Diamond Knurling Operation on CNC Lathe

Knurling is to feature patterns onto the CNC machined components.
Knurling is to feature patterns onto the CNC components.

As mentioned previously in “Cross Knurling Profile DIN 82-RGV”, knurling is a manufacturing process to feature straight, crossed, angled, diamond-like lines or pattern onto the CNC components. Usually, we use DIN 82 knurling specification standard for most CNC machining cases. If diamond knurling is required, we shall use DIN 82-RGE which is featured with diamond-like 30° cross male knurling. Also, we may consider DIN 82-RGV which is featured with cross knurling pattern as an alternative for customized purpose.

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Effects of CNC Machining on Part Distortion

With recent increase in demand for more ultra precision machining designs for improving performance requirements, we are facing a great challenge in this kind of CNC machining services. Generally speaking, the greatest challenge when machining these components is part distortion. For instance, removing material up to 80 % on CNC machines to produce monolithic components replacing multi part assemblies has become common in aerospace, automobile, precision instrument industries. These kind of components might have similar appearance features such as thin wall, very long length, etc.

What Is Part Distortion?

Part distortion is defined as the deviation of part appearance from original shape after released from the fixture. Generally speaking, distortion could come from several variables such as type of material, inherent residual stresses in bulk material, residual stresses induced from CNC machining, part design, etc. In the most cases, the dominant factor of part distortion is the inherent residual stresses in the part. In general, these inherent residual stresses usually come from different manufacturing processes, i.e. quenching, stretching forging, extrusions, casting, welding, machining, forming, and etc.

CNC Machining Part Distortion
Residual stresses induced from CNC machining may cause parts deforming.


How Can I Minimize Part Distortion?

Distortion is a common challenge in manufacturing industrial components. The suggestions to minimize or eliminate distortion shows as below:

1.) The length to thickness ratio of the part design is lower than 10:1.

2.) Pre-heat treating the metal part prior to manufacturing for stress relieve. For instance, the general stress relieve condition for AISI 4340 alloy steel is at 650-670°C for 2hrs, slow cooling furnace.

3.) As per our experience of CNC machining service, distortion increases with the cutter size at constant feed, speed, depth of cut and material removal rates.

4.) Considering that WEDM process involves being fully-submerged, it imposes nearly no stress on the metal part.


With optimized manufacturing process flow, we are able to minimizing any deformation on all the CNC machined parts. Also, to select the suitable cutting tools and CNC machining parameters is of utmost importance. Note that the choice of cutting tools size is key to strike the balance between the productivity and geometrical constraints of the component. By the way, you can learn more about:

1.) Larger Corner Radii Reduced CNC Machining Cost

2.) 4 Things That Will Impact Your Manufacturing Costs



4 Things That Will Impact Your Manufacturing Costs (Part 1)

So far, to exactly predict machining time and manufacturing costs can be very difficult. For instance, factory location, facility or even politics do have impact on the quotes of manufacturing. Sometimes, to request a quote for your manufacturing project feels like looking for a needle in a haystack. In fact, you can still have an initial concept of cost even without 2D and 3D CAD drawings.

Various factor which have impact on manufacturing cost for CNC machining services
Top-end CNC machinery can manufacture high quality parts.


 What is included in Manufacturing Costs?

Generally speaking, there are various factors which directly have impact on the cost of CNC machining services. For instance, materials used, dimensions of the part, quantity per batch, manufacturing process applied, post processing used. Furthermore, auxiliary processing equipment can also affect the cost of manufacturing project such as customized cutting tools, jigs and tooling. In spite of above, there are still some basic guidelines which will have impact on your project. Hopefully, this can be grateful for your evaluation in early planning stage.

1.) Material Costs

Obviously, different type of material costs are largely various from each other. Nowadays, material cost is getting more transparency of pricing due to freely global trading. You can get a roughly idea of material cost by looking for local price for raw material. Furthermore, parts made of cheaper material is likely lack of durability or poor quality compared to high-end material. However, parts made of high-end material usually means more manufacturing lead time for good quality.

Manufacturing costs is relative to many factors.
Various factors may affect your manufacturing costs.


2.) Surface Treatment Costs

Surface treatments are generally for cosmetic and anti-rust purpose. In the past, the chemical solution used in most of surface treatment process are usually with toxic hazards. Actually, the proportion of surface treatment cost in total manufacturing cost were not so high. Nowadays, the directive of RoHS(*Ref.1) has strictly restricted these hazardous substances. At the same time, surface treatment costs are getting higher due to stricter environment policy. For a roughly estimation, the heavier the weight, the more expensive the surface treatment cost.

