Komatsu PC138USLC Operation & Maintenance Manual page 216

OPERATION
MACHINE OPERATIONS AND CONTROLS
Operations Using Travel Force
Do not dig the bucket into the ground and use the travel force to
carry out excavation. This will damage the machine or work
equipment.
Prohibition of Operations Using Hydraulic Cylinders to Stroke Ends
If the work equipment is used with the cylinder rod operated to its
stroke end, and given impact by some external force, the hydraulic
cylinders will be damaged, causing personal injury. Avoid
operations with the hydraulic cylinder fully retracted or fully
extended.
Operations Using Bucket Dropping Force
Do not use the dropping force of the machine for digging, or use the
dropping force of the bucket as s pickaxe, breaker, or pile driver.
This will drastically reduce the life of the machine.
Operations Using Machine Dropping Force
Do not use the dropping force of the machine for digging.
3 - 161