science

Punch press

Punch press is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Punch press rather than just read about it. In short: A punch press is a type of machine press used to cut holes in material. It can be small and manually operated and hold one simple die set, or be very large, CNC operated, with a multi-station turret and hold a much larger and complex die set.

Key takeaways

Punch press belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Punch press to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Punch press from memory before moving on to harder problems.

Reference excerpt

A punch press is a type of machine press used to cut holes in material. It can be small and manually operated and hold one simple die set, or be very large, CNC operated, with a multi-station turret and hold a much larger and complex die set.

Description Punch presses are large machines with either a 'C' type frame, or a 'portal' (bridge) type frame. The C type has the hydraulic ram at the top foremost part, whereas the portal frame is much akin to a complete circle with the ram being centered within the frame to stop frame deflection or distortion. C type presses have a bed plate which is used to lock the die bottom bolster. For locking the die, T-bolts are used and so this plate contains T-slots into which T-bolts are slid in. These slots are placed diagonally and with a slot horizontal to the longer side of the plate, is the general practice. These slots run up to a central hole made in the plate, the hole being large enough to accommodate another bush with a hole, the hole being used for dropping the punched part to the bottom of the press. The top of the tool butted against a vertical sliding ram with a clamping system which accommodates only a particular diameter of a threaded cylindrical member called the "shank" of the tool. The bottom portion of the tool is locked to the bottom bed plate and the top portion of the tool is locked to the sliding ram. Top and bottom portions of the tool are generally guided by suitable pillar and bush assemblies, which gives safety to the punching elements of the tool. Generally the tool is placed slightly above the bottom bed plate by providing two parallel blocks accurately ground to the same size. This is a necessary action since many tools, scrap (cut pieces which are a waste) is discharged through the bottom element of the tool, not necessarily in the centre of the tool. The scrap or the blank (the required portion) come out from the die at different places. These have to be taken out horizontally from between the parallels placed. Otherwise they get accumulated inside the tool itself and cause severe damage to the tool. In very heavy presses with higher tonnage, the sliding ram has also a thick plate with T slots for locking the top plate of the tool (called the top bolster). In such cases the threaded cylinder called shank is not attached to the tool. The clamps are either mechanical (manually operated using spanners) or air operated varieties. Turret type punch press machines have a table or bed with brushes or rollers to allow the sheet metal workpiece to traverse with low friction. Brushes are used where scratches on the workpiece must be minimized, as with brushed aluminium or high polished materials. The punch press is characterized by parameters such as:

Frame type Mechanism of delivering power to the ram (mechanical, electro-mechanical or hydraulic) Size of working area (e.g., 2500 x 1250 mm) Single or multiple station Force rating (for example, 20 tons) The type of tool shop and its capacity (e.g., store revolving type, capacity 34 tool) Speed or productivity (typically characterized by the speed of strokes with a step movement of 25 and 1 mm) Speed of movement without shock (speed-load displacement) Maximum weight of workpiece Safety features Power consumption The type of software Punch presses are usually referred to by their tonnage and table size. In a production environment a 30-ton press is mostly the machine used today. The tonnage needed to cut and form the material is well known, so sizing tooling for a specific job is a fairly straightforward task. According to the requirement the tonnage may even go up to 2000 to 2500 ton presses.

Die set

A die set consists of a set of punches (male) and dies (female) which, when pressed together, form a hole in a workpiece (and may also deform the workpiece in some desired manner). The punches and dies are removable, with the punch being attached to the ram during the punching process. The ram moves up and down in a vertically linear motion, forcing the punch through the material into the die.

Axis The main bed of most machines is called the 'X' axis, with the 'Y' axis being at right angles to that and allowed to traverse under CNC control. Dependent on the size of the machine, the beds, and the sheet metal workpiece weight, the motors required to move these axis tables will vary in size and power. Older styles of machines used DC motors; however, with advances in technology, today's machines mostly use AC brushless motors for drives.

CNC-controlled operation To start a cycle, the CNC controller commands the drives to move the table along the X and the Y axis to a desired position. Once in position, the control initiates the punching sequence and pushes the ram from top dead center (TDC) to bottom dead center (BDC) through the material plane. (The terms BDC and TDC go back to older presses with pneumatic or hydraulic clutches. On today's machines BDC/TDC do not actually exist but are still used for the bottom and top of a stroke.) On its stroke from TDC to BDC, the punch enters the material, pushing it through the die, obtaining the shape determined by the design of the punch and die set. The piece of material (slug) cut from the workpiece is ejected through the die and bolster plate and collected in a scrap container. The return to TDC signals to the control to begin the next cycle. The punch press is used for high volume production. Cycle times are often measured in milliseconds. Material yield is measured as a percentage of parts to waste per sheet processed. CAD/CAM programs maximize yield by nesting parts in the layout of the sheet.

Drive type

Flywheel drive Most punch presses today are hydraulically powered. Older machines, however, have mechanically driven rams, meaning the power to the ram is provided by a heavy, constantly rotating flywheel. The flywheel drives the ram using a Pitman arm. In the 19th century, the flywheels were powered by leather drive belts attached to line shafting, which in turn ran to a steam plant. In the modern workplace, the flywheel is powered by an electric motor.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Punch press

Start with the simplest possible case. Write down what Punch press claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Punch press before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Punch press ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Punch press

In research: Punch press appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Punch press in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Punch press is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cutting machines, Machine tools, Metalworking cutting tools, so understanding it makes those chapters shorter.
In everyday life: Look for Punch press outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Punch press in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Punch press means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Punch press out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Punch press in simple terms?

Why does Punch press matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Punch press?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Punch press.