What is CNC turning?
Precision CNC turned parts are a type of component that uses CNC lathes or CNC screw machines to process. Most of the part manufacturers have a wide ranging of material capabilities include stainless steel, carbon steel, aluminum brass, steel brass, titanium, and so on. And we make turned parts include drive shafts, interface fittings, shafts, flanges, nozzles, and housings. CNC turning centers use the rotational motion of the precision parts and the linear or curved motion of the cutting tool. They remove material, change the shape and size of the blank. And precision turned parts manufacturers then machine them to meet the requirements of the drawings.
CNC turning machining is a method of producing turned parts by rotating them relative to the cutting tool on a CNC lathe or CNC screw machines. The energy of CNC turning is mainly provided by the machined components rather than the cutting tool. As we all know, CNC turning is the most basic and standard cut method. Besides, it occupies a vital position in high quality production runs.
CNC turning parts
CNC turning services are suitable for machining rotating surfaces. And mould part manufacturers can process most workpieces with rotating surfaces by CNC turning methods. For example, parts include inner and outer cylindrical, conical, end surfaces, grooves, threads, and so on. MLS Mold is a CNC milling and tuned components supplier in China. We have design engineer, support secondary operations, and provide a wide range of cost effective parts solutions. Equipped with live tooling, our services include design, rapid prototype, and high volume production runs. And the precision parts can reach 0.002mm tight tolerances. In general, we always use turning tools as the cutter and call these as precision turned parts. There are also many types of CNC turned parts, hard turning is famous due to maintaining the part’s thermal stability.
A reasonable hard turning system can reduce or even eliminate many costs. Such as grinding, the associated high tool cost of CNC lathes, and long CNC machining service time. Using a reasonable turning process can obtain 0.0028mm surface finish, 0.0002mm roundness, and ± 0.005mm diameter tight tolerances. The goal of hard turning is to remove at least 80% of the heat with the chips. Precision machining company can also achieve such accuracy by using “soft turning” before hardening on the same machine tool. Thus, it maximizes equipment utilization. But some precision turned parts manufacturers chose the blades by mistake. Or they do not know whether the turning mills have enough rigidity to withstand twice the pressure of ordinary turning. As a result, the precision CNC machining technology of hard turning does not fully play to its high efficiency.
1. CNC turning coolant
The biggest problem for CNC turning centers is whether to use coolant or not. For a rapid prototype of intermittently cut parts like gears, it is best to use “dry turning”. Otherwise, the thermal shock during advance and retreat may cause the blade to break and result in secondary operations. As for continuous turning in lathe or swiss screw machine, the high temperature generated during the heat treat process is enough to toughen (soften) the pre-cut area. It reduces the hardness of the material and makes it easier to shear. And this phenomenon shows that it is beneficial to increase the speed during dry turning lathe. At the same time, the coolant-free cutting method has obvious cost effective advantages.
Solution 1: high pressure coolant
In continuous CNC turning services, coolant may help extend the tool life and improve surface finish. The key issue is to allow the coolant to reach the cutter head. High pressure coolant is the best solution to this problem during the machined components making. Because it is not easy to evaporate at high temperatures. Also, high pressure can reduce chip material accumulation. Thus, it reduces the influence of chip clogging on the coolant flow to the cutter head.
Solution 2: release the coolant at the same time
Another method is to release the coolant to the top and bottom of the blade at the same time. It can ensure that the coolant reaches the cutter head continuously. If precision turned part manufacturers use coolant, it must be water-based. The removed material chips formed during the fully matched hard turning process can take 80% to 90% of the heat. And the largest temperature in the cutting area can reach 1700°F.
Once such hot chips after heat treat come into contact with low-fire point cooling oil, it may destroy the entire process. If precision turned part manufacturers operate on an open machine tool, they must add proper protection devices. Because it’s essential to prevent the operator from getting burned by material chips.
2. Albino layer
The whitening layer, also called heat-affected zone may appear in hard turning and grinding operations. It forms a thin (usually 1 μm) hard shell on the surface of the material, which is invisible to the naked eye. The whitening layer is formed during hard turning. In general, it’s because the blade passivation causes excessive heat and transferr it into the part. Usually, the whitening layer is formed on the bearing steel. And is very harmful to machined components such as bearing rings that need to withstand high contact pressure. Over time, the whitening layer may peel off and cause bearing failure.
For precision turned parts manufacturers that just start hard turning, conducting random spot checks. And the time is within the first few weeks of production. It is possible to determine how many precision parts each blade can turn without forming an albino layer. Also, even if a knife can process 400 machined parts, it may become blunt after handling 300 parts and begin to cause a whitening layer.
