Sizing a Busbar Multi-Punching Machine for Copper Thickness and Hole Diameter

Sizing a busbar multi punching machine starts with matching punching force to copper thickness, hole diameter, and material shear strength—not simply choosing the highest tonnage. An undersized machine can leave incomplete holes, excessive burrs, and damaged tooling. Unnecessary capacity adds purchase cost without necessarily improving hole quality or cycle time. The practical task is to establish your hardest production condition, then check whether the machine, tooling, and positioning system can handle it repeatedly.

One distinction matters immediately: “multi-punching” may describe several available tool stations, sequential CNC punching, or multiple punches cutting simultaneously. Those configurations do not impose the same peak load.

Calculate the cutting load before comparing machine ratings

For a conventional flat-faced punch, a useful preliminary calculation is:

Punching force (kN) = cutting perimeter (mm) × copper thickness (mm) × shear strength (N/mm²) ÷ 1,000

For a round hole, the perimeter is π × hole diameter. For a slot or shaped opening, use its complete cutting perimeter, not its width or equivalent diameter. Two openings with similar areas can require different forces because their perimeters differ.

Consider a 20 mm diameter hole through 10 mm copper. If the calculation assumes a shear strength of 250 N/mm², the estimated cutting load is π × 20 × 10 × 250 ÷ 1,000, or approximately 157 kN. The 250 N/mm² value is an illustrative assumption, not a universal copper property. Confirm the relevant grade and temper using material data or supplier-supported testing; do not substitute tensile strength directly for shear strength.

This calculation estimates cutting load, not the complete production requirement. Tool geometry, wear, alignment, material variation, and stripping resistance still need evaluation. A hydraulic pressure reading alone does not establish usable punching capacity unless the cylinder arrangement and rated operating conditions are known.

Build the operating margin around the actual job

Selecting a machine whose rated force barely exceeds the calculated load leaves little allowance for variation. However, there is no single margin that suits every copper busbar application. Ask the manufacturer to recommend an allowance for your material, tooling, and production frequency.

For illustration, applying a 25% planning allowance to the 157 kN example gives approximately 196 kN. That is a screening figure—not a substitute for tooling approval or a guaranteed duty rating. Stripping capacity also requires a separate check: the mechanism must withdraw the punch reliably without lifting or distorting the busbar.

Use the same method on the largest intended opening. A 36 mm round hole through 20 mm copper, using the same assumed shear strength, requires approximately 565 kN before allowances, or 707 kN with that illustrative 25% allowance. This explains why separate catalog statements for maximum thickness and maximum hole diameter should never be read automatically as approval to combine both maxima.

Six stations do not necessarily mean six simultaneous holes

If four 14 mm holes are punched simultaneously through 10 mm copper at the assumed 250 N/mm² shear strength, their combined theoretical cutting load is approximately 440 kN. With a 25% planning allowance, it becomes about 550 kN. If those same holes are punched sequentially, the theoretical cutting load per stroke is approximately 110 kN, although the complete pattern takes multiple strokes.

A six-station tooling arrangement may simply keep different punch sizes available. Confirm how many tools actually engage during one stroke, whether simultaneous punching is supported, and whether eccentric loading imposes additional restrictions. Station count alone answers none of those questions.

Small holes can be the harder tooling problem

Large holes drive force requirements upward, but small holes in thick copper can be more demanding for the punch itself. A slender punch faces compression, alignment, and withdrawal challenges that additional machine tonnage cannot solve.

Ask for the approved minimum hole diameter at each required thickness. A published diameter range does not necessarily apply across the machine’s entire thickness range. Where the diameter-to-thickness relationship is unfavorable, drilling or a different tooling approach may be preferable.

Punch-to-die clearance also deserves explicit agreement. Too little clearance can increase load and accelerate wear; excessive clearance can worsen burrs and edge quality. Specify whether clearance is quoted per side or across the diameter. For busbars that must sit flat at bolted joints, assess burr height and local deformation against the drawing rather than accepting “clean punching” as an inspection criterion.

Read an 800 kN specification as a starting point

Dexinjia, founded in 2014, manufactures CNC equipment for copper and aluminum busbar processing. Its DXJ-80NC PRO CNC Busbar Processing Machine is listed with 800 kN maximum punching force, six punching stations, a 4.3–36 mm punching range, and maximum punching dimensions of 300 mm width and 20 mm thickness. These figures provide a useful initial comparison for heavier copper work, but the intended diameter-and-thickness combinations still require confirmation.

Its servo-driven X/Y positioning and automatic feeding address a different production constraint: locating successive holes without repeatedly removing and resetting the busbar. For repetitive connection patterns, this capability may matter more than surplus force. Confirm the exact model designation and configuration on the quotation, together with the approved tooling envelope.

Also check how the stated X-axis travel of 200 mm and Y-axis travel of 1,000 mm relate to your drawing orientation and clamping arrangement. Maximum bar width is not the same as accessible hole-center travel. Long parts may need support, reindexing, or a defined feeding sequence.

Make the acceptance test reflect production

Send representative drawings and material specifications before requesting a final recommendation. Include the thickest bar, largest opening, smallest hole in thick stock, and any pattern close to an edge. These reveal different limitations; one easy sample cannot validate the entire workload.

Agree on hole diameter, center-location tolerance, burr limits, and acceptable flatness after punching.
Run consecutive parts to assess positioning consistency, stripping, slug discharge, and cycle time—not just one successful stroke.
Include loading, repositioning, and tool selection in the timing, rather than measuring hydraulic stroke time alone.
Confirm replacement punch and die availability, maintenance requirements, and technical support for the supplied configuration.

The right busbar multi punching machine has verified capacity for the difficult jobs and practical positioning for the frequent ones. Before approving the purchase, obtain a written operating envelope covering material condition, hole geometry, thickness, simultaneous loading, and tooling restrictions. That is more useful than an impressive tonnage figure without conditions attached.