wiring Once the task has been reduced to a wiring stage, there is still a lot to consider.  In fact, a well chosen system can perform poorly or not at all if mistakes are made in the system wiring.  Resulting inaccuracies may be experienced, or worse yet, system failure and hardware damage may follow. Current carrying capacity of conductors is defined as the amperage a conductor may carry before melting either the conductor or the insulation.  The mechanism of failure for an overloaded wire is excessive heat caused  by  electric  current  flow.    There  are  many  factors  which  limit  the  amount  of  current  that  can  be passed  through  a  wire.    The  major  factors  are  conductor  size,  insulation  temperature  rating,  ambient temperature, number of conductors bundled or twisted together, and installation conditions (heat dissipation is lessened by installation into conduits, races, and trays).  The following table acts as a guide to wire size selection.   4   6   8 10 15 19 27 36 47 65 Polyethylene Neoprene Polyurethane Polyvinylchloride (Semi-Rigid) Insulation Materials Copper Temp. 80°C 26 AWG 24 AWG 22 AWG 20 AWG 18 AWG 16 AWG 14 AWG 12 AWG 10 AWG   8 AWG Amperes Twisted Pair Wire Bundle # Derating Factor (X Amps)   2 —   5   6 — 15 16 — 30 0.8 0.7 0.5 Derating Factors for Bundled Conductors