Since the late nineteenth and early twentieth century, globalization has gradually led to international trade, capital and investment flows, migration, and the knowledge dissemination. From the Q&A below, let’s take a look at how Taiwan as a west Pacific island country reaches such outstanding achievements in the CNC machining industry, which blooms and stands out from the intense competitions of globalization.
– The origin of CNC machining service in Taiwan
1950-1980 is a period called “Taiwan Economic Miracle”, when Taiwan benefited from the late-development advantage of industrialization. The industrial globalization after WWII enabled multinational corporations to look for lower-cost manufacturing bases worldwide. Therefore, with low labor rates and production lines, economics in Taiwan began to prosper, led by the manufacturing industry that processed and exported.
– The strength of CNC machining service in Taiwan
The Industry of CNC machining service is quite dense in Taiwan. It features convenient transportation, vertical integration of services from raw materials, fine machining to surface treatment and so on, and horizontal integration of services, providing casting, forging, rolling, extruding, cutting, high energy beam machining, chemical etching, etc. Therefore, the industry of CNC machining service Taiwan is more capable of product structure breakdown and integration, allowing highly flexible manufacturing efficiency.
– The future of CNC machining services
Due to the breakthrough of Internet of Things (IoT) concepts and techniques, automatic control and wisdom management will play an important role in the industry of manufacturing:
1.) Multi-axis CNC machines with high performance and precision with data analysis, automatic corrective feedback to increase the efficiency of high precision machining.
2.) CAD softwares to complete component modeling and machining procedures to shorten the time from design to finished product, and to also increase the flexibility of production lines.
3.) CNC machines with sensors to measure online, collect production data, optimize plant activation, and overall capacity.
As a manufacturer, APPORO has quite an understanding of design of machine tools and the way they work. We figure how to optimize our CNC manufacturing procedures and to enhance the efficiency all the time, so as to reduce the manufacturing costs. Hence, when knowing there is so-called machine design which could conserve energy or enhance efficiency, APPORO surely looks into its operating principle in details and evaluates if it matches its advertised performance. Not surprisingly, the actual test result often falls short. Speaking of that, several well-known scams in history also adopted this kind of conceptual design, claiming to have created perpetual motion machine(*Ref) to defraud.
What is a Perpetual Motion Machine?
Perpetual motion machine refers to a machine that does motions constantly and works without energy input. There are two major categories in terms of perpetual motion machine. The first kind violates the first law of thermodynamics as it does work without energy sources. The first law of thermodynamics states conservation of energy, indicating the total energy stays constant in an isolated system, and that no extra energy emerges in that system. Any machine that claims to produce energy from nowhere falls into this category.
While the first kind of perpetual motion machine was proved to be impossible, discussions about the second kind of perpetual motion machine were put on table right away. Its design makes use of the energy outside of the isolated system such as heat and wind energy, striking the balance so that the system could operate perpetually. However, energy would eventually be exhausted from the working machines. The just balance could only be reached if there is energy input, so it still failed to forever motion without additional energy.
After Perpetual Motion Machine
The idea of perpetual motion machine has existed for centuries. Based on the scientific understanding nowadays, it remains a dream unattainable. However, there are still a lot of “scientists” engaged in the invention of perpetual motion machine, one after another. Basically these “scientists” are:
1.) Rookies: They barely know a thing about the concept of perpetual motion machine. They often mistake certain device for perpetual machine, which, in fact are device that absorb energy in the dark. For example, human body.
2.) Genuine scientists: They hold the firm belief that science has to be challenged all the time, thinking that thermodynamics could also be wrong or should be revised, as Newton’s law of motion was revised by theory of relativity quantum mechanics. It is never easy to overthrow a law, but their attitudes are admirable. These people are the most likely to invent perpetual motion machine.
3.) Fraud: Even in this era of information explosion, we can still see those who claim to have invented perpetual motion machine. They use sophisticated physics terms and fancy words to convince other to take their scientific results and defraud them of investment. But, until now, all perpetual motion machines are proved to be fraudulent.
Will The Dream Come True?
