LS SERIES SERVICE MANUAL
ISSUE 4.0 OVERVIEW 3
1.2 General
The machines are bench mounted, microprocessor controlled, single column loading frames.
The crosshead is driven by a preloaded ballscrew (leadscrew) that is rotated by a permanent
magnet DC motor via a toothed drive belt. On the 1kN frames, the motor is mounted below the
lower crosshead, under the lower cover. On the 2.5kN and 5kN frames, the motor is mounted
behind the vertical column, under the rear vertical cover. All motors are fitted with a digital
encoder that is used to measure the crosshead position. The motor is powered by a PWM
supply from a driver IC on the Motor Drive PCB. The PWM signal is generated on the Main PCB
by monitoring the motor encoder signals.
The rear of the crosshead is attached to a vertical linear rail assembly that accurately defines
the crosshead alignment. This system ensures minimal sideways movement of the crosshead
together with minimal vertical "rocking" of the crosshead under all loading conditions.
The lower eye end design provides accurate alignment to the loadcell eye end. This
arrangement also allows the grips to be rotated without affecting their vertical position.
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