What Are Joining Processes?
Industrial joining means connecting two or more pieces or components together in a permanent, semi-permanent, or removable connection. There are many types of joining, including permanent processes like welding, soldering, and adhesive bonding. Different presses can also perform many different joining processes with many different components. These processes are generally much faster than welding, soldering, and adhesive bonding, and often forms cleaner, neater connections and join material together with a range of permanence.
Industrial Joining with Press Machinery
A factory press can quickly and neatly join many different types of metals and many different components with various levels of permanence without the need for messy adhesives or time-consuming soldering or welding. Material can be joined by insertion, where a cylindrical piece or shaft is pressed into a fitting with material removed, or joined by deformation, where two or more pieces of material are formed together without removing or decreasing material from either piece. Both of these processes join materials with varying levels of permanence and are used in assembly operation across a wide range of industries.
Joining by Insertion
An industrial press can be used for joining through insertion, where one piece is inserted into another piece from which material has been removed, creating a hole or fitting. The fit, or ratio between the size of the hole and the diameter of the shaft, determines the level of permanence with which the pieces will be joined together, and how much force will be required. Components can be joined together so each can still move in a desired direction and be disassembled if needed, or be forced together to create a tight enough fit where the pieces cannot be disassembled without risking destruction. In general, there are three different levels of fit that determine both movement of parts and permanence.
A wide range of assembly processes can produce clearance fits. These connections are designed to allow controlled, guided movement between two parts, such as connections around shafts, spindles, crankshafts, pivots, latches, gears and more. Since these parts do not have to fit together tightly, less force is required for these assembly processes and the insertion can be completed with varying levels of accuracy. Clearance fits can typically be disassembled easily and require fastening to hold the parts together.
Transition fits, otherwise referred to as location fits, slip fits or push fits, must fit together tightly, restricting movement between the pieces while retaining the ability to be disassembled. Accuracy of alignment between the shaft and the hole is extremely important with transition fits.
Examples of these fittings generally include hubs, gears, pulleys, bushings, and bearings, as well as tighter connections between plugs, driven bushings, and shaft armatures.
Interference Fits / Press-Fit
Interference fits, or press fits, include a variety of very tight, high-friction connections that permanently or semi-permanently join two pieces or components. These processes require a high level of force and accuracy to ensure the components aren’t damaged in the joining process. With certain press fit applications, the force of the press can change the diameter of the shaft piece at a particular point, creating an interference fit where there was initially a very minimal level of clearance. Other press fit applications have zero or negative levels of clearance, and a shaft that is larger than the hole is pressed into the fitting with great force, permanently joining the two pieces. Disassembly becomes impossible in this case, without risk of destruction.
Many different factory assembly processes require interference fits. This might include cold-pressing hubs, bearings, bushings, retainers, hot pressing gears, shafts, and bushings, or shrink-fitting gears and shafts.
Joining Applications by Insertion
Assembly Presses for Joining by Insertion
There is an industrial press for every type of insertion. Press machinery can be used for clearance fits and transition fits to ensure accuracy of alignment. When combined with rotary index tables, pins can be inserted into an object several times in different locations automatically and with high precision. The level of force required for insertion depends on the degree of clearance. For clearance applications, very minimal force will be required, whereas light force will be required for most transition fits. View our line of pneumatic air presses for clearance fit and transition fit operations.
For interference fits, higher levels of force are required and accuracy becomes extremely important. In these cases, an air-over-oil press or even a hydraulic press may be required to achieve the required force, PLC controls and other modifications may be needed to properly ensure accuracy with every application.
Joining by Deformation
Two materials can also be joined together through press applications without the removal of material from either part. In these processes, joining is accomplished through deformation of one or both of the separate pieces, usually sheet metal or other flat, moldable objects with relative plasticity. As long as one of the parts has a degree of plasticity that allows for metal forming, an air press, air-over-oil press or in some cases a hydraulic press can be used to join the two objects with a wide range of permanence. For added strength or permanence in the bond, one or both parts can include ridges or grooves, or rivets could be added to the mix to restrict movement between the pieces and prevent separation.
Joining processes that use deformation of materials include clinching, which joins up to four flat pieces of sheet metal together, and crimping, which can join together two parts of a component or join one piece over another.
Clinching is a critical process for factory presses that combines metal forming and drawing. This process uses sheer force to join sheet metal pieces together without welding, soldering, adhesives, or bolts, rivets, or other fasteners. This not only creates a completely clean, smooth, and solid connection between the two pieces, but it is also exceptionally fast. Different metals require different levels of force and different parts require different press configurations. However, clinching is a very efficient method for joining many different flat metals where two or more layers are punched together and additional force spreads the material outward together, combining it in a way that it can’t be easily separated.
The crimping process uses press force to deform one object so it fits over and into another. This creates a tight, temperature-resistant, permanent connection between the two pieces. Joining pieces in this way is nearly seamless, so the component or product is smooth and flat. One example of a common crimping process is crimping an aluminum can lid over a can. However, there are many types of crimping processes with many different types of metals and the process is used across various industries such as automotive industries for use in car parts and batteries, appliances, medical devices and more.
Combining Insertion and Deformation Applications for Permanence
In certain cases, insertion and deformation applications may be combined for a more permanent hold. Riveting for instance can be used with the clinching process where multiple layers of sheet material have been formed into a hold for greater permanence, or in crimping scenarios where the movement of the metal components should be completely prevented. With the swaging process, a pin or object is inserted with a flared punch, which deforms the inserted material to flare out and flatten onto the object for a permanent connection. In some cases combining a cut and insert method with deformation is not ideal, like in instances where water tightness is critical, as a purely formed connection will be more leak resistant, but there are many instances where the two methods are combined, especially within the automotive industry.
Find the Right Press for Your Joining Application
Different joining processes require different levels of force. It’s important to find a press with the right level of force for your metals, as well as the right design for the size and type of components you’re working with. We are press experts, and we can help you find a press that suits your facility, and completes your joining process quickly and efficiently. Contact us to learn more about any press and get the right press for your joining application.