Parting Line

Clamp close is the stage of the molding cycle where the clamp advances the moving platen to bring the mold halves together and lock them up before injection. It is the first motion of every cycle. ## The three speed phases 1. Fast approach: the platen moves quickly across most of the stroke to save cycle time. 2. Slow / mold protection: near touch it slows to a low-pressure creep so the controller can detect an obstruction — a stuck part or misplaced insert — before metal hits metal. This is "mold protect". 3. High-pressure lock-up: the toggle or ram builds full tonnage, applying the clamp force tonnage that holds the mold shut against injection pressure. ## Why it matters - Mold protection prevents expensive damage: if a part did not eject, the low-pressure phase senses the resistance and stops instead of crushing the tool. - The speed profile trades cycle time against safety — too aggressive a close risks the mold, too slow wastes time. - Only after lock-up do the injection stages begin. ## Related terms - See also: clamp, clamp force tonnage, molding cycle, injection stages, part ejection ## What is clamp close in injection molding? It is the cycle stage that closes and locks the mold before injection, in three phases — fast approach, slow mold-protection, and high-pressure lock-up to full tonnage. ## What is mold protection during clamp close? A low-pressure, slow phase just before the mold touches, so the machine can sense an obstruction (an unejected part or insert) and stop before damaging the tool. ## What happens after clamp close? Once full clamp tonnage is reached, the injection stages begin — first-stage fill, then pack and hold.

Flash is the molding defect in which material escapes along the parting line, vents, ejector-pin clearances or between inserts, forming a thin film stuck to the part. It signals that internal mold pressure exceeded the clamp force locally or that sealing is poor. ## Common causes - Insufficient clamp force (actual tonnage < required tonnage) - Excessive injection or hold pressure - Injection velocity too high at end of fill - High melt temperature (resin too fluid) - Mechanical clearance: worn parting line, vents too deep - Misaligned mold or platen flatness out of tolerance ## How to detect - Visual inspection of part, especially around the parting line - Typical flash thickness: 0.03 – 0.3 mm - In multi-cavity tools, only some cavities may flash → imbalance ## Systematic fix 1. Verify actual clamp force (tie-bar sensor) 2. Reduce pressure / transfer velocity 3. Lower melt temperature 5 – 10 °C 4. If it persists: repair mold mechanics (re-grind plates, adjust vents) ## Cost of flash - Manual deflashing secondary op: $0.01 – 0.05 per part - Scrap if flash falls in a critical area - Accelerated mold wear due to poor sealing - Safety risk from sharp edges on technical parts

Projected area is the sum of the flat areas that a part —and the runners in cold-runner molds— occupies when projected onto the parting plane. It is the key input for calculating the clamp tonnage of the injection press. ## What it is used for The required clamp force comes from multiplying projected area by the specific cavity pressure (tonnage factor) of each resin: > Tonnage (t) = Projected area (cm²) × Tonnage factor (t/cm²) A safety margin of 10 – 20 % is applied to avoid flash at end of fill or due to imbalance between cavities. ## Typical tonnage factor by resin - PE / PP: 2.5 – 4 t/cm² - PS / ABS: 3 – 5 t/cm² - PA / PC: 4 – 6 t/cm² - POM: 4 – 6 t/cm² - Fiber-filled grades: +20 – 50 % - Thin walls (<1 mm) or long flow: +50 – 100 % ## How to measure projected area - In CAD: project the 3D model onto the mold's XY plane, export as a sketch and sum areas. - In 2D: planimetry on the parting plane. - In flow analysis (Moldflow, Moldex3D, Cadmould): automatic calculation with the resin factor. ## Common mistakes Forgetting to include runners in cold-runner molds (underestimates tonnage by 5 – 15 %), using the flat area instead of the projected one on parts with sloped walls, and changing resin without recomputing the factor.

Mold (Tool) is the mechanical assembly of plates, cavities, injection system and cooling that shapes the molded part. It is the single most expensive asset of the operation (10,000 – 500,000 USD) and its design dictates everything: cycle, quality, productivity and unit cost. ## Main components - Cavity plate (fixed half): nozzle side, usually houses the cavity - Core plate (moving half): ejector side, holds the core and ejector pins - Injection system: sprue, runners, gates (cold or hot) - Cooling system: water/glycol channels, conformal in premium molds - Ejection system: pins, sleeves, stripper plates, slides for undercuts - Standard components: leader pins, bushings, retainers, sensors - Replaceable inserts in wear areas ## Mold types - Single-cavity: prototypes, large parts, low production - Multi-cavity (2/4/8/16/32+): mass production - Family mold: different cavities for parts of the same assembly - Cold runner: with cold runners separated each cycle - Hot runner: no runner scrap, shorter cycles - Stack mold: two levels of cavities to double capacity - Two-shot / multi-material: two resins in the same part ## Mold materials - P20 (pre-hardened steel): standard for medium production, easy to machine - H13: hardened inserts, high thermal-wear resistance - S136 (stainless): polished cavities, corrosion resistance (PVC, PET) - Aluminum (7075): prototype or low-volume molds - NAK80: mirror polish without distortion ## Typical service life - Aluminum: 5,000 – 50,000 cycles - P20: 100,000 – 1,000,000 cycles - Hardened H13: 1 – 10 million cycles - Carbide / TZM in hot-runner gates: up to 50 million ## Critical maintenance Cleaning after every production run, vent inspection, lubrication of pins and guides, monitoring of cooling channels (scaling), and repair of cavity damage before it spreads.