CNC Machining Design E-book- CNC Machining Design Guide



We created a Machined Part Design E-book to help product developers design parts with the manufacturing process in mind, to reduce machining time and lower your cost. Sunrise Metal offers 1-stop CNC Machining manufacturing services for 10+ years. Our engineers review every product we manufacture to make sure each part is suitable for mass production. If you still have questions or concerns about your machining projects, feel free to reach out to us.

Here are the jump links for your quick access.

PrecisionTool AccessInner Edges
AccuracyWorkpiece StiffnessHoles
ToleranceTool StiffnessSmall Features
Wall ThicknessWorkholdingUndercuts
Internal RadiiSize LimitationsText & Lettering
PocketsMaterial SelectionOther Optimizing Guides
Tool GeometryComplexityDesign for Best Alignment


When it comes to precision, CNC machining is the process that comes into the mind of most manufacturers. Because it truly is a magnificent manufacturing method for very accurate and precise parts for any industry.

Although, the cost may be a bit high for tighter tolerance. But for most industries super tight tolerance is not mandatory so you might not have to worry about that.

Overall, industries that require complex parts with higher accuracy can depend on the CNC machining process for better outcomes. The key here is to make a design that is effective and creative at the same time. It’s not about creating the most complex parts, it’s about how you can easily make it with the machining process.

Precision cnc machining

Precision is a tool that can ensure better performance in all scenarios of machining:

Super tight tolerances with zero errors

● [Standard Tolerance: ±0.005 inches (±0.127 mm)

● Tight Tolerance: ±0.001 inches roughly the width of a human hair]

● A higher level of complexity is possible

● Extraordinary repeatability, even in higher volume

● Better, smoother and custom finishes for the parts

Design With Accuracy and Error in Mind

If you’re using a milling machine and want to make sure the cuts are what they should be. It’s always good practice to take some time out of your day for previews. For Roland mills that use Modela Player 4 software as this one does.

The process is: upload your .stl file with all the programmed cuts into their program >  see how things would turn out quickly!

The ball end is specially designed to show the rough-in work you have done. You can see the grooves left by the tools and any finishing steps or other operations that were done afterward. But be careful not to leave flat surfaces without finishing up because even a quick pass from an edge will leave stripes behind on them. Which could be avoidable if done earlier than later!


The star trek emblem should have a small fillet in the corners instead of a fully sharp corner. The end of the mill has a finite radius in which corners can never be entirely resolved. Vertical sharpness inside the corners cannot be wholly addressed. The end mills have a limited radius, regardless of how small.

Suppose the item is designed to fit into a pocket like this. In that case, both the sides of this cut pocket and the part fitting into it must be pinched. A smaller fillet implies more lines assist the part fit in. You can place fillets onto your model with the radius of a possible terminal to see an estimate if your software does not include a preview option.

It is sometimes wise to scale up your project to save material and yet fulfill your work. For instance, it wasn’t correctly defined if we used a pokemon valor design with a bigger end mill to cut off the design. But 1.5 hours would be necessary to execute it. Also, it would take around 3 hours to complete more details using a smaller end mill. You can see this compromise between obtaining more information about the costs of longer mill times.

If you have a more oversized design, larger end mills can get into detail and clear more quickly. But if you have a smaller design, they may not be apparent in one pass.

But it’s faster to achieve things with smaller end mills. Hence, the trade-off between going slow or fast is always present during these machining processes.

Tolerances of CNC Machining


Lathe: ± 0.005 inches  Router: ± 0.005 inches

3-Axis Milling: ± 0.005 inches 5-Axis Milling: ± 0.005 inches Engraving: ± 0.005 inches

In machining, tolerance refers to the amount of variation that a dimension is permitted to have. In other words, it’s the difference between a specification’s lower and higher limitations.

General Tolerances

Tolerance for standard parts: ±0.005 inches or ±0.127 mm

General tolerances are the ones that a company or machining shop might have as default when a customer doesn’t provide their own. This varies a lot from company to company, so there’s no standard tolerance between them.

However, not all companies or machining shops have a default tolerance, some of them require you to provide it to them.

Those who have them usually provide basic general dimensions. For instance, wall thickness, surface treatments or tapped holes.

Part Tolerances

For this type, you provide the part tolerance considering your parts’ size, shape, and requirements. You have more control and know how your part’s tolerance will turn out in the end.

Know that the tighter tolerance you determine, the higher cost will be. Also, the lead time will be higher compared to traditional toleranced parts.

