In manufacturing, the three proper terms of fixture, jig, and mold often appear. For non-manufacturing, mechanical engineers or mechanical engineers with little practical experience, these three terms are sometimes easily confused.
The following is a brief introduction, hoping to help those who are interested to have a basic understanding.
Fixtures:
The common English translation is Clamp, the main purpose is to fix objects; Clamps are not only used in production machinery and equipment, but are also widely used in many fields.
For example, the structure that fixes the sight on the gun is called a fixture; it is a very basic function to fix moving objects in automated machinery and equipment. As long as the material is solid, it is inevitable to fix the object during processing, assembly or movement. , the purpose is to prevent the object from shifting arbitrarily when the force or inertia changes (acceleration and deceleration changes), and clamping is one of the most important fixing methods; carefully consider the principle of object fixing, one of which is to give geometric constraints, The solid is stuck and cannot move, and the other is to provide the maximum static friction force that exceeds the inertial force of the object to avoid movement.
The first method, geometrical restriction, is the best method in theory. The reason is very simple, that is, as traditionally known in physics, "solids cannot pass through solids", and objects will not be subjected to additional effects during movement except inertial force. force, which can avoid the object being affected by additional force, but the fixture must be designed according to the shape of the object, and the tolerance needs to be reserved to cope with the tolerance and error in the production of the object, so it is rarely seen in real objects. This concept design is completely used. The reason is that the change elasticity is too small, and the error will cause the possibility of collision between the object and the fixture.
The second method maintains the fixed position of the object by providing the maximum static friction force that exceeds the inertial force. The friction force provided by this method needs to overcome the inertial effect in at least two directions, one is the direction of gravity, and the object will not fall down. , one is the movement direction (both translation and rotation are considered), so that the object will not shift during acceleration and deceleration, which is the most important application method at present.
Traditionally, for metal materials, because of the high strength of the material itself, a large force can be applied to ensure that the object will not move, so hydraulic clamps are often used to fix the object in some metal processing automation equipment.
It is also common in the fixation of some wooden objects, but the fixation force will be relatively small.
The gripper cylinder shown above can directly grip and rotate small objects for handling
The way to provide the maximum static friction force, in addition to providing a positive force in the clamping action and multiplying it by the friction coefficient to calculate the maximum static friction force, in fact, it can also use the vacuum suction to generate a pressure difference to provide a positive force, and then cooperate with a high friction coefficient material. Provide the maximum static friction force that exceeds the inertia force. This method has the opportunity to reduce the amount of force applied to the object. Therefore, it is often used in the fixing of some precision components or brittle materials. The disadvantage is that high friction coefficient materials will Residue and contaminate or scratch the surface of the object, which should be paid attention to on some products that require ultra-high cleanliness.
From the point of view of fixing objects during the moving process, there is a special way for iron materials, including other magnetic iron, cobalt, nickel, etc., to use electromagnetic force, which is commonly used in the work of milling, grinding, planing and other machine tools. On stage (magnetic mount),
However, this force is very large, and is usually not used to overcome the inertial force of the movement, but to overcome the force of the cutting process.
A few special cases are used in high temperature environments, and soft materials cannot be used. There are also some scenes where the above two methods are mixed, and one direction is changed to a geometric limit (such as the direction of gravity) to minimize the impact of force on objects. .
Jig
The usual English name is Jig, and the jig is derived from the Japanese pronunciation; the main function of the jig is to fix and locate the position of the object. Compared with the jig, it has an additional function of positioning, which is often seen The jig will use the geometric restriction method to position the object, so the positioning block and the positioning pin often have a sloped design, which is used to guide the object into a relatively small space and limit the position of the object.
In order to fix the object more precisely, a forced push action is sometimes added to make the object abut against the reference surface/edge; if this action continues and prevents the object from moving, it functions like an extension of the clamp; Therefore, misunderstanding is often caused, and the fixture is confused with the jig. Therefore, strictly speaking, the function and purpose of the fixture and the fixture are slightly different. The fixture focuses on fixing, and the fixture focuses on "precise" positioning. However, because the fixture sometimes requires more clamping and fixing, it is sometimes used with the fixture. It will be a bit similar; in practice, the mechanism design of the two is often placed in the same department in the factory, called fixture design. This department may be placed in production, equipment maintenance, or even in factory affairs or In product research and development, the basic educational background is mainly mechanical engineer.
Fixture improvement and design is a very important starting point in the development of automatic equipment. Many automation equipment companies start from helping factories to improve and design imported fixtures, plus drive devices and control circuits. After all the way, accumulate product and equipment experience and become a complete automation equipment company.
mold
The English name Mold, what is it? The function of the previous fixture is mainly fixing and positioning, basically it has no other effect on the product and will not directly affect the product itself, but the mold is different, and the mold will directly participate in the manufacturing process.
There are many kinds of molds, but the basic function is to limit the shape of the product, or to shape the raw materials into the desired shape. Etc. is the most easy-to-understand example, so molds can be said to be ubiquitous in the manufacture of goods. The more popular thing is that the wooden molds used for making moon cakes are also a kind of molds. As long as a large number of molds are finally sold to end consumers To manufacture goods, there will be a certain shape, and this shape must be completed by a mold.
The classification of molds will be determined according to the industry and the selected process. Apart from food molds, there are two main types of materials processed by molds in the manufacturing industry: plastic and metal (of course, other ceramics, composite materials, etc. will also use molds) , but the amount is relatively small), so first briefly introduce the largest number of plastic manufacturing molds in recent decades. Molds for metal manufacturing or plastic manufacturing can be classified differently depending on the process.
Post time: Dec-21-2022