PMMA acrylic injection Molding Defect Causes and Solutions

By Jackie | January 4, 2020 | 0 Comments
PMMA Acrylic injection molding

The defects in the injection molding of acrylic PMMA usually include: short shot, silver streaks, sink marks, voids, jetting, weld marks, gray / black specks, cracking, warpage, and material impurity, while the preventive measures against them are usually: Short Shot This is caused because the resin does not fill the cavity fully. To prevent its … Read more

Plastic annealing and Moisture conditioning process for plastic product

By Jackie | December 23, 2019 | 0 Comments
plastic annealing process

Plastic annealing process The purpose of plastic annealing is to eliminate internal stress. For example, in the area where the thin and thick parts meet, the cooling of the thick part is slower than that of the thin part, causing the joint to shrink unevenly. As a result, there is stress concentration in the area. … Read more

What causes ejector pin marks in injection molded parts?

By Jackie | December 17, 2019 | 0 Comments
ejector pin marks

Ejector pin marks usually refer to the glossy or white imprints on the surface of a injection molded product, as well as the different levels of glossiness – dark or shadow, without convex or concave – visible directly opposite to the ejector pin location. Factors that cause ejector pin mark  1. Product design:  Inappropriate product … Read more

What causes cracking in plastic injection molded parts

By Jackie | December 9, 2019 | 0 Comments
cracking injection molding defects

Cracking is a commonly seen defect in plastic injection molded products, of which the main causes are stress and deformation, mainly including residual stress, external stress and product deformation caused by external environment. (I) Cracking caused by residue stress The residual stress is mainly generated in the following three scenarios, i.e., overfilling, product ejection and … Read more

What causes black specks/black streaks in injection molding parts?

By Jackie | December 5, 2019 | 0 Comments
black specks

Black specks/streaks and impurities are the most important factors that lead to rejects in the normal production process. It mainly affects the appearance of the product and leads to scrap. Most of the impurities and black specks are usually caused by foreign substances, i.e., they have nothing to do with the raw material itself. Only … Read more

What causes parts sticking or sprue sticking during injection molding?

By Jackie | December 4, 2019 | 0 Comments

The causes of parts sticking and sprue sticking are multifaceted, among which mold failure is one of the main reasons. The reasons and corresponding solutions are described as follows: 1. The surface of the mold cavity and sprue bush is rough. If there are surface defects such as gouges, nicks, scars, and dents in the … Read more

What Causes Jetting in Plastic Injection Molding Product?

By Jackie | December 3, 2019 | 0 Comments

Jetting, also known as jet, worm track, or snake-like pattern, refers to the snake-like curves on a plastic injection molded part along the flow direction from the gate, as shown in Figure 1. Under normal circumstances, the molten plastic fills the mold cavity in a “fountain flow” manner, as shown in Figure 2, which depicts … Read more

What Causes Scratches in Injection Molded Products?

By Jackie | December 2, 2019 | 0 Comments

The scratches (scrape marks)on the appearance of an injection molded product usually occur on such deep-cavity products as chargers, routers, and chassis, etc. It is also a particularly common problem during the injection molding process, known as one of the 10 most challenging problems in the mold and injection molding industry. Glossy products, as well as … Read more

What Causes Weld Lines in Plastic Injection Molding Parts?

By Jackie | November 28, 2019 | 0 Comments
weld lines

The definition of weld lines: When multiple plastic flow fronts meet in the cavity after encountering inserts, holes, or areas with inconsistent flow rates or interrupted melt flows, or in the case of gate injection filling, the inability of two or more flow fronts to fully “knit” together will cause the linear weld marks. The … Read more

What Causes Burn Marks in Plastic Injection Molding?

By Jackie | November 27, 2019 | 0 Comments

Factor 1: Melt fracture causes burn marks When the melt is injected into a large-sized mold cavity under high-speed and high-pressure conditions, melt fracture will be easily caused. At this point of time, the surface of the melt is laterally fractured, with the fracture area coarsely mixed to form burn marks on the surface of … Read more