Contract manufacturing of Metal parts or products are very commonly used in many industries, as they are high strength, durable usage, high temperature resistance. Human history is underwritten by the thread of making – and making in metal has defined the stages of technological and social development for 5,000 years or more. The ‘ages’ of history are defined by the materials they most employed – resulting in complex and adaptable metallurgy and a wide options in forming and joining.
The wealth of materials, methods, processes and finishes has exploded through the digital age, so the options for producing metal parts and products are diverse, cost effective and highly accessible.
You’re reading this because you have parts to make – you know they ought to be metal – and likely you need someone with specialist knowledge to make them for you.
We will help you navigate the bewildering array of options, so you can see the path ahead. Generally, those materials and processing options narrow down quickly, once you can answer a few simple questions;
Is your driver ultimate strength? Cost? Cosmetics? Durability in harsh environments? Weight?
Which cosmetic qualities are you concerned for?
Do you require only one part? Or ten? A hundred? Thousands?
What level of precision do you need in the part(s)?
From these factors, it is not hard to select the type of materials and manufacturing processes, the type of contract manufacturer and the nature and quality of the finishes you’ll need. Ranging from basic ‘metal bashers’ – not to be neglected as a good option – through to precise and artful aircraft parts craftsmen, from one off jobbing shops to huge suppliers of high volume precision – your options are diverse and you must navigate these with care, to avoid over constraining your design process, or committing to excessive but hidden costs.
A great approach to finding suppliers who will understand your needs and suit your budget is to publish a detailed RFQ on Alibaba.com, made-in-china.com and similar platforms. You will likely get a variety of responses, from the craftsman to large factory – but filtering these down to a practical and appropriate few is not a hard task – and in the process you’re likely to get design advice and materials/process options that you’d not thought of.
If you’re asking yourself ‘“How can I manufacture a large quantity of metal parts, of moderate to high strength, with intricate and detail-heavy shapes, integrated features that reduce processes and part count, low weight and good cosmetics and LOW COST?” the answer is die casting.
Die casting forces high pressure molten metal into a mould cavity, so that when it cools it represents a perfect copy of that cavity. The complex, openable mould tool is a free standing device, fitted to a die-casting machine that does the molten metal handling, coolling and tool operation sequencing. This tooling must be made of the most durable steel and it will be unique to your part(s).
Generally referred to as tools or dies, these tools are made to very high accuracy and offer great repeatability and tight tolerances, when correctly operated. The molten metal feed pressure is held steady during cooling, to moderate shrinkage. Once cooled, the die is opened and the casting is ejected, by integrated pins that push it out automatically during opening.
The die can then be closed and will be immediately ready for the next shot, allowing this process to produce thousands of identical castings, quickly and cost effectively.
Manufacture of the die for a part or family of parts is a high cost process – but if you are sure of your volumes, one part can integrate MANY functions and processes – so this is an excellent way to go, but you must design with die-casting in mind and you must be able to assign/amortise the die costs over a large volume of product.
Die casting is only well suited to Aluminium, Magnesium and Zinc alloys, so it cannot produce the highest strength parts – but good design can compensate for any intrinsic material failings to a large degree.
When you want the complexity and flexibility of a die cast component, you can have basically all of the advantages – but at one off (or small numbers).
CNC machining is purely extractive – the required part is ‘carved’ from solid – and the machine capability is defined by the complexity of the part. Simplification of design is beneficial, so a part that can be cut on a 3 axis CNC will cost less than one that needs a 4 or more axis machine.
The lowest CNC cost will come from designing a part that can be made on an automated lathe – the simplest form of CNC machine and the best suited to larger volumes.
CNC part accuracy can be higher than diecast – there will be no shrinkage or cooling distortion – but the cost per part will be very high – so it really isn’t well suited to large volumes of parts. CNC also offers some design flexibility that is hard to achieve in die casting – unlimited undercuts, effectively unlimited part size and a wider range of materials options.
Stamping is applicable to sheet metal materials that are at least moderately ductile – a die-set consisting of a punch part and a hole part are cut in heat treated tool steel – and then sheet material is passed between them and the tool halves are pressed or punched together to cut a faithful 2 dimensional reproduction of the die shape.
The tooling for this type of process is surprisingly low cost – it is wire cut or spark eroded from pre hardened steel plate and can be very quick to make. Depending on the nature of the materials being stamped and the thickness, tool life can be considerable – tens of thousands of operations, as the tools can be re-faced very quickly and easily, as they wear.
