Introduction
CNC machining is a broad concept, but the goal is the same – to fabricate a component. When a CNC machining operation is complete, the surface condition can reveal much about the product. Will it be attractive enough? What about its usability and safety? Can it withstand the rigors of chemical exposure?
If you can answer such questions, then you have tackled the CNC machining project successfully. Two processes that you will have to consider are CNC roughing and CNC finishing. Many people think that these processes are the same.
However, there are differences between CNC roughing and CNC finishing. For instance, rough machining typically precedes the CNC finishing process. In this article, we compare the two methods.
Read on for more insights.
What is Roughing in CNC Machining?
Roughing is a conventional machining process that comes first in the CNC machining process. It transforms the raw material to a state or shape close to the envisaged final form. The machinist uses robust tools such as end mills and drill bits. These tools can remove excess material quickly and in large amounts.
The idea in the roughing process is to remove the material as fast as possible. There is not much focus on the state of the surface finish. Precision is also not a big consideration for the machinist at this stage of CNC machining.
Roughing leaves sufficient material for subsequent machining processes. That allowance is enough for the other material removal methods to attain the required component precision and surface quality. The machinist uses special tools for roughing and saves the more delicate finishing tools.
What is Finishing in CNC Machining?
Finishing is the culminating step in CNC machining. This step has several roles in the quality of the final product. These include the removal of surface irregularities, enhancement of resistance, improvement of appearance, and addition of strength.
There are different techniques of the CNC finishing process. The choice of the specific finishing process depends on the material and the intended application of the part.
At Aria Manufacturing, we are committed to quality CNC machining. Our finishing processes are designed to enhance the functionality and appearance of the part.
Note that there is a difference between finishing operations and surface finish. The surface finish of a part is the texture of the exterior of a part. Machinists define the surface finish using different parameters, including roughness average (Ra).
Surface finishing entails the processes or techniques that change the surface properties of a part. If you are wondering about the different types of CNC surface finishing, here are the options:
Anodizing
Bead-blasting
Galvanizing
Powder coating
Electropolishing
Benefits Of CNC Roughing Machining
Roughing in the CNC machining process is as important as the finishing process. Indeed, there are several benefits of the roughing process.
Removing Excess Material
CNC roughing is your best bet for removing excess material from the work piece. The design of the cutting tool and the cutting parameters are such that this removal takes place as fast as possible. The goal is for the work piece to assume a shape closest to the desired final shape of the product.
Identify Material Flaws
Roughing operations can help identify flaws in the workpiece. Examples are air holes and sand holes. If the material dimensions are insufficient, this operation can help you discover this problem. Such discoveries are important in the earlier stages of CNC machining because they give time for finding remedies.
Determine Feed Rate and Cutting Speed
During the rough machining stage, you can notice how the workpiece behaves under different feed rates and cutting speeds. The process can help you determine the process parameters changes to make for subsequent processes.
Benefits Of Finishing Machining
Finishing in machining process is a crucial stage of CNC manufacturing projects. Its effect on the durability, appearance, and functionality of the part is significant. It does not matter whether the CNC process is for aerospace, agriculture, automotive, or industrial applications. The finishing process plays an irreplaceable role.
Consider the following benefits of finishing in machining:
Enhanced Aesthetics
A big benefit of finishing in machining is the enhancement of the aesthetics of the product. The surface quality of a component can be hindered by surface roughness, the presence of rough edges, uneven surface finish, and so on.
A quality finishing method removes such imperfections and makes the product appealing. Glass beading, painting, and polishing are some of the most popular surface finish processes for a more attractive product.
Cleaning Ease
After the roughing operation, the component rarely has the desired surface qualities. In such a state, cleaning the component can be challenging. It is easy for debris and dirt to adhere to the surface and remain stuck even after cleaning.
With a good surface finish, cleaning the surface becomes much easier. A smooth surface is also helpful because it minimizes the need to use strong cleaning chemicals that can erode the surface.
Resistance to Chemicals and Wear
Talking of chemicals, poor surface finishing creates the ideal environment for chemicals to settle. When you want to enhance the longevity of a component, ensuring it has a smooth surface is a crucial step. After finishing the surface, the effects of factors that promote component deterioration are minimized. Friction on the surface is less, so the likelihood of abrasion and chemical adhesion is lower.
Safety of the Product
Achieving the desired surface also means making the component or product safer. We all have at one time used a rough product and probably developed blisters. A too-smooth surface may also not be desirable because of the risk of sliding. Creating the desired surface can help minimize these risks and ensure user safety. It is all about balancing different aspects of the surface finish depending on the item’s application.
Considerations For Roughing In Machining
When performing roughing in CNC machining, consider several factors for effective results. These considerations are the cutting tool, material type, coolant, clamping mechanism, and type of CNC machine.
Material Type
Materials have specific chemical and physical properties. These properties can affect how the material responds to different aspects of the CNC roughing operation. Determine the material type and the accompanying properties before moving to the other considerations of roughing operations.
