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T12 · Control / AutomationDigital Twins, Industry 4.0 & AIShop-Floor Standard
Cavity Pressure Integral (Mould Cavity Energy Work Done)
Integral of the cavity pressure sensor signal curve over time (bar·s). Serves as the primary Digital Twin metric for automated 100% part quality classification and sink/flash defect prediction.
Mathematical Canonical Relation
Plain Formula: W_cav = Integral [ P_cav(t) * dt ] from t_inj to t_freeze
Live Engineering Parameter Solver
Input your production or test values below for instant, verified output.
Verified Engine
P_peak_bar
Range: 100 – 1200 bar
t_hold_s
Range: 0.5 – 20 s
shape_factor
Range: 0.6 – 1 ratio
Calculated Engineering Result:
W_cav = 1428 bar·s
Engineering Verification:Good packing density.
When & Where to Apply
Use in piezoelectric cavity pressure monitoring systems (Kistler / RJG eDART) for real-time robotic reject degating.
Common Engineering Pitfalls
- Using hydraulic injection pressure instead of actual in-cavity melt pressure
- Failing to reset piezoelectric charge amplifier baseline between shots
Physical Assumptions & Validity Limits
- Cavity pressure sensor flush-mounted near gate or at end-of-fill
- Continuous sampling rate of at least 100–500 Hz
- Stable melt temperature and screw recovery dynamics
Variable Symbols, SI Units & Dimensional Specifications
| Symbol | Variable Meaning | SI Unit | Typical Industrial Range |
|---|---|---|---|
| W_{cav} | Cavity pressure curve integral | bar·s | — |
| P_{peak} | Peak holding cavity pressure | bar | 450 |
| t_{pack} | Packing and hold duration | seconds | 4.5 |
Worked Industrial Numerical Example: RJG eDART Cavity Pressure Integral Tolerance Monitoring
Problem Statement:
An automotive lens cavity pressure curve averages 420 bar over a 4.0 s pack/hold time with trapezoidal shape factor 0.85. Calculate W_cav and classify if nominal tolerance is 1400 ± 50 bar·s.
Step-by-Step Numerical Solution:
- Calculate integral: W_cav = 420 bar * 4.0 s * 0.85 = 1,428 bar·s
- Compare to tolerance: 1400 ± 50 bar·s => 1350 to 1450 bar·s
- Evaluate: 1428 bar·s falls within specification window
Final Answer: W_cav = 1,428 bar·s (PASS / In-Tolerance)
💡 Engineering Interpretation: W_cav of 1,428 bar·s confirms correct cavity packing without short shot or flash. The robot places the part in the pass chute.
Authoritative Technical Reference & Source Provenance
Cavity Pressure Technology in Injection Molding by Kistler Instrumente AG (Kistler Application Manual, 2021), 4th Edition, Page 22-29.
Connected Curriculum Lesson
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