Aluminum is the most loved machined material because of its unique features for machinability and this is why it is most commonly used in manufacturing industry. But the aluminum is not milled using any tool, it requires careful study of its properties and most importantly, an extensive knowledge of tool selection. Understanding the tool requirement by machinist can give them numerous benefits like product pricing, lowering the production cost and make required products with less effort and quality finishing.
The end mills are used to create profile, plunging and required pocketing in aluminum. The various properties of end mills decide which material they will mill easily. Besides, the end geometry of an end mill, factors like end mill coating, helix angle, number of flutes etc. play crucial role to get the job done and vice versa.
This article will explain all the factors of and end mill that must be considered before selecting the end mill. Additionally, the article will also cover the machine requirements for milling aluminum and lastly give names of some popular end mills that are perfect to use.
The best preferred material for making end mills is carbide because it says sharp for long time. Although carbide-made end mills are brittle in nature, but using it on aluminum makes it a great cutting tool. One of the downside of carbide end mills is that they are expensive compared to High-Speed steel. But if you can afford them, they can cut the aluminum with high speed and feed rates and will also last longer in comparison.
Since aluminum is soft when compared to other materials, during CNC milling, its chips can clog in the CNC tool, especially when you are plunging deeper. Coating the end mills with the right material can help resolve the problem.
Most common used coating on an end mill is Titanium Aluminum Nitride (TiAIN). These are slippery coatings and allows the chips to slip easily through the flutes while milling. It is also effective in case you are not using any coolant. The coating is mainly used on carbide tools.
But if you are using high-speed steel (HSS), you should use Titanium Carbo-Nitride (TiCN). This coating will also serve the purpose for lubricity required for aluminum milling. The only downside of this type of coating is its high cost. Other type of coating material is Titanium Diboride (TiB2) etc. Though there are uncoated tools available, using them will only bring damage to your tool and the work piece.
In 2021,HUANA develop DLC Coated for Aluminum cutting which is newest for milling Aluminum
Number of flutes are one of the most important factors while selecting the end mill. The end mills are available in 2, 3, 4, and etc. The purpose of end mill is removing the chips from the work piece while milling. The greater the number of flutes in end mill, the softer the material to use for milling.
End mills with 2 and 3 flutes are used for working on aluminum. Increase in the number of flutes can create difficulty for effective chips evacuation at high speeds because aluminum produce larger chips. So increasing the flute means smaller chip valley which is why the end mills with high number of flutes should not be used.
Normally, 2 flutes end mills are used for aluminum. However, using end mills with 3 flutes will get the job done more efficiently, easily, and will deliver more finishing operations. With the setting of right parameters, 3 flute end mills can also serve as roughers successfully.
Besides considering the number of flutes in an end mill, you should also consider other factors like rigidity, operation and required material removal rate that also impacts heavily on the tool’s selection.
The helix angle is the measure of angle between tool’s centerline and straight line tangent with the cutting edge. The higher the helix angle, the more easily chips of softer materials can escape. Therefore, end mills with comparatively higher helix angles than standard end mills are used. The angle with 35°, 40°, or 45° are preferred.
In the market, variable helix tools are also available which reduces harmonics and chatter and also enhances material removal rates efficiency.
35° or 40° helix angles are used as a standard for roughing and slotting in aluminum. But 45° helix angles are suitable for high efficiency milling toolpaths because end mills with higher helix angles makes more aggressive cut and wraps around the tool faster.
As discussed earlier, 2 or 3 flutes in an end mill will deliver the right results. But for specific usage and machine setup, you need to consider more tooling option to give better performance and to carry out specialized milling, slotting or profiling. Following are some of the tooling operation that can give better results.
Effective chips evacuation is one of the most crucial factor while machining aluminum. 2-3 flutes operating at recommended feed rates and speeds lets escape the chips fairly well. But there is another specialized tool more efficient than the standard ones. The 3 flute chipbreaker tool runs at more speed and feed rates and delivers better results. The geometry of the chipbreaker produces smaller chips for fast evacuation and leaves half-finished surface.
