Generally black Specks or gloss difference on plastic molded parts can tracked back to three sources : the mold itself ,the processing of the material in the mold  and the material being used to make the part.  Mold The surface of the plastic part is the reproduction of the cavity surface of the plastic mold.Therefore, if there are scratches, corrosion,small pit and other defects on the surface of cavity steel, all will appear on the surface of plastic molded parts as defects. When grease mark, excessive moisture, or improper use of mold release agent,  the surface of the plastic part will show different color gloss. So the cavity surface should be maintained in a gloss condition through mirror polishing or chromium plating. Meanwhile cavity surface must be kept clean with oil and water stains being removed in a timely manner.The type and amount of release agent should be appropriate. In addition, the other mold failure, such as the…

The color of plastic injection molded parts might be a huge issue if not controlled properly because it can make a big difference in the success of your product . For cosmetic or consumer products, colors and appearances directly affect aesthetic property of the whole product,which therefore can highlight your products from those next to it on the shelf. Uneven color (mixed color)   As a result,for a mold maker, it’s as important to be aware of some of the common problems involved with color variation or mixed color issues in plastics and how to avoid them. Generally, aesthetic flaws can be attributed to three different causes: raw material,machine and molding process.   Material   1.Poor thermal stability of colorant;   2.The dispersion effect of colorant is not ideal;   Too much pigment, eg, a bag of 25KG plastic contains over 300g of pigment.   Adding fiber glass and there is floating fiber on the product surface,…

There are normally four Interior door pannels in a car, including Front, Rear, Left and Right parts which are usullay made from PP material. As known, the quality is demanding for these A class plastic parts. No visible defect is allowed. However, ejector mark is a  commonly seen defect that is difficult to overcome with most injection molder. Below is a study case to show that how HSMold solves the headache. name Car door panel Injection pressure 40MPA     material PP Adhesive method Side gate Holding pressure 18MPA colour gray weight 1400G         The picture below shows the ejector mark defect of car door panel. There is a around ejector rod on the back of the white mark. This defect greatly affects the aesthetics of the car door panel,which is  an unacceptable 1) Possible cause analysis and improvement measures Possible cause: The main reason for the ejector…

For injection molders, it should be very common to see white ejector mark or pin push appear on the plastic parts in contact with the ejector pin during the process of ejection. This mark doesn’t only affect cosmetic look of the A class part, but also easily gets cracked during actual use of the products Therefore it is very important to prevent ejector pin marks before they happen. What are the reasons for ejector mark and how to eliminate them? Well, the glossy or white imprints defect is usually due to the excessive pressure at the white area of the plastic parts where the chemical resistance and mechanical properties were greatly weakened. The specific analysis could be traced to either plastic molds or molding process. Plastic injection mold ①If the surface of cavity is too rough, release resistance is increased and ejector white mark is caused. Therefore, the surface roughness in…

I believe that many mold manufacturers have encountered a plastic defect-shrinkage on injection molded parts. Few processors really know how to solve the shrinkage issue technically.In most case, mold makers just increase injection pressure,use longer injection time,or open larger injection gate, only annoyed to find that the issue is still there. Among the commonly used raw materials, the shrinkage problem of modified PC and PP are the most difficult to handle due to fast cooling rate. Through 20 years, we have made plenty of plastic components with different kinds of resins for our global customers and has mastered some unconventional molding techniques to improve the shrinkage problem on plastic molded parts with thick wall. Basically, the plastic shrinkage defect could be contributed to 3 aspects, molding machine, plastic mold, and plastic material. Injection molding machine Cause:1: The injection pressure in the cavity is too low.2: Insufficient plastic in the cavity.3:…

Nowadays most of our daily products are made from plastic materials.However, many plastic product manufacturers encounter one injection molding defect that happens from time to time and that is part brittleness.  Brittleness appears when the part breaks or cracks upon ejection or after it is ejected during handling.  According to our years of experience,  we found that the the likely causes could be contributed to either Material, Mold, or Machine causes.   Injection molding Process  Cause: (a) the melt temperature is too low (b) The plastic degrades in the shot cylinder, causing cracking of the molecular structure of the plastic. (c)  Mold filling speed is too slow.   Remedy: (a) increase the mold temperature. Keep sufficient supplementary material on the barrel of                              injection molding machine. (b) Reduce the temperature of the shooting tank in all areas.Reduce back pressure.Use…

More and more  large size of  plastic injection molding parts are used in automotive industry. For consideration of cost, the application of spray free injection parts is more and more extensive. However, this also requires higher cosmetic quality of injection molding parts. On some large parts such as bumpers, dashboards, door panels and long interior plastic accessories, it is very common to see an appearance defect characterized by a streak or stripes perpendicular to the plastic flow direction, which looks like a pattern on the skin of a tiger. We call this “Tiger Flow Line”, for more information on the flow line, please                                                              Tiger flow line   Below is an example to demonstrate how HSMold solve this kind of issues. Product name Dashboard Material PP Color black Mold Tem….

The amount of plastic used in automobile has become an important symbol to measure the level of automobile design and manufacturing technology. At present, more than 10% of the domestic automotive parts are made from plastic including exterior trims such as bumper, skirts and fenders, and exterior trims such as instrument panels, panels and pillars, also engine peripheral parts such as GOP, covers and inlet manifolds. Most of the plastic automotive parts are injection molded because the process has unbeatable advantages such as short molding lead time, high production efficiency and low manufacturing cost is low. However, the coin always have two sides. There are also some plastic defects such as Tiger Line that we could not overlook What is Tiger Flow Line then? Tiger lines are streaks, or wave lines –  look like patterns on tiger skin, with stripes about perpendicular to the direction of melt flow,which is a kind of flow mark.  It usually shows up on automotive…

Splay mark, is also called as Splash Mark or Silver Streak.It is a cosmetic defect that occurs in plastic injection molding process, when silver or white streaks appear on the surface of the molded part. Sometimes Splay can be quite difficult to determine, as the appearance is very similar to other injection molding defects, such as surface scratches, scuffs, flow lines, delamination from contamination, and flaking (also known as cold slugs).   Why there is Splay? There are many possible reasons for the appearance of splay mark, molding process, the mold itself, the machine, or the material.   Material The most common cause of splay is material moisture. It is easy to identify that.  The moisture splay does not occur in the same place every time, or in some cases the splay is all over the part. In this case, use dry material, review material drying process, review material storage for contamination issues Molding process  Too much heat can have an appearance similar to moisture splay. The…

One of the top 10 common defects in molded parts is bubbles. After demolding from the press, bubble or bump may occur shortly on the plastic area where the back of metal insert lies or where plastic wall is too thick. This is due to the expanded gas released by the plastic that are not completed cooled and molded under the action of internal pressure. The troublesome part defect not only results in appearance problems but impairs physical properties as well. In troubleshooting bubbles, many molders make the mistake of guessing at what the bubbles are, and then immediately start adjusting process parameters to eliminate them, only to find that the defect is really difficult to solve. At as a injection molder with over 20 years of experience, HS Mold has our own “unique secret ” to tackle such issue. No need too much talking. Look at below examples. Description Part name Automotive Rear…