Kılavuz matkapların aşınmalarının incelenmesi
Wear investigation of drill taps
- Tez No: 952989
- Danışmanlar: PROF. DR. ŞAFAK YILMAZ
- Tez Türü: Yüksek Lisans
- Konular: Makine Mühendisliği, Mechanical Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 2022
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Lisansüstü Eğitim Enstitüsü
- Ana Bilim Dalı: Makine Ana Bilim Dalı
- Bilim Dalı: Malzeme ve İmalat Bilim Dalı
- Sayfa Sayısı: 117
Özet
Bu çalışmada farklı tipte kılavuz matkaplarla diş çekme işlemi gerçekleştirilmiştir. Çeşitli kesme hızlarında farklı tipte kılavuz matkapların talaş kaldırma performansları değerlendirilerek raporlanmıştır. Takım ömrü, kesme takımlarının izin verildiği ölçüde aşınana kadar talaş kaldırma süresini belirleyen değişkendir. Takım ömrü işparçasını istenilen hızda ve kalitede işlenmesi için en önemli talaşlı imalat planlama değişenidir. Takım ömrünün artması, bir başka deyişle aşınmanın azaltılması, talaşlı imalatın verimliliğini önemli ölçüde etkilemektedir. Bu sebeple talaş kesme takımlarının yüzeylerine sert kaplamalar uygulanarak takım ömrünü artırma yoluna gidilmektedir. Yüzey kaplamayla sertleştirme işlemleri takımların dayanıklılığıyla birlikte maliyetlerini de artırmaktadır. Bu noktada, kaplamalı kesme takımı kullanıldığında takım yüzeyine doğru kaplama türünün uygulanmış olması maliyetler açısından önemlidir. Kesme takımları kaplamasız (HSS, yüksek hız çeliği) imal edilebildiği gibi birçok farklı kaplama türüyle (TIN, TIALN, TIX2, TICN) kaplanmış olarak da imal edilebilmektedir. Kaplamalı kılavuz matkapların malzemesi yine HSS çeliğidir. Kesme takımlarının aşınması; sertlik, sürtünme katsayısı, aşınma dayanımı, yorulma dayanımı, korozyon direnci gibi kimyasal ve/veya mekanik özelliklere bağlı olarak değişmektedir. Sürtünme katsayıları, aşınma ve yorulma dayanımları işlenen parçanın boyutsal doğruluğuna ve yüzey kalitesine doğrudan etki eder. Sertlikse dayanıma etki ederek takım hasarları üzerinde belirleyici olur. Tez çalışmasında kaplamasız ve farklı kaplamalara sahip kılavuz matkapların dış çap yüzeyindeki aşınma miktarları, belirli çalışma aralıklarıyla ölçülmüştür. Böylece kılavuz matkapların zamana bağlı aşınma miktarları tespit edilmiştir. Bu ölçümler, farklı türde kaplanmış kılavuz matkapların aşınma miktarlarının birbiriyle karşılaştırılmasına da olanak sağlamıştır. Ayrıca aynı kılavuz matkapların farklı kesme hızlarındaki aşınmaları da aynı aralıklarla ölçülerek kesme hızının aşınmaya olan etkisi anlaşılmıştır. Böylece kesme hızının takım ömrüne etkisi de karşılaştırılabilmiştir. Tüm veriler Taylor takım ömrü grafikleriyle somutlaştırılmıştır. Tüm bunların yanı sıra maçalara açılan vida dişlerinin kaliteleri de karşılaştırılmıştır. Yapılan çalışmalar sonucunda, en çok aşınmanın kaplamasız kılavuz matkaplarda oluştuğu tespit edilmiştir. TIX2 kaplamalı kılavuz matkapların, TIN kaplamalı ve kaplamasız kılavuz matkaplara göre daha uzun ömürlü olduğu belirlenmiştir. Bunun nedenleri çalışmada belirtilmiştir. Son olarak maça üretimi için sektör kalite standartları doğrultusunda kılavuz matkapların takım ömürleri belirlenmiştir.
