PART ONE ( 1-15 )
This article will tell you some common problems in the injection molding process and also the corresponding solutions.
The product runs off the edge (flash edge)when being turned on. The reason and solution of the product lacking glue after a period of production.
When the machine starts to work, the melt glue in the material tube of the injection molding machine has a long heated time, low viscosity and good fluidity. So the product is easy to run off the edge.
After a period of production, the melt glue constantly takes away the heat. Then, that results in insufficient melt glue, high viscosity and poor fluidity, which makes the product lacks glue. Therefore, you should gradually increase the temperature of the feed pipe to solve this problem.
Sometimes when the product is short of glue, it’s no use increasing the injection pressure and speed, why?
After a period of production, the melted glue continuously takes away the heat. And that results in insufficient melt glue, high viscosity and poor fluidity, which makes the product lacks glue. Now, you should increase the material tube temperature.
The reason and solution for ellipse-shaped product.
The ellipse shape of the product is due to the uneven glue input, resulting in uneven pressure around the product, making the product become ellipse shape. You can inject the glue from three point to make the injected glue even.
The requirements of precision products on the mold.
It is required that the mold material has good rigidity, small elastic deformation and small thermal expansion coefficient.
Purpose of acid resistance test for product.
The acid resistance test of the product is to detect its internal stress and the location of the internal stress focus point to eliminate the internal stress of the product.
Reasons and solutions for cracking of metal inserts in the product.
When inserts are placed in the product, internal stress will be formed due to hot melt meets cold inserts during injection, which reduces the strength of the product and make it easy to crack. During production, you can preheat the inserts.
Rationality and selection method of the mold exhaust point.
If the exhaust point of the mold is unreasonable. Not only does it fail to exhaust, but it will cause deformation or dimensional changes of product. So the exhaust point of the mold should be reasonable.
You can set the exhaust point at the place where the product is injected with glue and burnt in the trapped gas.
Reasons and solutions for brittle products.
The product is brittle because too many degraded material and defective material are used in the product, or the material stays in the material tube for too long, causing the aging of rubber and making the product brittle.
You can increase the proportion of new materials and reduce the recycle of degraded materials ( generally not more than three times ). That can avoid a long stay of the rubber material in the material tube.
Reason and solution for the products with fiberglass prone to reveal.
The low melt temperature or low mold temperature, and insufficient injection pressure can’t help to make a good combination of glass fiber and plastic in the glue, causing revealed fiber.
You can increase the temperature of melt and mold to increase the injection pressure.
Effect of feed inlet temperature on the product.
If the temperature of the inlet is too high or too low, it will cause unstable back feeding of the machine, make the amount of feed unstable, and affect the size and appearance of the product.
Reasons and solutions for white spots on transparent products.
Cause: the cold glue in the product or the dust in the material.
You can raise the temperature of the nozzle, add a cold feed well and keep the raw materials well to prevent dust from entering.
Injection ability PW = injection pressure ( kg / cm2 ) × injection volume ( cm3 ) / 1000
Injection horsepower PW ( KW ) = injection pressure ( kg / cm2 ) × injection rate ( cm3 / sec ) × 9.8 × 100%
Injection rate V ( cc / sec ) = л / 4 × d2 × rd2: diameter of material tube r: density of material
Injection thrust F ( kgf ) = л / 4 ( D12-D22 ) × P × 2D1: cylinder inner diameter D2: piston rod outer diameter P: system pressure
Have you learnt something from this article ? Do you have any other solutions to deal with the injection molding problems?