However, not all companies can match your expectation of tighter tolerance. Make sure you choose a capable manufacturer like Sunrise Metal to meet your needs.

As mentioned, there are many design opportunities that make this process truly effective and a favorite among manufacturers. However, while you or your designer is making the design, there are some restrictions to keep in mind as well.

For a greater result and successful project, these are equally important to know as well. So make sure you and your designer are considering them to make the final design before going into production. So the machining process becomes smoother and effective for both your company and the operator.

Wall Thickness


Standard Thickness: 0.8mm  Minimum Thickness: 0.5mm

Wall thickness is one of the most crucial factors in designing for CNC machining. You should design your parts according to the requirement, but also consider the restrictions closely to make the design work.

As a rule of thumb, the thinner your walls are, the more vulnerable they will be to the vibrations of the machine. And causes a negative effect on part precision. This is why we always recommend our clients to learn more on the thicker walls and avoid thinner ones.

While designing your walls, ensure your walls are at least 0.8mm thick or greater for metals. And for plastic, they should be 1.5mm or greater. Although, you could technically get walls as thinner as 0.5mm for metal and 0.1mm for plastic. But the feasibility and precision can be hampered due to the increased level of vibration and temperature.

CNC machining toolsets are capable of cutting very thin walls and work perfectly well for smaller features as per requirements. However, there are some limitations in every method and a feasibility limit.

In the previous section, we mentioned the recommendations for thin walls and smaller features according to the standard. If you need a more special treatment than that, Sunrise Metal can be your perfect choice for a critical part.

However, make sure that you’re going to that extent only if it is necessary. Unless so, stick to the standard size to save both money and time and have better end-product quality.

At Sunrise Metal, we are perfectly capable of machining walls as thinner as 1mm or less. But for better precision and quality, we suggest you keep the thickness to 2mm or 2.5mm to be on the safer side.

Internal Radii internal radii of cnc machining part

Standard Radii: 1mm or more than one-third of the depth

CNC machines are totally capable of cutting any surface at a 90-degree angle. But, when it’s an internal corner, the result of a 90-degree corner might not be as smooth as you’d want.

So to have a smoother corner, you have to design rounded corners with at least 1mm internal radius to avoid any rough corner. It not only ensures a smoother corner but also a finer finish.

There are several possibilities if you want a sharp corner. One of them uses a milling process that will automatically build a radius on the vertical inner corners. The two bottom corners must be drilled. The hole is large enough that the walls are straight all around. The two top corners are a different shape than the rest of the piece.

They have a design that gives the impression that they are sharp. These features are intended to allow mating components to have sharp corners. Something with sharp corners must fit. There is no method to modify the mating components. If that isn’t possible, EDM can be used to make the corners significantly smaller. If you want to avoid the cost and setup, you should not do it.

It is critical to include an undercut when constructing a mating component with a sharp corner. The radius of the lathe tooling creates fillets on the inside corners of your component.

There should be no space between these two parts to ensure that they can fully engage when these two pieces are in rotation. Otherwise, an undersized or oversized situation will occur where one item will not fit appropriately into another.

Pocketscnc pockets

Standard: 4 times the cavity width. Minimum: 25cm or 10 times the tool diameter

While designing unique features such as pockets, there are certain things that you have to keep in mind. The most important of all is to know the cutting lengths of the tool that will do the machining.

Because the milling tools have a limited length of their cutting tool. And for it to be able to machine your parts, your design must be compatible with the cutter’s length. Often, the cutting length of the tool is three to four times its diameter.

So while designing the pockets, ensure that the length of them is no more than 3 to 4 times the diameter of the tool that will be machining them. And if you need larger than this, consult with your manufacturer, before finalizing the design.

Tool Geometry

 tool geometry

Standard shape: Cylindrical. Expect Radius, diameter depends on the tool size

Generally, the cutting tools have a tubular shape with a flat end. And it applies to any size or type of cutting tool. Because of this, it’s hard to produce sharp corners like a square.

For example, if you have an internal corner in your design it will always have a radius. Regardless of the size of cutter you use. The bigger the cutter, the wider the radius will be and vice versa.

Tool Access

cnc tool access

Recommended: All surfaces are reachable and have no hidden parts.

In order to machine the parts, the cutting tool has to reach the workpiece. But if you have a hidden geometry or an ‘L’ shape geometry where the cutting tool cannot reach, it cannot be machined.

So in other words, your parts design should be completely accessible by the cutting tools in order to machine properly. If it cannot access a portion of the parts, it can’t cut the material.

