Interlinked, Automated Shot Blast System Provides Excellent Paint Preparation

With more than 80 years of experience, Rosler has developed, installed, serviced, and provided consumables for shot blast systems for a variety of industries and applications.

When a Polish manufacturer of complex steel weldments was ready to invest in a new shot blast machine, key selection criteria included quality, capacity, high equipment uptime, and integration into the existing manufacturing flow. As an essential part of the pre-treatment operation for a cathodic painting line, the system also needed to produce optimal surface preparation results within an interlinked workflow in a 3-shift operation.

The company chose a Rosler continuous feed spinner hanger blast machine because of its wear-resistant design and favorable operating costs.

The Situation

Stelweld Sp.o.o. (Stelweld) specializes in the production of complex steel weldments, including machining, laser and CNC cutting, and bending as well as wet painting and powder coating. Since its founding in 1997, the company has established itself as a key supplier for such diverse industries as automotive, agricultural and construction equipment, and cranes including all kinds of lifting equipment, renewable energy, and rail transport.

Among many others, Stelweld’s customers include Scania,  Volvo, Bombardier, and Cargotec.

In 2019, Stelweld erected a new building to provide space for a new, fully automated cathodic painting line (KTL) with 16 operating stations and a “power and free” transport system.

Danuta Dobrzynska, Stelweld Project Manager, said, “Within the framework of this expansion, we also wanted to automate the shot blasting operation and integrate it into the painting line. Prior to adding new space, the paint preparation process was predominantly done manually.”

The Solution

Among the five shot blast equipment manufacturers Stelweld considered as potential suppliers, the company selected Rosler and its continuous feed spinner hanger blast machine RHBD 17/32-K. High capacity, excellent shot blasting results, outstanding equipment uptime, and superior cost efficiency factored into the decision.

“I was familiar with Rosler through a project I dealt with when working for another company,” Dobrzynska said. “Rosler does not offer the lowest price, but, with regard to quality and technical features, this supplier offered many advantages.

“Compared to the competitive products, all essential components of the Rosler shot blast machine consist of wear-resistant materials, such as the throwing blades of the turbines which are made from forged tool steel.

“Another key factor for our decision was the results of the shot blasting trials that were conducted with some of our original components,” Dobrzynska added. “In the Customer Experience Center at Rosler, we achieved excellent shot blasting results, which provided valuable pointers for our actual shot blasting operation.”

The Specifications & Advantages

Rosler’s continuous feed spinner hanger blast machine RHBD 17/32-K allows the blast cleaning of a very wide spectrum of three-dimensional weldments with dimensions of up to 98 x 47 x 118 in (L x W x H) (2,500 x 1,200 x 3,000 mm) and weights of up to 2,800 lb (1,250 kg). In cycle times of 6-8 minutes, the automatic shot blasting process produces a finishing quality of SA 2.5 on the entire surface of the steel weldments and surface roughness values that are in full compliance with the standards defined by Stelweld and its customers.

Rosler’s Gamma G turbines feature specially designed Y-shaped blades for long life and quick changeouts.

Excellent paint adhesion is achieved utilizing 16 Gamma 400G turbines, each with a drive power of 15 kW. Each high-performance turbine is equipped with unique Y-shaped throwing blades developed by Rosler.

Compared to conventional turbines, the special blade geometry and precisely calculated curvatures produce very high throwing speeds while providing lower energy consumption. This results in an up to 20% higher shot blast performance compared to straight blades.

Because of their symmetric design, both sides of the throwing blades can be used resulting in a two-fold increase in the usable blade life.

Thanks to a special quick-change system, blade changes can take place without having to dismount the turbine.

The position and angle of the turbine placement within the RHBD were determined with a special simulation of the shot blast process to create a highly focused blast pattern. To achieve Stelweld’s desired blast media throughput of up to 440 lb/min (200 kg/min) and accommodate different work piece geometries, three different shot blasting programs are utilized. Frequency inverters adjust the rotational speed of the turbines according to the respective process parameters to create precise control of the impact energy of the blast media on the steel work piece surface.

For optimum wear protection and, thus, a long equipment life, critical sections of the inlet and outlet chamber are fabricated from .25 in (6 mm) thick manganese steel. The same material, this time .3 in (8 mm) thick, is used for the blast chamber. The blast chamber is also protected by overlapping, easy-to-replace wear plates made from high-strength materials.

Sturdy rubber curtains in the inlet and outlet chamber as well as the a multi-layer seal for the transport hooks using rubber seals and brushes prevent any blast media spillage to the immediate environment.

“The turbines, the entire equipment design, and the used materials guarantee a high uptime. This ensures a safe, trouble-free, and energy-efficient operation,” Dobrzynska said.

The Process

A “power and free” transport system moves the steel weldments, each containing a QR code for the automatic selection of the respective shot blast program, to the shot blast machine. As soon as a trolley with one work piece enters the inlet chamber, the double doors close, and the turbines, blast media return system, and dust collector automatically start.

The work piece passes through the blast chamber at a pre-defined speed. The 16 blast turbines ensure an intensive cleaning of all component areas with highly homogeneous and consistent shot blasting results.

Two dropout boxes placed in the duct connection between the shot blast machine and dust collector make sure that the generated dust is evacuated from the blast chamber, whereas reusable blast media is returned to the machine.

Access to the shot blast machine behind the outlet chamber allows for manual removal of residual blast media from the weldments, especially cup-shaped sections. An auger in the bottom returns the removed blast media to the media recycling and cleaning system consisting of two cascade air-wash separators.

After shot blasting, the work pieces are transported to the KTL painting line.

“Compared to our previous manual shot blast operation utilizing conventional blast rooms, the new shot blast machine achieves considerably better and much more consistent shot blast results in a much shorter time cycle and with a fraction of the labor costs,” Dobrzynska said. “This allows us to employ our qualified personnel for more productive work, helping us to create more added value.

“In addition, the overall shot blasting operation has become considerably more economical thanks to savings in energy consumption and other operating costs.”

The Rosler Way

Decades of experience and the ability to design, service, and maintain machines as well as provide the consumables and accessories required to get the finish you require make Rosler a well-rounded, single source for surface finishing expertise. Contact us to discuss your shot blasting needs and to learn how we can improve and automate your process including free test trials in our Customer Experience Center.

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