Dry Washing Technology
Ricoh has developed an environmentally-friendly technology that removes residue without using solvents or water. Instead, small thin films are air-blasted onto the object to be cleaned to remove the residue. This technology is applied to clean jigs used in the manufacturing process and parts during the recycling of products.
Principle of Dry Washing
Recycling can never be labeled effective if it generates significant environmental impact in its process. Based on this recognition, Ricoh has been making solid progress in developing resource-recirculating production systems. The development of original dry washing technology is among the latest examples.
This technology is based on the principle of using airflow to blast thin resin films of a few millimeters square onto the object to be cleaned and removing the residue with their impact or contact (Figure 1). The thin and lightweight film, which does not damage the object to be cleaned, effectively removes residue at the edges that cannot be removed by high-speed airflow alone.
This process uses neither solvent nor water, and it also minimizes the amount of material used for the thin and lightweight film. Its capacity for removing residue does not diminish after repeated use, so the resin films can be used continuously without being replaced. Only residue removed from the object is discharged, with the resin films used repeatedly through continuous circulation (Figure 2). These properties make it possible to reduce both environmental impact and operational cost.
Washing Adhered Residue
Drastic Improvement of Washing in Manufacturing Process
In order to recycle our products, such as copiers or printers, Ricoh has been researching and developing dry washing technology that eliminates waste liquid. Ricoh has applied this technology to the washing of jigs (pallets) used in the automated soldering process. Although pallets are generally cleaned with solvents, we have achieved solvent-free washing with this technology.
As shown in Figure3, jigs called pallets are used in the automated soldering process (flow soldering machine) to protect already-soldered parts from heat. In this soldering process, liquid flux is applied to eliminate the oxidized layer of the joining surface, but the flux gets laminated and adheres to pallets through repetitive use. The flux remaining on pallets must be cleaned off periodically.
Solvent cleaner is commonly used to remove the adhered flux, which places a burden on the environment and incurs disposal costs for the waste liquid. Also, in terms of safety and health, a solvent-free washing method is desirable.
Washing solder flux without solvent
Ricoh has been further developing dry washing technology, which was originally developed to remove toner from parts or components, and, while doing so, the company found a way to remove even adhered flux without using solvent cleaner.
Pieces of film can be easily separated from the removed residue (flux powder) because of the difference in the sizes between the film and the flux powder. Only the flux powder is collected by a dust collector and the films are used repeatedly through continuous circulation (Figure 4).
You can watch a video clip of the process of dry-washing a pallet.
Figure 5 shows the pallet before/after dry washing for 2 minutes.
Effect of the Reduction of Environmental Impact
This new method can reduce both environmental impact and washing costs by up to one tenth compared with the conventional method using solvent (calculated by Ricoh). Washing time (process lead time) has also reduced from more than 2 hours to less than 5 minutes.
This method comes into practical use for the washing of pallets used in the automated soldering process at Ricoh Group domestic and overseas production sites.
Washing Powdery Residue
Application in Washing Process for Product Recycling
Product recycling is a part of our environmental efforts as a view point of effective use of resources. When we devote to recycling resources, it is important not to increase the environmental impact in its process. The washing process accounts for the highest proportion of the recycling process of copiers and printers (Figure 7).
Washing by the dry washing method
The dry washing method is applied to remove toner in recycling process at Ricoh manufacturing site. Figure 8 is an example of dry washing machine for removing toner from parts during the recycling of products. You can watch a video clip of the washing of parts.
Effect of the Reduction of Environmental Impact
Ricoh has developed dry washing technology that does not require dewatering and drying. As a result, a process that used to take more than 1 hour has been shortened to about 1 minute, and wastewater has been reduced (Figure 9).
Rotation Airflow Type Residue Removal (Rotation Airflow Type Dry Washing Device)
Ricoh's dry washing technology works by whipping plastic film on residue using a stream of compressed air blown off from the nozzle of the washing equipment. It is used for washing both adhered residue and powdery residue. Environments where compressed air can be used, however, are restricted and there is room for improvement for use on a small scale and also from the standpoint of energy consumption. To solve this problem, Ricoh has developed a "rotation airflow type dry washing device," with which the dry washing effect is easily achieved merely by suction, such as by using a vacuum cleaner. Figure 10 shows the principle.
The rotation airflow type dry washing device takes plastic film to be used for washing inside the main frame, and is connected to a suction device, such as a vacuum cleaner. Suction places the interior space of the device in a negative pressure and the open air flows into the interior from the inlet. Inflow air accelerates the flow of air in the circular interior space (rotary drum), and generates a rotating airstream. This cyclonic air current causes plastic film to rotate at high speed and collide with the surface of the residue at the opening of the rotary drum. The residue is then removed by that impact. Only the residue removed with the air current is separated and discharged, and the film is used repeatedly in circulation. Because it is driven by suction force, in principle, this device disperses neither plastic film nor dust outside. For that reason, removal of residue by dry washing, without using liquids or solvents, can be easily achieved anywhere using an existing dust collector, such as a vacuum cleaner.
This device yields the following benefits:
1) Residue is removed powerfully without liquids or solvents.
2) Because it is suction driven, rubbish does not disperse, rendering no effect on the surrounding environment.
3) The principle is simple, so lightweight and compact design is possible.
Some recycling sites are beginning to use the technology where work space is limited. It is also used for maintenance to remove residue inside production equipment. Both applications are possible, taking advantage of the device’s distinctive characteristics.
Movie 3 shows how flux adhered to a glass board is actually removed by the rotation airflow type dry washing device.
Further, to simplify use, a model of the rotation airflow type dry washing device integrated with a dust collecting blower is under development (See Figure 11).