Surface treatment may cost more nowadays.
Surface treatment: Anodizing


Learn more: 4 Thing That Will Impact Your Manufacturing Costs (Part 2)


*Ref.1: See more about the directive of RoHS

Sheet Metal Prototyping Fabrication

At APPORO, we specialize in high quality metal work production at a great price. Apart from general CNC machining services, we also provide rapid prototyping service for custom metal fabrication. With our systematical arrangement of a range of technologies, we are a perfect one stop shop to meet all your prototyping need. Our professed team can help you validate your prototype quickly and efficiently. Therefore, this will be also grateful for starting mass production seamlessly.

What is Prototyping?

Generally speaking, prototyping is one of the best way to evaluate the function and profile of a part, or to test a innovative design. It is to build a real model which is generally used for concept testing or replication for some purposes. Consequently, Our prototyping service can offer a rapid production for producing a real sample according to product design.

Since early stage, our skilled engineering team will take quick decision on the project details for optimal production. For instance, material, surface treatment, processing method, packaging. Furthermore, we also specialize in complex assemblies. Our engineering team are good at improving cost effective manufacturing process. Thus, our high quality prototyping services make us a one stop shop for your product.

Prototyping Production Lines

Rely on our experienced production team, we are able to take rapid reaction for prototypes production. Furthermore, APPORO has cooperated very closly with other specialists for many industrial projects. Basically, our trans-disciplinary team are capable of below production capability:

1.) Laser Cutting

To use a high power fiber laser beam to cut materials. Our trans-disciplinary team owns two laser cutting machines. One is TRUMPF TruLaser 3030 with 3,000 mm x 1,500 mm working range, 20 mm maximum sheet thickness. The other is Mazak SUPER TURBO-X48 with 2,400 mm x 1,200 mm working range, 22 mm maximum sheet thickness. You can look at the short film showing how our laser cutting machine work.

2.) NCT Punch Press(*Ref. 1)

To use various standard punch tools for blanking, piercing, straight edges, different size of holes. Our team owns AMADA PEGA-357 Turret Punch Press.

Turret Punch Press, a high efficient machine for prompt prototyping prior to building stamping tools.
AMADA PEGA-357 Turret Punch Press


3.) Water Jet Cutting

To cut a wide variety of materials by using extremely high pressure jet of water. Sometimes, we use a mixture of water and abrasive substance for cutting hard materials. Our team owns OMAX 55100 JetMachining Center.

OMAX 55100 Water Jet Machine

4.) Wire Cutting

Also, known as wire-cut EDM. Typically use a brass wire to cut punching tooling die or metal plate which is too hard to be machined by other methods. Undoubtedly, wire cutting is the slowest cutting method compare to above three. However, the production tolerance can be down to less than ±5 µm.

In conclusion, get your design ready and make your own drawing. Next, send your 2D and 3D drawing files to our international team of engineers for a free quote.

*Ref. 1 See more about NCT(Numerical Control Turret) in Wikipedia

Make Your Own CAD Drawing

Computer-aided design(*Ref. 1), so called CAD, is widely used in most industries to improve the efficiency and quality of design. Furthermore, CAD drawing output in the electronic file is highly conducive to communicate with designer and manufacturer. Also, it creates a great platform carrying complete information for CNC machining service manufacturer. Generally, we prefer reading, modifying and creating 2D and 3D CAD drawing files by using CAD software.

The way to create your own CAD drawing.
Create Your Own CAD Drawing


The Way to Create CAD Drawing

Recently, CAD software do helpful for rapid and easy engineering modeling in various industries. For example, automotive, aerospace industries, reverse engineering(*Ref. 2), PCB design, animation design, industrial and architectural design. In summary, below procedures show how we use CAD software to create 2D and 3D CAD drawing:

1.) to start from creating 3D CAD object

  • create 2D elevation drafting
  • form and modify 3D object by extrusion, revolve, sweep, emboss functions

2.) to create 2D print from 3D CAD

  • start a new .dwg drawing file
  • place various but less view sides of 3D model
  • mark dimensions detailed but simplified
  • mark important notices

How to Get CAD Software?

Currently, CAD program is a necessary powerful tool to use in CNC machining service project. A CAD software with good design should be capable of creating both 2D drawing and 3D modeling. Generally, it is usually hard to choose the best modeling software for different market sector. It is because various aspects and the wide range of features are available in these CAD tools. The essential elements of good CAD software are as below:

  • 2D Drawing Tools
  • 3D Modeling Tools
  • Textures
  • Transparency Options
  • Lighting Effects
  • Hatching
  • Photo-realistic Rendering


At present, it is easy to get lots of free CAD software for personal or professional modeling purpose. Should you have any questions about CAD software application, do not hesitate to send us email.


*Ref. 1 Computer-aided design-Wikipedia

*Ref. 2 Reverse Engineering: From Real Component to Print

Reverse Engineering: From Real Component to Print

Reverse engineering, so called back engineering, is to get the design information from the item already made. Afterwards, to reproduce the item total according to the obtained information. Laser scanner, CMM, profile projector, industrial CT scanning are the most powerful measurement tools for reverse engineering. Furthermore, you can refer to Wikipedia for more understanding about reverse engineering.