If you want one part, stamping is not appropriate – if you want a hundred, it might be, if you want a thousand and upwards it’s likely to be ideal.
Laser cutting uses a high power industrial laser to CNC cut sheet materials – similar to stamping, but more flexible in several regards;
It is well suited to large and VERY large parts, as the biggest systems are only limited by the size of the sheet raw materials
It is well suited to very THICK sheet materials, as the laser cut depth is essentially unlimited
It is tolerant of low ductility materials that will not stamp/punch
Done well, it can produce an easy cleanup and good preparation for follow on processes.
Laser cutting is best applied to low volume parts – if you want one to a hundred parts, it’s THE option – and it can be the right high volume option, in special circumstances.
Sheet metal fabrication
Almost any metal part can be made by sheet metal fabrication. That is a big claim – but sheet metal parts are the underrated backbone of most technologies and consumer products (by weight if not by volume).
From cars to laundry machines, from building cladding to aircraft wings, fabricated sheet metal parts are everywhere. The range of processes available for making parts and assembling them is huge – and though the skills are commonplace, the range of quality of outcomes is almost as large.
Parts can be stamped and laser cut as discussed above. But there are many more options in rendering 2D shapes out of a wide variety of sheet metal materials and thicknesses
They can also be waterjet cut, using a stream of water carrying abrasive particles of garnet or carbide to erode through the material. This process has advantages over laser-jet when volumes and parts are relatively small.
They can be plasma cut – using superheated gas plasma to melt the shape through sheet materials. This process lends itself to highly skilled manual prpcessing as well as CNC machines.
Parts can be guillotined, using hand or machine shears to cut both simple and complex shapes.
They can also be CNC punched (‘nibbled’) by repeated small-feature punching under computer control, delivering complex 2D shapes, low material distortion and very low wastage as parts can be nested in complex orientations for efficiency
Forming 3D shapes into sheet metal parts can produce complex features that can add huge strength, reduce material use/weight and part count, by allowing one port to serve multiple features/purposes. Complex net shapes can result – and this opens up significant design options.
Such features can be pressed into the sheet, using a simple two-part tool that forms the shape. This is common as a post process of parts that have been cut from flat – but it is also common as part of a single stage or multi stage net shape formation that develops features in several steps, possibly with material ‘normalisation’ between steps.
As an example, a soda can is first explosively deep drawn from a strip blank (fast, plastic deformation to make the deep profile), then the lip is pre-formed, then the lip is mated to a cap part and the two are swaged together to form the closure/seal.
As a simpler example, ridges and ribs are pressed into large side panels of a domestic laundry machine, to increase the overall stiffness and reduce drumming
Parts are often 2D bent on a press-brake – a manual or CNC bending jig that restrains the sheet material and bends a straight feature into it – such as an edge lip at right angles, to provide the welding attachment point to a second component.
Often parts are manually or CNC spun, literally the plastic deformation of ductile sheet material to an axially symmetrical 3D shape by flowing the materials around a spinning former. This can be a very low cost way to make aesthetically satisfying parts – it is commonly used for objects from saucepans to missile nose cones.
Complex 3D shapes can be superformed or hydroformed, which is a family of processes that can form tube and sheet materials into a tooled cavity, allowing very high strength and complex shapes to be formed with low disruption and great grain alignment. While tooling and process costs can be high for these methods, they’re often a practical choice for the most difficult parts – exhaust manifolds and vehicle framing for example.
Complex 2D (and limited 3D) profiles can be formed by rolling sheet metals – allowing pleasing and low cost structural elements to be formed without complex tooling. Examples of this are common in aerospace construction and can be seen in Spacex products – building complex and leading edge machines using old and essentially primitive tools.
Sheet metal parts can be joined by a plethora of methods – selection of which offers cosmetic, cost, strength and weight benefits that can be exploited to suit desired design characteristics. No list can be comprehensive, but these are the more common examples of jointing methods.
Sheet metal parts can be spot welded. For example, this is how steel and aluminium car body panels are joined together. Hidden joints, fast robotic or manual processing, very low cost and great strength and fatigue characteristics are all possible
In more closely integrated structures, for gas/watertightness, seam welding can be performed both manually and automatically. Various options are available such as roller seam welding (like elongated spot welding, melt-joining between pinch rollers), arc, TIG, MIG, laser welding and more can be employed
Sheet metal structures are often directly screwed together, using thread forming screws that tap into plain or indented holes. This is a low cost option – not suited to high stress applications and NOT SUITED to service after assembly.