HIGH–BALANCE END MILLS
These end mills are manufactured to improve performance in highly balanced machining centers that have elevated feed rates and elevated RPM. They are used to main precise balance in high velocity machining aluminum up to 33,000 RPM.
If you want to optimize your productivity and achieve optimum machine results, then you need to have the right parameters settings. The settings also help in selection of end mills. The aluminum is indeed an easier material to machine but if you can optimize your machine with the right settings and push it to its maximum limit, you can achieve maximum result out of the machine.
There are some general guidelines that you should follow for machining aluminum. For milling cast aluminum alloys, 500-1000 SFM surface footage is recommended. The RPM is based on cutter’s diameter. For wrought aluminum alloys, 800-1500 SFM surface footage is recommended. Following is one of the widely known running parameter to follow.
HIGH EFFICIENY MILLING
HEM or High Efficiency Milling strategy is become rapidly popular in manufacturing industry. There are CAM programs that include HEM toolpaths. While any machine is capable of performing HEM, it is important that CNC machines should also contain fast processor.
MACHINE REQUIREMENTS FOR ALUMINUM MILLING
Having the right machine for aluminum milling is vital to have maximum advantage of machine. Ideally, the machine should have 200 IPM feed rate and 18,000 RPM spindle capability. Following are some standard machine settings for aluminum milling
For peripheral rough milling
- Climb mill having coated carbide end mill of ½” diameter 3-flute.
- Width of cut: 30 percent of cutter diameter
- Axial depth-of-cut: 0.750”
- SFM: 2000
- RPM: 15,280
- IPT: 0.004
- IPM: 200
Milling carried with these machine settings will remove metal at 22.5 cubic inches/minute.
For full width slotting
- Recommended 2 flute end mill
- Plunge in vertical direction 1 x diameter before moving X-Y direction.
- SFM: 1,000
- RPM: 7,640
- IPT: 0.003
- IPM: 46
With these settings, the metal removal rate will be 11.5 cubic inches/minute
Note: ensure to program feed and speed once the slot is in for peripheral milling to open up the cavity.
TYPE OF END MILLS
The types of end mills with different end shapes are used to create different profiles, slotting, and different texture in a work piece. Following are the various end mills used to slot aluminum:
ROUGHING END MILLS
These end mills have teeth at their flute’s periphery used to create rough texture on the surface. The purpose of these teeth is they transform material into small chips and then evacuates the material quickly. It also reduces vibration during milling.
FINISHING END MILLS
These end mills deliver smooth finish. They have smooth outside dimeter and one square end. This diameter creates smooth finish on a work piece.
BALL-NOSE END MILLS For Aluminum
They are also called full-radius end mills because they have a ball-shape edge. On Aluminum they are used to create 3D contouring, arc grooves and profile milling etc.
SINGLE FLUTE END MILLS
The single flute end mills are designed for applications that require fast and high-volume material removal. They are very versatile and delivers great rough texture. You can use them to mill brass, plastics, aluminum or exotic composites but do not use them on steel.
Their single cutting edge design provides more space for chips to evacuate resulting in higher chip loads and faster feed rates.
Aluminum is highly workable and light weight material. Products manufactured from this material are used in almost every industry. Its low cost and flexibility makes it a demandable material for CNC milling.
Due to its specific properties, it is necessary to carefully select the end mills otherwise it may damage the work piece. End mills made of carbide are highly durable and has high speed and feed rates. When end mills are coated, they perform better in milling because they provide smooth and slippery surface for quick chips evacuation.
The single flute and 2 or 3 flute end mills are widely used for aluminum. Do not select end mills with flutes greater than 3 otherwise the chips will clog the flute and cause material damage.
The more angular the helix angle, the more easily and quickly chips removed. Typically, 35°, 40°, and 45° helix used to mill aluminum for good efficiency due to more aggressive cutting.
Apart from the selection of end mill, setting the right machine requirements will result in maximum output. The above parameters are typical but they will need tweaking for special applications.