Shot blasting technology: how to operate and modernise machines efficiently
If production is not running at full capacity, new investments take a back seat. For many small and medium-sized companies, it makes sense to optimise existing capacities. This is includes modernising, because downtimes are easier to absorb then than when operating at full capacity. The investment pays itself back in the medium term. Alternatives are outlined below.
Maintenance of existing shot blasting machines
It is wise to start by determining the efficiency level of the existing shot blasting machines. However, this is beyond the scope of routine maintenance work. Is the machine operating optimally, or can its performance be enhanced by relatively simple means? An inspection of the various individual modules will provide the necessary information. In addition to in-house maintenance, specialists can point out sources of error or make suggestions for improvement. Therefore, it makes sense to have shot blasting machines inspected at least once a year by a specialist. Further inspections can then be performed by in-house personnel.
AGTOS, 48282 Emsdetten, builds proprietary shot blasting machines, deals in preowned machines and supplies wear and replacement part for other makes of machine. Its service technicians are familiar with the critical aspects of all machines, and thus are able to detect and remedy faults. After an inspection has been made, a schedule of supply and services is prepared, summarising for the operator the condition of the individual modules.
The abrasive used in the machines not only has an erosive effect on the workpiece surfaces to be machined. It also attacks many areas inside the blasting machines, necessitating major repairs in some cases. This can also impair the performance of the machine. Many users are unaware that fine material in the abrasive, i.e. dust and granular fragments, can cause much greater wear than the abrasive itself. For that reason, a great deal of attention must be paid to this factor.
On the one hand, minor design improvements can significantly improve the wear resistance of existing shot-blasting machines, thus cutting repair costs and shortening repair times. Selection of the right protective material is another important factor when it comes to minimising wear and tear. Therefore it makes economic sense to seek expert advice.
the AGTOS magnetic/air separator with dual magnetic cylinders separates sand and abrasive reliably.
In addition to analysing the wear and tear within the machine, the inspection of other modules helps to achieve the desired increase in performance. A key module is the abrasive conditioning machine. The circulating abrasive is purified by removing dust and fines (i.e. abrasive fragments) and subsequently returned to the turbines through abrasive silos. Next to the turbines, this module has the greatest influence on the performance of the blasting machine. It depends on various factors: the abrasive veil (the flow of air containing abrasive) must be distributed evenly and the air flow must be set correctly in order to remove fine particles of the right size. If the air flow is too strong, usable abrasive will be eliminated from the blasting process, resulting in high cost.
Upgrading of existing blasting machines by modification
Once the above-mentioned possibilities for the optimisation of existing shot blasting machines have been exhausted, it advisable to try modifying the machine to enhance performance. AGTOS has achieved very good results through the replacement of turbines. By so doing, many blasting machines with obsolete technology can again be made competitive in a cost-effective way, allowing customers to meet the deadlines and quality standards expected by the market today.
The AGTOS high-performance turbines have very favourable characteristic features. Design modifications often allow higher abrasive flow rates to be attained without increasing shaft power. This means better blasting results can be achieved using the same amount of energy. A prerequisite for this is that the blasting machine be able to deliver the required amount of abrasive. Further modifications will otherwise be needed. Since many machines have now been modified, AGTOS specialists have an enormous wealth of experience. The AGTOS high-performance turbines have single-disc blasting wheels with six throwing blades. In comparison with the double-disc blasting wheels available on the market, these units require fewer wear parts. They are more cost-effective and time efficient because they can be assembled in less time and without the need for special tools.
If the existing abrasive conditioning machine does not have enough capacity, an increase in output can be achieved by modifications. One possibility is to increase the volumetric capacity of this module, which is almost the equivalent of replacing the module. A low-cost solution is to use the blasting machine for the purification of abrasive while it is running but not abrasive-blasting. This is done by creating a continuous abrasive circuit by installing an additional hose or pipe between the abrasive silo and the collecting hopper. The abrasive is cleaned more intensively.
When shot blasting machines are operated in foundries, the ingress of moulding sand into the abrasive circuit can cause high levels of wear. This problem can be remedied by using magnetic/air separators which separate the abrasive from the sand. AGTOS can supply highly effective magnetic/air separators which achieve high separation efficiency by means of dual magnetic cylinders. These components can be retrofitted or installed as replacements for obsolete systems.
