TL;DR

Ram drift at rest means hydraulic fluid is bypassing a valve spool or piston seal. Isolate the counterbalance circuit first, then test each valve for internal leakage.

What you might see

ram creeps downward at rest
press won't hold top-of-stroke position
die gap closes slowly between cycles
hydraulic pressure drops at idle

Likely causes

Tap to mark as ruled out

Internal leakage past a worn directional control valve spool
Worn or damaged piston seals allowing fluid bypass
Counterbalance valve set too low to hold the ram weight
Hydraulic cylinder bore scoring from contaminated fluid

Required tools

Dial indicator with magnetic base
Hydraulic pressure gauge
LOTO kit
Die block (press-specific)
Seal replacement kit (Aida-specified)
Hydraulic hose caps and plugs

Safety first

Insert the die block before any measurement or inspection inside the press stroke area. A drifting ram is an active crush hazard.
Never enter the press work zone without a locked-out die block in place, regardless of how slowly the ram is moving.
Bleed all hydraulic pressure before disconnecting any hose or port. Pressurized fluid causes severe injection injuries.

Procedure

9 steps · ~90 min

1
Press the Emergency Stop and insert the die block before inspecting the ram position.
2
Lock out and tag out the main disconnect and hydraulic isolation valve.
3
Observe the drift rate at rest over five minutes with a dial indicator on the ram face. Record the measurement for the maintenance log.[1]
4
Isolate the counterbalance valve circuit and check its setting against Aida specification. A low setting fails to hold ram weight.
5
To test the directional valve: disconnect the load-side hose from the valve, plug it, and check whether the cylinder holds pressure. If drift stops, the valve is leaking.
6
If the cylinder holds pressure with the valve isolated, the valve body or spool is the source of leakage. Remove and inspect the spool seals.[1]
7
If drift continues with the valve isolated, the piston seals are bypassing fluid. The cylinder must be rebuilt or replaced.
8
Replace all seals with Aida-specified elastomers rated for the hydraulic fluid type in service.
9
Flush the hydraulic circuit and install a new filter element after seal replacement to remove wear debris.

Sources

Aida NC1 Mechanical Servo Press Operation Manual, Aida Engineering
Aida NC1 Mechanical Press Operation Manual, hydraulic cylinder and valve maintenance procedures (general)
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