Workpiece Stiffness

workpiece stiffness cnc

Recommended; Minimum Vibration

In the process, there can be a significant amount of friction and vibration generated during cutting the workpiece. And all these can cause an increase in temperature and also deform the parts.

Manufacturers take certain precautions and actions to prevent these to happen in any project. However, to be on the safer side, you need to have a better design as well. For instance, avoiding thinner walls can be beneficial for you. So even if the vibration and temperature is high, there will be less risk of part deformation.

Tool Stiffness

tool stiffness cnc

Recommended: Reduced deflection and vibration

The workpiece is not the only item that vibrates during the process, the cutting tool can vibrate as well. And when it happens, it can lead to low tolerance and sometimes, tool breakage.

And the chances of it increases when the cutting tool has to use its maximum length. Often, for the deep cavities or pockets, operators have to utilize their maximum length. This is why making cavities and pockets are very tricky for the machining tools. If not done correctly, this can cause a lot of issues and problems.


Depends on: Part geometry and design. Recommended: Minimum setups to reduce cost

The way a part will be held during the process has a significant impact on the accuracy of the parts. It also has an effect on the cost of the overall process. The more setups it requires, the higher the cost. And it is dependent on the parts’ geometry directly.

Without the proper setups and repositioning system, there can be minor positional errors. And for certain industries, those minor errors can be a deal-breaker. This is why people are leaning more towards 5-axis machining for better accuracy and quality.

When you’re designing the part, you should always consider the functionality of work holding. The work holding determines how the workpiece is gripped during the process. Additionally, if your project requires multiple setups, the operators need to instruct and point out the different locations to the machine.

Size Limitations

The size of your parts is one of the most important factors to consider while designing. It’s best to limit your parts’ size for better performance in machining. And if it’s still too large, consider breaking it into sections to overcome the size limitations.

Milling Machine:

cnc machined larger parts

Standard size: 400 x 250 x 150 mm

With CNC milling you can get more advantages regarding the part size and feature. In this technique, your part and features work as a determiner for the milling tool’s size.

However, the dimension of the tool does not represent its feasible size. As a result, the travel distance of the tool along the Z-axis doesn’t correlate with your part’s depth or height.

Lathe Machine:

Standard size: Ø 500 mm x 1000 mm

The lathe machine is different from the milling machine in terms of size. Here, you’ll have to be considerate of the workspace’s length and the diameter as well. This machine can’t work on parts that are larger than their diameter.

Although the size limitation is higher on this type of machine, there are exceptions. At Sunrise metal, we can offer you live tooling lathe machining, which can boost the performance of your project to a certain extent.

Material Selection

For CNC milling and turning, there are hundreds of metal alloys to choose from. There are many factors to consider when selecting a material for CNC machining. These include pricing, workability, and corrosion resistance, as well as strength and weight.

Listed below are a few materials and their properties that you may consider.

AluminumStainless SteelBrassCopperPVC
500 MPa of physical strengthExtreme hardness (>500 MPa)Corrosion resistanceLow chemical resistanceCorrosion-resistant
A high degree of machinabilityHeat resistance (more than 500°C)Good workability


High conductivityTemperature resistant
Corrosion resistanceCorrosion resistance (very high)Extreme tensile strength


Good workabilityChemical resistant
It can be machined faster than other metalsGood workabilityAccessibleWidely accessibleEasy to machine
Lower costLower costHigher costHigher costLower cost

Complexity and Details


Precision and repeatability are not the only two that you get from a successful CNC machining production. One of the major advantages and strengths of CNC machining is its ability to produce complex and detailed parts.

Compared to any other manufacturing method, you can rely on this particular manufacturing method for any intricate design with great details. Higher technology like 5-axis milling or turning introduced a new era of the machining method.

You or your designer can utilize the opportunity to have more detailed and accurate parts for your design. All you have to do is make a design that is easily done by the machine and is optimized for the process.

However, the more complex your design is or the harder it is for the machine, it will result in more lead time and a higher cost.

Complexity Limitations

cnc technical drawing

Tool access is a significant complexity limitation for CNC machining. To reach numerous surfaces on a piece, it must be rotated repeatedly. A new coordinate system and calibration of the machine are required each time turning a piece. As a result of having to do this repeatedly, a project’s completion time and cost can be increased.

Four or fewer rotations of a piece should not be a problem. To rotate it farther, you’ll need to use five-axis CNC machining. It is possible to follow more complex tool paths with five-axis CNC machining, decreasing machining times and improving surface finish quality.