At APPORO, we provide reverse engineering service for parts made by CNC machining, stamping, plastic injection, die casting. Generally speaking, we use CMM and profile projector to extract the dimensions accurately from the original workpiece. Below showed a CNC machining service project for our USA client who were asking reverse engineering for Rotary Tattoo Machine components.

Original Sample of Rotary Tattoo Machine Components from USA client
Original Sample of Rotary Tattoo Machine Components

Reverse Engineering Step by Step

1.) To extract the sample dimensions by CMM, profile projector and Venier caliper.

Original samples sent from USA client. Firstly, sent for extracting all the dimensions by CMM, profile projector and Venier caliper. After that, all the dimension information are to create 3D CAD drawing for further CNC machining process. See more about our quality inspection instruments.

Reverse Engineering: Rotary Tattoo Machine - Frame dimensions extracted by CMM
Rotary Tattoo Machine – Frame

Material: Aluminum Alloy 6061-T6

Surface Finish: Red, Black and Silver Anodizing

Type: CNC Milling

Reverse Engineering: Rotary Tattoo Machine - Motor Housing Cap from USA Client
Rotary Tattoo Machine – Motor Housing Cap

Material: Aluminum Alloy 6061-T6

Surface Finish: Red, Black and Silver Anodizing

Type: CNC Milling

2.) From 3D to 2D prints for CNC machine programming

Generally speaking, to convert 3D CAD drawing into 2D CAD print is a must for CNC machine programming. A CAM software can both read and output CNC programming code for production from 2D prints. After that, we will confirm with customer by using the 2D CAD prints marked with dimensions and detailed descriptions. How to make a good 2D CAD print? For instance, various but less view sides of workpiece, detailed but simplified dimensions, marked with important notes if any. After intensive discussions with client, we have reached a consensus to integrate frame components into one part as below.

CNC Machining Services: Rotary Tattoo Machine - Frame for CNC machine programming
Reverse Engineering: Frame


CNC Machining Services: Rotary Tattoo Machine - Motor Housing Cap for CNC machine programming
Reverse Engineering: Motor Housing Cap


3.) Move to production

At last, the customized jigs, cutting tools and CNC programming were ready for production arrangement. You can visit our website for more understanding about our core service. After CNC machining, the items were sent for with high quality anodizing.

CNC Machining Services: Rotary Tattoo Machine Frame
Frame with Glossy Red Anodizing


CNC Machining Service: Rotary Tattoo Machine Motor Cap
Motor Cap with Glossy Black Anodizing


APPORO are still working closely with our USA client for cases with innovative new design, whilst improving the cosmetic surface with clear machining action. Do not hesitate to contact us should you have any interesting cases. We look forward to cooperate with you.

Improved Precision Measurement

Regarding quality inspection, we mostly use vernier scale and micrometer for measuring the dimensions of precision manufacturing CNC parts. As per our policy of IPQC, we can obtain fast and easy readings of the measurements by using vernier scale and micrometer.

Does Vernier scale and micrometer work for measuring most items?

The answer is “it depends”. Both Vernier scale and micrometer have their own limits. For example, Vernier scale and micrometer cannot measure CNC machined complex profile or tiny hollow workpiece with thin wall. For CNC machined part with complex profile, we will recommend to use a coordinate measuring machine (CMM). The CMM can take readings of dimensions in up to six degrees of freedom and high accurate down to 0.001 mm. After that, it displays those measurement readings in mathematical form. You can transfer the readings into profiling for reverse engineering purpose.

How to measure tiny and hollow CNC precision parts by micrometer?

To measure a tiny and hollow workpiece by hand tool such as Vernier scale or micrometer is likely deformed the items but not able to get correct dimensions. An alternative method is to against dimensions misreading from deformed workpiece.

Therefore, we will suggest to insert a solid mating part inside the tiny and hollow CNC precision part. See below photos showed tiny hollow CNC precision manufacturing dental component. We used a Sylvac S_Mike PRO micrometer made in Swiss with a φ6.5mm measuring anvil. To against deforming, we use a brass CNC turned part machined for transition fitting with workpieces.

Improved Precision Measurement by using solid insert
Improved Precision Measurement


The Precision Measurement Readings after improving.
The Precision Measurement Readings


Any other more direct and correct measurement?

So far, we know that a hand micrometer with measuring anvil of φ6.5mm usually with a measuring force between 5-10N. However, the measuring force 5-10N can be large enough to easily deform tiny and hollow CNC precision parts.

Here is the problem: how to measure tiny and hollow CNC precision parts? An alternative choice is to use a bench table with measuring anvil of φ2mm. Smaller measuring anvil is usually with a measuring force between 0.2-1.0N. It is good to  measure CNC parts diameter with tolerance less than 5 microns.


Should you have any questions about quality inspection, kindly send us email without hesitation.