Verktygstillverkaren Mircona har rapporterat om kvalitetsbrister för deras frässkär, där skäreggen tenderar att flisa och orsaka abrupta brott. Eftersom Mirconas nuvarande skärsortiment till deras slitsfräsar är hämtat direkt från deras svarvsortiment är skärgeometrin inte anpassad för den intermittenta bearbetning som skapas från en fräsoperation. Syftet med arbetet är att utveckla ett mer högpresterande verktyg för Mirconas slitsfräs NGOT 27. Målet är att ta fram ett nytt förslag till en förbättrad skäreggsgeometri för Mirconas slitsfräsar med fokus på skärets förslitning. Därför har en mindre avfasning med varierande lutning och bredd tillämpats på skäreggen. Dessa testas experimentellt. Litteraturstudie visade att avfasade skäreggar förstärker skäreggen, reducerar förslitningen och minskar energiförbrukningen med upp till 20 procent. För att utföra experimentet gjordes en försöksplan med ett fullständigt faktorförsök, där den uppkomna förslitningen på skärets spånyta och släppningsyta studerades. Insamlade data analyserades med det statistiska, analysprogrammet MODDE. Dessa visade att avfasningens bredd hade störst inverkan på spånytans förslitning och en mindre samverkanseffekt med avfasningens lutning. Insamlade data för skärets släppningsyta visade låg statistisk signifikans. Med utgångspunkt från bearbetningsmaterialet och använd skärdata orsakar en fasbredd på 0,3 millimeter spånhamring vilket ger en överdriven förslitning på skärets spånyta. Avfasningen behöver inte överstiga 0,2 millimeter fasbredd och 20° negativ lutning för att tolerera slagpåkänningar från fräsoperationens intermittenta bearbetning. / Tool manufacturer Mircona has reported problems involving chipping of their disc slot milling inserts. At present, Mirconas is using inserts with edge geometries adapted for turning, which is not customized for the intermittent cutting of a milling operation. The purpose of the thesis is to develop a better performing tool for Mirconas slot milling tool NGOT27, with the goal of a new insert geometry assortment adapted for a slot milling application. Therefore, in this project a small chamfer has been applied with different widths and angles on Mirconas MT-4 insert to increase the cutting edge strength, which is tested in a experimental trial run. A literature review showed that a chamfer will create a new cutting edge from a bulit up edge, which enforces the cutting edge strength, reduces wear rate and reduces the energy consumption with up to 20 percent. To perform the experimental trial runs, a design of experiments was utilized with a full factorial design, where the inserts flank wear and rake wear was studied. Collected data was analyzed with the statistical software “MODDE”, which showed that the chamfer width had the biggest effect on the rake face wear, and had a slight synergy with the negative chamfer angle. The data collected for the flank wear showed poor statistical significance. In relation to the cutting data, and workpiece material used in the experiment, a chamfer width of 0,3 millimeters will generate chip hammering which will cause excessive wear to the rake face. The inserts, cutting geometry, does not need to exceed 0.2 millimeters of chamfer width, or a greater negative chamfer angle then 20°.To withstand the intermittent cutting climate, from the slot milling application.

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Denna rapport är resultatet av ett examensarbete omfattande 15 hp på C-nivå utfört vid Högskolan Väst. Arbetets första del bestod av en litteraturstudie och undersökning av befintliga temperaturmätningssystem som används i skärande bearbetning. Arbetets andra del bestod av att rekommendera temperaturmätningssystem och skapa en implementeringsplan för det rekommenderade systemet i utrustning på Produktions Tekniskt Center (PTC) i Trollhättan. Sex stycken olika tekniker för att mäta temperatur har undersökts med avseende på lämplighet för skärande bearbetning. Varje teknik presenteras med sammanfattande tabell med egenskaper samt för- och nackdelar. En teknik (pyrometri via optisk fiber) har valts ut för PTC och för den finns två tekniska specifikationer. En specifikation för ett system som kan anses vara kommersiellt tillgängligt (om en i mycket liten skala, 4-5 installationer i världen). En specifikation är framtagen baserat på forskningsresultat redovisat av prof. Ueda vid Kanazawa University men anpassad för att vara generell. För dessa system finns en implementeringsplan framtagen för att anpassa systemet och utrustning för att fungera vid PTC.

