Office furniture manufacturer Robberechts in Turnhout, Belgium, is planning to further optimise the flexibility of its production processes to deal with its large number of product variants.
For this purpose the company recently commissioned 2 new welding robot cells, with the programs for the welding robot being generated on the basis of CAD data. The next step is to servo-mechanically automate the configuration of the welding jigs. Jef Van Gael, Manager, CPIM Production, Investments, Product and process development: "Price and delivery are important aspects when it comes to maintaining a competitive edge in this market.”
Robberechts recently delivered an order for 1,200 cabinets, desks and drawer units within 4 weeks, some of which customised. "That mustn't happen too often, but it does show what our company can do", says Jef van Gael. With office furnishing as our core business, the manufacturer produces some 20,000 office furniture units under private label for the professional office trade in France and the Benelux. The legs for these units are made in 250 variants, and the frames also vary in width and height. Each variant requires a separate welding program and a separate welding jig configuration. Jef Van Gael: "Until recently we did this manually using the teach pendant. It might be possible to quickly call up recurring programs in this, but you can only programme a new product when the welding robot is not in production. Panasonic DTPS software makes it possible to do this completely outside of the robot."
Large variation within the same family
The differences in the measurements of the tubular legs and frames for the workplace furniture may be small, but each size difference in one of the tube sides needs another welding program. "When we made the investment in new Valk Welding robot systems we therefore switched to offline programming software with Panasonic DTPS software. This has greatly increased the working time on the welding robots, but the programming time for all variants still accounts for a lot of time spent on the work preparation. "Valk Welding can offer their APG solution to automate the programming, but we have seen a way of developing this ourselves with our own software", explains Jef Van Gael.
Geometrics from CAD data
The tubes are pre-cut with tube lasers, with a triangle cut out on three sides so that the welding robot operator can simply bend the tube 90 degrees. The U-shaped legs are then clamped onto the jig so that it can be welded on three sides by the robot. The welding programs are based on the CAD data geometrics, for which a different welding torch position is programmed in the Robberechts software for the internal and external angle. The positions are linked to the right welding parameters in DTPS. We started with APG for the automatic programming but have since developed our own application for this. All in all this saves a lot of programming time on the job preparation", emphasises Jef Van Gael.
Two identical welding robot cells
Robberechts still had a Valk Welding robot system dating back to 2000, with 4 stations served by 1 welding robot. Jef Van Gael: "The old Panasonic AW-660 (from 1990) was due for replacement. To get everything completely up-to-date we invested in complete renewal in order to work with the latest state of technology. Instead of 1 welding robot system with 4 stations we opted for 2 identical welding robot cells, each with 2 stations. This arose from the idea of always duplicating strategic production processes so that there was no downtime in the event of production malfunctions. Also, having 2 welding robot systems gives us more space for loading and unloading.”
Universal jig and Siegmund table
Of the two parallel stations, one station has a universal jig and the other a fixed Siegmund table. Both stations are fitted with controllable work piece positioners. A Panasonic TM- 1800WG over an 8 m track serves both stations in alternation. Jef Van Gael: "The universal jigs can be used for parts that are used in many furniture items. We therefore make them in series of 100 to 1,000. We use the Siegmund table for unique pieces. That way we retain maximum flexibility."
Automatic welding jig configuration
The operators currently set up the jigs manually. Jef Van Gael: "For minor width differences this means that the operators now mechanically adjust the clamps. Despite the implementation of a quick change system, we would ultimately like to also automate our system by servo-mechanically implementing the clamp configuration, with the configuration linked to the welding robot programs. Once we've done that we'll also be able to have single pieces welded on the robot."
Looking for similar products
The extensive digitisation of new works has sharply reduced the demand for cabinets in offices. Jef Van Gael: "That's why we're looking for similar products that we can make out of steel for hospitals, schools and so on. But office furnishing remains our core business. With our current production method the future is looking rosy. The new welding robot systems in particular make it possible for us to produce competitively and in high quality, without compromising flexibility." www.robberechts.be
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