How to Save Money When Buying brass casting process

Whether you're looking to produce a new product or save money on products you're already manufacturing, cast parts can be a great option. Metalcasting has been around for over 5,000 years, and today's processes, along with cnc machining, can produce just about any part imaginable.

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Purchasing cast parts can be a long and difficult process, and there are many variables to consider. Overall, you want to make sure that you find the right balance between quality and cost.

Before you dive right in and start choosing the right manufacturer, here are three things to keep in mind when purchasing cast parts.

1. Know How Your Product Works

If you're bringing a new product to market, it's OK not to know everything about how it will work, and your supplier can help you figure out the details. In order to choose the right supplier, however, you need to know at least the basics about the shape and function of your product.

For example, is it a standalone part, or does it interact with other parts? Is it a new part, or an improvement on an old part? How will it move, and where will the friction points be?  

While engineers at a foundry or machine shop can help you finalize your design, they won't know the whole story right away. It's up to you to decide what's most important in terms of your part's shape, size, stength and function.

2. Know Your Product's Tolerances

Almost as important as the part's functionality are its tolerances. Before shopping around for casting quotes, you need to know where your design can change, and where it can't.

Most parts require machining in the finishing stage, but some casting methods can meet tight tolerances without additional machining. To complicate things even more, different types of metal are more machinable than others.

Knowing where your part is more (or less) flexible in terms of tolerances will help you decide on the best process and material to use farther down the road.

3. Know Where Your Product Will Go

A logical extension of knowing how your product works is knowing where it will be used.  One of the most important factors in determining the right materials and process for a casting is knowing what kinds of physical hardships it will be exposed to during its lifetime.

Every part–whether it goes in a car antennae or holds up a crane arm–will experience stresses, strains and exposure to the elements. Parts that stay outside are much more prone to oxidation, and will either have to be made of corrosion-resistant materials or painted. Day-to-day use can push and pull a part until it exceeds its tolerances, and can no longer be used. Some materials are more susceptible to this type of wear than others. 

Choosing the Right Supplier

These three tips are really meant to help you choose the right supplier, or the right manufacturer for your product. Foundries and machine shops around the country–and around the world–offer a wide variety of capabilities, specializations and expertise. The best companies will work with you to determine the most cost-effective way to produce your product, while also ensuring that each part meets or exceeds its requirements.

Knowing how your product should work, its tolerances and where it will be put to use can help you narrow down the list of suppliers.  Last but not least, look for companies with an emphasis on customer service. You want to make sure you choose a supplier that's helpful, cooperative and responsive every step of the manufacturing journey.

Buying metal castings is not always straight forward. No matter your knowledge base, there is a lot to understand – on both your end and the Foundry’s. Factors like Alloy selection, moulding/finishing processes, core requirements, supply terms… to get the most value for your money, all of these need to be understood. But by simply expanding on your knowledge on Metal Casting, well, you will have already started the process of evaluating costs and benefits. Before we gear up for the more well-known costs of metal casting, there are a few considerations you may not have thought about.

Economies of Scale – Weigh it Up

Let us say you have a casting order requirement that’s less than 100 kg, but the Foundry you are currently working with accommodates for Medium to Large Scale Casting. You will be wasting crucial capital on both their Furnace’s power and casting yield. It is essential to ensure that the Foundry you have chosen is right for your requirements. For example, for order volumes over 1 metric tonne you should choose a Foundry geared for medium and high economies of scale, ideally with a Furnace 500 kg or larger.

Foundry Alterations – Be Prepared

When negotiating the purchase of castings from any Foundry do not expect your product to be supplied at cost. If your Foundry goes out of business, you are likely to face a large expense from new patterns at a new Foundry. Or at least, modifying existing patterns to suit another Foundry’s moulding equipment. Make sure to partner with a Foundry that will remain in business for as long as you will be requiring your castings, so be reasonable on price when finding your best Foundry partner.

Local Scrap and Supply Chain – Check for Kinks

So much of your Foundry’s raw material cost will be down to supply chain and local scrap availability. It is important to identify not only what your chosen Foundry’s costs are during the casting process but also what costs might be included before anything has even touched the Furnace. Read on to find more about material costs below.

The Metal

To calculate the cost of metal you need to know three things: Alloy Type, Casting Weight, and Total Tree Weight (including runners and risers). Alloys are a combination of a base metal like Iron, Copper, or Aluminium, all in conjunction with a range of Additives. These Additives can cause huge changes to the properties of metal even in very small amounts. When the correct, specific Alloy or Composition is determined, the casting process will begin to take shape.

The Foundry

Your Foundry will calculate the correct amount of base metal required per Kg of casting and the number of Alloys and Additives required to achieve the desired Composition. But take note, in some cases a higher amount of additive is required to allow for melting loss and oxidisation, depending on your casting process.

Once the amounts of base metal and Alloy additives have been determined the source of the metal should be selected to achieve the lowest cost of raw materials. Global metal exchanges are often used as cost benchmarks such as the London Metal Exchange (LME), a great way to analyse the costs of the raw materials you need.

LME Index Price per Tonne in USD Steel Scrap India (Fe) $612 Aluminium (Al) $3,582 Copper (C) $10,278 Nickel $35, Tin $42,528 Zinc $4,072 Lead $2,345

Ref. © The London Metal Exchange, 25 March .