Özet (Çeviri)
In this study, threading was performed with different types of cutting tools. The chip extraction performance of different types of cutting tools at various feed rates has been evaluated and reported. Tool life is the parameter that determines the chip extraction time until the cutting tools wear to the permissible extent. Determination of tool life is one of the most important inputs for processing the material at the desired speed and quality. Extending tool life, in other words, reducing the wear, significantly affects the efficiency of machining. For this reason, the tool life is extended by applying hardening coatings to the surfaces of the cutting tools. Additional coating and hardening processes extend the life of the tools while increasing their costs. For this reason, while choosing between uncoated cutting tools and coated cutting tools, it is important to determine which coating type is applied since this will affect the cost of the production. Cutting tools can be produced uncoated (HSS, high speed steel) as well as with many different coating types (TIN, TIALN, TIX2, TICN). The base material of coated cutting tools is also HSS. Coated tools are produced by coating HSS material with different coating types. The chemical and/or mechanical properties of cutting tools such as hardness, friction coefficient, wear resistance, fatigue resistance, corrosion resistance vary depending on the type of coating. Coefficients of friction, wear and fatigue resistance directly affect the dimensional accuracy and surface quality of the workpiece. The hardness of the cutting tools, on the other hand, affects the strength of the cutting tools therefore is effective in tool damage and life. In this study, tapping and the wear mechanisms of taps in goujon production was investigated. Goujon is an important semi finished part in cookware production, which is necessary for installation of pot/pan handles. It's manufactured from AA 6063 T8 raw material. Aluminum is a ductile raw material which is hard to machine due to the problems in chip extraction. Especially when it comes tapping operation of M5 threads, the extend of tool wear becomes very important. There are totally 7 types of Goujons for different types/dimensions of pan/pot products. In all of these types of goujons, M5 threads have to be machined. We have investigated M5 thread machining for the longest goujon type. This type of goujon is 18 mm in length and has a thread depth of 10,5 mm. During our studies, three different types of taps were investigated: Uncoated HSS taps, TIN coated HSS taps and TIX2 coated (multi layer titanium coated) HSS taps. All the taps were helical fluted taps. These kinds of taps are more suitable for machining of ductile materials like aluminum. Helical fluted taps also allow for the cooalant to reach cutting surfaces more efficiently than straight flute taps. The next reason for choosing helical fluted taps was the nature of the holes. The study was on blind holes. Thus the chip exraction was not possible by pushing the chips forward. Machined chips should be removed to the opposite of feed direction. Therefore all three types of taps were chosen from right helical fluted taps. Experiments were made with a CNC rotary transfer bench which is also used in series manufacturing conditions. The trasfer machine had 7 stations, 16 units, 11 servo hydraulic motors (29 axes). In addition to servo-hydraulic motors, there were pneumatic-mechanical drives at 3 stations (2 bar feeders and the unit that discharges the finished product). In order to achieve the desired production quantities, production is carried out with two units at the same time at each station. There are 8 stainless steel gripper jaws on the rotary drum, hydraulically driven, adjustable clamping force (maximum 2.750 kg). The jaws are hardened by quenching. The software of the CNC machine is KEBA Motion PLUS and the control screen is KEBA Motion brand, high resolution, 32-bit, 15 inch, touch-enabled. To produce the goujon, 6063 T8 series, 10 mm x 10 mm x 3000 mm solid bar, which can be seen in Figures 3.3 and 3.4, was supplied. Incoming quality controls of raw material were carried out to ensure the production and experiment quality. The chemical composition and hardness of the aluminum in the certificate were subjected to input quality control tests in KOSGEB laboratories. Chemical and mechanical values were tested and reported. Hardness, which is the most important parameter for processing aluminum, was reported in the range of 78-81 Brinell. There rates were in accordance with the certificate which was submitted by the raw material supplier. During production, the previous process before tapping was drilling holes to the back side of goujons. 4,20 mm diameter uncoated HSS drill bits were used in our experiment. The experiments were conducted on 10.000 goujons for each tap. Flank wear of the cutting tools without coating and with different coatings were measured at regular intervals. The radius of taps were measured after every 1.000 goujons were produced. So, for each tap 10 measurements were made. During the measurement process the machine was stopped and the diameters of the taps were measured and recorded. Thus the amount of flank wear of the tools were found out. After tapping a total of 10.000 goujons, the taps were removed from the machine and the wear mechanisms were visualized with a stereo microscope. Main variable was the cutting speed. Three different cutting speed parameters were conducted: 12 m/min, 15 m/min and 18 m/min. For each typ of tap, at each cutting speed, 3 taps were experimented (3 uncoated HSS taps were used at 12 m/min, 3 uncoated HSS taps were used at 15 m/min cutting speed and 3 uncoated taps were used at 18 m/min cutting speed). This process has been applied to all types of taps. Totally 27 taps were experimented, 270 measurements were made