Equipment for snow removal and cutting of fire wood is generally used under rather severe operating conditions. For this reason, it must be extremely robust. Especially, the paint must protect the equipment against corrosion and impingement. Of course, this requires careful pre-paint surface preparation by shot blasting. To improve the shot blast results and, at the same time, reduce the cost, the Norwegian Duun Industries AS invested in a fully automatic continuous spinner hanger system RHBD 15/20-K from Rösler. The customer was not only impressed by the design of the Rösler system but liked especially, how the Rösler engineers resolved the problem of the prevailing space constraints in the area where the shot blast machine was to be installed.
Located in the Norwegian town of Asen, the family owned and more than 50 years old Duun Industries AS specializes in the manufacture of tractor implements such as snow plows, snow blowers and sand/salt spreaders. In addition, the company produces automatic wood sawing machines and log splitters. Nearly half of the production is sold abroad. Production Manager Roald Duun explains: „Another business activity of ours is a job shop for laser cutting and bending of sheet metal. And, last but not least, we build gun cabinets. But this is more a hobby of ours.”
Coping with extremely tight space conditions
Duun Industries does most of the component manufacturing for its snow removal and wood cutting implements in-house. The company purchases steel sheets already etched and de-greased, before they are laser-cut, shaped, welded, blast cleaned, powder coated and, finally, go into the equipment assembly. Says the Production Manager: „Until recently our “shot blasting” was performed by manually grinding weld seams etc. This was very time consuming and labor intensive.“ An important customer requirement was to place the new shot blast machine next to the powder coating line. Considering the extremely tight space condition this posed a real challenge fort the Rösler technical team. Roald Duun discussed his requirements with two manufacturers of shot blast equipment. Says Mr. Duun: „Our decision to purchase a Rösler shot blast machine was based on the convincing Rösler technical design and value for money. But above all, we were impressed by the close cooperation with the Rösler engineering team”.
Custom engineered all the way from the parts transport system to the shot blast process
The tailor made shot blast system from Rösler Oberflächentechnik is based on the design of the continuous spinner hanger shot blast machine RHBD 15/20-K. It allows the blast cleaning of single large components as well as processing batches of metal sheets, beams and complex welding fabrications with dimensions of up to 4,000 x 1,600 x 2,000 mm (LxWxH). The maximum payload of the hanger amounts to around two metric tons. For the transport of the parts through the blast machine Rösler expanded the existing power & free transport system of the powder coating line.
In a first step the parts to be blast cleaned are transported into the inlet chamber of the blast machine. Once the parts are in the chamber, the doors close automatically. Subsequently, the parts are passing through the blast chamber at a defined travel speed which can be adjusted with parts specific PLC programs. The complete cleaning of the parts, i.e. the removal of rust, scale and residues from the laser cutting and welding process is ensured with eight (8) Hurricane turbines, model H 42, with a power of 11 kW each. The placement of the easy to maintain single disk turbines in the shape of two rings guarantees that all surface areas of the parts including the narrow front and rear sides are perfectly cleaned. To ensure a high uptime and long life of the blast machine, the blast chamber is fabricated from manganese steel. In addition, in areas directly exposed to the blast stream, the blast chamber is protected with replaceable liners made from highly wear resistant steel
The finished parts are transported from the blast chamber into an outlet chamber with dimensions allowing the longest parts to fit into this outlet chamber. Once the blast process for one part or a batch of parts is complete, an optical sensor sends a signal to the PLC controller which shifts the system into „reverse“. This solution became necessary, because the space constraints did not allow a complete loop of the power & free transport system through the shot blast machine and back to the machine entrance. On their way back through the blast machine the finished parts are „parked“ in the inlet chamber. After the doors of the blast chamber are automatically closed, and the lighting has been turned on, the operator can enter the outlet chamber through a side door to remove residual blast media and dust from the parts with a heavy-duty vacuum cleaner, preventing carry out of blast media.
The possibility to double the system productivity
The cycle time including the time for parts loading, parts transport, the shot blast process and the removal of residual blast media and dust, amounts to about 15 – 20 minutes. If necessary, this cycle time can be nearly cut in half by blasting the parts in forward and reverse transport mode. This is a highly welcome technical feature for Roald Duun: „We are thinking about expanding our job shop activities by offering shot blast sub-contracting services. Compared to manual blasting our RHBD-K shot blast machine is considerably more cost efficient”.
Media classification on „the first floor“
Another technical feature of the Rösler system is the integration of the dust collector and media classification system. Both were placed on the first floor by opening the ceiling between ground floor and first floor. The “back pack“ solution for the dust collector resulted in valuable space savings of about 10 – 15 square meters. The standard dust collector with a residual dust load of less than 3 mg/norm cubic meter was complemented by a so-called „police filter“ which further reduced the residual dust load to below 1 mg. This allows the return of the cleaned air into the building during the winter season resulting in considerable savings for heating. During the summer season the cleaned air can be guided outside of the building.