Looking for ways to improve their machines’ usability and to economize on manufacturing costs, the Swedish company Comeco decided to launch a new line of rebar benders with electric drives instead of hydraulics. NORD DRIVESYSTEMS supported the company from the early planning phase, during the development of the prototype, and through to production, configuring an AC vector drive with an integrated PLC that controls all machine functions. The current solution is simpler, more robust, and easier to maintain. In addition to substantial savings for parts procured, the assembly time was halved.
Focus on the Customer
Comeco Trading AB is a small owner-managed company based in Enköping, in the Stockholm–Uppsala metropolitan region. Comeco has been manufacturing heaters for the construction industry since 1991. In 2009, the portfolio was expanded by rebar cutting and bending machines. Comeco markets, sells, and services the machines directly or via trading partners mostly in Scandinavia. The company employs seven people.
Focus on the Project
While some are installed in rebar factories, most portable rebar bending machines are used on construction sites. One or more steel bars are manually inserted at a time and bent to a set angle in these machines. 80 percent of the rebar benders from Comeco go to rental businesses. Most of the rest is sold to building companies and a few to rebar manufacturers. The factories use automatic lines for thin rebar, in order to produce large quantities of identical pieces in a short time. However, even they need to use manually operated bending machines like Comeco’s for thicker pieces of rebar. Bars for large-scale construction projects such as bridges or tall buildings are usually ordered to specification from the factory. But construction companies still need the machines on site to accommodate for late changes. Working on small sites, construction companies usually just bend all the rebar they need on site.
Small Swedish manufacturer Comeco offers bending machines for different rebar diameters to suit all demands. Working with NORD DRIVESYSTEMS, they have retrofitted one line for rebar diameters up to 20 mm with electric drives and are currently following it up with another line for up to 40 mm.
When Comeco first designed rebar bending machines, they used hydraulics. This is a very common choice for rebar benders. But the specialists for construction-site machinery found several problems with the tried and tested technology. Fredric Hallberg, owner and manager of Comeco, says: “We have two hydraulic bender models which we developed from scratch. The electric system is very complex. The engineer who built it is practically the only person who can repair it, if it fails to perform. The installation of the hydraulic power unit, piping network, and sensors takes a lot of time. This machine design is much more complex and more prone to problems than our new electromechanical machines.” Comeco therefore researched ways to make the machines more robust and ideally cheaper to build, but without compromising on quality. “Analyzing competitors’ designs,” Hallberg recalls, “we found that we could build the machines cheaper with an electric drive. The electric rebar benders that were available in the market were much leaner designs, but also more basic in functional terms than the hydraulic ones. It was also important to us, that we would integrate top-of-the-line functionality and provide more user value and comfort than the available low-end machines.”
Per Comeco’s wishes, all machine functions were to be controlled by a PLC. NORD therefore proposed the NORDAC FLEX AC vector drive. The motor-mounted inverter integrates a PLC for precise speed control and positioning. Machine operators can select from two speed settings according to their skill level and the thickness of the steel bar. The 20 mm machine allows two angles to be programmed at a time – operators can then conveniently go from one setting to the other with a switch button. The parallel shaft geared motors of these drive systems deliver high torques at a very compact size. NORD manufactures all components and can thus ensure highly efficient gearing with minimal loss.
The drives are delivered pre-assembled and pre-parameterized with a ParameterBox, which Comeco takes as is and installs in the machine operation panel. Instead of complex wiring of the hydraulic control system, the electronic drive only needs a power connection. “We certainly save money here as well,” says Hallberg. “The ParameterBox saves us a lot of switches. NORD delivered it with the buttons and the display programmed according to our specifications. The speed, angle, and operation mode are shown in the display and can be controlled via the keypad. You change the angle with the up and down arrows, the speed with right and left. It is very simple. Operators do not need to navigate through a menu.”