Use of preowned machines as an interim solution
Temporary, and often unforeseeable, production peaks of unknown duration can be easily accommodated by using preowned machines. These machines are also available on lease. AGTOS has special warehouses which stock various types and makes of preowned machine. These machines are initially taken into storage and then supplied directly by arrangement with the customer. Modification and modernisation work can be carried out beforehand depending on the customer's requirements and budget. Once given a final respray, these machines often hard to distinguish from new ones. A number of preowned machines are briefly described on the AGTOS website. They will often bridge the time to delivery of a new blasting machine.
AGTOS high-performance turbines are often used to boost the output of older blasting machines.
Energy-efficient design of blasting machines
Blasting machines consume large amounts of energy. The energy efficiency of blasting technology therefore merits special attention.
When designing blasting machines, attention is paid to make sure that all motors are correctly rated. Additional reserve capacity is factored in to ensure that the machines run smoothly even in overload conditions.
Another way to reduce the power consumption of AGTOS blasting machines is to use servomotors for the abrasive control valves. They enable the flow of abrasive flow through the turbines to be regulated automatically. The less abrasive is needed to achieve the required output, the less power the turbine driving motors will consume. This also helps to save abrasive, because the rate of wear is reduced. A side benefit is longer replacement intervals.
Turbines are the beating heart of every shot blasting machine. They come in various shapes and forms. The differences are to be found in their design (i.e. in the configuration of the units), in their technical features, and in the materials from which the wear parts are made.
The turbines are equipped with frequency converters which allow rotational speeds to be regulated. This offers various benefits. For example, custom programs can be developed for specific workpiece groups in order to achieve previously defined surface finish qualities. Many customers attach great importance to the reproducibility of surface finish qualities. A further advantage is the fact that various surfaces and geometries can be machined differently using the same abrasive. Depending on application, abrasives with grain sizes of up to 3 mm can be used on AGTOS turbines. This means that industrial-scale systems with, in some cases, large distances to the workpieces can be realised. As regards energy efficiency, frequency converters have the advantage that the optimal output of the turbines can be tested with a minimum of energy consumption.
A further way of reducing energy consumption is to put the blasting machine into an idle state if no workpieces are to be fed into the machine for a defined period of time. This strategy can only be adopted for a small number of motors (e.g. turbines) if the intervals are short. If the intervals are longer, then all the motors can be shut down. That can be achieved in roller conveyor and monorail shot blasting machines, for example, by using light barriers, switching thresholds or other optical sensing devices. In the case of rubberband and rubber crawler shot blasting machines, the power supply to the turbines must be shut off if the doors go up after the abrasive has been transferred from the bucket elevator to the storage hopper.
The filter cartridges in AGTOS systems are not cleaned in the conventional manner using pulsed compressed air. Filter cartridge in AGTOS filtering systems are cleaned depending on the differential pressure. The greater the differential pressure, the shorter the intervals. This has the advantage of saving energy when the filter cartridges are still relatively new. The filter medium is also conserved, because pulsed compressed air causes damage due to the movement of the filter medium and the entrained dust.
Other design features of the AGTOS blasting system include filter cartridges with a reusable support basket. This saves material. This also has a positive effect on the prices of replacement parts. The same applies to several turbine parts. The control cages, for example, are made up of multiple parts so that only actual worn parts have to be replaced.
The drives of the blasting machines also offer potential savings. Where technically possible, they are designed in conformity with higher efficiency classes. Turbine motors are an exception. They can only conform to efficiency class "2" because of their sealing and bearing elements. This not the case with modules such as filters, bucket elevators, worms and bucket elevator drums.
Click here to enlarge
the diagram showing the flow of abrasive in AGTOS high-performance turbine 3.6.3. reflects the high blasting power of the units.
Further potential savings will be reviewed. In this area, too, AGTOS is working in close co-operation with customers to jointly find optimal solutions.
The AGTOS range of products and services includes new machines, preowned machines, servicing work, spare parts and wear parts for many types of blasting system. AGTOS stocks turbine parts for a range of different systems. Many replacement parts are manufactured in-house and, therefore, are subject to continuous improvement. In this way, it is often possible to supply parts which are even better than the original.