Many machine and tool manufacturers use a significant amount of components for efficient High Speed Machining (HSM) processes. It is known that HSMs have a powerful impact on CNC machines, cutting tools, control elements, tool holders, and spindles. However, this impact on the tool path and technical programming is often overlooked. Currently, CAD/CAM technology is constantly evolving to meet the specific requirements of new tool path strategies, tailored to the HSM environment. HSM is a process that uses higher spindle feeds and speeds to remove material faster without degrading part quality. The main goal is to finish the form to net shape, to improve geometric accuracy and surface finish, so that polishing can be eliminated or at least minimized. What should the optimization of the tool path in CAM systems and other machines look like? How to implement this in production and improve the quality of the machine tool and your services? We write about this below!
How does the tool path strategy work?
To facilitate high-speed machining, the following requirements are set for the CAM system:
- it should maximize the processing speed of the program,
- it must minimize losses,
- it needs to maintain a constant load.
It should be noted that many CAM programs solve this problem by assuming that different specialized tool path strategies can be applied to make the part as specialized as possible in machining.
What are the different types of tool path strategies?
There are different types of tool path strategies that can be used to optimize CNC machining services. Here are a few examples:
Consistency
The tool path in which the tool follows the shape of the pocket using parallel paths separated by constant steps. The benefits include that such a path provides a very consistent and regular appearance, it is the simplest, default and may not even be named in the CAD program.
Constant "Z" machining
This strategy is particularly useful in finishing, where the tool path is tracked around the machined contour with a constant Z. It is usually used on steep walls, while in other cases a different strategy is used. Less steep areas can be avoided by limiting the path to a wetting angle from 30 to 90 degrees. The undeniable benefit is that the elements are of the same quality and height.
Pencil milling
A finishing technique mainly used for corner constructions and concave areas, which were not covered by the tool path strategies used earlier in the programs. Milling pencil allows the tool path to have the same diameter as the milled part. In the absence of pencil milling or remaining machining, operators are forced to identify corners that require machining. If you have efficient machining of remnants, you don't need pencil milling. The high quality of surface finish, convenience and productivity are considered benefits.
Rough internal machining
Roughing technique in which only the Z axis goes through the cutting technique, similar to multiple drill insertions into the workpiece, takes advantage of the fact that most machines are rigid in the Z axis and can use higher feeds and/or larger mills when used in this way. Plunge milling works best when the tool path is designed to provide oblique milling. The benefit is the efficiency that can be improved during roughing. By ensuring the delivery of a dynamic tool path strategy, we can not only increase tool durability, surface finish, and spindle life, but also improve overall cost efficiency and cycle time. You can implement any of the above strategies according to your own requirements.
Optimization of the CNC tool path
"Optimize the CNC program" is a command you hear in your head after finishing the machining program. As we all know, time is money, so we will try to free you from the work of rebuilding the program. Below is a list of quick, easy ways to optimize the CNC machine, which will start to be associated with better performance:
Keep the coolant on
This may not seem difficult, but profits can indeed increase. If you are using coolant in your program, consider switching it from cut <0> to traverse <1> in the position/feed settings. You may not notice this, but a very short stop has been programmed into the software to allow time for the coolant spray to start. This command change will cause the coolant to spray between positioning movements, avoiding the initial stop.
Change the cutting method
If you want to cut along the contour, consider changing the method. If you are currently making plunge cuts, try using ramps. A ramp always keeps the tool in the desired amount of material (except for the very beginning and end) and does not retract. Assuming that the part has 200 retractions, the contour is cut out on 20 different elements (10 retractions per element). Thanks to the ramp, you will reduce this number from 200 to 20, and if each retraction takes half a second, you only save 90 seconds.
Fluid Function
If you're doing complex carving or 3D contouring, you may have noticed that the machine slows down to accurately follow all contours. It's just executing commands, but if you're a bit lenient when it comes to sticking to contours, smoothing can make a huge difference. Optimize your CNC programs with smoothing features to improve jagged geometries. Smoothing takes jagged geometry and applies arcs to the contour to achieve a smoother, more continuous movement. This is not only good for surface finishing, but also saves a lot of time as the machine doesn't have to slow down on arcs compared to vectors. Using it is as simple as writing code in a macro, editing the preset setting (which works well in most cases) and pressing the "Start" button.
Add dynamics
High dynamics combined with a smoothing filter means that very little delay is required for quick turns, which further shortens the cycle time.
Reduce parameters
It's usually obvious, but changing the retraction height from 0.5" to 0.050" (or less) takes about 10 seconds. Even if you only save 5 seconds per part, if you produce 20,000 parts a year, you can save over a day of machine work. Every second counts.
Keep your tools in order
It may seem obvious, but try to organize your operations in such a way that once the tool has finished its job, it is never used in the program again. Sometimes this is inevitable, but each tool change takes about 15 seconds. Consider using combined tools to limit tool changes. Most importantly, if you have nested parts, use the tools in sequence, not part by part. If you need to cut out 24 parts with 4 tools per part, you will spend 24 minutes on multiple tool changes or 1 minute on changing all the tools at once.