Inner Edges

cnc inner edge

Recommended: ⅓ x cavity depth (or larger)

When you’re designing the inner edges of your parts, the vertical corner radius should be one-third of the cavity depth. If you can make it more, it’s even better because you can do the cuts in a circular motion. And that can result in a finer surface finishing and better machining compared to a 90-degree angle.

However, if you just need a 90-degree angle, make sure you follow the radius recommendation and use the T-Bone undercut.


holes cnc

Recommended diameter: standard drill bit sizes. Recommended depth: 4 x nominal diameter.

Max. depth: 10 x nominal diameter

A quick rule of thumb for holes is that the more you keep the drilling depth low, the better. In numbers, 40 times the nominal diameter is feasible or compatible with for machining, while most projects require only 10 times the diameter. However, if you require tight tolerance and accuracy, we recommend limiting the holes between 20mm max.

While designing, you should stick to a standard size 1mm drill bits or end mill tools. For tighter tolerance, we use reamer and boring tools at the standard tolerance for better performance.

In the case of edge drilling, you have to be concerned about fitting the drill diameter completely within your workpiece. If you fail to do so, the drill can break in the process, leaving a bad surface finish and poor condition parts. One way around this is to first design a hole, and then mill material away beside the hole to make it an edgy hole.

When designing a part with an undercut on the internal wall, make sure to leave enough space for the tool. You’ll need at least four times the depth of the undercut between the machined wall and the inside walls.

This is because the standard ratio of the cutting diameter to the shaft diameter is 2:1. Machine shops can develop custom tools for non-standard depths, but this addition to the project takes both time & cost.

Making a perfect hole can be tricky, especially if you fail to make the right design. Machinists use standard drill bits to machine the holes, so make sure the hole diameter fits well with that. On top of that, making sure the hole is no wider than 6 diameters can be a hard thing to achieve for the endmill.

Having an optimized hole design can result in a better surface finish, lower lead time, and save in costs.

In addition, tapped holes are often overlooked when we talk about optimizing the CNC design. Most of the machining shops or clients choose the M2 thread size for making tapped holes. However, M6 or above are actually better for greater results. Also, you should limit the thread length size to 3 times the hole’s diameter.

Smaller Featuressmall features cnc

Standard: 0.100 inches or 2.5mm. Minimum: 0.020 inches or 0.50 mm

Adding small features to your parts can be tricky many times and you have to follow certain rules to make them right. For instance, if you’re designing a small hole, you should make it at least 2.5mm wide.

With Sunrise Metal, you can go far beyond that on your small features. However, for most machining shops, they’ll be only to do the standard sizes. So ensure choosing a specialized machining shop or make a design that can be suitable for general shops.

Undercutsundercuts cnc

Recommended Width: 3 mm to 40 mm. Maximum Depth: 2 times the width. Minimum Clearance: 4 times the depth

A general tip for the undercut is that you should avoid having them if they’re not absolutely necessary. Machining undercuts are harder than regular machining and often requires special tooling and multiple setups to complete. As a result, the cost of the machining and the lead time may increase.

Most companies use T-slot and Dovetail methods to machine undercut. These two specialized tools are chosen based on the kind of design and method. While using the T-slot method a horizontal cutter is used on a vertical shaft. The diameter of the undercut can be between 3 to 40mm.

Based on the angles, there are different types of Dovetail cutting tools available, starting from 10 ° to 120 °. The 45° and 60° cutting tools are the most common and considered standard sizes. In this method, you’ll have to ensure enough room to make the process work.

When designing a part with an undercut on the internal wall, make sure to leave enough space for the tool. You’ll need at least four times the depth of the undercut between the machined wall and the inside walls.

This is because the standard ratio of the cutting diameter to the shaft diameter is 2:1. Machine shops can develop custom tools for non-standard depths, but this addition to the project takes both time & cost.

Texts and Lettering texting lettering cnc

Recommended Font Size: 20 or larger. Recommended Engrave: 5mm

If you need texts and lettering, there could be two ways, e.g. engraving and embossing. At Sunrise metal, we recommend the engraved for general texts and lettering instead of embossing. As engraving can cost you less and it removes less material from the workpiece.

For texting and lettering, it’s good practice to have the font at least 18 and the depth should be 5mm.

Texting and lettering might not have a huge impact on the machining, but you can ensure they are optimized as well. As we mentioned in the above section, you should consider texting your parts following the recessed method instead of the raise method for better results.

