What is the benefit of switching to 5 axis machining?
Updated: Jul 1, 2021
Modern-day CNC machine shops have multiple challenges to face with. Being it cost-effectiveness, time, machining accuracy, ease of use, or other reason the right solution often finds the same solution. And if you thought of 5 axis machining, yes, this one of the nowadays' key of success and advantage in the competition with other machine shops and we are about to find out why.
Maybe you are asking yourself why aren't all machine shops having them? The answer is simple - due to the higher complexity of these machines, their price is significantly higher in comparison to the more standard 3 or 4 axis machines as they have 3 linear and 2 rotary axes to give access for milling, drilling, and boring even the most inaccessible areas of a part. However, despite the initial cost of the 5 axis machine in the long term, it will most likely be a better investment.
Why 5 axis?
Analyzing the advantages of a 5 axis CNC machine we have to mention a few distinctive ones:
The complexity of parts - having 5 axis mill at hand is a great asset for every CNC programmer. It gives the man creating the tool paths the full variability of using the tool library at the shop. There are 2 main utilizations of a 5 axis machine - using the 2 rotary axes for positioning and the 3 linear axes for machining the part in a single plane or ultimately when having a complex surface part when simultaneous feeding of all 5 axes might be required. When running all 5 axes simultaneously features like NURBS and splines could be activated to allow for better toolpath transition and acceleration between changing direction cuts allowing for improved surface quality and tool usage employing the correct cutting angles by tilting the tool axis to be used. Both 3+2 and full 5 axis machines are available on the market of course with a prevailing higher price of the latter Basically the larger the number of axes to be commanded, the more complex the calculations the controller undertakes so a higher version of the controller being it Fanuc, Siemens, etc. to be employed.
Fewer setups - despite oftentimes having to use especially elongated and more expensive tools for the difficult to reach areas, here comes another great joker for the 5 axis machines in terms of cost-effectiveness - because of the rotary axes there is now the possibility to machine a part in fewer setups compared to a 3 and 4 axis machine. This is an extreme time and respectively cost saver as it won't require pricy custom fixtures to grip the part to be designed, programmed, and machined for the next operation. So instead of having 3 or 4 operations for complex aerospace, oil & gas, or medical part a much more straightforward approach can be employed. Having a lower number of setups has always been vital not only to accuracy but also when concerning large parts machining. Due to having the mounting time of sometimes over a few hours due to the heavyweight, it is of extreme importance for such parts to have them machined in as many setups as possible.
Tool utilization - with multi axis machining, modern tools can be pushed to their limits and, at the same time, a less costly tool can substitute some expensive slot mills, dovetail cutters, profile cutters, etc. just by exploiting the great advantage of the rotary axes.
Due to its versatility and applicability the simultaneous or positioning 5 axis is being implemented not only in milling machines, but also turning machines, grinders, EDM, routers, etc. By extending a machine's capabilities with it a part can be machined to a greater extent and with fewer setups. You probably wonder how is it so flexible? Here are the most common configuration designs and applications
1. 2 rotary axis at the head - this machine configuration is giving all rotary movements to the head, which usually has a double column design. This makes it ideal for large size machines as any pivoting is taken out of the CNC machine table allowing the setup to remain rigid. This on the other side will require a greater length of the machine axes and the table as any pivoting of the head while machining around the periphery will require it. To give an illustration of the machine size these machines can reach despite their complexity they can be as large as a 3 story house.
2. 1 rotary axis at the head and 1 rotary axis at the table - it has great versatility in terms of the machines it is being applied to. It could be to the top-notch turn milling machines having B axis to tilt the head and C axis at the spindle or again to larger sized CNC mills, routers, EDM machines, etc. As far as it concerns the milling machines of this type, wherein terms of rigidity and stability in comparison with other machines, the demands are much higher. Due to the high cutting forces, such milling machine types are a preferred configuration for complete machining of large parts. Here one of the design challenges comes with the balance of the ram which, to have a good accuracy combined with a long reach, should be counterbalanced by utilizing nitrogen gas balancing cylinders.
3. 2 rotary axes at the table - these are one of the most common types of 5 axis machines for small to mid-sized machines. They are characterized by having the rotary axes built into their table, which allows for a footprint nearly comparable to the same size VMC. They have limited rotary axis rotation, however, still making the workpiece easily accessible from all sides. A great advantage can come from the linear motors some machines are built with making them extremely fast. The most common types are having either 2 joints at the table and A and C rotary axes or 1 mounting with B and C rotary axes of which in terms of rigidity the first is getting closest to what a 3 axis machine has to offer.
5 axis vs 4 axis - this is a common question that may occur while deciding to go multiaxis. Understandably, why inverse in a higher-priced 5 axis machine if you can simply retrofit a 3 axis machine and attach a 4th axis to it or even a 5th. Well, here is why...
The 5 axis machine accuracy and rigidity are unsurpassed by any alternative retrofitting. Additionally added rotary axes will of course be a good way to adapt to a given situation having a 3 axis machine on-site but compared to all high-end features a full 5 axis machine has to offer it can never reach the full scope of potential. Moreover, if retrofitting controller adaptation issues may occur, simultaneous 5 axis milling functions could be limited affecting accuracy and capabilities.
Programming and setting 5 axis - having said all so far it may sound quite a challenging job to program such machines. But in reality, modern 5 axis mills being a top-notch state of art machinery have so many user-friendly features that they make the transition from 3 axis very easy. Programming could be done not only using CAM systems that have the real programming power and allow the use of the most modern machining techniques but also directly on the control panel of the machine. Also, a great asset is the possibility to avoid multiple setups, fixture design, and being able to apply a straightforward strategy when programming. Swiveling, coordinate system translation and rotation, even full 5 axis machining have never been as easy to program directly on the machine panel either with the user-friendly interface or a direct G-code.
5 axis is the future - with the higher demands of industries like aerospace, defense, oil and gas, medical, etc. there is no doubt a 5 axis CNC machine is the key to success for achieving the production goals, which makes it one of the best solutions when trying to make improvements to your shop.