Farewell to Burrs

It is inevitable to have burrs on the cutting or hole-drilling edge during the milling while milling parts. The size of burr is usually relevant to tool wear condition, feeding and rotary speed, material properties, cutting fluid, etc. The left burrs on the workpiece not only could get operatives scrapped, but also could lead the dimensions exceeding the tolerance. Therefore, CNC manufacturers all regard burrs as a huge enemy against workpiece quality. Previously, APPORO shared a case study on deburring the die casting parts. In that case, burrs formed on account of reamer wearing, and after APPORO promptly renewed the reamers, conducted a full inspection, and removed the burrs, we coped with the quality crisis.

Most burrs on the end/edge of the parts could be removed on the CNC machine through chamfering(*Ref). However, some have to be manually removed as the burrs are where the machine can hardly perform, resulting in the high overall manufacturing cost. If you ever encounter the above situation, take a look at two concrete cases below. See how APPORO make excellent use of decades of experience in CNC manufacturing to overcome all kinds of challenges.

Across Milling Burrs

Basically, milling is about cutting round bar materials into required ID/OD dimensions with high-speed rotary tools. If we are to mill flat surface onto the cylindrical side of round bar materials, the CNC milling machine should be installed with driven tool holders, where face milling cutters are mounted. When it comes to the step of face milling on the side, the round bar stops spinning and aligns the face milling cutter with the part to be machined. Then, the milling cutter starts spinning in right/down or left/right direction to side mill the workpieces, until the depth and width across flats are as required.

 

but highly possible to cause burrs at the end of the flat surface.
We use two cutters to precisely and quickly face mill the rod, but highly possible to cause burrs at the end of the flat surface.

 

From the poppet stem photo above, the head of this OD 8.0 mm workpiece features 7.0 mm width across flats. In other words, the surface has to be 0.5 mm in-depth on one side. First, APPORO used two cutters with 7.0 mm space in-between to face mill the 8.0 mm OD with symmetry from the end of the workpiece, in the same direction with the axis. The processing was precise and quick, but highly possible to cause burrs at the end of the flat surface, which was also around the edge of finish part of the workpiece. As there were not sufficient tool holders in that CNC lathe machine, it was impossible to remove the burrs on the machine. In that way, APPORO could only manually remove the burrs with a pneumatic deburring tool. However, the inconsistent force exertion led to the uneven chamfers and the disqualification.

To manually remove the burrs with pneumatic deburring tool led to the uneven chamfers.
The inconsistent force exertion led to the uneven chamfers marked by red arrows. The undercut marked by red circle is very rough due to the fact that the cutting tool is worn out.

 

When APPORO reviewed all the milling process, we decided to substitute a better CNC lathe machine with more functions, installing face milling tools in its driven tool holders on the side. So, we can machine the 7.0 mm across flats directly. When the 0.5 mm deep surface is completed on one side, the C axis of the lathe machine rotates by 180 degrees and machines 0.5 mm deep surface with an end mill. In the following, APPORO uses the chamfering tool to remove the burrs from the four edges. After this adjustment, APPORO stays away from the risk of inconsistent force exertion of manual deburring and enhances the production efficiency.

To mill the across flats and remove the burrs directly on a powerful CNC lathe.
To mill the across flats and remove the burrs directly on a powerful CNC lathe machine.

 

Burrs from Hole Drilling on Slopes

Generally, after hole drilling, noticeable burrs formed around the edge of the exit surface. If there is still enough space around the hole, chamfering to deburr is still available. However, if the exit surface is not perpendicular to the hole, meaning that the exit surface is a slope or curve, chamfering is not an option to deburr. Here are some alternative plans we can adopt:

1.) Blast

Using the momentum of the high-pressure gas to strike the surface of the workpiece. Available to polish the surface and deburr with evenness and efficiency. However, after blasting the surface could turn slightly matte.

2.) Tumble

The tumble theory applied to have tooling rub against the workpiece with high frequency. Available to polish the surface and deburr with evenness and efficiency. Unavailable for overlong/overweight workpiece or workpiece with external thread.

3.) The universal deburring tool

A unique chamfer tool with its cutter and spring attached. It allows removing the burrs around the edge on both ends at a time. Unavailable for hole under 3mm ID.