Now you have your materials, let us breakdown your Foundry’s Furnace.

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The first processing of metal is the melting process, which is performed in your Foundry’s Furnaces. Induction is the most common Furnace type for production casting and Cupola, for example, for Cast Iron.

But, as always, there are costs.

The main cost of Metal Melting is electricity. But operational labour and maintenance have a significant impact too. Most Foundries know how these costs translate to their metal melting cost per Kg at spout – it is the average cost for them to get 1kg of any molten metal prepared for pouring from the Furnace. But with varying Foundries comes varying work force sizes and power needs, so be sure to take these into account.

Cost of material procurement is not the only material cost in casting. The type of Alloy is an obvious consideration too – some Alloys have a higher melting point and so require more Furnace time. That said, a highly efficient Foundry can achieve a cost of as low as $0.30 USD for Cast Iron. Whereas low volume Furnaces with expensive electricity can cost as much as $1.50 USD per Kg. The melting cost then needs to be multiplied by the casting weight and divided by the casting yield. The yield is the percentage of casting tree that is the actual casting. This is where partnering with a Foundry that uses the correct economies of scale comes into play. Remember – bigger is not always better as Furnace melting cost is regulated in part by the Kilowatt capacity and efficiency of the Furnace. So, what type of costs can you expect to face when it comes to types of casting?

Moulding Costs

Moulding costs vary substantially depending on your favoured process. From low to high – Die Casting and Continuous Casting, Green Sand Casting, Hard Sand or Resin Sand Moulding, and then Shell Sand and Investment Casting.

Let us break them down.

Die Casting and Continuous Casting – Low material usage with a high output to labour cost ratio.

While the low cost of this process is a relief on expenditure, the geometry possible with these production processes is limited and the tooling cost is high. That said, moulding cost of this production process is normally a small fraction of the metal cost going in.

Green Sand Moulding – Relatively low cost due to reuse potential of sand and output per labour hour being high.

This is made achievable with the common Semi-Automatic Jolt-Squeeze moulding machines and less common fully automated moulding machines. Using a Semi-Automatic moulding machine producing small moulding boxes 600mmx400mm a moulder could typically produce 8-15 moulds per hour. As moulds become more complicated or larger the output slows as moulders needs to insert cores and take more care to ensure forming of detailed impressions. For a small moulding box, the factory cost allowance would be about $0.50 USD per box plus the allocation of labour.

Hard Sand Moulding – Reasonable cost due to sand reclaiming technology

Includes Sodium Silicate sand and Furan resin sand casting. These moulding processes involve mixing Silica Sand with a Resin (normally 0.75%-1.2%) that sets when a catalyst is added. With these moulding processes using Chemical Resin and often an acid as the catalyst the cost is normally higher than green sand moulding. The moulding cost would typically be double the cost of green sand process, but this varies depending on the chemical used, the output of the mixer and moulder.

Finishing Costs

Shot Blasting – This is done after the castings are poured and knocked out of their mould to clean up the casting and remove sand particles. The cost of shot blasting would normally only be 5-10 cents per casting kg.

Fettling – A process involving deburring during pouring. This is a labour-intensive process and particularly required for castings produced by Green Sand moulding and Hard Sand moulding. The time requirement ranges depending on the complexity and size of the casting. A simple casting that weighs 5kg would typically take 0.5-1 minute of fettling, whereas a complex casting weighing 100kg could take over 20-30 minutes.

Machining Cost – Usually the most expensive finishing process. Machining cost is dependent on the number of set-ups, the time required per process, cost of the machine, cost of cutting tools, cost of labour and volume. With this number of variables, we cannot give any suggested rule-of-thumb costs here. For Sand castings where the machining cost is high, we would suggest considering if the Lost-Wax moulding process would allow you to save more effectively. The Lost-Wax process can achieve complex geometries with a smooth accurate surface finish that often results in reduced machining time or the elimination entirely.

Other Finishing Processes- Painting, Laser Etching, Polishing and Plating. The costs for all these processes are dependent on the volume, quality requirement, level of automation and the cost of labour. For when these processes are required, the costs are normally only a small percentage of the overall cost.
Before we conclude, however –

Supply Terms

Supply terms are a critical cost that many firms fail to consider when assessing costs. Supply Terms determine the freight cost will be incurred getting your castings delivered and the cost of capital if you need to pay for your castings ahead of when they are required.

Remember to consider the incoterms in any Foundry’s quote. If Ex-works or FOB, then ensure you get a freight quote and add an administrative factor to cover the cost of you needing to arrange the inwards freight.

Remember to factor in the cost of capital. This is the time from when you need to pay for the castings to when you actually need the castings. If the Foundry stipulates high minimum order quantities and is based far away, then the time between when you pay for your castings and when they are finally used may be significant. Apply a cost-of-money rate to this time to ensure you are factoring this in. Most firms would apply a 15-25% per annum interest rate to the capital outlay to cost this.

Conclusion

In any case, as times change, and the market fluctuates, what processes, materials, and Foundries you value will do too. But one thing will always stay the same – knowledge is the most valuable tool at your disposal.

Keep yourself informed so that you can cut down costs and balance quality and value. You can contact Kormax’s experienced team for more information and/or advice.

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