By Dan Kitts

On average, 20,000 copper connectors, aka busbars, ship from Storm Copper’s loading dock every day. Thousands of unique designs are included in those 20,000 pieces of copper busbar. Needless to say, we have seen countless bus bar prints from many different industries.

When our process engineers look at a print, there are a handful of key design elements they are immediately drawn to. These design elements largely dictate how an OEM’s busbars will be manufactured. It also determines the price we must charge to the customer.

When considering the design of a busbar, several critical points can favorably impact the cost of fabrication. Each falls within a quality process that Storm calls “Value Engineering.”

Point # 1: Keep costs in check by selecting the exact amount of copper you need.

Although it may sound obvious, the number one factor in keeping busbar pricing low is often overlooked: the amount of metal content. Storm’s quality team members can help you to determine the exact amount and size of copper stock needed for the job. Whether you are using copper or aluminum for your busbar application, reducing the metal content is your number one opportunity to reduce cost. To this end, Storm Copper has provided this link to a set of  ampacity tables to help in sizing busbar. These tables relate data relevant to environmental temperature, emmissivity, as well as the sizes and the numbers of bus bars needed for better ampacity.    

Point # 2: Using standard bus-bar thicknesses can seriously reduce lead time.

Storm’s value engineering also advises a note of caution; a customer’s desire for thickness optimization should not conclude in a special mill run sizes of busbar. Unless you are a very large user of busbar, utilizing readily available busbar thicknesses (these are .062, .094, .125, .250, .312, .375 and .500 inches) enables Storm to select copper bar-stock from multiple sources of supply to reduce lead times. As of the writing of this article, lead times from the two domestic copper mills in the United States are approximately 8 weeks. Most of the OEMs in business with Storm only require a lead time of 2 weeks or less on their busbar requirements.

Point #3. Punching holes in copper busbar is much more cost effective than milling holes.

On busbar less than .500” thick, Storm’s quality team may point out that there two design parameters which force busbar to be routed to the mill. The first is a hole location so close to a formed or bent area of the busbar that the hole becomes deformed. Value engineering dictates that busbar is always punched when flat. The only way to get a hole into a bent busbar is by mounting it on the mill or machining center. This process is slow and expensive. In this situation Storm may recommend that you allow a distance of 1.00” or more from a hole location to a bend in the part, and then eliminate a stop at the mill.

Tolerance is the next reason a busbar must be fabricated at the mill. Once tolerance gets under +/- .005” on hole placement, Storm is unable to  hold the dimensions on our punch presses. Also, whenever the tolerance of the hole diameter is a concern, +/- .001” Storm has no choice but to use a mill to drill the hole. To be sure a bus bar connector stays off the mill, allow +/- .020” for your tolerance, since punching copper busbar does slightly deform the surface of the part.

This slight deformation may result in indenting or rounding the surface of a busbar, which can result in a loss of contact area – although rarely a problem, but still worth noting.

To sum up the critical points in reducing busbar cost:

1. Use the smallest possible size to reduce metal content of the busbar.
2. Design in standard thickness busbar to improve availability whenever possible.
3. Review hole placement and tolerance to reduce the chance the busbar would need to be routed to the mill.

Our Busbar Capability Brochure is another source of information that may be of assistance in your design efforts.

If you already have a print of your custom Busbar, you can use our online send-print form for a fast, reliable quote. Or, feel free to contact us with any questions. Our OEM HOTLINE is 1-800-394-4804.