CNC Machined vs Forged. High Level Manufacturing For Very Different Needs.
When manufacturing metal parts, it’s important to consider all the different variables needed to ensure that you are making the best decision. Each manufacturing process is a viable option in its own right, and so it all depends on so many factors like the intended use of the part, the cost, the amount, the tensile strength needed and the materials. It’s for this reason that George Sewell Forgings offers both the forging process and CNC Machining. Although our incredible team is more than willing to help you decide which is right for you, here are a few key differences between them.
What’s the Difference?
Let’s start by taking a look at each process.
Forging is a process by which heat is applied to the metal to make it malleable and soft. The metal is then shaped and manufactured using heat and compressive forces. The metal is pushed against a mould made from very tough steel and forced to bend into the desired shape.
Computer Numeric Control Machining is a computerised process that passes a piece of metal into a machining tool. The machine is programmed with sensors built to position the piece of metal, and a rotary tool effectively cuts away unwanted parts of the clump of metal to form the specified part. This process can create smooth curves, and it is fully motorised and controlled by a computer panel.
The excessive force by which the metal is hammered means the granular structure of the metal remains intact. Rather than reaching its melting point and reducing its elemental lattice of metallic bonds and positive ions, it is manipulated by condensing those bonds without breaking them. This significantly alters the microstructure of the metal, resulting in finer grain and improved fatigue resistance. By compacting the structure in this way, the forging process allows the metal to retain its strength, eliminate defects and porosity in the product.
Forging is perfect if you need to make tens of thousands of replicas of the same moulded piece of metal.
One way to think about it is that forging compresses the metal, resulting in a substantial component perpendicular to the grain. This can be ideal for basic things like nails, as they will stand strong when being hammered into a surface.
Setting up the moulds is not the cheapest option; this process can be optimal if you are mass manufacturing identical pieces. Not only this, but it can also reduce the frequency in which you will need to replace the parts. So, if you need to mass-produce one thing with no more machining, forging is definitely your best bet.
Forged metal is usually only reinforced perpendicular to the grain flow. This is not ideal for pieces that must have strength all over. Sharpened points are also out of the question because forging cannot produce pieces with sharp angles. After all, they are too difficult to separate from the mould. This means that alternative machining will need to be done on the part, and often, further polishing with an abrasive mechanism is required to achieve a better surface finish.
What are the pros and cons of CNC machining?
CNC machining is suitable for producing pieces of complicated or acute-angled shapes. CNC machining is more convenient and cost-effective for one-off production and those looking to manufacture multiple designs. Some forges also use CNC machines to make moulds for their forging presses due to pre-program accuracy. Surface finishes on CNC machined parts are usually high quality and look very consistent, while cast or forged parts are typically rougher.
If you have unique needs, such as internal threads or sharpened edges, and you are not aiming for mass production output, CNC is the best choice for you.
CNC machining takes time, as opposed to forging, which can produce basic parts easily and quickly. The true expense, however, is in the amount of waste produced. As metal is removed from each fabrication, resulting in shavings that can only be sold for scrap, this means that production costs can easily add up if you’re producing a huge amount of complex pieces with excess waste.
CNC machines are complex pieces of equipment with multiple motors and moving parts. This means that running the machine and upkeeping maintenance like oiling and constant repairs will increase the operational costs. Although we calculate these expenses and add a fraction of them to the quote, the more products you want to get produced, the cheaper you will be quoted for each part.
Making a decision
Given the scale of a standard volume of runs in Australia, CNC machining is probably the most useful alternative in a wider variety of situations, however forging is definitely the way to go if you’re looking for a stronger, more tactile production.
If you’re still unsure which manufacturing process is right for you, be sure to consult one of our team of highly experienced team members, including our team of engineers. We have over 50 years of experience in metal processes for a wide range of industries, so contact us today on +61 3 8301 1500.