Dump trucks for tough construction site conditions

Application Story

3/22/2023

Boulders weighing several tons, hot asphalt, or endless loads of gravel day in, day out: the commercial vehicle superstructures from Moser AG Kipper- und Fahrzeugbau based in Steffisburg, Switzerland, have to withstand enormous loads in tough construction site conditions. When it comes to welding steel and aluminum sheets for the dumper and loading systems, Moser has been using Fronius welding systems for 24 years. Significant increases in manufacturing efficiency have been achieved with the Fronius TPS 500i in conjunction with PMC welding characteristics. This has sped up welding processes considerably, especially for out-of-position welding.

Reduced tare weight: “Always one load ahead”

Moser AG manufactures vehicle superstructures for trucks with a total weight of between 18 and 40 tons, with 40-ton trucks capable of taking more than 25 tons of payload. “The highest possible transport volumes per trip are the top priority in our industry. To enable our customers to transport as much material as possible with a specified total weight, we design our dumpers and loading systems to be as light as possible – without compromising on strength, durability, or user-friendliness,” emphasizes Stefan Rolli, operations manager at Moser AG.

Depending on the size and number of axles on the vehicle in question, the truck superstructures produced in Steffisburg usually weigh between 3 and 4.5 tons. “The benefit in terms of payload for our customers from using our lighter superstructures compared to competitors is often between 500 and 700 kg per trip. This results in much more efficient use of the vehicles in line with our motto ‘Always one load ahead’,” says Stefan Rolli.

Customer proximity favors customization

The superstructures custom-made by Moser AG to meet individual customer requirements fit all common truck types. The company, from the Canton of Bern region, is particularly proud that all dumpers and loading systems - from the supplied sheet metal and profiles onwards - are produced at the company's site in Steffisburg.

“Today, we are the only company in Switzerland that manufactures commercial vehicle superstructures for the construction site sector with such a high real net output ratio. Control over all key production processes and our proximity to our customers mean that we can respond to special requests very quickly and flexibly,” explains Moser operations manager Stefan Rolli.

More than 200 trucks leave the Steffisburg plant every year, and the manufacturing time for a new dumper is 6 to 8 weeks on average.

Manufacturing processes at a glance

The manufacturing processes at Moser AG are essentially divided into the following steps: The trucks are measured thoroughly after delivery. Once the superstructures have been designed with the help of CAD and production planning, the next steps involve cutting the sheets on a CNC plasma cutting machine, bending them with a CNC press brake, and further mechanical processing in a CNC machining center.

In the metalworking shops of Moser AG, the components are welded together, finishing the raw form. The truck superstructures are then sandblasted and painted. After installation of the hydraulics, pre-assembly and final assembly take place. Before a truck and its new superstructure leaves Moser AG in Steffisburg for its new destination, it is subjected to a thorough final inspection.

Welds in all components

“Welds are found in virtually all our components. In day-to-day construction site use, they have to withstand shocks, vibrations, and torsion – for example, when boulders weighing several tons hit the dumper from the bucket of a wheel loader. Since faulty seams have serious consequences, our requirements regarding the professionalism of our welders and the equipment they use are extremely high,” emphasizes Stephan Zingg, design engineer at Moser AG. Particular attention is paid to flawless welds in the load-bearing components such as the dumper substructure or subframe.

Steel and aluminum up to 70 mm

At Moser, conventional S355 construction steel, steels from S690 to S700, and Hardox 450 in various thicknesses from 3 mm to 70 mm are welded when manufacturing the truck superstructures. The material most frequently used is 4 mm-thick Hardox 450 sheet.

The aluminum sheets processed in Steffisburg generally have a thickness of 2 mm, and aluminum checker plates are 3/4.5 mm or 3/6.5 mm thick. Last but not least, relatively light aluminum alloys are used for the side walls of the dumpers. These are extruded using a casting mold developed by Moser AG, and the MAP Moser Aluminum Profile System enables modular construction of the side walls. Other application areas for aluminum sheets include fenders, covers, and running boards.

PMC arc during welding of components to form a dumper.

Focus on MAG manual welding – frequent out-of-position welding

The vast majority of welds at Moser AG are welded manually using the GMAW process. In addition to considerable welding speeds, this process delivers high deposition rates, while relatively little energy per unit length is input into the dumper parts to be welded.

For series production parts or repetitive processes, such as welding the subframes of the dumper bodies, a gantry system with a welding robot is used in Steffisburg. The gantry system makes it possible to turn the entire dumper so it is in the appropriate welding position.

“The characteristics of the weld are provided by the WPS. For the thicknesses of the fillet welds, we generally adhere to the A dimension, i.e., the thickness of the thinnest sheet element multiplied by 0.7,” explains Stefan Rolli.

