How degreasing and rust prevention is essential for stored metal parts in flexible manufacturing processes.
Flexible batch production for variable numbers and colours of finished products is very difficult to achieve when producing fabricated items in mild steel sheet due to storage of the unpainted parts being subject to rusting and corrosion when processed by conventional water based processes. This paper describes a typical manufacturing cycle for office and educational equipment where rust free storage allows JIT deliveries.
To satisfy contracts to produce a wide range of metal cabinets, chests, and lockers in many different sizes with a range of cabinets and shelving, all in different colours, for the education sector which have to be delivered within 7 days, needs very careful production planning. It is necessary to stock drawers, tops and backs, punched, laid flat, unpainted, and then produce sides to order. Three pieces of equipment allow successful operation of this production process. A CNC controlled sheet metal folding and bending centre an automatic DriPHOS combined degreasing and metal pre-treatment process tank and a fast colour change powder or paint coating plant and an oven.
In the case of the bending operation, a stock of pre-punched blanks is carried which when a ‘rush’ order is received the automated CNC folding system, will typically produce the end folds in a pair of sides, within ten minutes – without disrupting normal planned production.
The DriPHOS pre-treatment operation is critical to achieving these very tight schedules. A fully integrated CAD/CAM system enables a product to be taken from concept to finished item. Manufacture of batches of storage cabinets from tens to 500 off will need up to 20,000 items of sheet metal work and shelving. Batches of machined parts which must be stored, for long periods, can be transferred to the pre-treatment cell and loaded into a basket or jig, positioned to allow good circulation of DriPHOS solution around the parts.
The loaded basket is placed onto an automated handling system to raise and lower work within the enclosed process tank to a defined cycle. The DriPHOS process is similar to vapour degreasing and requires minimal space as only one tank is involved rather than the altern ative multi tank water based systems. Held in the vapour zone above the boiling DriPHOS solution, vapour condenses on the components until the temperature equalises at 31°C. This degreases the surfaces and removes loose dirt as it is flushed away by the condensed DriPHOS. After immersion in the solution for 2- 3 minutes, the basket/ jig is raised into the vapour zone where it is spray-rinsed for 30 seconds with cooled DriPHOS distillate to remove traces of process liquid. Residual condensate flash evaporates as the basket is slowly removed from the tank. The whole cycle takes only five minutes.
DriPHOS enables finished parts to be degreased, pre-treated and protected prior to assembly. Any other process would have to see parts painted in no more than an hour after treatment during which time rusting may occur. DriPHOS on the other hand presents a physical barrier against moisture, inhibiting rust and corrosion. Parts can be assembled and painted up to a year after treatment.
Whether direct from the degreasing and pre-treatment cell or from pre-treated stock from storage, cabinet ‘carcases’ are assembled, TIG welded and ‘jigged up’, along with shelving, doors etc on a motorised overhead carousel. They progress into an automated paint or powder booth with two open stations, for manual spray operations, for operators to ensure all internal corners are covered. The complex crystal structure applied by the DriPHOS process uses thin layer technology (TLT) to produce a crystalline bond that is integral with the metal substrate, increasing the surface area and providing an excellent key for paint, powder and other finishes.
Painted units are passed through ovens from where final assembly sees shelves, doors, handles etc fitted. Finished units can be packaged and despatched the same day. Providing metal storage systems from stock would not be possible without DriPHOS as a pre-treatment solution for rust and corrosion free storage of the sheet metal parts.
For information or advice on the use of DriPHOS or to arrange validation trials at the new test centre or visits by product specialists, appointments can be made by phone or through the product website www.metal-treatment.com.
Share this Article: