Reduced assembly effort
Engineering a bracket from sheet metal reduces assembly effort when compared with a version incorporating parts bought on the market. That, in turn, cut manufacturing costs.
Switches or push buttons are to be found in every industrial plant and at virtually every machine. They serve, for instance, to power systems up or down. The push buttons are either attached directly to the machine’s housing or, if that is not possible, are mounted on brackets. Such brackets vary widely in appearance: rectangular, rounded, with or without protective guards. Their designs may differ, but the function is always the same.
TRUMPF engineers developed and compared two different versions of a push button bracket. The first bracket comprises 14 separate bought-in parts; the second is made of sheet metal and five bought-in parts. The button is located over a cable opening so that it cannot be fixed directly to the machine’s frame. To avoid damage to the cable, a distance of 35 millimeters between the push button housing and the machine was planned. Both versions carry out the desired functions. But when the manufacturing processes are compared, the sheet metal design is far more convincing.
Bracket made of bought-in parts
The first version of the bracket comprises 14 parts available on the open market: two spacer studs 35 millimeters long and four that are 60 millimeters long; six countersunk screws; an acrylic protective panel; and a metal plate. The spacer studs maintain the specified distance between the machine and the bracket and between the metal plate and the acrylic panel. The metal plate, to which the push button is attached, is first cut to size and shape.
It is also fitted with six threaded holes and two holes with conical countersinks. Then fitters assemble the individual parts. The design behind this version is simple and each of the parts is inexpensive. By contrast, the assembly effort for this version is very high. Particularly when operating in a high-wage country, looking at alternates is worthwhile.
Bracket made of sheet metal
The engineers at TRUMPF thus developed an alternate solution, made of metal cut and bent to shape. At first glance, this version would seem to be more complicated, especially for the part designer. Armed with the required technical knowledge, however, sheet metal designs often offer advantages. Thomas Bronnhuber, a lecturer at workshops for parts design at TRUMPF Werkzeugmaschinen GmbH + Co. KG, is thoroughly convinced of this. “Sheet metal is an all-purpose material that makes many components not only less expensive, but in some cases better. In this specific case we achieved a 27-percent cost savings.”
The work required to make up the complete sheet metal bracket is comparable to the preparation of the metal plate in the first bracket. However, instead of sawing and drilling machines, a combination punch and laser cutting machine followed by a brake press are used. The punch-and-laser machine cuts the sheet metal part to the desired form and, in addition, shapes the threads, all in a single operation. The TruMatic machines made by TRUMPF are perfect for work like this. They use high-performance lasers to cut the sheet metal to any desired shape and, thanks to the integrated punching functions, the parts can be shaped and threads tapped.
A brake press then uses eight bends to bring the part into its final form. TRUMPF offers a wide selection of brake presses in its TruBend Series. Depending on the needs, the user can decide among differing sizes, performance classes, and versions with and without automation. Once the sheet metal part has been bent to its final shape, only the push button and the protective panel need be screwed in place.
The better solution
The amount of assembly work required for the sheet metal design is considerably less than for the first version of the bracket. The throughput time and the number of manual steps required are reduced considerably. The sheet metal version is also more sturdy.
On the one hand, the push button is protected against impact and grime on four sides, since it is also shielded by the metal at the top and bottom. The version made from standard components offers protection only at the front and rear. Moreover, the surface area in contact with the machine’s frame is much larger than the two spacer studs in version one. This makes the sheet metal design not only 27 percent less expensive, but better, too.
This proves that comparing various design options can certainly pay off – especially for parts that are made in large numbers. In the present case, it is a question of making a bracket for a push button. But by applying the same principle, companies could also save costs for other kinds of brackets and holders.
Contact us: MastersofSheetMetal@trumpf.com
This article was first published in spring 2013.