A virtuose welds in a spiral path

At Lucas G, a manufacturer of agricultural equipment, a robot performs spiral welding on a conical hub. A true virtuoso of complex trajectories, its numerical control simultaneously manages nine axes of movement plus a lateral scan over a few millimetres.

Lucas G

With the cabin closed, the welding robot begins a cycle that will last 65 minutes (compared to 120 minutes in manual welding). The aim of this robotised cell is to join pointed elements together, including a metal spiral on a hollow conical axis. Eventually, this screw, weighing about 400 kg, will be one of the elements mounted at the heart of the Lucas G machines.

The trajectories of the torch are complex because they are alternately carried out on the surface and on the underside of the conical screw with a constant transverse sweep of a few millimetres perpendicular to the progress of the welding. In addition to the six robot axes, the numerical control continuously manages three additional axes, one linear and two rotational, for a total of nine axes.

Before this step, the 15 elements of the conical screw are pre-assembled on a special tooling jig by manually pre-assembled. Then, the tooling and the part are introduced into the cell on the gantry. A Schunk interface ensures precise clamping and positioning of the assembly on short, tapered seats. Once the cabin is closed, the cycle is started.

This cell is currently designed to receive six screw references as well as other elements. Eventually, it will process 25-part numbers for cycle times of between 45 and 150 minutes and a total of 3,000 hours of activity over a year.

Since 1965, Lucas G has been the French specialist in cattle, goat, and poultry breeding. Located on two production sites near Cholet, the company employs 200 people and achieves a turnover of €30M by selling 3000 machines each year.

Deployed in the main breeding countries with 215 distributors, the company has a unique know-how articulated around nine product ranges specialised in the distribution and automatic mulching for farm animals.
The mixers are machines dedicated to the creation of rations loaded with corn, grass, and concentrates. Everything is mixed by a screw to form a homogeneous mixture that is distributed to the cows in the feeding alleys of the farms.

The straw blowers are machines where round or cubic bales are loaded, capable of projecting straw inside the buildings in order to guarantee a clean litter for the cattle, avoiding the risks of diseases or infections.
In the case of the “distributive silage unloaders”, several silage products are introduced into a tank to be mixed and kneaded in a homogeneous way. The machine then moves linearly to distribute the feed to the animals.

These machines are usually driven by a tractor’s power take-off. However, some are mounted on a self-propelled engine. The latest trend is 100% electric units powered by batteries. Once their work is done, these true “robot farmers” return to their base to recharge their batteries.

“In our two local plants (16,000 m² of workshops), we operate in two shifts and process 2,500 tons of steel each year, 80% of which is sheet metal between 1.5 and 8 mm. To cut them, we have two laser centres of 4kW and 5kW. Next year, a 6kW fibre laser will replace the 4kW laser. For forming, we have three bending machines, two of which weigh 170 tons and one of which weighs 220 tons, as well as a hydraulic rolling machine capable of bending sheets up to 10 mm, or 8 mm over a length of three meters.

Two CNC saws are used to cut the profiles, while a CNC lathe is used to produce the revolution parts. In addition, we subcontract a large part of the machined components to local workshops, which are generally very well equipped. After cutting, bending, rolling and possibly machining operations, our parts are welded together by means of the Valk Welding robotic cell, dedicated to large sub-assemblies. Received in October 2019, this robotised unit was operational by January 2020.

Finally, to finish our small parts, we have a painting line and a large cabin for our large assemblies,” explains Stéphane Godet, maintenance and methods manager at Lucas G.

And to keep up with the more than 30,000 hours of welding per year, “we still need to modernise our robotic welding equipment to increase our capacity by 50% in order to keep up with the increased production rate of our new product lines,” he adds.


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