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Storytelling (3)

Usually, alloy steel with a mass fraction of chromium greater than 12% (mass fraction) or a mass fraction of nickel greater than 8% is called stainless steel. Stainless steels are classified according to their metallographic structures, including martensitic stainless steel, ferritic stainless steel, austenitic stainless steel, austenitic + ferritic stainless steel and precipitation hardening stainless steel.

After the stainless steel is cut, the cutting surface and the machined surface are severely hardened, which can reach 1.4 to 2.2 times the hardness of the substrate, and the depth of the hardened layer is 0.1 mm, which brings difficulties to subsequent cutting; due to the high plasticity, toughness and tensile strength of stainless steel , the unit cutting force is 1.25 times that of cutting 45 steel; the thermal conductivity of stainless steel is 1/4~1/2 of that of 45 steel [50.2W/(m K)], so under the same cutting conditions, The cutting temperature is about 200 °C higher than that of cutting 45 steel; due to the plasticity, toughness, high cutting temperature and affinity of stainless steel with other metal elements, the tool-chip bonding and diffusion occur, and the tool is bonded and diffused. wear.

Also due to the serious hardening phenomenon when cnc machining stainless steel, it will increase the wear of the tool.

  1. The tool material for turning stainless steel is required to have high heat resistance and wear resistance according to the above-mentioned cutting characteristics of stainless steel, and has a small affinity with stainless steel.
  2. High speed steel. Ordinary high-speed steel (W18Cr4V) tools have low durability. W6Mo5Cr4V2Al and W12Cr4V4Mo high-performance high-speed steel should be used, which can double the durability of the tool.
  3. Carbide. YG-type TaC or NbC fine-grained or ultra-fine-grained cemented carbides should be used, such as YG6X, YW4, YS2, YS8, YD15, 813, etc. If a coated blade is used, it is best to use TiAlSi coating, which can prevent adhesion and wear during the cutting process, and at the same time increase the surface hardness of the blade to 3600~4200HV.
  4. Tool geometry parameters The rake angle of the stainless steel machining tool is γo=20°~30°, the clearance angle αo=8°~10°, the main declination angle κr=45°~75°, the secondary declination angle κr=8°~15 °, the edge inclination angle λS=-3°~0°, the radius of the tool nose arc rε=0.5~1mm. The form of broken (rolled) chip groove is full circular arc or straight circular arc, with groove width Bn=3~5mm, groove depth h=0.5~1.3mm, and broken (rolled) chip groove radius Rn=2~8mm.
  5. Cutting amount Due to the cutting characteristics of stainless steel, the cutting speed is 40%~60% of that of cutting 45 steel, and the cutting depth ap and feed f should be greater than 0.1mm.
  6. When the cutting fluid is rough turning, use emulsion or extreme pressure emulsion; when fine turning, use vulcanized oil (that is, mineral oil containing 2% sulfur).
  7. Attention should be paid to turning stainless steel, especially austenitic stainless steel, should use a lower cutting speed (high-speed steel tool vc=18~20m/min; cemented carbide vc=40~60m/min) and a higher cutting speed than the hardened layer The depth of ap and f; when drilling with high-speed steel drills, the cutting edge of the drill should not stay on the cutting surface, so as not to aggravate the hardening of the cutting surface and bring difficulties to the next feeding; when reaming stainless steel holes, vulcanized oil should be used. Isobaric cutting fluid.
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The Classification Of CNC Machine Tools


There are many classification methods for CNC machine tools, which can be roughly classified according to the type of machine tool structure, control method, china cnc machining movement method, and machine tool processing method.

1. Classification by machine tool structure

If it is classified according to the machine tool structure, then the main distinction is in the number and method of machine tool motion axes, usually two-axis linkage lathes, three-axis linkage machine tools (such as those with tool magazines are called machining centers), and four-axis linkage machine tools (which move The axis consists of X, Y, Z, A four axes), five-axis linkage machine tool (usually consists of X, Y, z, A, C or X, Y, Z, B, C five axes).

