Autocad yardımı ile çalışan kartezyen sac kesme robotu

Abstract

ÖZET Kartezyen kesme robotu, bu tez kapsamında iki ana konuda incelenmiş ve dizayn edilmiştir. Birinci konu, saclardan kesilerek çıkartılacak parçaların resimlerinin 1:1 ölçekte AutoCAD çizim programı ile çizilerek, bu resimlere ait bilgilerin DXF dosyalarına aktarılması ve bu dosyaların deşifre edilmesi, ikinci konu ise deşifre edilen bilgileri referans konum bilgileri olarak kullanarak PD kontrol algoritması ve runge-kutta metodu ile AC servomotor konum ve hız kontrolünün gerçekleştirilmesidir. AutoCAD ile sadece LINE ve ARC komutları kullanılarak kesilecek parçanın resmini çizmek mümkün olmaktadır. DXF dosyasından alman bilgiler yörünge takibi yapılabilmesi için önce sıraya dizilir daha sonra dairesel ve doğrusal yörünge takibi için hazırlanmış programların faydalanacağı dosyalara referans bilgileri olarak aktarılır. Ana software tarafından programlar çağrılarak yörünge takibi gerçekleştirilir. Programlan yazmak için Turbo Pascal dili kullanılmıştır. Çember şeklinde parçalan sacdan çıkarmak için resim çizmek yerine çember yançapı girilmektedir. Ayrıca kesilerek çıkarılması istenen basit parçaların resimlerini çizmek yerine tezgah başında koordinatların elle girilmesi suretiylede kesim işlemi gerçekleştirilecek şekilde program hazırlanmıştır. Robotun mekanik konstrüksiyonunda yörünge takibi konum hassasiyetinin önemli olması nedeniyle bilyalı vidalar ve kendi kendini ayarlayan yürütme arabaları tercih edilmiş ve kullanılmıştır. Tezgah 3mm'den 75 mm'ye kadar sacları kesebilecek şekilde dizayn edilmiştir. Saclar plasma torçu ile suyun yaklaşık 10 cm altında kesilecek olup bu sayede kesilen bölgelerdeki malzemenin distorsiyonu minimuma indirilir, dolayısı ile malzemenin ömrü artar. Bu yöntem ile havaya kansan cüruf miktarıda yok denecek kadar az olduğundan insan sağlığını tehdit eden etkiler ortadan kaldırılmış olur. Altıncı bölümde çeşitli kalınlığa sahip sacların yörünge takibi yapılarak kesilmesi ile elde edilen konum, hız ve kumanda akımı bilgilerine ait simülasyon sonuçlan gösterilmiştir.

SUMMARY AUTOCAD AIDED CARTESIAN PLATE CUTTING ROBOT Operation principle of plasma plate cutting robot Two dimensional shapes drawn by using AutoCAD programme are transferred to DXF codes by AutoLISP programming language. DXF codes are the initial conditions for the main software which is written in TurboPascal programming language. The main software includes all of the mechanical and dynamical criteria which belongs to system. The main software provides driving the AC servomotors and uses PD control algorithm to control velocity and position of the cutting torch. Figure 1. Movement directions of the torch The designed plasma cutting machine is able to cut plates which has to maximum dimensions of 8 x 4m2. The cutting speed varies depending on the plate thickness and material. The maximum cutting speed of the machine is 4500 mm / min which is the cutting speed of 3 mm plates. Electric - arc torch has been selected for designed cutting machine, which gives an ability of cutting up to 75mm plate thickness. Plates can be cut inside the water by using this electric - arc torch. Plates which was cut inside the water have been observed to have a life of approximately ten years, which is longer then the life obtained by other conventional cutting methods. Any closed shapes can be drawn in AutoCAD by using LINE and ARC commands only. Therefore two separate following trajectory programmes were prepared for LINE and ARC. DXF file of the geometry drawn in AutoCAD is decoded and written in a file. In this file, LINES and ARCS are represented by XIdifferent codes. By using these codes, the main software decides to call either LINE or ARC trajectory - following programme. Some simple basic geometric shapes, such as circles, squares and rectangles, can be cut without drawing them. The parameters defining these shapes can be input to the software in numerical format directly. The movement of the plasma torch is realised through ball screw, reduction gear, chaia mechanism and AC servomotors. The trajectory - following is the main problem in the system design. Position and velocity control of the torch should be in maximum accuracy. In order to increase the position accuracy ball screws and ball rail system was selected in this system. The advantages of the ball screw over the acme screw drive are : a. The mechanical efficiency of an acme screw drive is a maximum of %50, whereas a ball screw can reach a mechanical efficiency up to %98 b. Higher life expectancy due to negligible wear during operation c. Less drive power required d. No stick - slip effect e. More precise positioning f. Higher travel speed g. Less heat up As shown in figure 2, the efficiencies of the ball screw and the acme screw are compared. t c S> u £ LU ; i 7 8 9 Lead angle {') ? Figure 2. Comparision of ball screw to acme screw xuDue to their high mechanical efficiency, ball screws are not self- locking. The ball rail system with self aligning feature automatically compensates for errors in alignment up to 10` of arc with no reduction in load carrying capacity. The positioning of the burner carriages is an important step on the way to fully automatic cutting. For the running of automatic production processes a number of parameters are stored in the numerical control as machine constants. The machine's zero point and the machine's fixed point are normally identical. Relative X and Y coordinates will be given for that reference point and together with the defined working area. The zero point defined to the programme is usually the point at which all automatic processes start. All cutting processes will be automatically controlled, and monitored within the programmed working area. Efficient plasma cutting The plasma cutting is an economical and effective process not only for the cutting of stainless steel, aluminium or nonferrous metals, but also for mild steels and thin plate. For high quality cutting mainly water injection plasma cutting is mostly recommended, with which a 10 mm mild steel can be cut up to 6 times faster than by the conventional oxy - fuel cutting methods. Nitrogen or oxygen is used as plasma gas. Plasma cutting with oxygen is particularly benefical due to significant dross free performance over a wide range of cutting speeds with lower power requirements. The plasma torch is equipped with an automatic ( burner ) height adjustment device and special collision protection ( option ) which stops and re - centres the burner by means of permenant magnet system. In case of collision the safety switch stops the cutting process. Trajectory following control algorithm System : The Loads driven with AC servomotor. : Je.â>m + Be.ffim +Mdm = Ma = km.u ( 1 ) State space equation: (2) (3) (4) (5) Xll]x,(0) = 0; x2(0) = 0 x, 1 -B. k2 J u + M dm (6) X = A.X + B.U +C.W Transfer function of the system: Control type : PD; u = Kp ( 6^- xl ) - Kv (aw - *2 ); (7) (8) B. K`-km p. Ht 0mvf Je.s2+Be.s + km.Kv.s + Kp.km (9) K. <»0 J e (10) K.. 2g.co0.Jt-Be (11) X axis motor: Fnxi: xi=x2;. -B, km Fnx2: x2 = - -. x2 +ux.-r (12) Y axis motor: Fnyt: yi=y2;. -Bt km Fny2: y2=--yi+«,--j- (13) XIVBlock diagram of the system Arc block diagram Figure 3. Arc Block diagram Line Block Diagram e ref CO ref -6 Kn *0 Kv km / (Jes + Be) 1/s ffl + - o Figure 4. Line block diagram XV