and 270.000 goujons were manufactured. With these 270 measurements, tool life graphs were produced for all types of tools at 12 m/min, 15 m/min and 18 m/min cutting speeds. Taylor Tool Life graphs were drawn for different cutting speeds of all types of taps based on wear values. Taylor Tool Life charts were created in two different ways. First, the performance of each tap type at different cutting speeds was compared. In this way, the wear values of each tap type could be compared depending on the cutting speed. Secondly, the wear values of different tap types at the same cutting speeds were compared. These graphs gave us the opportunity to compare the wear performances of different types of taps. Initial wear zone, steady state wear zone (continuous uniform wear zone) and rapid wear zone (accelerated wear rate) (except 12 m/min and 15 m/min cutting speed in TIX2 coated tap) are observed in all Taylor Tool Life graphs. In the next stage of the study, curves were drawn by curve fitting method to Taylor Tool Life graphs. Curves and equations fitted to the Taylor Tool Life plot were treated as tertiary functions. High R2 values of the functions are important in terms of ensuring the study. In the studies conducted with the cookware manufacturers, the importance of the handle assembly to be of the expected quality was discussed. In this direction, thread quality was the most important parameter for the bolt-goujon connection in handle assembly to have the strength determined by the industry. In terms of pot/pan handle strength, 150 micron wear of the taps was determined as the limit value. Since taps reaching 150 micron wear value were scrapped, tap tool life was accepted as 150 micron wear value. At this point, the wear times of the goujons at different cutting speeds for 75, 100, 125, 150, 175 and 200 microns were calculated using the wear equations. Calculated cutting times are presented in the charts in Section 5. Log-Log graphs were drawn for cutting speed-cutting time for 75, 100, 125, 150, 175 and 200 micron wear values at 12 m/min, 15 m/min and 18 m/min cutting speeds for each tap type. For Log-Log graphs, the correct equations were found by plotting the curves with the correct curve fitting (line fitting) method. The determined high R2 values of the equations and fitted lines verified our study. Our aim in finding the line equations was to find the constants“n”and“C”in the Taylor Tool Life equation. The slopes of the fitted lines gave us the constant“n”. Constant“C”was calculated afterwards by mathematical methods using Taylor Tool Life equation. At this point, the simplified Taylor Tool Life equation was found to be sufficient. In our study, the Modified Taylor Tool Life equation was not considered necessary since the threading depth and feed rate were constant. With the Taylor Tool Life equation,“n”and“C”constants for 75, 100, 125, 150, 175 and 200 micron wear values were calculated and presented in tables. In the study,“n”and“C”values were calculated in line with expectations. In accordance with the philosophy of the Taylor Tool Life equation,“n”and“C”values were found to have low volatility, except for the first wear zone and the rapid wear zone. This was important in terms of verifying the data in our study. Also crack wear and notch wear mechanisms are observed under stereo microscope. These measurements allowed us to compare the wear of different types of cutting tools with each other. In addition, the wear of the same cutting tool at different feed rates was measured at the same intervals and the effect of feed rate on wear was understood. Thus, the effect of different feed rates on different types of cutting tools could be compared. All data is demonstrated in Taylor tool life graphs. In addition to all these, the thread qualities of the goujons were also compared in Section 5. To achieve this, the goujons were cut in half with a saw and monitored under the stereo microscope located in the materials testing laborataries of Istanbul Technical University (I.T.U). As the result of the studies, it was concluded that TIX2 coated cutting tools have a longer life than uncoated HSS and TIN coated cutting tools. It has been interpreted that there are two different reasons for this. The first reason is the difference in the coefficient of friction. As a result of the lower friction coefficient in TIX2 cutting tools, it was understood that the machining temperature remained lower, and accordingly, the cut aluminum chips adhered to the surface of the cutting tool less. The other reason is surface hardness. In TIX2 cutting tools, the cutting tooths appear to sustain less damage. This shows that the surface hardnesses specified in the technical data of the cutting tools play a role in wear. TIX2 coated cutting tools with harder surfaces are less worn during machining. TIN coated tools performed better than uncoated HSS tools. However, considering the price-performance parameter, TIN coated tools were not evaluated as sufficient enough. Another important result was the relation between cutting speed and chip length. The chips became longer for each type of tap as the cutting speed was increased. Thus it became harder to remove the chips while machining. This also increased the probability of tap failure. Especially by increasing cutting speeds for uncoated HSS taps, the productivity decreased because of too many tap failures. The helical flutes had to be manually cleaned as longer chips couldn't be removed during machining by the helical flutes and cutting fluid. Therefore we had to stop the CNC machine at uncertain periods to clean the chips manually. This was also the reason for decreasing productivity. For all types of taps, at all cutting speeds, R2 value for tool wear equations was calculated as 0,95 (95%) or higher which prooved the mathematical model was accurate.
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