20 or larger fonts are usually better for the lettering and you can choose any common font such as Arial, Sans-Serif, Verdana, etc.

Below are the general rules of thumb while designing your CNC machine parts. Keep these in mind when finalizing the design for the process for ensuring better performance and quality in your parts.

  • Limit your cavities and make sure that they are no more than three times wider than their diameter.
  • We recommend interior vertical corners should have large fillets at least a third the depth of the cavity.
  • Make sure to include a technical drawing with the original design to avoid any mistakes and confusion in special cases. For instance, if you have requirements like threads, high or low tolerance, surface finish etc.
  • Ensure better optimization of your design for the largest diameter tool that is able to machine easily.

Other Optimizing Guides

Split Up Complex Parts

Machining complex parts is critical for any toolsets. Especially when your parts have deep cavities, small features or pockets. This could increase the cost and make the process more timely and can cost you more.

On the other hand, You could simply split up the parts and do the same. In the end, you’ll get the same result, with less cost and lesser risk of damage. In this way, the operators have more control of the process and result in better quality parts.

Limit the Number of Setups

simple CNC machining

Multiple setups can cost more for any part compared to parts that require one setup. Because parts that require one setup usually have side or back features and don’t need repositioning. Multiple setups not only cost you more but are time-consuming as well.

More setups are the last thing that you want for your machining project. When you have a part design or features that require multiple setups, it will have a huge impact on your cost and the part quality.

For each setup, there is an additional waste of machine time and it also increases the chances of errors.  Although, here at Sunrise metal, we use 5 axis cutting machines to make the process easier and less costly. These multi-axis machines are capable of accessing multiple sides of a part without needing to have more setups.

Imagine the Bigger Picture

Shapes with numerous minor features, on average, take longer to create. For example, a CNC machined pocket will have a circular interior radius. Figures that utilize this feature should use a more significant or comparable radius to .260 rather than the standard of .100.

The more tiny tooling is not suitable for cutting large objects. It doesn’t accomplish much more than make minor cuts. As a result, the smaller radius would require the use of a different tool and more programming.

 think bigger cnc

In general, it is harder to machine features that have a small radius. If you can avoid this and design your part with larger radius, making a CNC-controlled system will make it easier.

CNC machining solutions require some creativity when designing components. It’s essential to think of different ways in which you may be able to improve the part on a CNC-controlled system.

Remember to Specify the Scale of Your Vector Image

CNC precision work can be done in millimeters with precision or tolerance of 0.5 µm. Make sure you’re rightly specifying the size to ensure a better outcome.

vector image scaling

Create a Single Layer on Geometry

cnc cam design

When importing your drawing in CAM, make sure you’ve cleaned up all the lines and sketches to avoid any technical issues.

To get the best results, you should follow these steps:

  • Lower the number of vector lines in your design to the fewest possible without deteriorating the quality.
  • Only take the parts of your drawing that are important and put them in the final DXF file.
  • Lock layers you don’t want to change to keep the editing cursor from moving on and off your desired layer.

Converts Arcs and Splines

polylines in machining

Many machines prefer to work with polylines. Like many lines, polylines are connected, which is better than using broken, disconnected entities like arcs and beziers.  In Scan2CAD, you can turn a line into a polyline by using vector editing tools.

Follow the below steps, so you can convert any Bezier curve to polylines.

  • Go to Vector Edit Menu
  • Click “Modify”
  • Then convert Bezier to Line

Remove Spaces and Draw a Consistent Path

In AutoCAD, there are many tools for editing that make your design process more efficient. One of these is the snap tool in the PEDIT command which makes sure you never lose any clean-cut lines with a simple click. Also, drag motion on the line to change it into something else like an ellipse or polyline.

In Scan2CAD, this process is simplified because we have defined our own special Grab Snap Distance between two grab points. After all, nobody wants their beautiful designs ruined by an errant cursor movement!

Choose and Transform Touching Items Into a Single Entity

For Scan2CAD, Follow the steps:

  1. Click Vector Edit Menu,
  2. Go to Modify
  3. Make Polylines like previously mentioned.

convert line into single entity

When you have arcs in your drawings, it is vital to check Include Arcs before converting them into polylines. If they aren’t, the conversion will leave out a segment of lines and create missing segments. And it can cause misalignments with other objects on the drawing.

Follow the steps to include Arcs:

  1. click Vector Edit Menu,
  2. Go to “Modify”
  3. There are “Polylines Options.”
  4. Include Arcs.