Can’t figure out how to deal with the nightmare of burrs? It is time to contact APPORO now. APPORO is going to help you overcome all the problems in manufacturing, based on our experience for decades in this field!

 

*Ref: Learn more about Chamfering.

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

 

 

Shrinking and Distortion in Deep Slotting Parts

Parts after machining, cold rolling and welding usually generate internal residual stresses which may result in serious and unacceptable shrinking or distortion. Whatever the parts are made of metal or plastic. Recently, we are running a CNC machining project of rotor shaft for our Singapore client. At current, this project is still in First Article status. The rotor shaft is part of motor assembly which basically includes a rotor shaft and motor shaft. The motor shaft will be inserted into a deep, accurate, diameter Ø5 H7 (+0.012/-0mm) hole on the rotor shaft. There is a deep slotting cut for enlarging the hole when assembling. However, after deep slotting, the hole size will be slightly reduced and also out of tolerance which lead to a complaint happened. Our customer was using pin gauge 5mm to check the hole. When checking, the pin gauge must go all the way till depth 18.0mm, but failed.

 

CNC machining Rotor Shaft, shrinking may happen after deep slotting.
The rotor shaft shrinking after deep slotting

 

Root Cause for Shrinking Parts

In the meantime, after inner discussion, we believe that the downsize hole was caused by internal residual stresses. Prior to slotting, we had full inspection that the diameter 5mm pin gauge could go all the way as it is indicated in the drawing. In that way, we list two possible reasons for the situation below:

  1. The drawing says the internal hole is Ø5 H7 x 18mm, and we did machine the hole into 18mm in depth accordingly, even into 18.5mm.
  2. Besides, the internal stress would be very likely to lead the hole to slightly shrinking after slotting. Then, it will be unreasonable to meet the tolerance H7 standard after slotting. We suggest our customer to insert the pin gauge harder. So, it will not be a problem for the pin to go into the internal hole.

 

In conclusion, as the dimension was machined exactly based on the drawing, we think the situation is taken full control of by us.​Therefore, We recommend our customer to move forward to the mass production.​​

 

If you have similar design with deep slotting, send your 2D and 3D drawing files to our international team of engineers for a free quote. We look forward to cooperating with you. Please check our RFQ process and send us email.

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

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.

Cross Knurling Profile DIN 82-RGV

Standard specification of DIN 82 (link)

 

After CNC fabrication processing, the workpiece is usually with smooth metal surface. Knurling is a manufacturing process to feature straight, crossed, angled, diamond-like lines or pattern onto the CNC components. Generally speaking, knurling can perform better grip for finger/hand operation, plastic injection insert or decoration purpose. Sometimes, we also machined multiple shallow slots or polygonal for same above purpose. DIN 82 is most commonly used knurling spec in CNC turning machining field. For example, DIN 82-RGV is with cross knurling pattern. DIN 82-RBR/RBL is with right/left hand spiral. DIN 82-RGE is with diamond-like 30° cross male knurling.

 

Failure Cross Knurling

Our Belgium textile industrial customer had sent us the original sample made of stainless steel 304. The sample made by Belgium local prototyping manufacturer was with failure knurling surface. See the shorter item in below photo. The measurement of sample was precise and within tolerance, but with bad knurling which was with improper length, too light pattern, and also lack of lead in chamfer at the threaded hole.

Cross Knurling DIN 82-RGV
Cross Knurling DIN 82-RGV Compare Zoom-in

 

The improper length of knurling do bad for its appearance, a customized full length cross knurling tool can solve this issue. Too light patter may result from the CNC programming or limitation of CNC lathe. Moreover, our CNC production lines can easily machine the lead in chamfer on the edge of threaded hole.

Improved knurling

Therefore, we ordered a customized full length knurling tool to meet the required pattern spec of DIN 82-RGV 0.8. An automatic Japaneses CNC turn-mill machine also helps improving the quality of surface and dimensions. Above photo shows the longer workpiece machined by APPORO is with improved knurling pattern.

