What causes jetting in injection molding?
The chief cause for jetting is excessive injection pressure. When molten polymer or other material is injected through a small gate at high pressure it often squirts rapidly through the gate, rather than filling the mold cavity gradually.
How to design parts for injection molding?
Having a basic understanding of the injection molding process will help you understand what features to consider when designing parts for injection molding and also how to forecast production schedules. Choose the color, texture, and resin.
What causes discoloration in injection molding products?
A common cause of discoloration is leftover pellets in the hopper or residual resin in the nozzle or mold from a previous production run. Poor thermal stability of the coloring agent or improper mixing of the masterbatch are other potential causes. Take the following precautions to limit the risk of discoloration in your injection-molded products:
How do you fix flow lines in injection molding?
Here are some common remedies for flow lines in injection-molded products: Round the corners of the mold where wall thickness increases to help keep flow rate consistent and prevent flow lines 2. Burn marks Burn marks typically appear as black or rust-colored discoloration on an edge or surface of a molded plastic part.
What is injection molding?
Injection molding is a common manufacturing process used to make components made of metals, polymers, glasses, confections and other materials. Pellets of material are melted and then injected at high pressure into a mold that will set to form the desired component. Here are 11 common injection molding defects to watch out for when inspecting ...
How to prevent short shot mold?
Consider the following steps to prevent short shot: Redesign the mold with wider channels or gates for better flow. Increase injection speed or pressure or choose a thinner base material to improve flow.
Why does mold have voids?
One of the chief causes of voids is inadequate molding pressure to force trapped air out of the mold cavity. Other times, the material closest to the mold wall cools too quickly, causing the material to harden and pull the material toward the outside, creating an abscess.
Why do injection molding parts burn?
The usual cause for burn marks in injection-molded parts is trapped air, or the resin itself, overheating in the mold cavity during injection. Excessive injection speeds or heating of the material often lead to overheating that causes burns. Consider the following preventative measures to avoid burn marks in molded components:
Why does mold warp?
Often excessive temperature or low thermal conductivity of the molten material can worsen the problem. Other times mold design can contribute to warping when the walls of the mold are not of uniform thickness—shrinkage increases with wall thickness. Here are some common ways to prevent warping in your molded parts:
How to prevent mold defects?
You can typically avoid these defects relatively easily simply by adjusting the flow rate, temperature or pressure of your mold. 1. Flow lines.
What causes warping in injection molding?
Warping is deformation that can occur in injection molded products when different parts of a component shrink unevenly. Just as wood can warp when it dries unevenly, plastic and other materials can warp during the cooling process when uneven shrinkage puts undue stress on different areas of the molded part. This undue stress results in bending or twisting of the finished part as it cools. This is evident in a part that’s meant to lie flat but leaves a gap when laid on a flat surface.
How does Kastaplast work?
Kastaplast does this well. They eliminate the human factor by having a robot pick the disc out of the press and let them cool on a conveyor belt. Unfortunately, most companies do not have the space to let discs cool in a single layer for 24 hours in a climate controlled environment. It would just take up too much valuable warehouse space.
Is injection molding a good 3D printer?
Modern technology allows manufacturers to go beyond the basic straight drilled cooling channels, resulting in lower cooling times and improved quality. Injection molding is actually a perfect application for metal 3D printing since just a single mold needs to be printed that produces millions of parts.
The Injection Molding Process
Having a basic understanding of the injection molding process will help you understand what features to consider when designing parts for injection molding and also how to forecast production schedules.
Uniform Wall Thickness
Wall thickness is the most important factor to consider when designing parts to be injection molded. Wall thickness influences many key characteristics of the part, including mechanical performance, cosmetics, and cost.
Bosses
A boss is a localized, raised area used to fasten and connect parts. Bosses can be a helpful way to strengthen your part, without compromising manufacturability, by means of injection molding. In injection molding design, everything must be thin-walled, to increase mold life, part quality, speed, and more.
Ribs
Ribs are used to add structural integrity to your part and increases its load bearing capacity. They’re a simple concept to introduce to your part that can get complicated with plastics. Plastic injection molded parts should have a uniform thickness, but for ribs, we break this rule.
Parting Lines
The parting line, where the mold opens and closes, determines the direction of your draft.
Gates
The four most common types of gate designs are edge, sub, hot tip, and sprue.
Ejector Pins
Ejector pins push the part out of the mold when your part has finished cooling, and most of the time, they leave a mark. You may have noticed these ejector pin marks on some household products. Typically, these are ejected on the surface of the part that may not be visible, such as the inside of a housing.