Perpetual motion machine has always been the dream in the field of science. Just like alchemy for development of chemicals, as many efforts are put into this probably impossible techniques, many relevant techniques are then created. As a pragmatic CNC manufacturer, although we might not believe the concept perpetual motion machine would be ever realized, we could not deny the fact that the progress of science and mechanic design derives from the constant efforts of researchers. Holding the same attitude, APPORO will non-stop updates and introduces new techniques and shares more case studies, hoping to have in depth academic exchange and to contribute to the manufacturing field.
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.
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.
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.
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:
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.
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!
Unified National is a standard commonly used by the United States and Canada in for Inch Screw Threads where the flanks of the V have an angle of 60° to each other. At first, UN(*Ref) only included four basic categories: UNC, UNF, UNEF, UNS, and then UNJ and UNR were gradually added to the standard. Originally developed to meet aerospace requirements for a screw thread, to provide maximum fatigue strength for fastening safety critical components subjected to high stress loads, is the UNJ threading profile. Nowadays, it is also widely used in high-end automotive and robotic automation.
UN Thread Classes
According to UN standard, there are three different classes (1A, 2A, and 3A) when it comes to external threads, and for internal threads there are three as well (1B, 2B, and 3B).
1A and 1B: Refers to the thread fitting with the most loose tolerance, where there is a huge allowance. This class of thread fit is applicable to easy assembly and disassembly.
2A and 2B: The major class in the industrial and commercial applications, such as machine screws and fasteners. This class of thread fit is interchangeable and stable in regard to quality and assembly.
3A and 3B: Applied to commercial products with high quality, this class of thread fit requires compact assembly with an extremely small allowance. Therefore, 3A/3B thread fitting is usually seen in crucial design with safety requirement in commercial or aerospace industry products.
As for external threads, the tolerance of 1A class thread fitting is larger than it of 2A class fitting by 50%, and by 75% than it of 3A class fitting. Samely, for internal threads, the tolerance of 1B class fitting is larger than it of 2B class fitting by 50%, and by 75% than it of 3B class fitting. Taking the 5/16”-18 UNJ-3B thread as an example to show how to read UN thread specification, the 5/16” stands for the major diameter, the 18 UNJ suggests that there are 18 threads per inch in the UNJ threads, and the 3B refers to the finest class of the UNJ internal threads.
Trivia about lathe UNJ threading
In the following, APPORO is going to introduce UNJ threads. Initially released December 1965, the military specification MIL-S-8879 is mainly applied to aerospace fasteners. There are internal thread and external thread specifications when it comes to UNJ threads, which based on the pitch can be categorized into UNJC, UNJF, UNJEF, and UNJS. UNJ threads are different from UN threads in the respects below:
external threads: The roots of regular UN threads will be V shape bottoming, while the roots of UNJ thread are strictly specified to be semicircular bottoming. This kind of circular roots can slow down the wear rate of sharp cuts during processing and increase the fatigue strength of threads.
internal threads: In order to assemble with the semicircular bottoming of external thread, the minor diameter of an UNJ internal thread will be slightly larger than it of a regular UN internal thread. As internal threads are rather unlikely to break from the internal stress, there is no specifications for the major diameter roots of UNJ internal threads to be semicircular bottoming.
The symbol for all UN external threads is “A”, while for all UN internal threads is “B”. In addition, for J series threads usually the required thread class is 3A/3B, which is the highest fit, and the second most common thread class for J series threads is 2A/2B. On the other hand, for UN threads the thread class is commonly 2A/2B.
In the process of lathing UNJ external threads, sharp cuts should be equipped according to the specified root radius (between 0.15011 pitch and 0.18042 pitch), so that the roots of the external threads could be smooth semicircles in a row in shape. As the roots of an external UNJ thread are special semicircles in shape, its minor diameter is slightly larger than it of a regular external UN thread, and that is why it could not match other Inch Screw Threads of the same specifications. For example, if we drive an ⅜”-16 UNC nut with an ⅜”-16 UNJ screw, the minor diameters of these two would interfere with each other, resulting in the assembly failure. However, using a larger tapper to manufacture the internal thread of the ⅜”-16 UNC nut could prevent the minor diameters from interfering and avoid other assembly problems.
On the contrary, if we would like to drive an internal UNJ thread with a regular external UN thread, since there is no specifications about the major roots of an internal UNJ thread being semicircles in shape, basically an internal UNJ thread could match an external UN thread of same specifications. The difference between an internal UNJ thread and an external UN thread is that the minor diameter of an internal UNJ thread, as known as the size of its tap-drill hole, is larger; therefore, the minor diameter of the internal UNJ threads could match the semicircular shape external roots of the external UNJ threads. For instance, under some special circumstances, there will not be any problems driving an ⅜”-16 UNJ nut with an ⅜”-16 UNC screw.
In comparison with hundreds of thousands of thread specifications and applications, thread manufacturing and inspection are rather simple. However, their importance is often underestimated, leading to assembly failure and possibly affecting the overall product equality. Find yourselves a CNC expert with thread manufacturing proficiency and experience like APPORO so that the quality of your products are guaranteed!
As it is mentioned previously, the goal of OD control can be easily reached under stable CNC processing. Generally, after CNC processing, the threads of a non-plated component have to pass the thread gauge inspection so as to pass the QC inspection. Nevertheless, for components that need to undergo plating process, the manufacturing and inspection procedures will be different from the former. According to the requirement of our Swiss dental equipment supplier client, APPORO has to be discreet than ever for inspections. See the examples below:
Based on the required plating film thickness, APPORO has to leave some room for it during CNC processing, and use the pre-plated thread gauges for inspections. See the photo below. If the required plating film thickness is 1-3um, the major, pitch, and minor diameters should all be +0.02/-0mm larger than the standard dimensions when manufacturing the internal thread M13.2×0.3-6H. Then, the threads need to pass the inspections of the enlarged customized M13.2×0.3-6H +0.02/-0mm plug gauge before plating. After plating, the internal threads need to pass the inspections of a standard M13.2×0.3-6H plug gauge. Once they pass the inspection, they can be approved for shipment. If there is an external thread on the plated component, after CNC processing, the pre-plated ring gauge inspection will be necessary. And then, the inspection of a standard ring gauge should then be conducted.
What we can do without pre-plated gauges?
However, the customized pre-plated plug/ring gauges are all expensive, which are only needed for components that demand extremely high precision, but not for all components. With the long time CNC manufacturing experience, APPORO suggests to use NO GO of the standard thread gauge for the inspection criterion for threads before plating. That is, the threads could perfectly screw in the NO GO of the standard thread gauge without loosing. After plating, the threads have to pass the standard thread gauge inspections, a.k.a. GO and NO GO inspections.
This inspection is more available for components with plating film under 5um thickness. For components with plating film over 5um thickness, as its plating is for anti-corrosion purpose, and the precision requirement of it is usually lower. Even the ready made standard screws and nuts can be the inspection tools. Or, before plating the threads should be able to screw in the NO GO of the standard thread gauge but slightly loose. And then, the threads should pass the GO and NO GO inspections after plating.
Plating and thread making are common techniques when speaking of CNC manufacturing components. Before and after different procedures, the concern will also be different. APPORO has devoted long time and and much efforts to CNC processing techniques, systematically learning from the processing experience in this field and turning it into application to increase the manufacturing efficiency and yield rates. Should you have any technical questions relevant to controlling size before/after plating, do not hesitate to contact us.
There are numerous items in our daily lives that need threads for assembly and secure. In the applications of some precision industries, the precision of thread is highly relevant to the smoothness of component assembly, so rigorous manufacturing and inspection are necessary. Regarding manufacturing threads, previously we publish an article about it in details, where you can select your best ways for manufacturing depending on materials, amount, and precision. We will also talk about how to manufacture pre-plated thread later in this article.
How to inspect the threads?
As you can choose the most appropriate ways to manufacture threads depending on the needs, you can also customize the thread inspection based on the precision, functionality, and so on. Generally speaking, if tolerance and the intensity of threads are not really the concern, ready made bolts and nuts are available for shop-floor inspections. When the nuts/bolts successfully run onto/into their counterparts, they pass the shop-floor inspections. But if tolerance and the intensity of threads are the concern, advanced inspection methods such as thread gauges, 3-wire method, micrometer, vernier caliper, projector and coordinate measuring machines, can be used to measure the threads accurately. Regarding the basic introduction about thread inspections, you can take a look at the previous case study from APPORO.
