Basic Methods and Steps of Fixture Design
Preparation before design The original data of fixture design includes the following:
a) Design notice, finished part drawing, blank drawing, process route and other technical data, understand the processing technical requirements of each process, positioning and clamping scheme, processing content of previous process, blank situation, machine tools, tools, inspection measuring tools used in processing, machining allowance and cutting amount, etc;
b) Understand the production batch and the demand for fixtures;
c) Understand the main technical parameters, performance, specifications, accuracy of the machine tool used, as well as the connection dimension with the structure of the fixture connection part;
d) Inventory of standard materials of fixtures.
Considerations in fixture design
Generally, the fixture design has a single structure, which gives the impression that the structure is not very complex. In particular, the current popularity of hydraulic fixtures greatly simplifies the original mechanical structure. However, if the design process is not considered in detail, unnecessary trouble will inevitably occur:
a) Blank allowance of the workpiece to be machined. It causes excessive blank size and interference. Therefore, the blank drawing must be prepared before design. Leave enough space.
b) The chip removal smoothness of the fixture. Due to the limited processing space of the machine tool, the fixture is often designed in a compact space. At this time, it is often ignored that the iron filings generated in the processing process accumulate at the dead corners of the fixture, including the unsmooth flow of the chip liquid, which brings a lot of trouble to the subsequent processing. Therefore, we should consider the problems in the processing process at the beginning of the actual situation. After all, the fixture is based on improving efficiency and facilitating operation.
c) The overall openness of the fixture. Neglecting the openness makes it difficult for the operator to install the card, time-consuming and laborious, and the design is taboo.
d) Basic theoretical principles of fixture design. Each set of fixture has to go through countless clamping and loosening actions, so it may meet the user’s requirements at the beginning, but the fixture should have its accuracy retention, so do not design anything contrary to the principle. Even if we can get away with it now, it will not last for a long time. A good design should be tempered by time.
e) Replaceability of positioning elements. The positioning element is seriously worn, so quick and convenient replacement shall be considered. It is better not to design it as a large part.
The accumulation of fixture design experience is very important. Sometimes design is one thing, and it is another in practical application. Therefore, good design is a process of continuous accumulation and summary.