 

We can offer CNC precision parts with several types of knurling surface, such like straight knurling, cross knurling, diamond-like knurling. Our production lines are also capable of knurling on precision plastics parts. Should you have any inquiry for above knuring surface on your CNC workpieces, kindly send us RFQ for free project reviewing without hesitation.

Aluminum Anodize Coating Failure

Aluminum anodizing is to produce oxide layer on the surface of aluminum parts to improve the capability of anti-corrosion. Actually, we had talked about this topic in previous case study. But, in this topic, we are talking about aluminum anodize coating failure. The failures caused by various issues on a aluminum CNC machining part generally fall into some of the following categories:

1.) exposure to chlorine based solution

Chlorine is very reactive and causes pitting corrosion by removing the oxide layer. Be careful if Chloride ion in a sulfuric acid electrolyte exceeding a critical level of chloride of 80 ppm. Please also notice that chlorine based solvents are for degreasing which may also cause acid pitting.

2.) exposure to very acid or alkaline solution

Solutions, pH lower than 4 or higher than 9, has the ability to break down the oxide layer and make the underlying aluminum susceptible to corrosion. Generally speaking, to rinse completely the aluminum anodize part is the most satisfactory method of eliminating this problem.

Blind holes v.s. anodizing failure

The anodizing failure rate can be high if your CNC aluminum parts featured with blind holes. If the high acidity anodization solution are not well removed from the blind holes, the liquid will flow out and damage the surface of CNC aluminum parts resulted in flaking-off and spots on its anodiizing surface.

 

Below photo showed an aluminum CNC milled part etched by acid residues. The white, dirty, flaking off oxide powder surrounding the threaded hole is gradually getting worse if no further action against it.

Aluminum anodize can be failure on occasion.
Aluminum anodize failure because of acid.

 

Preventive action to against failure of aluminum anodize

As described above, to rinse and clean the blind hole on a CNC aluminum anodize part is the best way to remove acid solution. It is a MUST to take this preventive action to against failure of anodizing.

 

Should you have any questions about aluminum anodize or other RFQ, feel free to send us RFQ for project reviewing.

Inner Thread Machining by Using Fluteless Tap

There are many ways for thread drilling in metalworking. As for external thread, both thread rolling and thread dies are most common used. As for inner thread machining, we generally use taper/second/bottoming three steps thread tapping or fluteless tapping.

Frankly speaking,  to drill a deep and small inner thread on high hardness or malleability raw material is a difficult mission. Thread machining is all about factors. Such as hole diameter, the forming speed and types of drill bet on the responses: torque, hardness, feeding rate, and thrust force of the form tapping process. Fluteless tap is the one of the best tooling for machining inner thread on CNC turning machines.

Fluteless tap thread machining
Thread machined by using fluteless tap

 

What is the Advantages of Fluteless Tap?

Fluteless tapping, so called form tapping. The screw thread is formed by plastic deformation of a working metal under high level of torque. And, well monitored operation processing to avoid tool bit breakage when thread machining.

Fluteless tapping can form a perfect screw thread with no waste material in a pre-drilled hole. Besides, it is kind of opposite style of external thread rolling method. The inner screw thread machined by fluteless tap is with higher strength and less error of pitch diameter. So, we mainly use fluteless tap machining inner thread on aluminum part, brass part and zinc part when in CNC precision manufacturing.

 

Thread Machining in Industrial Application

Let’s consider automobile industrial application as an example. Mechanical components need to have threaded parts allowing quick and precise assemblies and dis-assemblies. The engine heads manufactured with non-ferrous metals have a excellent capacity to deform and maintain an acceptable mechanical strength. As a result, thread formed by fluteless tapping can guarantee perfect full threading and high tensile strength.

 

Inner thread formed via fluteless tapping
Zoom in on the inner thread of cut part

 

However, inner thread machined by fluteless taps have some peculiarities. For example, the appearance of a split crest on the top of the thread. Above phenomenon is directly rely on the initial pre-drill hole diameter. In addition, the smaller the inner diameters, the slighter the split crest on the top of the screw thread after flutless tap forming.

 

the appearance of a split crest on the top of the thread
Split crest on the thread

 

Feel free to ask us if any questions about fluteless tap on CNC precision machining parts. Pls send us your RFQ for free project reviewing.