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An environmental SEAL of approval

In addition to an improvement in productivity and reduced production costs, porosity sealing in diecastings via vacuum impregnation has numerous environmental benefits, says Dr Mark Cross of Ultraseal International.

Porosity can lead to leak paths which results in the cast part not being functionally sound, clearly a big concern for pressure tight parts such as for engine, transmissions and fuel systems. Vacuum impregnation provides a permanent seal against porosity and saves castings that would otherwise be scrapped.

With foundries needing to achieve specific yields, the implications of increasing production by 5-10 per cent to account for that percentage loss in scrap castings, results in additional use of energy, logistics and incurs added production time, but it also means an increase in materials and the knock-on effect throughout the supply chain. “By working towards recovering parts that would otherwise be considered defects, companies can save all the associated costs with having to produce an additional percentage of parts to cover the scrap components,” Cross tells Foundry Trade Journal. “They will save on die costs, with ten less die shots the die life increases; they will save on the extra energy that would be required to make more parts and there is a time saving element. In addition, because the diecaster is operating the equipment less, they will use less consumables. This has an impact further down the supply chain and means that all concerned are using less material, less energy and less manpower.”

Cross enthuses that minimising waste in such a way is not just of benefit to customer finances but is also helping diecasters meet their environmental responsibilities. “There are very clear benefits to minimising scrap castings such as the reduction in waste material and costs. A less obvious result is a reduced use of chemicals, which in turn leads to less inventory to stock, less chemicals being shipped and less being made. This all has an impact on the company’s CO2 emissions.”

Cross explains how, although we mostly refer to micro porosity (a defect less than 1mm diameter), impregnation is possible in most cases but he warns there is always a compromise when applying the liquid resin. “We can seal any size hole but the pertinent question is what feature the customer wants to keep clean. By clean, I mean not blocking deliberately designed features on the part with sealant, such as tapped holes,” he says. “We can’t have both at the same time, for example you can keep a 2mm feature clean or you can seal a 2mm defect.”

In-house or out source

Cross says many foundries still use external services for impregnation, particularly in the United States, but that has not stopped Ultraseal in broadening its range of service options from selling equipment to offering both in-house and external impregnation services, accommodating a growing desire for companies to have more control. “There are basically three options,” he says. “Captive line, where the customer buys the equipment and runs it themselves; managed, where the equipment is housed on the customer’s site but Ultraseal manages the service; external service centres, where the impregnation is outsourced and Ultraseal provides that option from its service centres around the world.”

Managing the process

If a customer decides that they would prefer the impregnation process to be undertaken in-house but without distracting from existing production, Ultraseal offers the managed solution. In this instance they make the investment in the equipment on the customer’s site, it is dedicated to the customer and charged as a “job shop” expense on either price per part or on a kilo basis. Cross says this is a good option for some companies, those that want the service under their own roof but do not want to detract from their main production process, where they would prefer to concentrate their staffing efforts.

Working with the customer to select the most appropriate option for them is second nature to this respected company but Cross says it is all about responsibility. “It comes down to who wants to own responsibility for the process – what do our customers want? The systems are easy to operate and if the customer is happy to accept responsibility and has a significant need, they go down the captive line route and make the investment accordingly. If the customer believes the service should be on-site but they don’t see it as core and would rather leave it to the expert, then the managed option is a nice solution. It is specifically for high volume needs. We embed the system and match their exact requirements. This offers them a high quality process but at a lower cost than capital expenditure.”

Customers can of course purchase the relevant semi or fully automatic equipment, which can be integrated into an existing production line.

An environmental champion

The process itself of course produces waste but Cross is quick to point out that Ultraseal has been championing a resin recycling process since the 1980s. “Stage three is where most of the effluent traditionally occurs in vacuum impregnation, where most non-recycling systems can’t separate resin from water. Around 95 per cent of solution used generally gets washed away as wastewater. It gets treated or diluted with more water but the chemicals and a huge amount of water effluent still ends up in the drain. However, in our resin recycling process the water is washed off, processed and cleaned, it is then returned for re-use, thus creating a closed loop. This takes away 95 per cent of the pollutant from impregnation and it means less chemicals are needed. We dominate the world in this technology. At Ultraseal, we talk of non-recycling systems as ‘old technology’. We can retrofit recycling systems to any existing equipment, not just our own.”

Working with customers through difficult times

Cross acknowledges the difficulty of managing a business during the current times. “You have to accept that die cast parts will leak – so it comes down to how you deal with this. We already offer upgrade packages on our equipment and we can incorporate options for whatever the customer needs, including remote access and data collection as per Industry 4.0. Financing options are also available. These are difficult times and we have all had to embrace massive changes overnight but the world is still operating and our impact on the environment has to be a consideration.”

Final thoughts

The range of options available from this market leading company provides total system flexibility for the diecaster, resulting in an overall improvement in yield but not at the expense of the environment. Cross says “owning the impregnation” of the part means a diecaster can provide quality components with peace of mind that they have given their best in terms of quality, sustainability and environmental responsibility – at a fraction of the cost of scrapping castings. It’s a win-win for the diecaster, the customer and the planet.

Impregnation process

The four module system is totally flexible in terms of number of parts and whether designed with a front-load or fully automated capability. Whilst the core equipment is standard, using a basket style, the handling systems are bespoke and fit specific customer requirements, they can be manual or robotic.

The parts – the numbers of which are dependent on size – are loaded in baskets into chambers. The liquid resin is applied to the parts in chamber 1; excess resin is removed, by gravity, in chamber 2 where excess resin is drained; the cleaning of the parts takes place in chambers 3 and 4 where washing occurs with water or an aqueous solution in chamber 3 and the parts are heated, which turns the sealant to a chemical or thermally resistant polymer, in chamber 4.

Contact: Dr Mark Cross, commercial sales director, Ultraseal International Ltd, Tel: +44 (0) 24 7625 8444, email:  web: