o Sheetplate cutting o Bulk part cutting Machining

o Sheet/plate cutting o Bulk part cutting

Machining: Family of Material Removal Processes q Material is removed from a starting solid work part to create a desired geometry

Principle of the process Structure/Configuration Process modeling Defects Design For Manufacturing (DFM) Process variation Module 6 3

Machining Process - idea Material In Removal of chips Material Out - Not any type of materials could be cut: ceramic not - There is a family of machining processes: abrasive, etc. , which do tiny material removal for ceramic handout 9 machining process 4

Various types of machining processes Drilling Turning Peripheral milling Face milling handout 9 machining process 5

What job and quality level can machining processes achieve? - Dimension accuracy: 0. 025 mm - Surface quality: 0. 4 µm - Any shape handout 9 machining process 6

What are generic features with any machining operations to make cutting processes work? - Two motions: tool motion and work motion - Primary speed and secondary speed (or feed rate) - Relative motion between the two motions along with force to form chips and remove them o The above is for turning process by equipment called lathe o For drilling, work does not have motion, the tool will perform both primary motion and secondary motion. handout 9 machining process 7

Cutting Tools Mechanics of cutting (generic) handout 9 machining process 8

Frank face handout 9 machining process 9

Cutting Tools Major cutting parameters Material Removal Rate MRR = (v)(f)(d) handout 9 machining process 10

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Engineering Analysis - Material removal process: Chip formation, energy, and power - Tool life: tool failure causes quality problem - Productivity - Quality assurance handout 9 machining process 12

Theory of chip formation Orthogonal Cutting Model –converts 3 d to 2 d tc to Ls - Chip thickness ratio, r = to/tc (tc > to) - MRR = (v)(to)(w) )( handout 9 machining process 13

Theory of chip formation Cutting power Cross cutting power Specific cutting power E- Efficiency that accounts for loss of the machine tool handout 9 machining process 14

Tool life o Fracture failure: force becomes excessive, causing sudden brittle fracture o Temperature failure: temperature is too high, causing the material at the tool point to soften o Gradual wear: (1) crater wear (2) flank wear handout 9 machining process 15

o The objective of selecting tools should ensure that only the gradual wear mode will occur o Tool design: materials and geometry o Besides tool itself (system parameter), tool life is a function of operating parameters (d) (f) (v) Cooling methods ( fluids) handout 9 machining process 16

Productivity is also called removal rate which is computed by the following equation: (d) (f) (v) Quality System parameters Operating parameters Example: o Rough cutting (f: 0. 4 -1. 25 mm/rev; d=2. 5 -20 mm) o Finish cutting (f: 0. 125 -0. 4 mm/rev; d=0. 75 -2. 0 mm) handout 9 machining process 17

Summary System and product parameters Operating parameters (d) (f) (v) Power Tool Material Cooling methods Goal: Select operating parameters to ensure no failure with the whole system and satisfactory quality handout 9 machining process 18

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Design Considerations in Machining 1. Design parts that require little, and if possible, no machining • Use net shape or near net shape processes 2. Specify tolerances • Use tighter tolerances only where required 3. Specify surface finish • Use better surface finishes where required 4. Avoid machining sharp features (i. e. internal corners) where possible • Require sharp cutting tools that can break more easily q Avoid deep holes that must be bored • Difficult to maintain tool stiffness q Provide seats for drilling q Design part so standard cutting tools can access easily

Design Considerations in Machining q q Design with materials that have good machinability Design part features that use standard cutting tools • Avoid unusual hole sizes, threads, angles, and shapes requiring special form tools or special contouring Design part with simpler geometries • Minimize or avoid angles and contours where possible Design parts to have as few setups if possible • Changing position of part and changing cutting tool

Design Considerations in Machining q q q Design the sizes of machined parts, which are close to the standard available stock sizes • Less material to cut Design machined parts to be rigid enough to withstand cutting forces and clamping • Avoid thin and narrow parts Avoid undercuts as they require additional setups and special tooling

Summary: 1. Machining is a material removal process by cutting tools on work material (stock). 2. For machining, one need to select tools and operation parameters (v, f, d). 3. The selection criteria: tool life, quality. 4. The productivity is the multiplication of v, f, d. 5. Operating principle: chip formation with two important angles (rake angle, and frank angle). 6. DFM rules

Drilling machining https: //www. youtube. com/watch? v=om 6 GQKfo. S 1 g Milling machining https: //www. youtube. com/watch? v=Hf. Ia. ISnq. HOk