Machining Processes

Not applicable

In theoretical and theoretical-practical classes, the expository and inquisitive method is used. In laboratory classes, students train the main tasks performed on conventional machine tools, producing various mechanical components with the help of machine tools available in the laboratory. In a machining center, programs are developed in CNC language, and the created programs are executed.

The Machining Processes unit intends to transmit the theoretical and practical knowledge of the process of obtaining parts in a gradual way, starting from an initial form, raw or semi-finished, to its final shape and dimensions, through cutting by machining. Principles of working with conventional and CNC tool machines are learned.

– know how to use different conventional and computerized machining processes involving equipment, tools, cutting parameters and programming.

– Know how to elaborate and interpret drawings and technical schemes, making use of the latest computer-aided design tools.

– Know the properties and fields of use of a wide variety of engineering materials.

– know how to use technological manufacturing processes, including computer-aided manufacturing systems.

– Know and know how to use the main measuring instruments used in mechanical components.

1. Tool Machines and Main Machining Operations
Conventional machine tools and CNC machine tools and nomenclature of machining axes.
Accuracy, resolution and repeatability of tool machines.
Machining principles relating to the main cutting operations: Sawing; threading, grinding, boring, drilling, turning and milling.
Mathematical formulas for calculating cutting parameters for different machining operations.

2. Geometry of cutting tools
Geometry of the tools for turning, milling and drill.
Rake face and rake angle, relief face and relief angle.
Main cutting edge and secondary cutting edge. Tool tip.
Left, right and neutral tools. Edge radius.
Analysis of the geometry of the main cutting tools.

3. Machining force and power
Cutting force, feed force and penetration force
Specific cutting pressure.
Calculation of machining power and material removal rate.
Characteristic torque and power curves of the machine tool spindle

4. Machinability of metallic materials.
Machinability assessment methods and indicators.
Properties that influence the machinability of the materials to be cut.
Machinability Analysis of metallic alloys: Alloyed and unalloyed steels; Gray Cast Irons; Aluminum alloys; Copper alloys; Nickel and Titanium Alloys; Stainless steels.

5. Materials and wear of cutting tools
High speed steels; Sintered carbides; Cermets; Ceramics; Ultra-hard materials.
Cutting tools with and without coatings.
Characterization of the main modes of degradation and evaluation of tool wear.
Wear curves and tool life

6. Lubrication and cooling in cutting and chip formation
Classification of cutting fluids;
Cutting fluid application methods;
Chip formation mechanisms and chip shape classification;
Built-up cutting and chip breaking edge;
Friction and heat generated during cutting.

7. Dimensional metrology
Measuring devices used to measure mechanical components: Caliper and micrometer
Standard blocks and gauges.
Measurement operations with different instruments.
Evaluation of the roughness of machined surfaces.

8. Conventional machine tool operations
Execution of operations of turning, milling, grinding and drilling.
Interpretation of technical drawings

9. Computer numerical control programation (CNC)
Coordinate system.
Relative and absolute coordinates. Cartesian and polar coordinates.
Codes used in CNC: Preparatory functions (G codes), auxiliary functions (M codes).
Reference points: Rules for selecting reference points. Tool change procedure.
Tool length and radius compensation.
Linear and circular interpolation.
Main program and subprograms.
Drilling and Threading Cycles.
Execution of the main operations in the Leadwell Machining Center with Fanuc Series O-M Controller and execution of CNC programs, using metallic and non-metallic materials.
Demonstration of turning and milling operations on CNC machine tools.

For the purpose of evaluating the curricular unit, it is divided into 3 components with the following designation:

- Component 1: Conventional Machining Practice
- Component 2: CNC laboratory practice
- Component 3: Theoretical and theoretical-practical concepts

The evaluation of the curricular unit is carried out solely by written test, it being possible for the student to submit to a form of evaluation in which a test is carried out in the middle of the semester and the rest is carried out during the period of normal or recourse exams (evaluation method I) .
Alternatively, a single final exam taken during the exam period (evaluation method II).

• Evaluation Method I

a) After finishing the laboratory component of conventional machining, in the eighth week of classes, a test is carried out on the contents taught in the laboratory classes. This test includes the syllabus mentioned in points 7 and 8 (component 1 – conventional machining practice).

b) At the normal or alternative exam period, the test consists of two components: One component concerns the syllabus taught in the laboratory classes mentioned in point 9 (component 3 - CNC laboratory practice) and the other component concerns the syllabus taught in the theoretical and theoretical-practical classes, mentioned in points 1, 2, 3, 4, 5 and 6 (component 3 – Theoretical and theoretical-practical concepts).

c) In each of the 3 components the student will have to obtain a minimum grade of 6.0 points, the final grade being the arithmetic average of the 3 components performed. To pass the curricular unit, it is necessary that the final grade is equal to or greater than 10 values.

d) In case the minimum score of 6.0 is not achieved in the component carried out during the semester, in the test carried out during the exam period, it is necessary to answer this component additionally.

e) To follow this evaluation method, a maximum of 2 absences from laboratory classes are allowed (1 absence from conventional machining classes and 1 absence from CNC classes).

f) Students who attended laboratory classes in previous academic years may opt for this evaluation method, without the need to attend laboratory classes in the current academic year. However, it is mandatory to perform  all components evaluations.

• Evaluation Method II

a) Evaluation by a single test, carried out at any time of exams and related to all the contents covered in theoretical, theoretical-practical and laboratory classes (component 1 + component 2 + component 3).

b) The final grade is the arithmetic average of the 3 components performed, requiring a grade greater than 6,0 in each component.

NAO