Parts are often riveted together – providing a quick and low cost method of jointing. Ritits ca be single sided (blind or pop rivets) or more cleanly formed by pressing from both sides.
Parts can be folded/swaged together by overlapping features that are then folded or roller compressed to make low profile, very high strength couplings.
Parts for framing, enclosure or support of other sub assemblies very often have threaded inserts/screws (PEMS) added, swaged into the sheet as strong-points and standoffs. A hge range of such devices are readily bought from manufacturers and they offer strong, integrated and low cost three dimesnionality that can remove design constraints.
Finishing of sheet metal parts is often a critical factor – for cosmetic, corrosion and temperature control purposes.
Parts can be electroplated or painted before or after assembly, for a variety of functions.
They can be grained/linished, for cosmetic purposes, hygiene etc.
Commonly, sheet steel can be pre-plated before cutting, allowing a cut/folded/jointed structure to be customer ready (for non challenging environments).
They can be press textured, for scratch resistance and friction purposes – examples being stainless steel seating or handrails having a pattern or texture pressed into them, or treadplate for walkways having diamond traction embossing.
Surfaces can be chemically etched for pattern or adhesion, anodised and finished in a very wide array of ways.
The end result can be highly repeatable, complex net shapes that serve a wide range of applications – and details in the process selection lend themselves to higher or lower volume, greater or lesser operator skill and more.
If you need a sheet metal part, seek guidance from experts, as some of the choices open to you will surprise and delight. Remember that sheet metal solutions can be cost effective, offer good cosmetics, and enable weight and part savings, making final assembly easier and products lighter and cheaper than many alternatives.
They can also be very fast, both in design and manufacture – so they are a good design choice more often than you might imagine.
Where your parts have a complex 2D cross section but only length as the third dimensional feature, this may lend itself to extrusion.
Extrusion process uses bulk plastic deformation, turning metal into a 2D cross section, elongated long part that retains this section throughout. It can result in high strength, good cosmetic finish with little post treatment and low cost. It is ideally suited to high volume production.
However, extrusion dies are not overly expensive, so even modest quantities of end product can be extruded cost effectively.
In a high powered extrusion press, a billet (usually of of Aluminium alloy) is heated to its glass transition temperature, to prepare it to flow plastically, when pushed very hard. The heated metal is then forced through a profile cavity tool (or die) that shapes the material to the cross section. Like tooth paste from a tube.
There are design restrictions – such as nested closed sections being impossible, thicker and thinner section mixing requiring great care, minimum feature size etc – all of which are basic rules that can be discerned from online design guides, or the advice/review of an excerpt Contract Manufacturer.
Forging is a critically important manufacturing process, shaping metal parts through hammering, pressing or rolling – generally when red hot, sometimes cold. This is dependant on the properties required in the finished part and the nature of the materials being processed. Compressive forces are applied with a hammer or die, forming a grain structure within the part that ‘flows’ with the shape of the part – often maximising the strength of resultant parts significantly, compared with processes that do not control this grain formation. A stamped or cast metal part is plastically deformed to the final required geometric shape, increasing fatigue resistance and ultimate strength. The highest stress parts are commonly forged.
Hand forging is applicable to small numbers of parts – whereas a single or multi stage forging tool is required for precision and this can be manually operated, or partially or fully automated to be suitable for any volume from one to many thousands.
A surprisingly wide range of metals lend themselves to forging. Typically, forging is used on alloy steels, but soft metals such as Aluminium, brass, and copper can also be forged. The forging process can produce net shape parts with remarkable mechanical properties and minimum waste.. The process is economically sound with the ability to mass produce parts, and achieve specific mechanical properties in the finished product.
When you have need of metal parts, you should consult with those with expertise and practical experience in the space. Finding the right contract manufacturer to act as either executor of your parts, or as an engineering design consultant to help direct the early design phases – or stages between the two – will equip you to succeed.
Try to avoid allowing yourself to be channelled towards particular solutions that SUIT A SUPPLIER, unless they also deliver what YOU need!
Use your own and your contacts’ experience – you already know someone who knows more – and they know someone who can direct your work into productive channels.
In case, you need any additional help, Inno manufacturing team is ready here to help you out. We, Inno manufacturing, are very professional contract manufacturing company for metal and plastic products fabrication. We are looking forwarder to hearing from you!