Aluminium Extrusion CNC Machining
Long Length Aluminium Extrusion CNC Machining
CNC Machining involves using computers to control machines Axis Spindles clamps etc, By using this process, we can create high precision aluminium products time after time,
Traditional machining operations, such as Milling centres, can easily be performed on Aluminium and their Alloys. However, to achieve conditions such as rotational speeds and feed rates, CNC Machines need to be used. Therefore, we use both 4 Axis & 5 Axis CNC Machines to reach optimum machining conditions for all products.
Why use 4 & 5 Axis CNC Machining
By using CNC Machining, no prototypes are required as the software can stimulate the product before production, which saves time and money. As well as this, products can be replicated as many times as required, which is useful for our clients who have a custom-made product and require a large quantity of that version. Finally, the process is easy to setup and increases the production effectiveness.
Machining Aluminium and Aluminium Alloys
The specific cutting force needed to machine aluminium alloys is far less than is required for steel. For the same section of swarf, the force is one third of that required for aluminium than for low-carbon steel, so it follows for the same cutting force, chip removal is three times higher with aluminium alloys such as 2017A whose level of mechanical properties is on a par with that for low-carbon steel.
The geometry of tools must be specially designed for use with aluminium alloys. Edges must be very keen and cutting tool faces must be highly polished so as to remove swarf efficiently and prevent it from bonding to the tool. Cutting angles will depend on the alloys. The rake angle of the cutting edge must be greater than 6 o and can attain 12 o. The use of tools tipped with TiN or TiCN by PVD deposition only is highly advisable for machining alloys that contain no more than 7% silicon. (Angle of 15 o for diamond coated carbide (CVD Diamond) tools and polycrystalline diamond (PCD) tools.) Provided tooling is designed for aluminium alloys, tool life is much longer than for machining steels, all other factors being equal. All wrought alloys can be machined very rapidly. With special machines (high speed spindles) the machining speed can attain (and exceed) 2 to 3000 m/min with 2000 and 7000 series alloys. Thus for a 12 mm diameter tool the cutting rate can be as high as 50,000 r.p.m. for a feed rate of 10 m/min. With very high cutting rates it is possible to obtain very thin sheet and much lighter components.
Rate of Advance and Depth of Cut?
Given the low modulus of aluminium alloys, high rates of advance are not advisable, even for rough machining. The feed rate should be limited to 0.3mm per revolution. For finishing operations the rate of advance will be determined by the specified surface roughness for the finished product. The depth of cut will depend on the specified accuracy.
Lubrication is a very important factor in the machining of aluminium alloys, and has three main functions: cooling to dissipate the heat generated by cutting and friction, preventing swarf from bonding to the tools, removing swarf from the point of machining. Although three types of lubrication are available- spray mists, full cutting oil, and oil emulsions- the latter option is the most common because this method dissipates more calories per kilo of lubricant, of the order of 200 kg/J. Cutting fluids reduce friction and aid tapping operations. Lubricant spray mists are not advisable where a lot of heat has to be dissipated. The composition of cutting fluids must meet other requirements: they must be compatible with aluminium alloys, they must not cause stains or surface corrosion (no chlorine or sulphur compounds, they must have an anti-bacterial action to prevent fungal growth, they must be environmentally friendly.