Why can case raw material preparation not judge regrind by ratio?

Answer: Ratio says how much went in, not how many cycles. After three passes the chains break, and old against fresh regrind can differ 15 percent.

Which number on the grade sheet is most often missed?

Answer: Density. It sits in the fourth decimal but drives unit weight and cost, and 0.5 percent is a batch of difference by the tonne.

Does case raw material preparation need a new trial mould for a new supplier?

Answer: Yes. Catalyst systems differ, melt flow can move 1 to 2 g per 10 minutes, and thin walls show it first.

Does more talc mean less distortion?

Answer: No. At 15 parts modulus gains 25 percent, at 25 parts impact halves. Flatness needs even wall and balanced cooling.

Must an outdoor case use a light stabiliser?

Answer: Depends on years. Under one year, 0.2 part scrapes through; past two, 0.4 part keeps 20 points more impact after 1,000 hours.

After a 25 kg Bag: What Case Raw Material Preparation Decides

Quick answer: Case raw material preparation does not start at the hopper. It sets four layers against a grade sheet: resin for stiffness, toughener for cold impact, additives for outdoor life, regrind for cost.

Four layers inside one case
Five numbers on a grade sheet
Where the properties land on the case
Cold and ultraviolet cut half the grades
Incoming inspection: three papers or no unloading
FAQ

1. Four layers inside one case

A 3.2 kg case eats about 3.6 kg of compound from hopper to ejection; the surplus is runner and sprue. That compound is four layers: resin as the frame, toughener and filler for properties, additives for life, regrind for cost.

Resin takes 100 parts. Injection bodies use block polypropylene copolymer at 0.90 to 0.91 g per cubic centimetre, which all but fixes unit weight; rotomoulded shells use high-density polyethylene at 0.94 to 0.96, 6 percent heavier per wall. The two never interchange: a rotating mould needs a higher melt index.

Layer	Parts	Job	Overdose
Resin	100	Density, wall, flow	New process window
Toughener, filler	10 to 15	Cold impact, stiffness	One must give
Additives	0.8 to 1.0	Antioxidant, UV	Blooming, tacky
Regrind	0 to 20	Cost	Brittle at 3 passes

Toughener is the layer most often rebalanced. Ten parts of polyolefin elastomer lift the -20℃ drop height from 0.6 to 1.1 m; fifteen parts of talc add 25 percent to modulus and take 30 percent off notched impact. Additives near one part set the years outdoors: 0.2 part antioxidant, 0.4 part hindered amine, 0.1 part stearate.

2. Five numbers on a grade sheet

A grade sheet prints two pages; case raw material preparation copies five numbers. Melt flow, at 230℃ under 2.16 kg, sits between 8 and 12 g per 10 minutes; notched impact at 23℃ runs 6 to 10 kJ per square metre.

Case Raw Material Preparation: white case fully open on a metal table, black gasket along the lid rim, four foam compartments, stacked bins behind

Then flexural modulus at 1,100 to 1,400 MPa, deciding whether a lid face feels soft; heat deflection at 95 to 105℃ under 0.45 MPa; density, which turns volume into weight. At a 60℃ cabin the deflection figure leaves about 35℃ of margin, so a dark case in direct sun is the harder duty than the same case in shade.

Property	Range	If it drifts
Melt flow	8 to 12 g per 10 min	Short shot, or yellowing
Notched impact	6 to 10 kJ per square metre	Cracks at the radius
Flexural modulus	1,100 to 1,400 MPa	Sags when stacked
Density	0.90 to 0.91 g per cubic centimetre	Volume quotes lose money

Melt flow is the number case raw material preparation treats as a constant. Batches drift 10 percent: at 8.8 against 8, a 600 mm path can starve a thin wall; at 7.2, torque and melt temperature both climb. Density hides in the fourth decimal, where 0.905 against 0.910 is 16 g on a 3.2 kg case, or 160 kg across ten thousand units.

3. Where the properties land on the case

Properties land in four places, each asking something else. The lid face wants stiffness: at 3.0 mm over a 600 mm path the ratio nears 200, so a melt index under 6 will not fill. The hinge boss wants toughness, thickened to 6.5 mm, where sink marks and stress collect; at 1.8 percent shrinkage that boss pulls roughly 0.11 mm of sink, enough to shift the hinge axis and make a lid drag on one side.

The handle root wants fatigue life: eight cycles a day for five years is about 15,000 reversals, plus snatch loads. Homopolymer polypropylene embrittles at -10℃ and block copolymer holds, so case raw material preparation never chooses resin on strength alone.

The gasket groove wants stability. Six millimetres wide, five deep, 0.15 mm of flatness error and the seal will not compress: 30 kPa fails to hold 60 seconds. At 20 percent regrind, shrinkage moves from 1.8 to 1.9 percent and sinks the groove, so sealing faces stay at 10 percent.

4. Cold and ultraviolet cut half the grades

A grade that looks good at room temperature often fails at -20℃. An 8 kg head from 1 m passes in summer and needs the height cut to 0.6 m in the cold; anything holding under 60 percent of notched impact is off for northern sites.

Case Raw Material Preparation: white case on a shelf with the lid ajar, two latches on the front, moulded handles at both ends, rounded corners

Ultraviolet is the second sieve. After 1,000 hours of xenon arc, an unstabilised surface chalks and impact halves; at 0.4 part hindered amine the sample holds above 70 percent, colour shift inside 3. Grades meeting -30℃ impact and no sag at 60℃ cost 15 percent more, so case raw material preparation runs two sample sets.

5. Incoming inspection: three papers or no unloading

Three papers first: the delivery note for grade and batch, the certificate for melt flow and impact, the colour chip. If they disagree, the 20 tonnes stay outside, and that line belongs in the work instruction for case raw material preparation.

Sampling takes one bag in twenty, 100 mm below the mouth, avoiding lumps. Above 0.05 percent moisture the pellets cannot go to the hopper; a size outside 2.5 to 3.5 mm gets segregated, and fines over 0.5 percent mean bridging at the throat.

Check	Sample	Limit	Action
Moisture	50 g, three points	0.05 percent max	Re-dry 2 hours
Pellet size	200 g sieved	90 percent in 2.5-3.5 mm	Segregate
Melt flow	One test per batch	Within 10 percent	Reject, re-qualify

Storage belongs to case raw material preparation: one tonne per pallet, three high, first in first out over six months, window bays screened, because daylight through woven bags yellows the surface in a summer. Bags also carry batch and cycle marks, without which a suspect lot cannot be traced to a machine or a shift.

Conclusion

Case raw material preparation answers one question: where the case goes, and which layer gains parts. Resin fixes density and flow, toughener and filler fix cold impact, additives fix outdoor years, regrind fixes cost. The five numbers, four landing points and three papers are facets of one decision, which is case raw material preparation.

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.