Delta MMC120 User Manual

Page 108

108

This mode is intended for use with a two-valve system, one controlling the flow rate and

the other the direction. This axis controls the flow-rate valve. The directional valve must

be controlled by other means. In this mode, the axis generates a positive drive output

regardless of the direction of the move. The drive will not go negative if the motion

controller overshoots the target. This is useful for some injection and blow-molding

applications.
When the axis is stopped, you must go into open loop mode.

Warning: This bit must be set properly when the

Set Parameters

command is issued.

Bit 12 - Continue Mode bit

This bit affects what happens when the module loses contact with the PLC. When this bit

is set, the module will finish any move it has started, otherwise it will halt immediately

upon detecting loss of contact with the PLC. This is useful for finishing a move that must

complete to prevent machine downtime (for example, a partial shot in an injection

molding machine).

Bit 13 - Simulate bit

When this bit is set, the drive output is set to zero and the magnetostrictive transducer

inputs are ignored. Internally the

TARGET POSITION

is used as the

ACTUAL

POSITION

. This mode is used for debugging. (The transducer error bits and LEDS will

be cleared.)

NOTE: Drive output is always 0 volts while in simulate mode; no commands,

including

open loop

, will change this.

Bit 14 - 15 - Prescale Divisor Bits

Prescaling may be desired on systems with long strokes. The prescale bits are used along

with the

SCALE

parameter to convert

TRANSDUCER COUNTS

ACTUAL

POSITION

. The effect is to divide the

SCALE

by 1, 2, 4, or 8. The divide-by factor is

specified as follows:

Counts ÷

Bit 14Bit 15

The advantage of these bits is that they let you maintain a higher resolution in the

SCALE

parameter. For example, a

SCALE

of 31027 and a divide-by of 4 gives an effective scale

of 7756.75. Without using the divide-by bits, the

SCALE

would have to be rounded up

to 7757, which has less resolution—with a 64” rod, the rounded value would make a

0.002” error at 64”. Note: with the stroke is always limited to 220 inches due to the 18-

bit transducer counter resolution.

Bit 16 - Integrator Limit

When this bit is cleared, the integrator limit is 20% of full drive. When the bit is set, the