This project has as main goal to study the influence of the coating thickness, deposited by arc-PVD- technology, on the wear resistance of coated cemented carbide inserts in three different turning operations. An additional effort has also been made to develop a new test method for evaluating flank wear resistance. Three different coating types (Coating A, Coating B and Coating C) have been studied in three distinctive thicknesses (2, 4 and 6 μ m) for each type. For two of the coating types (Coating A and B) special studies has been done with the thickest coating, creating two additional coating versions of the thickest coating, by changing various deposition parameters, with the aim to enhance the cohesive properties of the coating and lower the residual stresses at the cutting edge. The results show increased crater wear resistance with increased coating thickness for all coating types, but the amount of increase changes with coating type (Coating A>B>C). Flaking wear resistance decreased with increased coating thickness for all coating types. Further the high temperature version of Coating A, showed a significant increase in the flaking wear resistance compared to the standard version of Coating A. The flank wear test showed an increased resistance with thicker coatings in all cases except for the 6 μ m version of Coating C. The flank wear resistance of the most flank wear resistant coatings (Coating B, C) was also successfully examined in a new developed test method. The method suppressed excessive crater wear on the rake face and presented a high abrasive wear rate on the flank and some flaking on the rake face. The amount of flaking is judged not to influence the testing of the flank wear resistance. For all the tested coatings in the new test an increase in the coating thickness resulted in better flank wear resistance.

The adhesive mechanism is one of the most significant degradation processes of the edge in metal cutting. Although knowledge about adhesion and edge buildup (BUE) has increased in recent years, there are still areas that are less explored. The adhesion has a regularity in the form of clusters: In a cluster, the chips vibrates with a certain frequency. The frequency varies with several influencing factors. In this thesis, a possible connection between acoustic signals and wear of the cutting edge is researched. Audio signals from cutting edges with varied wear must be analyzed. To investigate the adhesive mechanism, the machining process turning will be used. The cutting edge is analyzed optically with a microscope. According to previous research, the adhesive wear has been shown to be mostly dependent on the cutting speed. The size of the stagnation zone depends largely on the friction angle and the shear plane angle, where the friction angle changes depending on the rake angle and the shear plane angle changes depending on the cutting speed. Adhesion wear has been shown to be a fatigue process. This thesis aims to investigate the development of the adhesive mechanism towards the wear status of the tool. The end goal is to construct a model that explains what happens in the wear zones on the edge and to detect changes in the acoustic signal from the cutting zone that occurs during adhesion wear. The cutting zone sound from two cutting tools with different cutting times is used in Fourier analysis. Insert number two will be worked until chipping occurs and examined optically with a microscope between each cycle to verify if chipping was present. One chip was examined after each cycle under a microscope to see if residues from the insert got stuck on the chips. Cycle number one with insert number one (new edge) shows no clear adhesive mechanism while cycle number one with insert number two shows a clear adhesive mechanism. The same cutting speed is achieved during cycle number five and number 18 with cutting tool number two. The frequency increases 11% and the amplitude decreases 42% from cycle number 5 to cycle number 18. Chipping occurred in cutting tool number two after 25 cycles. The frequency of the adhesive mechanism increases, and the amplitude decreases when the insert wears. A reasonable hypothesis is that the surface that is welded together becomes larger with increased wear: The spring in the adhesive system becomes stronger while the mass remains constant. A hypothesis that the amplitude of the adhesive mechanism is low during cycle number one with insert number one may be due to the fact that the workpiece used was at room temperature. No significant degeneration has occurred of the chip surface.