Five-axis machining is more and more popular in our mold industry, because of High precision and high efficiency.
Moldmakers know that a three-axis approach to deep and tall features requires the use of long, skinny tools, but this approach doesn’t work very well. Speeds and feeds suffer because the entire process must be slowed down to accommodate the longer, weaker tooling. This means overall mold-production time suffers as well. Five-axis machining, however, enables the tool body to be tilted away from the contact point, ensuring that the tool does not extend too far from the holder, and permitting the use of shorter, more stable tools when cutting deep cavities or tall-core molds，
It’s no secret that five-axis technology offers other huge benefits to mold manufacturers. More efficient mold production, improved surface finishes and decreased polishing requirements, to name a few. But what is it specifically about five-axis technology that yields the biggest benefit to mold shops working with deep and tall features? What actually provides the ability to keep the tool tilted in all the varying directions with total control and without the worry of part interference or collision? The answer is tool center point management.
Visualize exactly what is happening as a tool moves around a part in five-axis simultaneous machining, and then try to imagine the types of calculations that are necessary to maintain control during this fluid dance of the tooltip. It doesn’t take long to realize that there is much more going on behind the scenes than what meets the eye.
Tool center point management, or rotary tool center point, is a feature within advanced machine tool controls that significantly simplifies five-axis programming and setup complexity. It makes the program and the part setup independent from machine setup and configuration. Without tool center point management, the programmer has to account for the distance from the center lines of rotation for the rotary and tilting axes, either in the program or in the postprocessor. With tool center point management, the setup is as simple as it is on a three-axis machine, and the control tracks the relationships among the tooltip, axis center lines and part setup.
The Path to Programming Efficiency
All five-axis machines, regardless of the actual axis configuration, have a fixed mechanical center line for the machine’s rotary or tilting axes, around which each axis rotates . The machine table surface, workpiece position, spindle gage line and cutting tooltips are all located at some measurable distances away from the center line. When the programmer performs the machine’s part and tool setup, something needs to account for and track the varying distances as the part is machined, and as the tool and workpiece move throughout the machine’s space . Before tool center point management was an option, this tracking was accomplished within the CAM program itself. This proved problematic and time-consuming. The machine tool control isn’t smart enough, or advanced enough, to account for the relationship between the machine tool’s kinematics and their relationship to the workpiece and program, so the responsibility falls on the CAM program or postprocessor.
Without tool center point management, the programmer must program all settings from the center line of rotation instead of the traditional workpiece zero point. This means that the solid model must be moved away from the zero reference point in the CAM system the exact same distance as it is physically on the machine tool. Then the program is created with the use of the postprocessor and tested on the machine. If any positional adjustments need to be made, the solid model must be repositioned in the CAM space, the program must be reposted, and the entire process must be repeated as many times as necessary. After all of this, the program will finally be ready to run successfully, and the job can be completed. However, even after all of this preparation is complete, once the workpiece is removed from the machine, this tedious process will be required to complete a future repeat job for that part. The entire process is not efficient.
Tool center point management grew out of the need to ease the implementation and use of five-axis technology and increase its efficiency. Machine tool manufacturers realized that the machine control itself should accommodate all of the machine’s kinematics and movements as well as automatically control the correlation among all necessary data points (machine center line, spindle gage line, tooltip and workpiece zero point). Tool center point management accomplishes these goals.
Better Control and Simplified Setup
Tool center point management makes the entire machining process more efficient, quicker and easier for the programmer and machine operator to complete. It streamlines the programming process. The programmer does not need to wait until the part is actually located on the machine to program the process, because he does not need to account for any machine-related data in the program or postprocessor. This is all taken care of by the software within the machine control.
When the operator sets up the five-axis machine, he simply locates the zero point of the workpiece using an edge-finder or indicator, just as he would on a three-axis machine. He does not need to be concerned with the location of the part within the machine’s workspace. Also, if corrections are necessary, he can simply make the adjustments to the part setup as opposed to altering or reposting the program to make the adjustments. This eases the setup of subsequent runs of this part.
At present, there are true and false 5-axis on the market, and the way to distinguish between true and false 5-axis mainly lies in whether it has RTCP function.
RTCP is the abbreviation of “Rotational Tool Center Point”, which literally means “rotating tool center”. The industry often translates it slightly as “turning around the tool center”, and some people literally translate it as “rotating tool center programming”. In fact, This is just a consequence of RTCP.
