How to Know The Sheet Metal Punching Basics
Sheet metal punching is a great technique for shaping metal forms. At Creatingway, we use the process to punch holes even in the hardest of metals. We can cut large panels, form embosses, louvers, and other complex shapes. Since the punch press can do a lot, the chances of making mistakes are greater. Thus, it is important to get a few basics correctly.
The Overview of The Entire Process and Fundamental Principles
How does It work?
Sheet Metal punching uses heavy machinery to make indents and holes in a piece of metal. The process starts by pressing a sheet metal a punch and a die. Then, the punch moves downwards into the die. It causes shearing away of the sheet metal underneath from the surrounding material. We collect the cut metal in a container for later recycling or use. To get the desired shape, we repeat the steps mentioned. A great way to achieve custom shapes is through nibbling. It makes long series of small holes at one time. Then, they are connected to create customized contours for specific needs. however, at Creatingway, we may use laser cutting to more precise shapes. It also induces less stress on the workpiece.
Factors Affecting Punch Quality
- The shape and size of the punch press and die.
- The quantity of force applied on the sheet metal. The amount can reach up to 20 tons of force.
- The metal thickness punched. It is harder to punch thicker metal neatly.
- The metal type punched. Harder metals need more force.
Metal Punching Strategies for Great Parts
Management of Slugs
Suction forms, during the deformation of a slug. It thus sticks to the face of the punch slowing down the punching process. Also, lubrication on the slug makes it stick. There is a need to break this suction to reduce lead time. One way is through cutting slots in the punch face. It reduces the suctioning effect. Also, the use of a slug retention system is helpful. The die should be of a negative-positive geometry to achieve this. The system works by having the die diameter narrower at the top. It retains the slug on the return stroke once the punch goes up. however, the punch needs to move a certain distance for the system to work consistently. Generally, it is effective.
Galling Prevention
Galling occurs due to high heat and pressure between the workpiece and punch. It results in the two adhering to each other. To avoid this from happening, we need to avoid using the same grade of material against each other. We use different materials to make the punch and workpiece. The modern tools have a coating to help reduce heat formation during the punching process. Switching stations to reduce overheating of the hunches also helps. It is important, however, to ensure the tools are identical for similar results. Die clearance also plays a role in reducing galling occurrence. One way of determining the right die clearance is through experimentation. Test out the different kinds of die clearance with materials to get determined which works best.
Minimizing Sheet Distortion
Sheet distortion happens after the punch comes into contact with the material. The punch draws in some material inward while penetrating and shearing it. To lessen this effect, some changes need to happen. The first is through holes shaving. This sheet metal punching method uses the same die but of two different punch size diameters. We first use the smaller punch to make a hole in the material. Then, we follow up with a larger punch. The second larger punch removes the stressed area that surrounded the whole perimeter. It leaves behind a cleanly punched hole. Another way of reducing distortion is by providing clamping pressure.
Elimination of Pinch Points
Pinch points form when a rectangular punch cuts out a large part. The hard corners of the punch curve out overlap marks that are aesthetically displeasing. The use of round punches helps eliminate the formation of these overlap marks. Also, the use of pincher roller wheel tools helps mitigate this problem. They coin a groove just before the punch tool penetrates the metal sheet punching. However, it needs extra cycle time on the press but is overall cost-effective. This is because it does not require secondary operations like deburring to correct the defect.
Mitigation of The Sheet Shake
At Creatingway, we use shaker tabs in nests to manage to punch a lot of parts from one large sheet. As the sheet emerges at the end of the process, we shake it to remove parts from the nest for sorting. This creates the sheet shake as it distorts the initial positioning. It happens for the nest that is nearing the end of the process. Changing the punch sequence helps reduce the sheet shakes. The correct sequence ensures the web has adequate strength for the entire punching cycle. The parts only hang on their micro tabs for a specific duration of time. Also, the use of a different tab avoids the sheet shake. A stronger and longer tab allows workers to take out the sheet more easily without causing the sheet to shake. Contact Creatingway now for metal punching services.
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