On average, 17,000 copper connectors (also known as busbars) ship from our loading dock everyday. Thousands of unique designs are included in those 17,000 pieces of copper busbar. Needless to say, we have seen countless 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 these busbars will be manufactured. It also determines the price we must charge to our customer. In this article, I would like to share with you these critical points and perhaps favorably impact the cost of your busbar fabrication.
As obvious as it may sound, the number one thing you can do to keep your busbar pricing low is don’t design in more copper than you really need. On our website you will find ampacity tables to help with sizing your busbar. To do this properly, you must know the amount of temperature rise you are willing to accept. Whether you are using copper or aluminum for your busbar application, reducing the metal content is your number one opportunity to reduce cost.
One word of caution while we are on this subject, your desire for thickness optimization should not take you into 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) permits your fabricator multiple sources of supply and reduced 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 OEMs we do business with require a lead time of 2 weeks or less on their busbar requirements.
From a fabrication standpoint, punching holes in copper busbar is much more cost effective than milling holes. On busbar less than .500” thick, there generally are two design parameters which force busbar to be routed to the mill. A hole location so close to a formed or bent area of the busbar that the hole becomes deformed. You see, busbar is always punched when it is flat. The only way we can get a hole into a bent busbar is by mounting it on the mill or machining center. This process is slow and therefore expensive. If you can allow a distance of 1.00” or more from a hole location to a bend in the part, we can most often eliminate a stop at the mill.
The next reason a busbar often stops at the mill is tolerance. Once your tolerance gets under +/- .005” on hole placement, we can no long hold these dimensions on our punch presses. Also, the tolerance of the hole diameter is a concern, +/- .001” and we must use a mill to drill the hole. To be sure your part stays off the mill, allow +/- .020” for your tolerance. It is important to note, that punching copper busbar does slightly deform the surface of the part. Occasionally this indenting or rounding of the surface of the busbar can result in lose of contact area. This minor deformation of the hole is rarely a problem, but worth noting.
To sum up the points we have covered, use the smallest possible size to reduce metal content of the busbar. Design in standard thickness busbar to improve availability when ever possible. Review hole placement and tolerance to reduce the chance the busbar would need to be routed to the mill.
Good luck on your busbar design efforts. Please feel free to contact us if you have any questions.
We have many design resources at our website dedicated to custom copper connectors . Daniel Kitts is VP of Sales and Marketing at Storm Copper Components Co.