Cutting Tool
The cutting tool factor is crucial because tools come in different shapes, sizes, and material properties. As you embark on the roughing operation, ensure you have the right cutting tool. A tool that deals with a high chip load may not be similar to one that handles significantly fewer chips. Consider requirements such as proper chip evacuation and sharp edges when choosing a cutting tool for roughing operations.
In the same argument, remember to couple the cutting tools with the right software. The software controls the cutting speed, whether they are smaller or larger cutting tools for rough cutting.
Coolant
As the sharp cutting edges of the rough machining tool dig into the workpiece, they generate heat. You should control this heat to prevent poor machining process and damage to the cutting tools. Adjust the cooling process parameters accordingly.
As the depth of cut increases and higher cutting speeds take effect, the amount of heat generated also increases. The choice of coolant is therefore paramount. Note that liquid-based coolants are preferable to oil-based coolants.
Clamping Mechanism
One of the leading causes of surface defects in CNC machined items is poor clamping. The solid workpiece undergoing the roughing operation is under intense forces. If loosely held, the workpiece can move or even vibrate violently. Ensure machining accuracy and safety by using a quality and secure clamping method.
Type of CNC Machine
Ensure that you have the right type of machine to perform the roughing operations. This machine should also have the appropriate software to guarantee dimensional accuracy and tolerance.
Considerations For Finishing in Machining
When considering which option for finishing in machining to use, there are a few factors to remember. They include the following:
Cost of the manufacturing process
While pursuing the ideal surface finishing is okay, the cost aspect can hinder you. The more you specify finishing in machining, the higher the cost of the manufacturing process. That’s mainly because it not only requires better tools and equipment but also takes more time.
The specification of surface finishing also affects the packaging method. Therefore, it is advisable to find a balance between the level of surface quality and cost.
Electrical and Mechanical Properties
Depending on the component’s application, the electrical or mechanical properties are worth considering. For instance, an electrical component needs to conduct electricity smoothly. A poor choice of machining tools or machines for roughing and finishing can mean poor surface finish.
A well-done surface finishing process is important for unhindered flow of electrons. For mechanical properties, aspects such as fatigue strength and corrosion resistance depend on the effectiveness of surface finishing.
Aesthetics of the Product
Do the aesthetic requirements of the product demand visible tool lines or a mirror-like finish? As a designer or machinist, you want to consider the aesthetics of the product during the finishing process. Different customers have different finishing requirements, from matte to high-gloss surface finish.
Type of Material
Different materials have their specific CNC roughing and finishing requirements. For instance, the material removal rate on stainless steel may be different for aluminum. For a conductive material, electroplating is a perfect surface finishing method. Anodizing works excellently on aluminum. Stainless steel is popular for chrome plating. Therefore, consider the type of material you are dealing with before choosing your finishing operations.
Roughing Machining Vs Finishing Machining: What is the Difference?
Knowing the differences between rough and finish machining is the first step to getting the best from each of them. The application, approach, and form of these machining processes differ, as you will notice next.
Materials Feed Rate or Material removal rate
The finishing end mill and roughing end mill have different feed rates. Roughing end mills typically support a faster material removal rate. The feed rate for finishing end mills is lower. This difference in material removal rate and feed rate makes the two processes usable under unique machining circumstances.
Surface Roughness
The kind of surface roughness or smoothness from the two CNC processes is different. Since the rough machining end mills are designed for rough results, the resulting surface is relatively rough. You can even identify the tool marks in some instances. On the contrary, the lower feed rate for finishing end mills results in smoother surfaces. That’s because the cutting tools for finishing machining make shallower cuts. This process is a requirement in precision machining.
Production Cost
Being a faster process that aims to remove excess material, rough machining is typically less costly than finishing. Since it takes longer to complete, the finishing operation may be more expensive. The high dimensional accuracy, the high level of machining accuracy required, and the level of care required can all contribute to a higher cost.
Production Time
Rough machining is typically a faster process as compared to finishing in machining. The focus in roughing is to remove as much material as fast as possible. In each pass of roughing, the CNC machine provides a fast material removal rate.
The production time in finish machining equipment is longer. The goal in this process is different. The machinist will be looking to attain the smoothest surface with tight tolerances. For this requirement for higher dimensional accuracy, the finishing operations take longer.
Dimensional Accuracy and Tolerance
Rough machining end mills are not as accurate as end mills for finishing in machining. Therefore, expect the dimensional accuracy and tolerance for roughing to be lower than in finishing machining. A finishing end mill can easily provide the results you need in terms of tight tolerances.
Conclusion
CNC roughing and finishing are both crucial for their protective, aesthetic, functional, and process optimization benefits. With expertise in both processes, you can trust experts at Aria Manufacturing to produce the best results.
No matter the CNC machining results you are looking for, you can rely on us. We match your requirements, provide high dimensional accuracy, adhere to the ideal feed rate and depth of cut, and much more.
Reach us for professional CNC rough machining and finish machining today!