VARIASI KECEPATAN PEMOTONGAN PROSES PEMBUBUTAN BAJA AISI 4140 TERHADAP KEAUSAN DAN UMUR MATA PAHAT KARBIDA

In the machining process, increased production can be done by increasing the use of cuttingparameters. However, the use of high cutting parameters has an effect on the wear of the cutting toolused. The aim of this research is to analyze the wear and tear that occurs on cutting tools and tool lifewhen cutting AISI 4140 steel by using variations in cutting speed. The machining process uses a CNClathe by turning the surface of the AISI 4140 steel workpiece. The wear criteria are determined when thecutting tool has reached the edge wear limit (VB) of 0.3 mm. Observation and measurement of carbidecutting tools are carried out every 5 minutes the machining process is carried out. If the cutting tool hasnot shown the specified wear value, then the cutting tool then cuts, so that the wear value is obtained.From the research conducted it was found that at a cutting speed of 160 m / min the cutting tool iscapable of cutting for 39 minutes, 13 seconds. At a cutting speed of 180 m / min the cutting tool is capableof cutting for 38 minutes, 14 seconds. At a cutting speed of 200 m / min the cutting tool is capable ofcutting for 33 minutes, 8 seconds. At a cutting speed of 240 m / min the cutting tool is capable of cuttingfor 26 minutes, 3 seconds. Taylor's advanced tool life for the coated carbide cutting tool in turning AISI4140 steel material is: Vc. Tl.0.073 = 8203.

A Response Surface Methodology to Optimize Multiple Discharge Step Parameters for Sinking Electrical Discharge Machining

Conventional die-sinking electrical discharge machining (EDM) employs a single electrode operating under constant discharge conditions. We explored a two-electrode scenario, in which roughing and finishing were coupled. We developed a multiple discharge step (MDS) method that uses three discharge depths. The discharge current is highest in step 1 and lowest in step 3. Response surface methodology (RSM) was employed to optimize the discharge conditions. Experimentally, the MDS method combined with RSM decreased electrode edge wear and surface roughness compared to the conventional method, with no increase in the average discharge current.

Advances in efficiency in the groove milling of aluminium EN AW 2024-T3 with zig-zag and trochoidal strategies

Manufacturing process engineers must continually take decisions to make the processes efficient. Manufacturing time, surface finish and energy consumption are aspects to be optimized in machining. This study analyzes the efficiency of groove milling in milling aluminum alloys EN AW 2024-T3 with zig-zag and trochoidal strategies. Dynamic milling is designed to maximize the removal rate and optimize the tool performance. This generates a discontinuous cutting with minimum of heat reducing build-up with an optimal chip removal minimizing cutting edge wear. The influence of lateral pitch, feed per tooth, cutting speed and coolant pressure has been analyzed. The depth of curt has been adapted for each strategy and tool type. The study was proposed through a factorial design of experiments by the Taguchi method. The machining time (T) and energy consumption (EC) show a strong influence of the lateral step (a e ) in conventional milling. A similar level of influence appears with the feed per tooth (f z ) on the trochoidal. The roughness (Ra) is more influenced by cutting speed (V c ) for conventional milling and by feed per tooth (f z ) and lateral pitch (a e ) for the trochoidal.

The in vivo location of edge-wear in hip arthroplasties

Aims Acetabular edge-loading was a cause of increased wear rates in metal-on-metal hip arthroplasties, ultimately contributing to their failure. Although such wear patterns have been regularly reported in retrieval analyses, this study aimed to determine their in vivo location and investigate their relationship with acetabular component positioning. Methods 3D CT imaging was combined with a recently validated method of mapping bearing surface wear in retrieved hip implants. The asymmetrical stabilizing fins of Birmingham hip replacements (BHRs) allowed the co-registration of their acetabular wear maps and their computational models, segmented from CT scans. The in vivo location of edge-wear was measured within a standardized coordinate system, defined using the anterior pelvic plane. Results Edge-wear was found predominantly along the superior acetabular edge in all cases, while its median location was 8° (interquartile range (IQR) -59° to 25°) within the anterosuperior quadrant. The deepest point of these scars had a median location of 16° (IQR -58° to 26°), which was statistically comparable to their centres (p = 0.496). Edge-wear was in closer proximity to the superior apex of the cups with greater angles of acetabular inclination, while a greater degree of anteversion influenced a more anteriorly centred scar. Conclusion The anterosuperior location of edge-wear was comparable to the degradation patterns observed in acetabular cartilage, supporting previous findings that hip joint forces are directed anteriorly during a greater portion of walking gait. The further application of this novel method could improve the current definition of optimal and safe acetabular component positioning. Cite this article: Bone Joint Res 2021;10(10):639–649.

Grinding Energy Distributions and Wear Behaviors of Grain Cutting Edges in cBN Deep Grinding

This paper deals with the grinding energy distributions in wheel-workpiece contact zone and the wear behaviors of grain cutting edges in cBN deep grinding. By measuring the tangential grinding force distribution in the grinding zone, the grinding energy distribution form could be approximated to be triangular. However, the grinding energy distribution forms changed a little occurring workpiece burn. The wear behaviors of the grain cutting edges were observed by a Scanning Electron Microscope (SEM) and quantitatively evaluated in terms of attritious wear flat percentage. It is shown that the variation of the grinding energy distributions has an effect on the cutting edge wear characteristics.