Milling curved surfaces falls under the term CNC profile/contour milling. Irregularly shaped profiles or continuous curves with different degrees (oblique, concave or convex) are processed. This is a critical process in the production of most custom molded parts that requires CNC machining service providers to have advanced knowledge of basic machining principles and programs.
Basics of CNC Profile Milling
1. Profile CNC Milling Processes
Before the finished part is created, it is first divided into different categories: roughing/pre-roughing, semi-finishing, finishing, and fine finishing. The larger the workpiece, the more types of processing will be required. It is important to divide machining operations into subcategories when machining a part so that you can explore the full potential of the tools and parameters used.
roughing This operation is always the first phase of machining and usually begins with cutting the block of raw material to give the part approximately the desired shape or profile, leaving enough metal residue for later operations.
pre-finishing This process involves machining the part to dimensional requirements or removing remaining material from the part. Semi-finished parts may also undergo additional processing to achieve a specific surface quality requirement.
Completion- This process takes place after pre-finishing. Finishing aims to improve the surface finish of the part, removing obvious burrs and other surface defects. The use of powerful tools is essential in this process, as it significantly affects the final appearance of the part.
Super Finish The process continues to the finest finish when parts require a high gloss finish or a super smooth profile. To achieve this, high-speed machining techniques and high-precision tools are used.
2. Learn the tools used in CNC milling of curved surfaces
To obtain curved and smooth surfaces on a part to be manufactured, different variations of rounded end mills are used. These include rounded inserts, ball end mills and carbide ball end mills. Round profile tools are preferred for contouring applications because they do not leave visible traces of the tool path.
Indexable insert cutter with rounded indexable inserts These tools often have large diameters. End mills with rounded inserts are suitable for roughing operations due to their high stability and impressive productivity.
solid ball mill – These end mills can leave a very good surface finish on a machined part. Due to their structure, they may have low stability. For this reason, they are more commonly used for finishing than for roughing.
Ball End Mill with Indexable Insert Indexable end mills are similar to solid carbide end mills but have indexable heads. These special tools have a removable end that can be replaced if necessary.
General Tips for CNC Milling of Curved Surfaces
1. Necessary preparations
Before you decide to produce your custom parts through profile milling, it is also important that you are aware of the various factors that can affect the entire CNC milling process. Furthermore, there are certain things that you need to identify so that you can correctly choose the appropriate editing technique. Below are some of the things you need to be prepared for:
- Consider the cavity depths of your part designs. These play an important role in selecting the correct cutting tools and the required measuring length.
- Know how much material is removed from the raw block. This will help you better plan the operations required to produce your part and determine if additional operations are required after pre-finishing and pre-roughing.
- Consider how you want to secure the workpiece. This will help you prepare the necessary accessories.
2. The old and the classic: set the correct feeds and speeds
Feed and speed determine the rate of material removal from parts, so they have a significant impact on obtaining an excellent surface finish. To do this, calculations must be carried out. The feed rates to be used may also depend on the depth of cut, the tools used, the material to be cut, the profile of the part to be machined and the precision required.
Disclaimer: We will not provide actual speed and feed values in this article as these values can vary depending on several factors. It is still recommended to consult reliable references for actual speed and feed. However, here are the basic rules:
The cutting depth and feed rate vary depending on the hardness of the material to be processed. Note that in harder materials the feed and depth of cut are much smaller than in softer materials such as aluminum. Furthermore, the harder the material to be cut, the higher the cutting speed must be.
The feed and depth of cut are much more aggressive in roughing operations than in finishing operations. Excellent surface finish is achieved through the combination of high-speed techniques and the right tools.
3. Use of tools
There are many different tools available on the market today. During grinding operations, the focus must be on tool stiffness to withstand the high depth of cut and feed requirements during grinding. However, for finishing operations, end mills must be very sharp so that no visible traces of the tool path remain. Another difference is the diameter of the tool used. Typically, roughing tools have a larger diameter than finishing tools.
4. Minimize vibration in your CNC milling processes
Vibration is a major cause of unwanted surface finish, chatter and cutting tool damage. During a milling process, vibrations can have several causes, including clamping stability, tool rigidity, material hardness and inaccuracies in the machine spindle. Below are some of our tips for minimizing these processing hurdles:
- Use tools with good concentricity
- Avoid excessive protrusions on your end mills when carrying out roughing work. Use extension rods or extension tool holders
- Protect your work supports by ensuring proper support and balance during the cutting process.
- Avoid aggressive cuts when machining hard metals.
University Degree
CNC milling of curved surfaces is usually divided into different operations (roughing, semi-finishing, finishing and fine finishing) so that the desired profile is gradually achieved. The tools used for this type of milling generally have rounded profiles or so-called ball-end mills. In summary, CNC milling of curved surfaces requires the necessary preparations, setting the correct feeds and speeds, paying attention to the tools used and minimizing vibrations.
