Friends who do non-standard mechanical design basically draw pictures every day, and some design problems will inevitably occur more or less. Today, I will share with you some common design problems, and also provide you with reference when designing to avoid similar problems.
Unreasonable rounded corner design 01. As shown in Figure 1 (left), the rounded corner design of the part is unreasonable. Some engineers who have just started working often make this mistake. They may draw the step transition position into a rounded corner for aesthetic reasons. In this way, they need to perform milling as shown in Figure 1 (right) during processing, but the rounded corner of the part is too long, and the cutting edge length of the tool is not enough during processing, which will easily cause the tool to give up. Therefore, the reasonable design should be as shown in Figure 2, and it can be directly designed into a right angle, so that the above processing problems will not occur. Figure 1 Unreasonable rounded corner design
Figure 2
Editor's comment: When we judge the rationality of the structure, the essence is to consider the convenience and cost of processing. If an ordinary milling machine is used for processing, right angles are more convenient than arc angles. If it is fast wire or CNC processing, there is no such problem. With the development of processing technology, the processing technology has also changed greatly. Laser cutting or fast wire cutting is a very common process.
Irrational hole design 02. In the figure below, the punching position is next to the bending position of the sheet metal. In this case, the drilling position is not guaranteed. If it is a threaded hole, the thread will be easily deformed. Therefore, when designing, the hole position needs to be far away from the bending position.
The hole position is close to the bending position of the sheet metal. For example, in the figure below, the part is a rack welded by a welded square tube, and the punching position is close to the welding area. The hardness near the welding position is high, and the processing is difficult and the drill bit and tap are easy to break. Therefore, when designing, it is reasonable to keep the punching position away from the welding area. The hole position is close to the welding area
Editor's comment: After the 3D design of the sheet metal structure is completed, the holes on the bending or welding edge should be adjusted appropriately according to the specific structure.
Irrational design of shaft parts 03. As shown in the figure below, a simple schematic structure is drawn in order to express it. In the middle is a shaft part connected in the middle of the 2 parts. The shaft parts in the figure are designed to be two small and large in the middle. This requires secondary clamping during processing, which is complicated and difficult to guarantee the size. It can be designed to be large at one end and small at the other without affecting the function. This shape is easier to process.
Unreasonable design of shaft parts Editor's comment: Not all shafts designed to be small at both ends and large in the middle are unreasonable. In fact, most structures with two bearing positions have such characteristics. Reducer shaft
One-piece part design problem 04. As shown in the following figure, the left side is made of two parts spliced together. In fact, the volume of this spliced structure is not large, and it is better to process it directly from one part. Dividing it into two parts will lead to complex processing, difficult size control, and waste of installation time. The right side is a one-piece part, which is simpler to process, does not have so many holes to be processed, and the size is better guaranteed.
It is more reasonable to design small-volume parts into one
As shown in the figure below, the volume of this part is relatively large. If it is designed as an integrated part, it will lead to problems such as large processing cutting, complex processing, and increased costs. It is better to design large parts separately. In short, when we design a structure, whether it should be designed as a separate part or an integrated part, we should comprehensively consider processing, cost, installation and debugging. Generally, when the length, width and height of the structure are less than 80*80*80mm, we generally design it as an integrated part, and when the length, width and height of the structure are greater than 80*80*80mm, we design it as a separate part. Editor's comment: Whether to design it as a whole or split, in addition to considering the size, the focus is on whether the processing technology is the simplest, the easiest to ensure the accuracy requirements of the parts, and whether the overall cost is the lowest.