3. CNC turning machines
The rigidity of the turning mills determines the machining accuracy of hard turning. Almost all machine tools made in the last 15 to 20 years have high quality rigidity. Also, it is enough to withstand hard CNC turn. In many cases, the overall condition of the machine tool is much more important than service life. And CNC machined parts manufacturer can also use a well-maintained ordinary CNC lathe for hard turning.
4. Automatic screw machining
The thread is formed on the surface of the cylindrical precision CNC parts along the spiral line. Screw machine parts have continuous protrusions and grooves with the same cross section. In machinery manufacturing serve industries including precision medical, electronics automotive and HVAC marine medical, they widely use swiss screw machine parts. Turning screw machine products is a common CNC machining method. On standard CNC lathes (such as CA6140), they can turn four standard threads: metric, inch, modulus, and diameter control.
Using the proper blade geometry is the key to thread rolling on hardened materials. And the best threaded inserts are similar to the triangular inserts installed on the boring bar. When thread rolling on hardened materials, we take measures to control the CNC turning pressure and extend the blade’s life. For example, it is necessary to increase the number of passes and reduce the depth of cut. Another option for automatic screw machining is to use alternate side cutting method. It can change the cutting force bearing position and extend the tool life.
5. CNC turning parts
45HRC hardness is the starting point for hard turned precision parts. But precision turned parts manufacturers always use 60HRC hardness material for processing. And they are always a wide ranging of unique articles like tool steel, bearing steel, carburized steel, Inconel, stellite, Hastelloy and so on.
According to metallurgy, materials with small hardness deviations (less than 2 HRC) in the depth of cut range are good. Because it can show the best process predictability. The turned precision parts most suitable for hard CNC turn have a small aspect ratio (L/D). In general, the L/D ratio of unsupported precision turned parts is not greater than 4:1. And that of supported CNC machined parts is not greater than 8:1.
Although the slender parts are supported by the tailstock, it may still cause knife vibration due to excessive cutting pressure. To maximize the rigidity of the hard turning CNC system, we should minimize the overhang. The tool extension length shall not be greater than 1.5 times the height of the shank.
Boring hardened materials requires a lot of cutting pressure. Therefore, it is often necessary to increase the torsion and tangential forces of the boring bar by multiples. A small tip radius blade can reduce the cutting pressure using a positive rake angle (35° or 55°). While increasing the cutting speed, reducing the cutting depth and feed speed is also a way to reduce the cutting pressure.
When boring, the tool must be concentric with the part or slightly above the center of it. Because the deflection caused by cutting reduces the position of the actual centerline. The best form of clamping is a full-length split sleeve. When boring hardened materials, the full-length split collet chuck provides the highest tool holder rigidity. The second is the collet chuck and single-point screw chuck.
7. Turning process
The core of the CNC turning machines is to remove material. And chips can take away most heat generated by hard turning services. Check the chips before and after the CNC machining service to determine whether the whole process is coordinated. When cutting continuously in CNC turning centers, the chips should be a blazing orange yellow and flow out like ribbons. If the chips are broken by hand pressure after cooling, the heat taken away by the chips is normal.
It is suitable for the external processing of various batches of shaft parts and has wide applications. Rapid prototyping and low volume machining often use bedroom lathes. Medium and high volume production runs use automatic, semi-automatic lathes and special lathes to complete the turning process.
Suitable for rapid prototyping and small batch production. Its application has become more and more common in recent years. Serve industries including HVAC marine medical, electronics automotive, petroleum and optical. MLS Mold has material capabilities include stainless steel, carbon steel, aluminum brass, steel brass, and titanium. Our precision turned parts have many advantages as follow.
First of all, it has excellent flexibility. The equipment adjustment, and preparation time are short when replacing machining components. Secondly, there is a less auxiliary time during machining. And it can improve efficiency by optimizing cutting parameters and adaptive control. Thirdly, the CNC machining quality is good and the special tooling is few. So we make the corresponding production preparation cost effectively. Finally, the machine tool operation technology requirements are low. It’s not affected by the operator’s skills, vision, spirit, physical strength, and other factors.
MLS Mold is a precision machining company located in China. We have design engineer and provide cost effectively one-stop solutions of design, sample, and mass-producing. Supporting rapid prototyping, low and high volume production runs, we serve industries of precision medical, electronics automotive, petroleum, and so on. Materials used for precision CNC milling and turned parts include stainless steel, carbon steel, aluminum brass, steel brass, tungsten carbide, titanium, and so on. Any inquiry about precision machined parts, contacting us today!
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