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Practical answers to common plastic material challenges

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Q

PC Injection Cycle Fluctuation—Drying Fluctuation

A

PC drying's enemy is 'secondary moisture absorption'.

Material Drying PC; drying; secondary moisture absorption; dew point; fluctuation

Q

PC Degradation from Excessive Barrel Residence Time

A

PC residence time is a 'hard indicator': machine matching is the premise, a large machine making small parts equals chronic degradation; calculating the residence time when selecting the machine is more effective than adjusting the process afterwards.

Processing Machinery PC; residence time; degradation; machine matching; melt temperature

Q

PC Hot Runner Gate Stringing

A

For PC stringing, check 'hot runner temperature control and valve pin action': temperature and timing are the two major variables; the state of the hot runner system directly determines gate quality and must be included in regular inspection.

Molds & Tooling PC; hot runner; stringing; valve pin; gate cooling

Q

PC Brittleness Caused by Regrind Use

A

PC regrind = 'dual deterioration of moisture content and molecular weight': the ratio must be strictly controlled, and it is firmly not used for optical parts and load-bearing parts; PC is sensitive to thermal history and hydrolysis, so regrind management must be stricter than for general-purpose...

Material Drying PC; regrind; brittleness; molecular weight; fine powder

Q

PC Birefringence (Rainbow Pattern)

A

PC rainbow pattern = 'optical development of internal stress': reducing pressure, raising temperature, and annealing can alleviate it; optical parts must minimize orientation stress from flow design, this is more of a design problem than a process problem.

Injection Molding PC; birefringence; rainbow pattern; internal stress; orientation

Q

PC Transparent Part Haze Exceeding Standard

A

PC haze = a comprehensive examination of 'moisture, thermal history, mold surface': losing control of any one causes haze; transparent parts must manage the three lines of drying, temperature control, and polishing at the same time.

Material Drying PC; haze; transparency; drying; polishing

Q

PC Black Specks (Carbonized Spots)

A

Transparent PC's tolerance for black specks is zero: dead-corner treatment must be normalized and institutionalized; intermittent black specks are a typical feature of dead-corner carbon deposits, and purging is far more effective than adjusting the process.

Molds & Tooling PC; black speck; carbonization; hot runner; purging

Q

PC Sticking to Mold (Demolding Difficulty)

A

PC has large demolding resistance, and mold draft and polishing must meet higher standards: reduce pressure and temperature to reduce gripping, draft and polishing to reduce resistance, deep cavities to prevent vacuum; PC's demolding margin design must be stricter than general-purpose materials.

Molds & Tooling PC; mold sticking; draft angle; polishing; holding pressure

Q

PC Ejector Whitening and Ejector Cracking

A

PC ejector whitening and cracking = 'large gripping force + concentrated force': first disperse the ejection force, then extend cooling, and finally reduce holding pressure; PC is both rigid and brittle, and the design margin of the ejection system must be larger than for general-purpose materials.

Molds & Tooling PC; ejector whitening; ejector cracking; ejector pin; holding pressure

Q

PC Sink Marks

A

PC sink marks are treated from both ends of 'structural wall thickness and holding feeding': rib thickness and thick walls are the root, holding and freeze are the technique; sink marks on transparent parts are also optical defects, and wall thickness must be controlled from the design stage.

Molds & Tooling PC; sink mark; holding pressure; rib; freeze

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All Topics 11636 Material Drying 1439 Injection Molding 1506 Molding Process 740 Molds & Tooling 1506 Processing Machinery 2025 Extrusion & Post 2239 Blow Molding 315 Thermoforming 141 Material Analysis 1343 Production & Quality 382