What Are Roughing and Finishing In CNC Machining

It is an important manufacturing process that has two main stages: roughing and finishing. These steps are important to produce high quality and accurate components. Knowing the differences between them is important. This knowledge helps improve the machining process. It also helps to get the desired results.

Let’s discuss the concepts of roughing and machining. We will also compare their characteristics and key considerations for each stage.

What is Roughing in CNC Machining?

It is the initial cutting process in CNC machining that quickly removes a lot of material. It makes a rough version of the final shape which leaves extra material for next stage. It also uses aggressive parameters to maximize material removal rates.

Proper roughing is important for proficient CNC machining. It decreases heat stress on the workpiece, extends tool life and total machining time. Good roughing lays the base for better quality finished parts.

What is Finishing In CNC Machining?

Finishing is the final cutting process in CNC machining that reaches accurate dimensions and surface quality. It removes the leftover material after rough milling up to 0.2-0.5 mm. It uses high spindle speeds, lighter cuts and slower feed rates to reach tight tolerances and smooth surfaces.

Good finishing is important for part functionality and accuracy. It determines the dimensional accuracy, final surface finish and quality of machined part. It also guarantees that parts should perform as intended and cover particular design needs.

Roughing vs Finishing In Machining

CNC machining process has two important steps: roughing and finishing. Each step plays a different role in making accurate parts. Let’s discuss how these processes are different from each other.

Purpose

Roughing quickly removes extra material to produce a near net shape. It usually prioritizes proficiency and speed. On the other hand, finishing refines the workpiece to meet accurate dimensions. Rough milling usually creates the basic form. Whereas finishing provides better surface quality and accurate dimensions.

Dimensional Tolerance and Accuracy

Rough milling mostly reaches tolerances between ±0.5 mm and ±0.1 mm. However, finishing milling can reach much tighter tolerances of ±0.025 mm or above. This level of accuracy is important for many operations. For example, aerospace parts usually need tight tolerances around ±0.005 mm. which only accurate finishing can acquire.

Material Removal Rate

Roughing focuses more on high material removal rates (MRR) which are over 100 cm3/min for metals. While finishing milling consider accuracy more than speed. Its MRR usually stays under 10 cm3/min. For example, when machining aluminum, rough milling might remove 500 cm3/min. Whereas finishing removes just 5-10 cm3/min to reach the desired surface quality.

Feed Rates and Depth of Cut

Rough CNC process applies feed rates that are 2-5 times faster than finishing. Its depth of cuts usually ranges from 1-5mm. whereas finishing uses shallower cuts and slower feeds mostly under 0.5 mm. For example, roughing steel may use 3 mm depth and 0.5 mm/tooth feed rate. But finishing would use 0.2 mm depth and 0.1 mm/tooth.

Cutter Types

Rough milling usually needs sturdy tools like multi-flute end mills with serrated edges or insert cutters. These can handle high material removal rates. Whereas finishing milling needs different cutters like ball nose cutters, single point tools or fine toothed end mills. For example, a 4-flute carbide end mill is used in roughing aluminum but then switch to a 6-flute ball nose cutter for the final surface finish.

Surface Finish

Surface finish quality differs between roughing and finishing. Rough milling mostly leaves a rough texture and visible tool marks. That’s because it focuses on removing material rather than surface quality. On the other hand, finishing milling focuses on producing accurate and smooth surfaces.

Timing

Time allocation varies between rough and finishing milling. Roughing usually takes 60-80% of total machining time. As it focuses on removing material quickly. For example, roughing a complicated aluminum part can take 2 hours. Whereas finishing is slower but more accurate which needs just 20-40% of total time.

5 Key Considerations for Roughing Machining

Roughing is an important first step in CNC machining. It needs careful planning. We will discuss five important factors that greatly impact the roughing process. The first one is:

Material Type

The workpiece material can heavily influence roughing plans. Harder metals like titanium need slower feed rates and speeds than aluminum. On the other hand, Brittle materials need gentler cutting forces to prevent chipping.

Machining Parameters

Machining settings are important in CNC roughing as they directly affect part quality, proficiency and tool life. These factors guarantee fast material removal while preventing workpiece damage and tool wear. Proper selection of these parameters guarantees better performance during CNC roughing operations.

Work Holding

Good work holding is important for successful CNC rough work. It provides stability during high-force cutting by preventing vibration and workpiece movement. Robust fixturing methods like vacuum tables, vises or clamps are also important to keep tool life and part accuracy.

Coolant Use

In rough milling, usually high-pressure coolant systems are used to increase the material removal rate and tool life. It decreases friction, dissipates heat and clears chips proficiently. The choice between mist, dry or flood coolant depends on the particular roughing needs and workpiece material.

Machine Type and Control Software

The machine tool and control software have a great impact on CNC roughing proficiency. Robust machines with high torque and spindle power are appropriate for aggressive material removal. These technologies help in improving rough milling processes. It also increases tool life during CNC machining processes.

This table provides a quick reference for optimizing CNC roughing strategies across various materials and machining conditions.

5 Key Considerations for Finishing Machining

Finishing in CNC machining is important to get the desired surface quality for your parts. We will discuss five important factors that you should consider in the finishing process, from dimensional accuracy to post-processing needs.

Dimensional Accuracy

Getting dimensional accuracy needs strict process control, accurate tool selection and optimal cutting settings. CNC finishing can reach tight tolerances ±0.001 inches. Advanced CNC controller settings can help to keep accuracy throughout manufacturing processes. It also guarantees that your parts should meet specifications accurately.

Workpiece Application

It is important to think about the part applications when planning CNC finishing operations. Determine surface finish details, functional needs and required tolerances of components. It is required as particular finishing techniques are needed for stricter tolerance and precision parts.

Tool Paths

Proficient and smooth tool paths decrease vibrations and tool wear which increases surface quality. Modern CAM software allows complicated 3D toolpaths. The reason is they can keep constant chip loads and cutting forces. Proper tool handling and lead in / lead out approach is very important to minimize marks on finished surfaces.

Cost

Finishing operations usually have high costs due to longer machining times and particular tools. Multiple passes and slower feed rates are needed for accuracy. High-end cutting tools and coolants also increase costs. However, these costs are usually justified by less post processing needs and outstanding part quality.

Post Processing

Better surface quality finishes mostly decrease the need for secondary processes like deburring or polishing. But some applications may still need coating, assembly or heat treatment. Careful planning for post-processing needs during the finishing steps can decrease cost and increase production proficiency.

This table provides a comprehensive overview of factors that influence the finishing machining process.

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Yijin Hardware is a top provider of CNC machining solutions in China. We provide a complete solution for different industrial needs. Our state-of-the-art facilities comprise of more than 800 advanced machines. These machines guarantee outstanding quality during manufacturing services.

At Yijin Hardware, we provide complete CNC machining services which include both rough and finishing machining. Our skilled technicians and advanced equipment with 20 years of experience guarantee accuracy in both processes.

For high-quality machining and finishing manufacturing process, contact Yijin Hardware today. We are the one-stop shop for all your CNC roughing and finishing needs in China.