Aluminium Extrusion 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.

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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.

Machining Aluminium and Aluminium Alloys

Cutting Force?

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 A whose level of mechanical properties is on a par with that for low-carbon steel.

Tooling?

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 m/min with and 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?

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.

 

This article covers 10 essential tips for CNC machining design.

1. Avoid Excessively Thin Walls

Decreasing the wall thickness affects the stiffness of the material and reduces achievable accuracy as a result of inevitable vibrations during machining. The standard minimum wall thickness is 0.794 mm for metals and 1.5 mm for plastics. If you require thinner walls, you can use other suitable and cost-effective manufacturing processes like sheet metal fabrication.

2. Avoid Designing Features That Cannot Be CNC Machined

An example of a feature in CNC machined parts that CNC mills, lathes or drills cannot produce is &#;curved holes&#;. If you require this feature or others that can&#;t be machined for your design, you can use electrical discharge machining (EDM) instead.

3. Avoid Excessive Use of Tight Tolerances

If you don&#;t specify tolerances in your design, the machine would simply use its standard tolerance. This helps save time and money. You should only specify tight tolerances when absolutely necessary. If you do specify tight tolerances, you should maintain consistency throughout your design. This helps reduce machining time.

4. Avoid Unnecessary Aesthetic Features

Some aesthetic features cannot be efficiently machined. As a designer, you should ask yourself: &#;What CNC machining process would this feature require?&#; or &#;Is it a 5-axis or a 3-axis machining process?&#;

You can improve your design by focusing on the accuracy of required features rather than aesthetics. It is best to use post-machining processes to change aesthetics.

If you want to learn more, please visit our website Aluminum Extrusion CNC.

Additional resources:
Tantalum Sputtering Target Plates

5. Design Cavities With Accurate Depth-to-width Ratios

CNC Tool Holders: What are They and What are the ...

Cavities that are too deep can result in tool hanging, tool deflection, chip evacuation issues, and tool fracture. Cavity depths should not exceed 3-4 times their width. If larger depths are required, you should consider designing your part with a variable cavity depth. Cavity depths higher than six times their width are considered deep.

6. Add a Radius When Designing Internal Vertical Edges

Most cutting tools are cylindrical and cannot machine sharp internal edges, meaning it is important to add a radius to internal edges in your design. To avoid unnecessary wear and tear of the tool, a good rule of thumb is to add a radius of 130% of the milling tool radius. If you need sharp internal corners, consider adding undercuts instead of reducing the edge radius.

7. Limit Thread Length

Unnecessarily long threads increase machining costs. The strength of the connection does not increase any when the thread length exceeds the size of the diameter by more than 1.5 times.

• Design threads should be no longer than 2 times the hole diameter 
• For blind holes, add an unthreaded length of at least half the diameter at the bottom of the hole

8. Avoid Extremely Small Features

Most CNC machines have a minimum tool diameter of 2.5 mm, meaning any feature smaller than 2.5 mm would be difficult to machine and would require special tools, which increases machining costs and time.

9. Design Holes With Standard Sizes

Holes are machined quickly and accurately when standard drill bits are used. This means you won&#;t need end mills or reamers to finish the hole size to a non-standard dimension.

Usually, increments of 0.1 mm are used for holes up to 10 mm in diameter, and increments of 0.5 mm are used for larger holes.

You should also limit the depth of holes to four times their diameter. It is possible to machine deeper holes (up to 10 times the diameter), but this will increase costs.

10. Avoid Unnecessary Text and Lettering

Any required text can be painted or laser engraved on the surface of the machined part during the finishing process. If machined text is required, adhere to the following rules:

• Choose engraving instead of embossing. This way, less material is removed.
• Use 20-point Sans Serif fonts to help keep costs low. Also, many CNC machines are already programmed for these fonts

CNC Machining Services at Xometry

At Xometry Europe, we offer CNC milling and CNC turning online services, as well as high-precision, fast, and quality CNC machined parts made of aluminium, stainless steel, steel, copper alloys, and many others. For any questions regarding CNC machining design, you can also refer to our CNC machining design guide.

We also carry out surface finish operations upon request. To get an instant quote, upload your models on our instant quoting platform.

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