When you design your project, pay close attention to the overlapping vectors. CNC machines will only cut off shapes accurately if there are not too many shapes in one area. If there are, the machine will stop or jump to another part of the object it is cutting. (such as holes).

The best thing is fitting two circles into one with a bit of creativity. You can cut out the overlapping section and still make them coexist in harmony with each other by combining their shapes. By following this,  they don’t overlap at all!

Always Set the Default Z-axis Value

In the CNC export options of Scan2CAD, you should use the default Z value for all vectors. This is a convenient way to ensure that your design always has specific depths on any 3D objects, just as it would if you were drawing by hand! It’s also possible to customize this setting per individual vector element should you wish so.

Get Acquainted With Your CNC Cutting System

When it comes to milling, the depth and width of the cut are crucial variables that you need to consider. When you are not careful, this can lead to problems. These problems include being unable to control the feed and speed of your machine.

cnc cutting system

The MRR might be too low for how long an operation will take if you get surface finishes that are too rough. For these reasons, we recommend paying close attention when designing pockets by considering what size tool is best suited for a particular task.

Some tools are small, like drills. These are used at construction sites. Other, more comprehensive tools have many cutting edges in woodworking operations, such as profiling or cross-cutting large wood slabs.

We’ve mentioned simplifying design can save you a lot of costs and lead time as well. Let’s see how you can do that by instructing your designer about the things that we mention below:


contours design

Contours can’t be considered as a critical or intricate feature, because it’s not very hard to make. Although, they require extended cycle times which results in higher cost and lead time. And if you want to avoid that, it’s recommended that you avoid contours and simplify the surface to save cost and speed up the process.

Fillets & Radius

fillet radii design

Recommended: at least ⅓ x cavity depth

Radius and fillets are great design features that can make your parts more aesthetically pleasing and easier to handle. Many companies choose them because of their ability to make the parts stronger and prone to cracking. In some cases, radius and fillets are mandatory and there’s no way of denying it.

But, you should consider your parts requirement thoroughly and examine that if it’s a must for your project. If not, you can reduce them to avoid complications during machining.

Non-Standard Fillets

fillets cnc

When designing a part, it’s good to use a radius that isn’t the typical size. It will be preferable to simply using the regular size. Instead of having a corner radius of.250 inches, make it slightly more significant, like.260 inches. Instead of enabling a tool to engage fully in a corner, the CAM software will generate the radius with cutting equipment.

If you don’t, the device will collide with the element’s corner. It may result in issues like vibration or tooling damage.

You can make a perfect circle with a .25 radius if you use a smaller tooling insert. But smaller tools are only used for finishing corners, which take up time. And you could use that time for other things.

Optimizing for the Tool Size

Like we discussed earlier, the depth and size of your features play a major part in determining the cost of your project. Smaller features and deep pockets are already costly and harder for the tools.

On top of that, if they are hard to reach for the cutting tools, this could increase the cost enormously. So, make sure you’re avoiding those features as much as you can. And if you do need them as a must, optimize the design for the tools.

Making the CAD Design More Effective

By reading and understanding the above topics, you already know the importance of proper design to make the process more effective. Now, let’s get a quick glance of things that you should or shouldn’t do during the design phase:

Things to AVOID:

  • Designing walls that are far too thin.
  • Using tolerances excessively, unless absolutely necessary.
  • Including unnecessary aesthetic features in the design
  • Including tiny features unnecessarily.
  • Unneeded texts and letters.
  • Design that requires additional machining unnecessarily.
  • too deep, thin-wall parts
  • Unworkable features

Things to Do:

  • Include cavities with precise depth-to-width ratios.
  • When designing interior edges, use radius.
  • Restrict thread length.
  • Ensure proper sizes for the holes.
  • Standard thread size

Internal and External Thread Designing

Industrial threaded products need to adhere to certain specifications for them to work correctly. Depth and diameter are important considerations when designing such a product, which is why you must have the right tools on hand. For example, long thread sections aren’t necessary because most of the stress placed onto these parts is used by threads. Having more than three doesn’t benefit beyond this point.

Likewise, designers should pay attention to depth and major diameters like the minor thread and pilot hole size. If your pilot hole has an identical dimensioning scheme across all features, namely length, and width. Then hardware will not be able to engage appropriately.

To avoid such annoyance, ensuring tap involvement is possible with every pilot hole in the thread. Most CAM applications have the functionality to allow you to measure correctly.

These are some additional tips and tricks to design internal threads.

