Clamp & Boost Stabilization Logic in G5 (with Mold Protection Region Handling)

1. Background

Direct-hydraulic clamp systems with spring-loaded molds generate rapidly increasing reaction forces near mold touch.

If hydraulic flow or pressure transitions occur in the low-pressure region, the clamp may bounce backward or oscillate during mold closing and early boost.

G5 introduces a stabilization concept based on hydraulic sequencing, controlled pump contribution, and a dedicated mold protection profile.

2. Root Causes of Instability

1. Flow collapse during pump de-joining
   If pumps are allowed to join in the mold protection region, turning the join valve OFF just before mold touch creates a sudden flow drop and pressure collapse, which leads to touch → rebound → re-touch.
2. Hydraulic ratio mismatch between booster and tie-pressure cylinders
   The tie-pressure cylinder has a higher effective ratio than the booster.
   Early high-pressure contribution from P2 pushes the clamp backward before the booster develops sufficient holding force.
3. Spring-loaded molds amplify small disturbances
   Near mold touch, the spring force rises steeply.
   Small variations in flow or pressure are magnified into mechanical bounce.

3. Stabilization Strategy Implemented in G5

3.1 P1-only mold close in the mold protection region

Mold close is performed with P1 only, with pump joining disabled in the mold protection zone.

This avoids abrupt flow reduction and stabilizes the mold-touch phase.

3.2 Mold protection based on s_target / v_target + time-based V-profile

• 그만큼 mold protection position is defined as s_target.
• 그만큼 mold protection speed is defined as v_target.
• Once the clamp enters the mold protection region:
  • The controller switches the velocity profile (Vprof) to time-based mode.
  • The booster cylinder continues to receive flow at the mold protection speed (v_target), instead of using tight position feedback.

Technical effect:

• The system behaves as a constant, low-speed feed into the mold protection zone.
• Position error is not aggressively corrected; instead, a stable, limited speed is maintained.
• This prevents overshoot and oscillation at mold touch, while still protecting the mold mechanically.

3.3 Mechanical role separation of P1 and P2

• P1 continuously drives the booster cylinder.
• P2 drives the tie-bar cylinders.
  Booster motion remains stable even if tie-bar movement introduces minor disturbances.

3.4 Early boost with P1 only until a minimum pressure (~10 bar)

In the early boost phase, only P1 is active.

P2 is blocked until the system reaches a minimum internal pressure (≈10 bar), at which point the booster can resist the tie-pressure cylinder.

3.5 Pump joining only above a higher pressure level (~40 bar)

Full pump joining (P1 + P2) is allowed only after the clamp pressure exceeds approximately 40 bar.

Above this pressure, the system is mechanically stable and can accept additional flow without backward movement.

3.6 Limited P2 contribution (≈0.7%)

Even after joining, P2’s contribution is intentionally limited to avoid excessive pressure rise rate and mechanical shock to spring-loaded molds.

3.7 “Valve OFF → Motion OFF” sequence at the end of boost

Boost ends by switching the valve OFF first, then stopping motion.

This prevents sudden depressurization, reverse flow, and clamp relaxation.

4. Technical Effects

Overall Result:

Stable mold-touch and boost behavior with no bounce, no backward movement, and no pressure collapse, even for spring-loaded molds.