In order to take out plastic parts and aggregate of gating system from closed mold, place insert, mold is appropriately divided into two or several main parts. These separable contact surfaces are generally called parting surfaces. Representation method of parting surface:
1. When mold is separated, mold plates on both sides of parting surface are moved;
2. When molds are separated, one of mold plates does not move, the other mold plate moves.
A. Number of parting surfaces: single parting surface, double parting surface, multi-parting surface.
B. Shapes of parting surface are: flat, inclined, stepped, curved.
C. Relationship between parting surface and mold opening direction: parallel to mold opening direction, perpendicular to mold opening direction, and an oblique angle with mold opening direction.

 

Parting is a compulsory course for every design. However, there are many places when parting a model, often because of some personal habits or working style of some factories, many problems are prone to appear. If you wait for molds to be made, you will find out. Sorry, it's too late, so many things must be prepared before parting. Many times, when you get product, you start to draw in 2D. 2D structure diagram can express structure at most. To process it, you have to play in 3D. When drawing in 2D, you can think of and discover structure. But some are like bumping, penetrating or something. It is rarely comprehensive. Therefore, some basic analysis and inspection of product before 3D parting can save a lot of trouble in the following. Here is a talk about what checks are usually done before parting:
1. Product wall thickness: This problem is primary problem. If you haven't checked it well before, usually product will be tested when you know problem. It is very troublesome to change at this time. Wall thickness is required to be uniform, and there should be no thinness and thickness. Uneven thickness, easy to shrink. The most troublesome thing about bone shrinkage is that you usually have to make inserts. If there is no water underneath, it’s okay. If there is water, you have to think about picking it up. Therefore, at the beginning of parting, I used to see a bit thicker bones. When they were not assembled, I just cut them off, so I didn’t bother to ask.
2. Crater: This product is given by many customers, and screw column is usually a straight long column. Basically, when I didn't see any painting products making craters, I had to do it myself at this time, and I didn't need to ask them. They won't do it for you either. Everyone wants to be lazy. Who would call them a client?
3. Draft angle: It's easy to say that rear mold is drafted, as long as it is not in assembly position, you can pull it as you like, don't be too exaggerated. Some bones can be pulled up very quickly. If it is a former mold, you have to communicate with customer. It's okay for smooth surface, and small degree is not a big problem. Some small draft angles can be repaired by yourself. If there is a texture, this has a requirement for draft angle, so you have to refer to pattern to do it. Most of time, front mold is exterior surface. If you want to modify it, it is basically product engineer who will do it, as long as you propose it in early stage.
4. Thin steel sharp corners: Generally speaking, in preliminary review, general glue position is still relatively obvious, but some places where inserts are to be removed are not easy to see. Before removal, it does not feel sharp. But as soon as insert was removed, it was discovered. If there is no way to change it due to product structure, then there is no way, just sharp corners. But you also have to inform before, leave a way for yourself. When you encounter nonsense, you have no reason to explain, and it is you yourself that is troublesome later.
5. Parting surface and parting line: Generally speaking, problem of large parting surface is still not big, mainly dealing with some corners, R angles, and when inserting. There may be too little sealant in some places, insufficient penetration angle, or front and rear molds are not easy to come out, sometimes there will be undercuts. This is sometimes not visible in early stage, and problem will be discovered as soon as actual model is removed.
6. Round holes and rotating shaft: Some round holes, position of rotating shaft has to be figured out for what it is used for, it involves assembly things, and special attention should be paid when disassembling mold. If it is made because of faults and misplacement, it will affect assembly at that time, and people will scold it.
7. Orientation of collision position: When collision is involved, whether front mold touches back mold or back mold touches front mold. If you use criticizing front, then which side will criticizing front be on? Whether it is repaired or not, will it affect appearance. Although bur doesn’t need you to fix it, its location directly affects quality of product.

Regardless of whether parting surface is specified in plastic parts data, mold designer must specifically determine; if there is an unreasonable part of specified parting surface, feedback to other party.

 

Mold Design Guide-3. Rubber Parts Structure
Pay attention to following points when analyzing parting surface of rubber parts:
(1) Determine surface clamping position according to appearance requirements, as shown in Figure 3.2.13.
(2) Place part of rubber part that requires coaxiality or is easy to be misplaced on same side of parting surface, as shown in Figure 3.2.14 and Figure 3.2.15.

 

Mold Design Guide-3. Rubber Parts Structure

(3) Consider size difference between large and small ends of rubber part caused by draft angle, as shown in Figure 3.2.16.

 

Mold Design Guide-3. Rubber Parts Structure

(4) Determine position of rubber part in mold so that parting surface formed should try to prevent side holes or undercuts to avoid use of complex mold structures, as shown in Figure 3.3.16 and Figure 3.3.17.

 

Mold Design Guide-3. Rubber Parts Structure