To withstand the high loads in day-to-day use on construction sites, many welds are welded with a root pass and up to two final runs. In addition to fillet welds, butt welds – with and without an air gap – are also very frequently used. One task that the welders at Moser AG are regularly confronted with is out-of-position welding: from “classic” vertical-up seams on the pipe and sheet metal to overhead welds.

Four generations of Fronius devices

Moser AG has been using Fronius welding systems for 24 years. Today, around 35 devices from four different Fronius generations are used daily in Steffisburg: the Fronius VarioSynergic 4000, the VarioStar 457, the TransSynergic 5000, plus the Fronius TPS 500i since 2018.

Fronius TPS 500i: efficiency through precisely adjustable welding characteristics

“Speed and flexibility in manufacturing are crucial for us, especially in the current situation. By using the Fronius TPS 500i and its welding characteristics, we have significantly increased welding speeds in all key areas. At the same time, there has been a noticeable reduction in the amount of rework required on the welds. Overall, the TPS 500i not only makes the welding processes considerably more efficient, but also the downstream work steps, which subsequently has a positive effect on our entire manufacturing process,” says Moser operations manager Stefan Rolli.

The welding specialists at Moser AG frequently use the PMC Fronius Welding Package in the PMC Universal, PMC Dynamic, and PMC Mix variants on their TPS-500i devices. PMC stands for Pulse Multi Control and is a further development of the pulsed arc.

“In general, the PMC characteristics feature a stable, dynamic, and low-spatter pulsed arc. The excellent welding speeds of the TPSi are made possible predominantly by their high processor performance and the corresponding measuring and control speeds,” explains Fritz Loosli, the application engineer and customer adviser at Fronius responsible for Moser AG. The PMC characteristics provide two stabilizer and two correction parameters: an arc length stabilizer and a penetration stabilizer, as well as arc length control and pulse correction.

Up to 40 percent faster welding of vertical-up seams

The welding specialists at Moser AG use the PMC Mix characteristic, among others, because it permits the welding of vertical-up seams without the usual oscillating motion. Overall, up to 40 percent faster welding speeds are possible with the PMC Mix process for vertical-up seams. The technical basis for this characteristic is the process change between a pulsed and dip transfer arc, i.e., the cyclical change between a hot and a cold supporting process phase. The heat input into the material is reduced by this process.

Many welds on dump trucks require out-of-position welding.

Steel Root is another characteristic that is often used by the welding specialists at Moser AG. This characteristic excels at bridging gaps of 2 to 3 millimeters in size when welding dumper parts. A soft and stable arc is a typical feature of the Steel Root characteristic. The detachment of relatively large droplets creates a viscous weld pool, which can be used to weld larger gaps with ease.

The PMC Dynamic welding characteristic is used at Moser for horizontal fillet welds. It delivers a relatively aggressive arc with high pressure and concentrated focus. Your advantage: High welding speeds with low energy input enable low-distortion welding results and save valuable resources such as gas, filler metal and working hours.

Aside from this, Moser still uses tried-and-tested standard arcs for many welding processes. As a rule, aluminum parts are welded with a conventional pulsed arc.

User-friendliness on the welding system and directly on the welding torch

In addition to its welding characteristics, the TPS 500i’s high degree of user-friendliness also helps to make welding processes simpler, faster, and more efficient. The large clear text display on the TPSi is adapted to the welding environment. It is easy and intuitive to use in the respective local language, even when wearing gloves.

In connection with the user-friendliness of their equipment, it is essential for the welding specialists at Moser AG to be able to make adjustments directly on the welding torch: “Dump trucks are components that can’t exactly be moved back and forth quickly and easily, so our employees move around the components. To give our welders maximum freedom of movement, all our welding systems are equipped with 10 meter-long hosepacks,” explains Stefan Rolli.

The welders use lightweight PullMig welding torches in the JobMaster version with their TPS-500i devices. The water-cooled welding torches are equipped with a small electric motor in the torch handle, which ensures smooth wirefeeding through the 10 meter-long hosepack.

Fewer trips – greater efficiency

With the “EasyJob” JobMaster setting, users have the option of saving up to five welding jobs directly on the welding torch and rapidly switching between individual jobs. Being able to call up all the important welding jobs for their day-to-day work directly on the welding torch means they save themselves numerous trips between the welding system and the component. This makes day-to-day work not only more convenient, but also significantly more efficient.

“We have been using Fronius welding systems for 24 years because we see Fronius as a partner who stands for quality, reliability, sound advice, and innovative products. The ongoing technical developments, such as the TPS 500i most recently with its welding characteristics, contribute significantly to our performance, especially in terms of the speed and flexibility of our manufacturing process. The welding systems from Fronius help us to provide our customers in the Swiss construction site sector with the quality they rightfully demand from us,” concludes Moser operations manager Stefan Rolli.

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Dump trucks for tough construction site conditions

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