Journal of Mechanical Engineering Research and Developments ISSN: 1024-1752 CODEN: JERDFO Vol. 43, No. 3, pp. 186-196 Published Year 2020 186 Hole Characteristic of CO2 Laser Drilling of Poly- Methyl Methacrylate PMMA Abeer A. Shehab †,††* , Iman M. Naemah ‡ , Abbas Al-Bawee † , & Athil Al-Ezzi † † Department of Material Engineering, College of Eng., University of Diyala, Diyala, Iraq. ‡ Department of Mechanical Engineering.College of Eng., University of Diyala,Diyala, Iraq. †† Institute of Laser for Postgraduate Studies, University of Baghdad, Baghdad, Iraq. *Email: abeerahmedshihab@gmail.com ABSTRACT: The use of laser drilling process to produce high quality end product is a potential for mass production. This process shows an important role in this field of industry, particularly in the drilling of many types of material includes metals, plastic, rubber, and ceramics. In this current work, an experimental investigation of the laser drilling process is carried out on 4 mm acrylic (Polymethyl Methacrylate, PMMA) thickness using Carbon Dioxode (CO2) laser. The study investigates the effect of laser power density and exposure time on hole quality characteristics, namely aspect ratio, circularity and taper. The results revealed that both laser power density and exposure time play a significant role on uniformity, roundness and drilled holes diameter. It has been observed that aspect ratio, circularity and taper increase with decreasing laser power density and/or exposure time for the drilled open holes. KEYWORDS: Laser Drilling, Poly-Methyl Methacrylate, Power Density, Exposure Time, Hole Quality Characteristics INTRODUCTION Poly-methyl methacrylate (PMMA) is usually known as acrylic which, has been used instead of glass in optic applications [1, 2]. This kind of material has many vital properties which lead to stand it among many polymeric materials. The main properties of this kind of polymers are lightweight, easy to fabricate, high chemical stability and good mechanical strength. PMMA has been utilized in many applications such as optoelectronic, microfluidic device, and vehicle industry also, in some medical applications [3-5]. Machining of PMMA is normally performed by using traditional processes, such as drilling and milling operations. These processes require special tools to produce the final required shape. However, the operating cost and service life of these tools have been reported to be the main issue that makes it limited in use to some extent. On the other hand, laser drilling able to machining different kinds of materials regardless of their physical properties such as hardness, softness, and absorptive [6-8]. Laser drilling process can be defined as a thermal processing method in which it has a veryhigh focused beam that causes a depth through the thickness of any materials. During this high energy beam, the material being processed is melted and then evaporated. Flowing that material particles are thrown out the drilling hole due to the steam pressure that generated from the process.[9 ]This technology has become one of the advancing drilling processes besides electrical discharge machining, ultrasound and electron beam [10, 11]. Laser processing is, therefore, an alternative method that able to cut and drill the PMMA precisely without the need for the conventional techniques. This is mostly important for obtaining high quality of drilling holes with small diameter size reached to less than 0.004 mm. It has been documented that laser processing method is extremely effective technique for drilling and cutting different materials such as polymers, composites, ceramics and metals[12-15]. This technique is commonly used to obtain holes characteristic such as diameter percussion and repeatability. Also, holes taper, edge finishing of the samples and small heat affected zone. [16, 17]. Since the last two decades several kinds of laser sources have been used to perform the