The Draft Select tool allows you to change the face highlight colors based on the angle. Generally, a positive color indicates a larger angle and a negative color indicates a smaller angle. Using this tool, you can see a color graph of selected surfaces with the angle measured between them and the selected plane.
Minimum draft angle
If you have a design that requires a minimum draft angle for a part, you’ll want to know how to measure the angle. This angle is the angle that divides the principle plane of the part by the normal of the surface under the cursor.
In CAD, it’s possible to measure the angle by using the draft angle command. You can find this command by clicking the Calculator button on the status bar.
Draft angles are important design considerations when working with thermoplastics during injection molding. They help the parts release from the mold cleanly.
They are measured in degrees from the vertical axis of the mold and account for thermoplastic shrinkage. If you’re not using the right draft angle, you may end up having to rework the part.
This injection molding draft angle applies to all parts in contact with the mold walls. The deeper the part, the more the draft angle needs to be. A shallow straight rib will require a smaller draft angle than a high cylindrical wall depth.
Also, textured or polished surfaces require a larger draft angle. If you want the parts to release easily from the mold, you’ll need to make sure that the draft angle follows the direction of the injection mold moving up and away. For example, if you’re molding a hollow box, you should aim to create a draft angle of one to three degrees.
Proper draft angles save you time and money. A proper draft angle is essential in the design and manufacturing injection molding process. A bad draft angle can ruin the product and cause mold problems. It may even require a redesign of the mold.
This could lead to the creation of a completely new design. It is also important to consider how well your design concept will work with injection molding before you begin the design process.
Techniques for determining the draft angle
To determine the draft angle of a mold, there are two common methods. One method uses a table rule. The other is using a drafting face. If both faces are drafted in the same direction, the angle between them should be the same. However, if the faces are drafted in opposite directions, there is an increased chance of interference.
A draft angle is a necessary design feature in injection molding. It helps release the part cleanly from the mold. It is calculated as a degree of draft from the vertical axis of the mold. It also accounts for the shrinkage of thermoplastic. It can be as small as 1.5deg or as large as 0.5deg.
Draft angles are also important to prevent vacuums during ejection. Without an adequate draft angle, parts can stick in the mold and can damage mold ejector pins.
In addition, improper draft angles can lead to a poor finish on the part. Adding draft angles can also reduce the cost of production by preventing the need for expensive ejection setups.
Draft angles can be difficult to determine. The process begins by defining the weft thread direction and calculating the angle between the weft thread and the center.
This is known as the central angle. If the weft threads are perpendicular to the conveying direction, they will run parallel to the center angle. Using this method will allow you to directly determine the draft angle of the part.
Impact of draft angle on the part finish
Injection molds have various features that affect the finish of parts, and draft angle injection molding is one of these features.
The right draft angle can reduce the force required to remove a part from the mold, improving the part finish and the cost of production. Natech’s engineers can help you determine the best ejection process for your parts.
Ideally, the draft angle of a part should be parallel to the draw direction of the mold. This minimizes the ejection of injection molded parts that are not smooth.
Moreover, a shallow straight rib is less likely to cause ejection problems than a high cylindrical wall. Besides, it is necessary to consider the type of surface a part will have before choosing the draft angle. If the part is a cover for an assembly, for example, scuff marks may not be acceptable.
If the draft angle is too high or too low, the parts may stick to the injection mold surface. This compromises the quality of the product and mold. Molds with a smooth surface are more efficient and reduce the need for secondary finishing. Using mold release agents before molding will help reduce the risk of mold damage.
Another factor to consider is the design of the mold. Some molds have stepped parting lines that require a special surface. Shut-off surfaces are crucial, as they prevent gaps between two parts when closed.
However, these surfaces should not be parallel to the draw direction of the mold, as this would create drag and tool wear. Usually, designers apply a 5deg to 7deg to calculate the draft angle to their molds.