  1. Add a flip towards the end.
  2. If feasible, decrease the number.
  3. To save production costs, use standard thread sizes and shapes.
  4. Be aware that coarse threads tend to be cheaper than fine threads.
  5. If possible, maintain the surface area in alignment with the central axis of your thread.

Turn the Threads

turning threads cnc

A thread on a CNC turning usually ends in a face. But the challenging matter is that when you make a thread with a CNC turning tool, it cannot wholly end against the face. It also means when a mating thread end binds against the edge rather than the beginning of a thread, it can stop.

If you cannot alter the mating component, cut the thread end to the root diameter of the thread. It is critical to employ a chamfer when designing threads. It is useful when the thread begins. The chamfer should be smaller in diameter than the thread. It will prevent a burr from occurring. It also serves as an ideal starting point for mating pieces.

Journey From Design to Fabrication

The first step in the process is to create a drawing used as a guide for your project. You can use CAD software. Then you need to convert this into DXF or DWG format. Once you have converted the design, you would import this file with CAM/CNC software. All of its necessary measurements are taken into account to generate G-code cutting paths on the CNC machine.

Journey From Design to Fabrication

Here is the process in short illustration

*CAD software > Transfer into G-code> Carried out on a CNC machine*

Tips: You can create G-Code formats from your Scan2CAD designs.

You can make your CAD design in a few different methods. Look at the examples:

Example 1: Trace a Picture Manually to Create Vector Cut Routes

To prepare your design for use on a CNC machine, follow these steps.

  1. Download this original image to use as a reference.
  2. Create an outline of the main features you want to cut out.
  3. Save it in DXF format
  4. Import into your CAM software
  5. Finally, generate G-codes for cutting.

Example 2: Convert a Picture to Dxf Drawing Format Automatically

You can follow this format too! Check below:

  1. Scan and save your drawing in a PDF or image format.
  2. Use conversion tools such as Scan2CAD to convert the file to DXF format.
  3. To produce G-code, import the DXF vector file to the CAM/CNC application.

A Step by Step Guide to CAD to CNC

Many engineers and managers have discovered that finding suitable machine parts is difficult by ensuring transparent pricing and various communication methods are available. Sourcing it can be stressful and time-consuming too. Also, finding a supplier who can meet the budget and engineering standards is not easy.

Delivering a quote for CNC components is also a considerable risk from the perspective of the supplier. A substantial investment in early-stage and resources is required without a genuine guarantee that the contract is won.

Artificial Intelligence (AI) can make these problems an ancient concern. We will show how neural networks manufacture CNC machining source components faster, easier, and more cost-effective. We will also discuss the steps to be taken to prepare your CAD files correctly for CNC machining.

Step 1: Export Your Design to a Cad File Format Suitable for Them the CNC.

STEP and IGES are the most widely used file formats for CNC machining. These formats are standardized and open-source and can be utilized across systems. Some production services accept 3D file formats such as SLDPRT, 3DM, IPT, SAT, and XT.

This is incredibly convenient, but remember that your models will probably be converted in STEP format at some stage in the production process. Exporting your STEP designs directly from the native CAD software is the recommended technique. You can check them before uploading so that no conversion mistakes exist.

Step 2: Prepare a Technical Sketch

It is strongly suggested that you include a technical sketch in your request because it contains information but not a STEP file. It’s because modern CNC systems can analyze the part geometry of a 3D CAD file with the automated system. Also, get the CAM software’s G-code output. A 2D drawing is not necessary to produce components with CNC-Machining.

The following points will enlighten why a technical sketch is necessary for some situations.

  1. Threads are present in your design
  2. Tolerances and crucial dimensions are stated
  3. Particular surfaces require a specific finishing.

It is generally good to incorporate a 2D drawing when placing a CNC order, even though your design does not contain those aspects. The majority of CNC machinery prefer 3D CAD files.

The main reasons are:

  1. The primary dimensions, functions, and essential characteristics of a component can be easy to recognize
  2. The machining processes they execute for manufacturing the part are easier to analyze
  3. In the event of a dispute, the technical drawing is used as the “true source.”

Designing for Best Alignment

It is crucial to cut the functionalities on the same surface as they are aligned when you have alignment dowel holes in your model. This is because end mills are errored, and any further faults would accumulate exponentially. When there was a problem with flipping or changing a cutting bit.

designing for alignment

To prevent this, keep the same endmill while cutting the two components simultaneously, so you can be confident that each element lines up properly as long as everything goes smoothly.

If we take a model picture, The four alignment holes on the top surface work as a guide for drilling your screws. They don’t go all the way through, so it’s not necessary!. The center circle is an extruded cut from the bottom of our block to determine a particular point and size for machining or shaping purposes and other reasons.

