In general, the basic principles of CNC machining include standard subtractive manufacturing operations such as turning, milling, facing, drilling, grooving, boring, etc. These processes involve removing excess material, layer by layer, from solid parts and performing high-quality finishing to obtain the necessary dimensional characteristics for a part to achieve.
However, it is impossible to achieve these properties in a single machining operation. Therefore, manufacturers often carry out production in two stages with variable parameters – roughing and finishing. This article explains the difference between roughing and finishing in machining.
What is roughing in machining?
Machining roughing is a process in which a significant amount of excess material is removed from parts. Roughing is usually the first step during the machining processing phases. Therefore, CNC roughing produces a material shape or figure close to the required geometry of the part, making subsequent machining processes easier and more efficient.
Furthermore, the purpose of rough cuts is to quickly remove rough scraps. Manufacturers typically carry out roughing processes with large depths of cut and high feed rates to remove large quantities of chips in a short period of time. However, these processing parameters affect the surface and dimensional characteristics of the product.
Although roughing processes offer high production efficiency, raw products are often poorly processed, inaccurate and inaccurate. Roughing processes therefore produce components that do not have high dimensional accuracy and tight tolerances.
What is finishing in editing?
Machining finishing refers to a manufacturing process in which the surface of already manufactured parts or components is altered to specific resolutions. This primarily includes removing cosmetic defects to improve the appearance of a part or to obtain certain mechanical properties that increase performance.
Generally, finishing involves several processes, such as: Such as fine machining, grinding, electroplating, shot peening, polishing, anodizing, powder coating, sandblasting, painting, etc. Therefore, depending on the required characteristics of the part, manufacturers use a specific finishing process or an appropriate combination of finishing operations to add or improve the characteristics of the manufactured parts, such as B. the following:
- toughness
- accession
- Weldability
- Electric conductivity
- Softness
- Corrosion resistance
- wear resistance etc.
In most CNC manufacturing projects, finishing is usually performed as the final step after the engineer machines the roughing parts. Furthermore, the objective of the finishing process is to remove the necessary excess material and finish the manufactured component to achieve the final dimensions in terms of flatness, roughness, thickness, tolerances and surface finish.
Difference between roughing and finishing in machining
In addition to the machining operations performed in a typical CNC shop, finishing and roughing processes are still important manufacturing processes to meet basic machining requirements.
Some people assume these processing steps are the same or confuse them. However, from a technical point of view, there are clear differences. Check out the differences between roughing and finishing in machining below:
1. Definition
Definition of thinning
Grinding is a machining process that quickly removes excess material from parts. This conveys the primary shape and dimensions needed to perform other subsequent machining operations more quickly and efficiently.
Definition of finishing
Finishing is a machining process that modifies the surface of manufactured parts to improve appearance or achieve certain properties that improve the performance of the part. Additionally, finishing is generally performed to meet standard machining requirements in terms of flatness, roughness, thickness and tolerances and to improve the surface finish of various components.
2. Material Removal Rate
During roughing, the material removal rate is high while the material removal rate during finishing is comparatively low.
3. Feed and depth of cut
Roughing uses higher feed rates and depths of cut. In contrast, manufacturers perform finishing operations at lower feed rates and depths of cut.
4. Roughness/surface finish
The higher feed rate and depth of cut when grinding produces more visible grinding or feed marks. Therefore, raw products generally have poor surface roughness. On the other hand, shallow cuts and low feed speeds during finishing leave fewer roughness or feed marks, facilitating the production of products with a good surface finish.
5. Dimensional accuracy and tolerance
Proper finishing completes manufactured components to achieve final dimensions with high dimensional accuracy and meet the requirements of tight tolerances, while roughing cannot meet the requirements of machining accuracy and tight tolerances.
6. Cutter Type
The sharpness of the edges and tips of the cutters influences the surface quality and the precision that can be achieved during machining. Fine machining requires sharp cutters that accept low chip loads to achieve better surface quality and dimensional accuracy. For rough machining, however, cutters with less sharp edges that can accommodate a high chip load can be used, since high surface quality is not a crucial requirement.
7. Time
Typical CNC roughing processes precede finishing, while finishing processes can only be carried out after roughing.
For better contrast and clarity, you can check the differences between rough and finish cuts in the table below:
| rough cuts | Final cuts |
| High feed | Low feeding speed |
| High cutting depth | Low cutting depth |
| Higher material removal rate | Lower removal rate |
| Poor surface quality | Good surface quality |
| Low dimensional accuracy | High dimensional accuracy |
| Poor adherence to strict tolerance limits | Good adherence to strict tolerance bands |
| Increased chip load on the cutter | Lower chip load on the cutter |
| Greater production efficiency | Lower production efficiency |
Rough Machining Considerations
Rough machining offers manufacturers an efficient and fast way to produce the reference shape of parts for later machining. However, certain considerations must be taken into account when carrying out thinning operations. Check it out below:
1. Processing parameters
The CNC roughing tool software includes preset feed, cutting speed, and depth options. However, these standard machining parameters cannot predict the considerations for each individual roughing operation. Additionally, applying these default parameters may result in processing errors. Therefore, you must select and optimize all grinding parameters to suit each workpiece and cutting tool to achieve efficient processing.
2. Type of machine tool and control software
Roughing processes require equipment with high performance, efficiency and rigidity. Therefore, manual equipment cannot handle the tool movements required for grinding. Likewise, software programmed for complex 3D milling operations may not guarantee consistent cutting performance on parts with tight corners. Therefore, you need to select machining tools and software that suit roughing operations.
3. Heat and cutting fluid
Roughing uses higher feed rates, resulting in greater feedback. This, in turn, creates a high cutting resistance that generates a significant amount of heat. Furthermore, heat is transferred to the cutting tool and the workpiece. At the same time, heat increases tool wear and thermal deformation of the part.
Therefore, you must take heat treatment measures during roughing operations to avoid machining complications. When grinding, machine operators often use water-based cutting fluids with significant lubricating and cooling effects. If necessary, oil baths or air cooling can be used to moderate the effect of the heat generated.
Final thoughts when editing
Finishing is as important in machining as any other operation in the manufacturing cycle. Furthermore, finishing nullifies all your manufacturing efforts. Here are some important factors to consider before carrying out the finishing touches:
1. Dimensional accuracy
It is important to note that applying surface treatments to manufactured components can alter their shape and position tolerances, as well as other dimensional characteristics. For example, applying a powder coating to metal parts can increase the surface thickness. Therefore, it would be helpful if you always checked these factors before applying surface treatments to ensure accuracy and precision in machining.
2. Application of the party
Careful consideration of a part's application and the possible conditions to which the component will be exposed will help select the correct finishing process. For example, the process of finishing hidden parts in a car places less emphasis on aesthetics and more on improving the durability of the part.
3. Costs
After considering the factors above, you also need to consider the total cost of your finishing project. The best finishes often require high-quality materials, tools and complex processes. Therefore, you should compare all of these cost drivers with your manufacturing project before selecting a finishing process.
WayKen Complete Editing Service
Manufacturers perform roughing and finishing operations on almost every machining project. But even after all requirements have been taken into account, high-quality machining services remain crucial to successful production.
Contact us today for personalized support service and receive a response within 12 hours.
University Degree
Performing the correct machining step at each stage of manufacturing is crucial to the success of the project. Therefore, understanding the working principle of roughing and finishing is essential to obtain precise parts with high-quality surfaces.
