Electricity and Control March 2016

ENERGY + ENVIROFICIENCY: FOCUS ON DRIVES, MOTORS + SWITCHGEAR

g p

= acceleration due to gravity (9,81 m/s²)

to eight tasks can execute simultaneously. Figure 4 is a picture of a typical Galil motion controller (www.galilmc.com).

= leadscrew pitch, mm

Although the motor could produce in excess of 1 Nm of torque, we decided to use a value of 0,4 Nm and efficiency of 0,8. This equates to 0,4 × 3 = 1,2 Nm on the screw.

Therefore force F = 1,2 × 644 × 0,8 × 9,81/5 N = 1212,98 N

This is far in excess of what is required on a small machine and should result in good axis rigidity. Leaving this calculation till the end is de- liberate, as experience has shown that, provided inertia and speeds are sensibly chosen, it is rare to find insufficient force produced. Note that no attempt was made to choose the smallest satisfac- tory drive motor. We regard this as false economy and a very bad idea on a new machine. Here endeth the first lesson!

System description Details are shown in Figure 3.

Figure 4: Typical Galil motion controller.

Programming Commands consist of simple two letter acronyms such as:

SH X Servo Here (X axis)

BG X Begin ST X Stop etc

Figure 3: System description.

The Galil motion controller receives an ASCII (American Standard Code for information interchange) file from the industrial PC. There- after, the program executes from the Galil’s onboard memory and the PC acts as an operator interface. This avoids the use of an HMI (human machine interface) and is by far the most efficient way to engineer a project of this type. Standard PC literacy is all that is required of the user. The Galil controls the axis movement and, in addition, performs the Programmable Logic (PLC) functions such as checking safety circuits, and control panel pushbuttons as well as driving indicator lamps and switched loads such as the coolant pump. In addition, an analogue output supplies 0-10 V to control the spindle speed. Up

Figure 5: A Galil programming tool.

In Figure 5 , the right hand screen is a text editor. The top left hand screen is used to execute the program and issue commands on the fly. The bottom left hand screen shows Galil messages and responses.

Electricity+Control March ‘16

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