The issue with this design is that the alignment troughs and the crucial feature are on the opposite sides of our plate. Therefore we have to turn it over. This tilt leads to an error when one side then another is tried because they don’t match. We produced four cut-offs to ensure that we didn’t worry about a flip piece or faults; both alignments are now machined without too much trouble flipping things around.

Making these holes wasn’t required for the piece’s purpose to work. If you can’t insert a 3mm dowel into the alignment hole, it won’t be able to connect with another plate of the same size and shape. However,  the alignment holes are through-hole cuts, the producer must mill the bottoms to make sure that there is nothing in the way. You can then use these same end mills and paths to mill out the critical features of the plate since they have already been completed. In this case, the crucial elements are milled out after completing the alignment holes. An easier way to explain it is like this: When you make a through-hole cut on your part, you have to make sure that the end mill doesn’t accidentally cut into something important below it.

How Design Influences Cost: CNC Machining

Manufacturers can lose cost-effectiveness if critical design features and machining capabilities are not effectively balanced. However, CNC machining can be a perfect fit for producing parts and prototypes.


In order to achieve the most cost-effective machining, it is necessary to establish a balance between the material’s cost and its machinability. Most plastics and softer metal alloys are more accessible to process than more robust, harder metals. As a result, parts can be made faster, and services are more affordable the more machinable a material is.

Time & Labor

The time that it takes to make an item is a substantial cost issue for CNC machining. Longer machining times are required for complex and massive products, which increases your overall expenses. But with larger quantities of parts, CNC machining set-up expenses are significantly reduced. Larger quantities of machined parts may offer cheaper unit costs at the beginning of a project.

Parts Design

By optimizing your parts design for fast production with less manual repositioning necessary, you can dramatically decrease expenses. These major design elements should be taken into consideration.


  • The Smaller design elements necessitate more machine passes and are more prone to vibration. Which makes accuracy more complex and takes a longer manufacturing time.
  • Cavity instruments can be utilized to make cuts in the body. It reduces the size and thickness of the pocket.
  • The thickness of the wall should be between 0.03 and 0.06 inches thick. Multiple passes with the tool at low cutting depths are required for thinner walls.
  • Standard-sized holes can be drilled quickly, while non-standard-sized holes require an end mill tool, increasing cost and machining time.
  • Reducing the number of milling passes is better if the radius inside corners has a length to diameter ratio of 3:1 or less.

These five techniques in part design or material selection can lower the cost of machined parts while increasing their usability and longevity.

Ease with Corner Pockets

Look inside an electronics enclosure or a bracket that holds a rectangular component. Leaving the vertical wall intersections on those part features completely crisp is a standard design error. To fix this, EDM machines are perfect but slow and expensive.

Using a small end mill on a CNC machine, you can round off corners. A 0.031-inch endmill in 304 stainless steel leaves a 0.016-inch corner radius. It’s sharp, delicate & cost-effective.

Avoid Text Until Molding

A more time-consuming, but visually efficient method is text engraving, which should be avoided if possible. Using another ball end mill, the letters, numbers, and symbols on the CAD model are traced. However, injection-molded parts are more likely to benefit from this type of finish since it is more visually appealing.

Keep an Eye on Thin Walls and Their Features

If you have 0.020-inch or smaller features, an automated quoting system will highlight a thin-wall geometry, but keep in mind that it will still need machining. Therefore the machined part may differ significantly from your original design. Thin walls of 0.020 in. or less are not only prone to breaking during the milling process, but they may also bend or distort afterward.

A Similar Type of Part Can Save You Money

In many cases, ordering numerous similar parts at the exact time allows for a significant reduction in the setup and programming time needed.

Selectively Use high-tolerance Features

Making sure you only specify high tolerances for crucial parts is the best method to save money on machining. For example, don’t rely solely on the default CAD system dimensioning in the cosmetic visual surface. Use +-.020 accuracy instead of +-.002 for some features. The cost of the part will be reduced by a significant amount.

Request for Quote or Information
We would be glad to receive your request for quote.
Please email us your detailed requirements including 2D drawing & 3D Model and Quantity.
  • +86-512-55291075
  • +86 13912651818
  • No 1456, Fushikang Rd, Kunshan City, Jiangsu, China
We are close to Shanghai PVG,SHA,& WUX Airportwe can arrange pick-up when you visit us.
Please fill out the form if you have any question.
Scroll to Top