2. Classification of control methods

The control of the machine tool is usually realized by the servo mechanism, so according to the different detection positions of the machine tool, it can be divided into three types: open-loop, semi-closed-loop and closed-loop control.

  • (1) Open-loop control: It does not detect any feedback device, and the information control feedback belongs to a one-way mode, so it is called an open-loop control mode. Advantages: The system is relatively stable. Disadvantages: There is no feedback device, and its accuracy is mainly controlled by the transmission accuracy of machine tool components, and the relative accuracy is not high.
  • (2) Semi-closed loop control: The total detection feedback device usually controls the feedback in the rotating part of the screw of the machine tool, not in the actual position detection of the moving parts, which is called semi-closed loop control. There is an error in the machine tool screw transmission, which is difficult to eliminate, so the actual detection position is not as good as the closed-loop control of directly detecting the workpiece, but the error can be debugged and compensated, so high-precision machining can still be obtained.
  • (3) Closed-loop control: The detection feedback device directly detects the workpiece, so it is called closed-loop control. Because the feedback can be detected and compensated for the entire transmission error, higher accuracy can theoretically be obtained. In practice, the stability of precision control is difficult, and there are many influencing factors.

3. The Classification By Machining Motion


CNC machine tools can be divided into point control machine tools, linear control machine tools, and contour control machine tools according to the movement mode. The differences between them are as follows.

  • Point control machine tool: Point control is simply point movement, similar to drilling movement. 189 top group
  • Linear control machine tool: The movement of the linear control machine tool is simple, and its movement is similar to that of a CNC grinder.
  • Contour control machine tool: The movement of the contour control machine tool is complex, which can complete the three-dimensional movement in space and complete the processing of complex profile workpieces.

4. Classification By Machine Tool Processing Method


According to the machine tool processing method, it can be divided into CNC turning, CNC milling, CNC grinding, CNC drilling, CNC planing, laser wire cutting and other special machine tools, special CNC machine tools also include CNC forming machines, CNC shearing machines, CNC spark machines, CNC wire Cutting machine etc.

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3 Actually Good Christian Storytelling Podcasts

Most Christian podcasts do 2 things: sermons and interviews. Finding a good Christian storytelling podcast, or really any Christian storytelling podcast, is like finding a cat person at a dog park. Odds are… it won’t happen.

I love storytelling podcasts like NPR’s This American Life, Pushkin’s Revisionist History, and Gimlet’s Heavyweight. The short audio stories of real people fascinate me, but until 1 year ago, I only listened to podcasts that at best ignored Christianity all together or at worst made fun of Christianity. But I still listened because the storytelling, the music, and the commentary blended to make entertaining and beautiful stories from people in all walks of life.

Then, 1 year ago, I discovered Love Thy Neighborhood. After being inspired by Love Thy Neighborhood, I decided to make Audible God. Because of my work on that, I discovered Unshackled again for the first time. I highly recommend all of these podcasts. Each one tells intriguing stories of normal people in a style that’s genuinely entertaining and thought provoking… and not every story ends in an altar call. Listen now.

Love Thy Neighborhood

Love Thy Neighborhood Podcast Cover Art

The storytelling is beautiful. The empathy is apparent. The theology is sound. Grace & truth, justice & mercy, righteousness & humility all co-exist together in an intimate space with a collage of human suffering and hope in Jesus. In a world of bumperstickers and mean tweets, Love Thy Neighborhood gives a refuge to Christians who seek truthful nuance.

Audible God

Audible God Podcast Cover Art

The Audible God podcast mashes up a hip hop soundtrack and humor with intriguing stories of ordinary people who claim they’ve heard from God. From an artist who sensed God telling him to paint a portrait for a guy in a coma to a former drunk who put diapers on his head, each story will fascinate you. And you’ll be pumped to share each one with your friends.

Unshackled

Unshackled Podcast Cover Art

This old-fashioned radio drama tells compelling real-life stories of actual people who found hope in Jesus in the midst of addiction, abuse, and desperate hopelessness. The vintage organ soundtrack, seamless narration, and stylized voice acting capture humanizing stories of brokenness and redemption.

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