What does case raw material preparation add in the wet season?

Answer: Hold humidity under 60 percent, read the dew point before opening, and finish an opened bag within 4 hours.

Why can regrind still run at the sixth cycle?

Answer: Because it is retested. Impact at cycle 6 is 12 percent down, which faces tolerate; bosses stop at 3.

Where does falling airflow show up first?

Answer: Thin walls and deep pockets. Below 85 percent of nameplate, deep pockets streak about 2 days before the flat faces.

Six Regrind Cycles a Year: Case Raw Material Preparation Savings

Q: Where should the colour stop line sit?

Answer: ΔE 1.5 for light parts and 2.0 for dark ones. A 0.3 spread across 3 points means the blender, not the masterbatch.

Quick answer: Maintenance in case raw material preparation is not about replacing parts. Hold the store humidity, the dryer air temperature and the regrind count, and a material that ran twice can safely run six times.

Inspection points and judgement lines
Storage: stacking height and dew point
Dryer and hopper checks
Regrind cycles: limits and the log
Colour and contamination: purging between colours
Abnormal handling: re-dry, downgrade, scrap
FAQ

1. Inspection points and judgement lines

The weak point is not the scale but the bag mouth. A 25 kg sack left open overnight takes on 0.3 percent moisture, and 90 minutes in the dryer will not bring it back to the limit.

Inspection runs at three levels: three points per shift, one measurement per week, one clean-out per month, each with its own limit and action.

Point	Frequency	Limit	Action when exceeded
Bag mouth and tie	Once a shift	Closed, upright	Tie at once; over 4 hours open, downgrade
Hopper level and feed pipe	Once a shift	Above the low mark	Top up and check the pipe for leaks
Dryer return air	Once a shift	Within 5℃ of setpoint	Stop, reload, check heater and fan
Granule moisture	Weekly	0.06 percent for regrind	Re-dry 90 minutes, then retest
Silo and floor	Monthly	No spillage, no oil	Sweep, run the magnet, relabel

The sheet hangs at the store door and is signed each shift in case raw material preparation; a signature makes someone walk to the hopper and look.

2. Storage: stacking height and dew point

Three layers of 25 kg sacks is the ceiling. A fourth presses the bottom row into slabs over 3 months, granules fuse, and the granulator runs 20 minutes longer on every batch.

Case Raw Material Preparation: a white case open on a workbench, black gasket inside the lid, grey foam and a paper bag, a vice behind

Pallets sit 150 mm off the floor and 300 mm off the wall, so ground moisture has somewhere to go. In a wet season a store can hold 85 percent relative humidity, and sacks closer than 100 mm to a wall condense first.

Opening is decided by dew point. Above -18℃, vapour condenses onto cool granules, and a handheld meter gives that reading in 10 seconds. Use an opened bag within 4 hours, then tie it with a desiccant sachet.

Hold about 3 months of stock, roughly 8 tonnes a delivery; treat 12 months as shelf life, past which colour drifts. Never put two colours in one bay, where a 25-minute purge stretches to 40.

3. Dryer and hopper checks

Dryers rarely fail outright. Return air drifts, airflow falls, dew point climbs, and the defect appears 30 days later.

Check	Frequency	Pass line	Tool
Return air against setpoint	Per shift	Within 5℃	Machine display, written log
Drying airflow	Weekly	At least 85 percent of nameplate	Anemometer at the outlet
Desiccant condition	Every 500 hours	No dust, no colour shift	Sight glass
Dew point	Quarterly	Below -20℃	Calibrated handheld meter
Hopper residence time	Per shift	Under 30 minutes	Handover record

Granules in the hopper beyond 30 minutes go back to the dryer, regrind especially. Regrind has seen one heat history and picks up moisture twice as fast, so 75℃ for 2 hours suits virgin stock while regrind needs 90 minutes more.

Desiccant is a consumable. Powdered desiccant looks present but holds 30 percent of its capacity, and one dew point reading exposes it.

4. Regrind cycles: limits and the log

How far regrind can be pushed depends on records, not feel. Mark the sack once per cycle; the sixth mark sends it to downgrade.

Case Raw Material Preparation: a half-open white case on rack beams, three latches at the front, a handle each side, dark trays inside

Part	Cycle limit	Blend limit	Retest each batch
Lid and base faces	6	20 percent	Drop, colour
Ribs and dividers	5	25 percent	Dimensions, warp
Latch and hinge bosses	3	10 percent	Impact, clearance
Gasket groove	2	5 percent	Compression set

After 6 cycles impact has fallen 12 percent. That is invisible by eye and obvious in a drop test, which is why faces take 6 and load-bearing bosses take 3.

The log holds three fields: batch, cycle, blend. With all three a fault is traced to one sack within an hour.

5. Colour and contamination: purging between colours

Dark to light costs 25 minutes of purging and the first 3 kg of output. Skip it and the next 200 cases carry a grey cast.

Contamination	Usual source	Detection	Limit
Colour shift	Incomplete purge	Colorimeter, 3 points averaged	Stop the line above ΔE 1.5
Metal chips	Worn granulator blades	Magnet plus 0.5 mm screen	One find scraps the sack
Oil	Compressor line carry-over	White paper wipe inside the sack	Any trace, downgrade
Mixed resin	Cross-feed between machines	Water float test for layers	Layers mean the sack is isolated

Colour is the one item argued with data. ΔE 1.5 is the line for light parts and 2.0 for dark ones; a 0.3 spread across 3 points means the blender, not the masterbatch. Mixed resin is harder: PP and HDPE differ by 0.05 g/cm³, so a water bath separates them faster than the eye.

6. Abnormal handling: re-dry, downgrade, scrap

The action goes on the sack, so an operator can read it and act.

Moisture above limit means 90 minutes at 75℃ and a retest; fail twice and it is downgraded to non-visible parts. Lumps are crushed through an 8 mm screen, oversize scrapped, undersize returned at 10 percent. Scrapping a 25 kg sack costs 230 yuan; a case that cracks on an inclusion costs 80 yuan plus a missed date.

One stop rule: 3 or more colour or streak defects in a shift means check the material before the machine.

Conclusion

Seven tenths of the cost in case raw material preparation comes from what was not caught early: a bag left open overnight, airflow down a tenth, an extra mark on a sack. Split inspection into shift, week and month, write limits as numbers, and six passes are no gamble. Case raw material preparation then saves the 42,000 yuan without arguing anyone down on price.

This article discusses only the container (case body) side of specifications and design intent, and does not cover any handling, loading or use of the contents.