RTCP is the abbreviation of the first few words of “Real-time Tool Center Point rotation”. HEIDENHAIN refers to the similar upgrade technology as TCPM, which is the abbreviation of “Tool Center Point Management”. Other manufacturers call similar technology TCPC, which is the abbreviation of “Tool Center Point Control”, which means tool center point control.
From the literal meaning of RTCP, assuming that the RTCP function is manually executed at a fixed point, the tool center point and the actual contact point between the tool and the workpiece surface will remain unchanged. At this time, the tool center point falls on the normal line at the actual contact point between the tool and the workpiece surface, the tool handle will rotate around the center point of the tool. For the ball end tool, the center point of the tool is the target trajectory point of the NC code. In order to allow the tool handle to simply rotate around the target trajectory point (that is, the tool center point) when executing the RTCP function, it is necessary to compensate in real time the offset of each linear coordinate of the tool center point caused by the rotation of the tool handle. It is possible to change the angle while keeping the center point of the tool and the actual contact point between the tool and the surface of the workpiece unchanged, to achieve the best cutting effect of the ball-end cutter Efficiency, and effectively avoid interference and other effects. Therefore, RTCP seems to stand more on the center point of the tool (that is, the target trajectory point of the NC code) to deal with the change of the rotation coordinates.
A 5-axis CNC Machine (also known as 5-axis Machining Center) is a precision CNC machine tool that uses a wide range of cutting tools to remove materials from a workpiece. It does so along five different directional axes, either by positioning the piece or by simultaneously cutting it along these axes, until the desired shape is achieved.
For a more specific representation, an example of a 1-axis machine would be a radial drilling machine, with up and down motion (Z axis). Following that same logic, a 3-axis CNC Machine can move up and down (Z axis), right to left (X axis), as well as forwards and backwards (Y axis).
A 5-axis CNC machine has two extra rotary axes which opens the door to an infinite number of machining possibilities. The types of rotary axis include rotary axes A, B and C which rotates around the X-axis, Y-axis, and Z-axis respectively. While these are three extra axes and not two, they’re still considered 5 axes in total. The combination of the additional axes is machine dependent and can come in any combinations of AB, AC or BC.
With the additional axes, the cutting tool can approach the part from all directions, enabling undercutting that is only possible on machines with fewer axes if the part was re-positioned with comprehensive fixtures. This situation in machines fewer axes is not only time consuming, but may present errors — situations which are avoided with a 5-axis CNC Machine.
A 5-axis CNC Machine (also known as 5-axis Machining Center) is a precision CNC machine tool that uses a wide range of cutting tools to remove materials from a workpiece. It does so along five different directional axes, either by positioning the piece or by simultaneously cutting it along these axes, until the desired shape is achieved.
For a more specific representation, an example of a 1-axis machine would be a radial drilling machine, with up and down motion (Z axis). Following that same logic, a 3-axis CNC Machine can move up and down (Z axis), right to left (X axis), as well as forwards and backwards (Y axis).
A 5-axis CNC machine has two extra rotary axes which opens the door to an infinite number of machining possibilities. The types of rotary axis include rotary axes A, B and C which rotates around the X-axis, Y-axis, and Z-axis respectively. While these are three extra axes and not two, they’re still considered 5 axes in total. The combination of the additional axes is machine dependent and can come in any combinations of AB, AC or BC.
With the additional axes, the cutting tool can approach the part from all directions, enabling undercutting that is only possible on machines with fewer axes if the part was re-positioned with comprehensive fixtures. This situation in machines fewer axes is not only time consuming, but may present errors — situations which are avoided with a 5-axis CNC Machine.
The primary function of Tool Center Point Control (TCP) (G43.4) is to translate the tool-tip path defined in the part program into the position and orientations for the machine’s linear and rotary axes. It also allows the cutting tool feedrate to be specified in feed-per-minute mode (G94). Running at the tooling manufactures recommended cutting rate improves tool life. However, the CNC will automatically adjust feedrates to stay within the maximum performance of a limiting axis.
Tool center point control solves the problem of local tool gouging. Since the CNC knows the profile of the workpiece surface, it can coordinate all of the axes to keep the tool tip in precise contact with the surface when moving between points. So when the program includes an X-axis move between A and B and a B-axis orientation change from -30° and +30°, the CNC automatically coordinates the Z-axis to keep the tool tip on the surface path. This eliminates the gouging characteristic of common machine-centric workflow using inverse-time feedrates (G93).
In our area, many mold companies have purchased five-axis processing equipment, but it is not easy to train a qualified five-axis processing engineer.