What is the correct method for daily cleaning of injection molds?

一, Cleaning cycle planning: dynamic management based on risk classification
1. Classify according to production frequency
High frequency production molds (running for ≥ 16 hours per day): Surface oil stains should be wiped off every shift (8 hours), and the mold cavity and exhaust groove should be thoroughly cleaned every 24 hours.
Intermediate frequency production mold (running 8-16 hours per day): Clean the surface after daily production, and clean the flow channel and top rod hole every 48 hours.
Low frequency production molds (running less than 8 hours per day): Conduct a comprehensive cleaning before each mold change, and regularly (weekly) start the mold to run empty to prevent the lubricating oil from drying up.
2. Classify by product type
High precision product molds (such as optical lenses and connectors): Clean the mold cavity every 5000 molds and use a microscope to detect surface scratches.
Appearance mold (such as mobile phone case, car interior): Clean the exhaust groove every 2000 molds to prevent the formation of weld marks.
Structural component molds (such as brackets and gears): Check the ejection system every 10000 molds and remove any remaining debris.
3. Abnormal situations trigger cleaning
Product defects: In case of burrs, black spots, or missing materials, immediately stop the machine and inspect the corresponding parts of the mold.
Environmental changes: When the workshop humidity is greater than 75% or the dust concentration is greater than 0.5mg/m ³, shorten the cleaning cycle to 50% of the original plan.
Material replacement: When switching from PC to high filling materials such as PPS, it is necessary to thoroughly clean the residual flow channel.
二, Cleaning tool selection: precise matching from physical cleaning to chemical decomposition
1. Basic cleaning tools
Soft bristle brush: used to remove plastic residue in the mold cavity and flow channel. It is recommended to use pig bristles or nylon material, with moderate hardness and no damage to the mold surface.
Air gun: Use 0.6MPa compressed air to clean deep holes such as the top rod hole and inclined top groove, and install an oil-water separator to prevent secondary pollution.
Ultrasonic cleaning machine: For small structural component molds (such as SIM card holders), using 40kHz frequency ultrasonic waves combined with neutral cleaning agents can remove 0.01mm level dirt.
2. Special cleaning agents
Alkaline cleaning agent: used to remove mineral oil and mold release agent residues, with a pH value controlled between 9-11 to avoid corrosion of mold steel (such as NAK80, S136).
Solvent based cleaning agent: For residual soft materials such as silicone and TPE, n-hexane or isopropanol should be used. It is necessary to operate in a fume hood and wear a gas mask.
Environmentally friendly water-based cleaning agent: suitable for food grade molds (such as medical device casings), certified by SGS, with a biodegradation rate of over 90%.
3. Protection and detection tools
Rust proof oil: After cleaning, apply it to the surface of the mold cavity. It is recommended to use dry rust proof oil containing nanoparticles to form a 0.1 μ m protective film.
Endoscope: detects the cleanliness of concealed areas such as deep cavities and cross holes, with a resolution of 0.01mm.
Roughness meter: After cleaning, measure the surface roughness of the mold cavity to ensure that the Ra value is ≤ 0.8 μ m (precision molds require Ra ≤ 0.4 μ m).
三, Step by step cleaning operation: standardized process from pre-treatment to final inspection
Step 1: Mold pretreatment
Cooling control: Reduce the mold temperature to below 50 ℃ before cleaning to prevent high temperatures from causing the cleaning agent to evaporate too quickly or the plastic to soften.
Safety lock: Close the safety door of the injection molding machine and hang a "cleaning in progress" warning sign to prevent accidents caused by misoperation.
Residual material removal: Gently tap the runner plate with a copper rod or plastic hammer to loosen the residual plastic and avoid direct scratching with metal tools.
Step 2: Partition deep cleaning
Mold cavity and core:
Use a soft bristled brush to gently brush the surface in the direction of the mold, removing 80% of visible dirt.
Spray neutral cleaning agent, soak for 3-5 minutes, and then wipe with non-woven fabric.
For mirror polished areas (such as car headlight molds), use specialized polishing paste combined with wool felt wheels for restorative cleaning.
Flow channel system:
Disassemble the hot runner nozzle and use a needle (with a diameter 0.1mm smaller than the flow channel) to clear the blockage.
Use an ultrasonic cleaning machine to treat the main channel lining and remove the degraded plastic layer.
Perform a pressure holding test after assembly to ensure no leakage.
Top out system:
Disassemble the top rod, soak it in kerosene to clean the oil stains, and check for any bending or deformation.
For the inclined top mechanism, use an Allen wrench to adjust the preload to 0.05-0.1mm.
Apply high-temperature grease (temperature resistance ≥ 250 ℃), manually push out 5 times after assembly to confirm smoothness.
Exhaust system:
Clean the plastic carbon deposits in the exhaust groove with a surgical blade, with a depth controlled between 0.02-0.05mm.
Check if the vacuum pump filter screen is clogged for the vacuum exhaust mold and replace it if necessary.
Step 3: Post cleaning treatment
Drying treatment: Blow dry the mold with compressed air or dry it in a 60 ℃ oven for 1 hour (for precision molds).
Rust prevention treatment: After spraying rust prevention oil, apply it evenly with a dust-free cloth, focusing on protecting the parting surface and slider guide rail.
Data recording: Fill out the "Mold Cleaning Record Form", including information on cleaning time, location, replacement parts, etc., to achieve traceable management.
四, Special scenario handling: coping strategies from material residue to environmental adaptation
1. Residual high-temperature materials
PPS/PEEK and other high-temperature resistant plastics:
Heat the mold to 150-180 ℃ to soften the residual plastic.
Gently scrape with a copper scraper (hardness HRC35-40) to avoid damaging the mold cavity.
Immediately apply molybdenum disulfide grease after cleaning to prevent high-temperature adhesion.
2. Treatment of corrosive materials
PVC/TPR and other chlorine containing plastics:
After cleaning, neutralize the acidic residue with a 5% sodium carbonate solution.
Rinse with deionized water and dry to prevent electrochemical corrosion.
The surface of the mold is treated with hard chrome plating to enhance its corrosion resistance.
3. Cleaning of multi-color injection molds
Two color/three color mold:
Before each color change, rinse the channel with specialized cleaning material (such as PMMA) to prevent color cross contamination.
For the rotating mold core, check if the sealing ring is aging and replace it if necessary.
After cleaning, conduct a trial mold to confirm that there is no color difference before mass production.
4. Clean room mold cleaning
Medical/semiconductor molds:
Operate in a Class 100 cleanroom, wearing dust-free clothing and gloves.
Rinse with ultrapure water (resistivity>18M Ω· cm) and wipe with isopropanol.
After cleaning, use a particle counter to detect and ensure that the number of particles on the surface of the mold cavity is less than 10/cm ².