DML Final Exam 2024 graded A

What is a waterjet used for? - 2D CNC cutting of soft materials What is an AWJ used for? - 2D CNC cutting of almost any material, regardless of STRENGTH 6 Advantages of AWJ process? - Virtually any material can be cut; quality, satin-like finish; no heat in the machining process; environmentally responsible; no tool changing; can create almost any 2D shape 3 Disadvantages of AWJ process? - Machines are expensive; machines require frequent maintenance; messy Water cutting pressure and cutting jet velocities of Modern AWJ - 80,000 psi and 2,000 mph T/F AWJ machines can cut at different speeds depending on the desired finish? - True Maximum Peripheral tool velocity equation - V = (pi) D N What is the purpose of peck drilling? - To help chips evacuate so they don't collect inside the hole. What happens if chips collect inside a hole while drilling? - They cause the drill bit to overheat, seize, and break What is the limiting factor for how deep to cut (per pass) with an endmill in a particular material - Cutting tool / workpiece / machine stiffness What is the limiting factor for how fast a drill or endmill can rotate in a particular material? - Head generated in the cutting zone What is the limiting factor for how fast a drill or endmill can feed thru any material? - Size / strength of cutting edges / lips What are six factors that affect optimum cutting speed for drilling and milling? - Strength and thermal conductivity of material Depth of hole Presence and efficiency of cutting fluid Type, condition and stiffness of cutting machine Stiffness of workpiece, fixture and tooling Quality of holes desired When should you use slower cutting speeds? - Roughing cuts Stronger materials Flexible workpieces When trying to maximize tool life Sheet metal - Workpieces with a high ratio of surface area to thickness Sheets - = 1/4" in thickness Plates - 1/4" in thickness T/F Pulling, pushing, and stretching are the most common sheet metal operations - False What sheet metal capabilities does the lab have? - Shear, brake (bending) , punch press (round holes) What is the structural benefit of bending sheet metal edges and flanges - The sheet metal becomes stronger/stiffer