Shot blast plants- different types and features

The different types of shot blast plants are named after the type of workpiece transport. For example, there are hanger type and continuous overhead rail shot blast plants, roller conveyor and rubber belt tumble shot blast plants, as well as many other types.

Hanger type and continuous overhead rail shot blast plants

What both types of machine have in common is that the workpieces are either hung up directly before they pass through the plant. Or they are placed on hanging racks, which in turn are fed into the machines.

What both types of machine have in common is that the workpieces are either hung up directly before they pass through the plant. Or they are placed on hanging racks, which in turn are fed into the machines.

In a continuous overhead rail shot blast plant, there is a line operation. This means that the workpieces are guided from one machining process to the next while suspended. A hanger type shot blast plant works according to the so-called " in and out principle". The workpieces come out of the machine in the same way as they came in.

The transport system is usually a continuous overhead conveyor based on the power and free system. This includes "dead-end stations" and flexibly connectable sections for intermediate processing steps or for storing/buffering the workpieces.

Manual overhead conveyors are still occasionally used in smaller companies, but the workpieces or workpiece racks are predominantly moved automatically.

The racks on which workpieces are placed or suspended are usually customised constructions for the workpieces. Depending on the size and shape of the workpieces and the quantities to be processed, these can be constructed in such a way that the surfaces of the workpieces are optimally loaded. The material used is normal steel or a more wear-resistant material such as manganese steel.

Roller conveyor shot blast plants

Sheets, profiles and welded constructions are moved through the shot blast plant on driven rollers, which are usually spaced 800 and/or 400 mm apart. The gaps allow processing from above and below, which avoids turning the workpieces. In the blasting area, the rollers are made of a wear-resistant material.

As the workpieces are also transported on rollers for the upstream and downstream machining processes, there is no need to change the type of transport. In some cases, cross transport devices are used here, which enable workpieces to be buffered and/or transferred in and out.

Like the machine, roller conveyor sections behind the shot blast plant are equipped with an abrasive hopper to collect and recover falling abrasive. It is then fed back into the aforementioned abrasive circuit.

If workpieces that are smaller than the roller spacing need to be processed, transport baskets are used, which are placed on the rollers.

Wire mesh conveyor shot blast plants

The horizontal wire belt appears to be similar to a wire mesh. However, it is made of stronger and more wear-resistant material. Compared to the roller conveyor shot blast plant, this type of machine is designed for smaller workpieces, which can also be processed from above and below.

Due to the relatively narrow meshes, a pattern may appear on the workpiece surfaces after the blasting process. This is prevented if the workpieces move on the wire belt during the blasting process.

Concrete shot blast plants

This type of plant is primarily used for concrete workpieces. Paving stones, block steps, palisades and other parts are given a more attractive surface by blasting. They often do not have to be blasted from below. However, a wire belt is not used as a workpiece conveyor as described earlier, which enables processing from above and below.

Instead, a horizontal rubber belt is used. The concrete slabs and/or paving stones are placed on it in pallets and then processed from above. The challenge is to also optimise the edges of steps, for example.

Rubber belt tumble shot blast plants

A flexible rubber belt is guided over transport and deflection rollers so that it forms a trough. When the door in front of it closes, the rubber belt starts to move and the parts inside are blasted by the turbine positioned above it.

The rubber belt is equipped with so-called turning bars to ensure that the parts turn and rotate. The abrasive ejected by the turbine at the top falls through the holes in the rubber belt into the abrasive hopper and is returned to the circuit in this way.

After the blasting process, the rubber belt runs backwards and thus transports the workpieces out of the blasting chamber. This is supported by the turning bars. They fall into a box or onto a conveyor belt and are transported to the next processing step. There are metal wear plates on the side of the blast chamber. The gap dimensions at the transition are minimised so that the workpieces do not jam.

Steel mill tumble shot blast plants

The principle is similar to that of the rubber belt tumble shot blast plant. However, the flexible rubber belt is replaced here by a so-called steel mill belt. This is made up of folded steel strips, the so-called steel mill belt flaps. The steel bars overlap and are connected with steel links on two laterally guided chains.

This type of machine is mainly used in foundries and forges for processing relatively large, robust mass-produced parts. The workpieces are usually large, relatively heavy and so robust that they are not damaged during the circulation process.

Drum shot blast plants

A loading device feeds the mass-produced parts into a seamless drum that is perforated for abrasive transport. This swivels to the turbine, which is located in the rear upper part of the machine. This exposes the workpieces to the abrasive and processes them. During the blasting process, a specially designed drum base, which is usually adapted to the workpieces, ensures the necessary mixing and turning of the workpieces.

After the blasting process, the drum swivels back to the front and empties the workpieces into a container or onto a conveyor belt. There is one decisive advantage of this type of machine over a rubber belt tumble shot blast plant. A drum shot blast plant has no gaps that can cause jamming and double processing of workpieces. This means that even the smallest parts can be blasted.

Diabolo shot blast plants

Steel bars and pipes are guided through the blast chamber on Diabolo rollers. Due to the inclined arrangement of the rollers, the workpieces pass through the shot blast plant and rotate on their own axis. This allows the surface to be blasted evenly all round.

The size of the machines and the number of turbines vary depending on the diameter of the workpieces.

Other special forms of shot blast plants

Depending on how the workpieces are transported, there are also other machine types such as walking chain conveyor shot blast plants and chain transport shot blast plants.