Specifications

Z Encoder System Introduction
The ability to place stitches precisely at high speed is dependent on the accurate
operation of the electronics and electromechanical assemblies. The "key" to this is
the Z encoder. The information provided to the CPU and 4 axis driver by the Z
encoder is the basis for all the embroidery head activity.
The Z Encoder is a two channel quadrature output with index pulse. If you send the
output to an oscilloscope you will see two square wave signals, one slightly ahead
of the other. You will also see a third signal, the index pulse. The CPU interprets
these signals to determine position, speed, and headup.
The CPU uses this information to determine when to move the beam, when to stop
the head for a color change, when setting home position is allowed, how fast the
head is running, how many stitches have been embroidered, etc.
It is important for the technician to understand that the peripheral operational
software handles the motor control circuitry differently when the Z axis is running
than it does when the Z axis is stopped. When running, the motor control circuitry
allows the X,Y, and Z axis motors only minute errors in rotation. Any error greater
than the allowed error will cause the motor to be driven to eliminate the error.
When the peripheral is stopped however, the software that controls the Z motor
allows a larger "window" of error. The purpose of this window is to keep the
motors from oscillating around the null, hunting for absolute position.
The third LED on the CPU, can be used by the technician to see if the CPU is in fact
receiving a headup (or mark) pulse from the encoder (indicating that the encoder
and associated cables are functional). It should be noted however, that "the
headup LED does NOT have to be lit when the peripheral is stopped, and the LED
CANNOT be used to make a determination of the Z encoder alignment status." If
used in conjunction with the proper headup tool, the LED can be used to see if the
headup pulse is triggering early or late as compared to absolute mechanical headup.
The use of the procedures described in the following pages will result in the most
proper, accurate alignment and repair of the Z encoder system that is possible and
or feasible for use in the field by a technician.
It can be seen that the proper alignment of the Z encoder can result in maintaining
embroidery quality and proper machine operation. Slight Z encoder misalignment
can cause many kinds of erratic operation and/or intermittent thread breaks. A
larger misalignment can be the cause of equipment damage and subsequent
electronic or mechanical failures. The careful application of the Z encoder
procedures by a factory trained technician will result in a machine that will operate
correctly and reliably.
2 - 16 Head Section
EMC 10/4 Technical Manual Melco Embroidery Systems