In the extremely rigorous precision industry, the design thinking ranging from purpose, materials, manufacturing, post-manufacturing, to even packaging are taken seriously, so as to ensure the quality of products during mass production and the various functionality. Take the design thinking of one of APPORO’s clients, the Swiss dental equipment supplier for example. The handheld dental equipment have to be comfortable for long-term use, able to prevent from occupational injury, and conforming with hand ergonomics. Therefore, details like size and the design of center of weight are highly valued.
What should we learn about pre-plated part?
APPORO is mainly in charge of the supply of medical grade stainless and brass components manufactured on CNC lathe. Besides, if there is cosmetic or anti-corrosion purpose for brass components, nickel or chrome plating will be added as surface treatment. In general, the film thickness of plating and its anti-corrosion ability are positively correlated. However, when it comes to the dental equipment, the anti-corrosion ability is not the a priority concern. Instead, what really matters is that the dimensions of the components are still within the tolerance after plating, to make sure the components are in a good assembly condition and function.
For instance, after 1-3um nickel plating, the outside diameter a cylinder brass component and its tolerance should be 9.50 +/-0.02mm. In practice, we manufacture the OD 10.0mm round rod materials into OD 9.48-9.50mm. With nickel plating which requires 1-3um thickness, the OD of the plated products could be within 9.50 +/-0.02mm.
Generally speaking, when it comes to deciding the thickness of sheet materials, the unevenness is often a concern. It then becomes necessary for the sheet materials to have additional thickness, so that we can machine the materials to the required dimensions and at the same time ensure the accuracy of the reference surface and the relative dimensions. Whether the sheet materials are rolled metals or extruded plastics, they all need molds for manufacturing purpose. However, mold precision goes down with time, which could lead to the poor quality of the sheet material surface, as well as the uneven material thickness.
Case Study on Uneven Sheet Materials
Recently, APPORO machined a batch of panels by milling, of which mostly are Eurorack & Modular Synthesizers, and delivered them to our Japanese customer. After assembling the panels, they found out the assembly acrylic plates were not completely coplanar with the panels, and turned to APPORO for solutions. APPORO digged into the situation and then figured out it was due to the uneven thickness of the acrylic plates, which resulted in the height gap between the metal panels and the acrylic plates.
How We Solve Unevenness?
The panels are 1.6mm thickness steel plates with drilled holes, milled grooves, and after powder coating. While the acrylic plates are 3.0mm thickness amber transparent acrylic, of which the outer areas were to milled into 1.4mm in height. Usually, the rest areas with extra 1.6mm lump of the acrylic plates could perfectly match the steel panels. However, only few suppliers provide amber transparent acrylic, and therefore the quality and precision of the molds are not satisfying. Consequently, those so-called materials with 3.0mm thickness are actually with thickness around 2.6-3.2mm, which are of considerably unstable quality. What’s more, even we can find the inconsistent thickness across one plate. After the discussion, our customer agreed to accept the panels with the 1.5-1.8mm gap between the unmilled and the milled surfaces. So, APPORO offered the solutions below for this problem:
1.) Cut the materials into plates from the 3.0mm thickness acrylic sheet materials. Then, checked the thickness of every sheet material, and eliminated the materials with thickness less than 2.70mm and over 3.0mm.
2.) Milled the parts into 1.2mm in height, with at least 1.5mm to 1.8mm lump on the top. So, after the assembly the acrylic sheet might be 0.1mm lower than the panel surface, which could still meet the assembly requirement of the customer.
Finally, the technical team of APPORO conquered the difficulties in production, assembly, and etc., helping our customer deal with the tricky situation. Again, APPORO won the trust of our customer and also the opportunities of further cooperation. If you are undergoing similar problems during design or assembly process, send us an email for the technical discussion with APPORO. APPORO will assist you of advancing in the product design.
Learn more about the importance of design in CNC manufacturing:
Undoubtedly, part warping is a nightmare for both manufacturers and customers. It can affect the functionality of a part or lead to assembly failure. Generally, part warping is due to residual stress, which can be highly relevant to the choice of materials, dimensions of the part, and manufacturing conditions.
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.
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.
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: