Busbar lead time and tooling

The four clocks behind a busbar date

A busbar lead time is usually quoted as a single number of days or weeks, but the number is made of several clocks that run in sequence or in parallel. The material has to be released and cut. The tooling has to be made or set. The part has to be punched, bent, machined and deburred. The finish has to be plated or coated. The parts have to be packed and moved.

Some of those clocks overlap. A fabricator can program a press while the material is in transit, and can prepare the plating rack while the parts are being formed. Others do not. Plating cannot start until the parts are formed and cleaned, and packing cannot start until the plating is dry and inspected.

The useful way to read a quote is to ask which clock is the longest. If the material is a standard grade and thickness, the fabricator's own process may be the critical path. If the bar is a wide copper section or a special temper, the mill may be the critical path, and the fabricator's schedule is almost irrelevant.

Material: grade, thickness and width

Most busbars are made from copper or aluminium sheet or bar. Copper is usually specified by grade and temper, and the common electrical grades are available in standard thicknesses and widths. A non-standard thickness or a width outside the mill's standard range adds a rolling or slitting step and a longer lead time.

The material also has a finish condition. A mill finish may be enough for a bar that will be painted, but a bar that will be plated needs a surface that plates evenly. If the bar is to be bent, the temper has to suit the bend radius. A hard temper that cracks at the bend may need annealing, which adds a process step.

The purchase quantity matters as well. A small order may be cut from stock, which is fast. A large order may need a mill run, which is slower. A fabricator who quotes a short lead time on a large order may be assuming stock that is not there, so ask for the material release date rather than the delivery date alone.

• Confirm the grade, temper and thickness before the quote is fixed.
• Ask whether the material is stock or a mill run.
• Check that the width is within the standard range for the mill.
• Match the temper to the bend radius.
• Allow for a test certificate if the part is traceable.

Tooling: what is actually needed

A simple flat busbar with drilled holes may need no hard tooling at all. A laser, a turret punch or a waterjet can cut the profile and the holes from a program. A bar with several bends may need a press brake setup and a bend program. A bar with a pierced pattern that repeats at volume may justify a dedicated punch tool.

The tooling clock is not only the time to make the tool. It includes the design, the trial, the first article and any correction. A new punch tool can be made quickly, but the trial may show a burr or a hole position that needs a change. A bend tool may need a radius correction after the first parts spring back.

The tooling cost also depends on the quantity. A dedicated tool is worth it when the volume is high and the shape is stable. For a low volume or a design that is still moving, a program and a standard tool are faster and cheaper to change. The quote should show which route was assumed.

Plating is often the hidden delay

Tin, silver and nickel plating are usually done by a specialist, not by the busbar fabricator. That means the parts leave the works, wait in a plating queue, are processed, inspected and returned. The queue can be longer than the fabrication itself, especially for a small batch or a special thickness.

The plating type changes the lead time. A barrel process is fast for small parts but can damage a long bar. A rack process is slower but suits a long busbar and gives a more controlled thickness. Silver plating may need a strike and a controlled bath, and a thick silver deposit takes longer than a thin tin deposit.

The specification also affects the inspection. A plating thickness check, an adhesion check and a visual check take time. If the part needs masking, the masking and unmasking add labour. A bar with a masked joint face and a coated body may need two process steps and two inspections.

Assembly, packing and freight

A busbar that is supplied as a subassembly adds a build step. Studs may be pressed or welded, insulation may be fitted, labels may be applied and a continuity check may be made. Each step adds time, and each step needs its own inspection. A subassembly that is tested before packing can save time at the customer's site, but it adds time at the supplier.

Packing is a real lead time item for a long or a plated bar. A bar that is stacked without separation can scratch, and a plated bar that rubs in transit can lose its finish at the joint face. Good packing uses separators, edge protection and a crate that stops movement. That takes time and material, and it should be in the quote.

Freight is the last clock. Sea freight is slower but cheaper for a large order. Air freight is faster but expensive and size limited. Customs clearance can add time if the classification or the documents are wrong. The Incoterm decides who books the freight and who carries the delay, so it should be agreed before the date is promised.

How to shorten the critical path

The first step is to identify the longest clock. If it is material, choose a standard grade and thickness, or accept a split delivery. If it is tooling, use a program and a standard tool for the first batch and invest in hard tooling only when the design is stable. If it is plating, confirm the processor's queue before the fabrication date is set.

The second step is to remove a step. A bar that is designed with a standard hole pattern and a standard bend radius can use existing tools. A bar that is designed with a non-standard thickness or a tight bend may need a new tool and a trial. A design review before the quote is cheaper than a change after the first article.

The third step is to plan the batch. A pilot batch can be made from stock and standard tools while the production tool is being built. That gives the customer parts for a trial and gives the fabricator time to prove the production route. It costs more per part for the pilot, but it can protect the programme date.

• Use standard material grades and thicknesses where the design allows.
• Keep the hole pattern and bend radius within the supplier's existing tools.
• Confirm the plating queue before promising a delivery date.
• Split the order into a pilot batch and a production batch.
• Agree the Incoterm and the customs documents early.

What to send for a realistic date

Send the drawing, the material grade and temper, the finish, the annual volume and the required delivery. Add the inspection level, the packing requirement and the destination. If the date is fixed, say which clock is flexible: a slightly different thickness, a standard hole or a split delivery may be acceptable.

Ask the supplier to quote the material release date, the tooling date, the first article date and the delivery date separately. A single date hides the critical path. A set of dates shows which step to protect when something changes.

• Drawing at the current revision
• Material grade, temper and thickness
• Finish, thickness and masked areas
• Annual volume and release size
• Required delivery and any fixed milestone
• Inspection level and packing requirement
• Destination and Incoterm