Carriage

Commands | Description | NVS Parameters | Parts | Procedures | Theory of Operation

Commands

carriage

Description

The carriage transports the exposure head along the length of the drum. The carriage moves in a set of parallel tracks, driven by a ballscrew that runs the length of engine casting.

NVS Parameters

carriage accel (max_accel)
carriage again (driver_accel_gain)
carriage coff (cos_offset)
carriage cph (centre_plate_to_home)
carriage eaccel (edge_search_accel)
carriage eatt (edge_attempts)
carriage esearch (edge_narrow_search)
carriage espeed (edge_speed)
carriage espot (edge_spot_width)
carriage fedge (fast_edge_search)
carriage gearing (srot_per_lrot)
carriage hgain (driver_hold_gain)
carriage ispeed (init_speed)
carriage kspeed (knee_speed)
carriage mgain (driver_move_gain)
carriage mspeed (max_speed)
carriage mtravel (max_travel)
carriage period (accel_period)
carriage pitch (mil_per_lrot)
carriage psteps (plot_accel_steps)
carriage pgain (driver_plot_gain)
carriage scyc (steps_per_scyc)
carriage soff (sine_offset)
carriage steps (steps_per_srot)
carriage wsearch (edge_wide_search)

Parts

For BOMs, see parts/tools page.

The main components of the carriage are:

• Carriage motor
• Ballscrew
• Tracks
• Home/away board
• Carriage motor driver board (10-1418A)

Carriage motor

• Drives the ballscrew through a timing belt.

• The carriage motor is a 200 steps/rotation stepper. It is operated in microstep mode in order to get smooth motion and position control. It is normal for this motor to run hot. To prevent this heat from being transfered to the frame, ensure that the thermal shim is installed between the motor and frame.

• The carriage motor drive pulley is carefully matched to the motor shaft to minimize runout. Do not remove unnecessarily.

Ballscrew

• Precision part which drives the carriage along the tracks.

• Ballscrew support:
  The ballscrew mount uses 2 angular contact bearings to support the ballscrew. These bearings are very easily damaged. If there's a need to remove the carriage, support the free end of the ballscrew with a support jig (Creo p/n 92-009A) to prevent damage to the precision bearings in the away side ballscrew hanger. Please note that a piece of foam is not sufficient as support.

Tracks

• Guide the carriage driven by the ballscrew.

• Never loosen the screws that hold the carriage tracks to the frame.

Home/away board on carriage (10-0345)

• Detects the home and away tabs at either end of the tracks.

Procedures

See the procedures page.

Theory of Operation

Carriage motion during plotting

Carriage motion is synchronized to image data output. From the home position, the ballscrew moves the exposure head at a programmable speed until imaging is finished.

If the workstation is unable to deliver raster data at the recorder imaging speed, the carriage drive switches to asynchronous mode. The carriage stops, reverses and waits at a retrace position until the DPE buffers have filled with data. At this time, the carriage accelerates to speed in time for the next image rotation.

Carriage position

Carriage position and velocity are locked to drum speed through the stepper synthesizer and digital PLL on the MPE board. This is an open loop system as there is no encoder on the carriage sub-system. Therefore, for the head position information to be accurate, the carriage cannot drag or stall.