Solids Work Models & Drawings

UNIVERSITY OF NORTHAMPTON FACULTY OF SCIENCE TECHNOLOGY SCHOOL OF ENGINEERING Year 1 Introduction to Design Module Code: ENG1004

1.0 Introduction & Objectives The objectives of this assignment are:

1 To demonstrate skills and competence in modelling 3D CAD solid parts 2 To demonstrate skills and competence in the creation of CAD assembly models 3 To demonstrate skills and competence in engineering drawing 4 To demonstrate skills in the processing and manipulation of CAD images

In summary, the assignment requires the production of: 1. Solid models of all parts shown in Figure 1 2. An assembly model of the complete Engine that is well constrained 3. A detailed part drawing of the Engine Block in orthographic layout 4. An assembly drawing of the complete assembly in orthographic layout

This substantial assignment has been designed on the assumption that you will allocate typically 15 hours to complete it.

2.0 Description This engine is a simplified version of a two-stroke engine often found in aero and car modelling kits. The two-stroke engine is an internal combustion reciprocating engine. The basic principle of operation of two- and four-stroke engines is essentially the same. These types of Internal Combustion (IC) engines are used in many engineering applications e.g. automotive vehicles, ships, motorcycles, electric generators, lawnmowers, chain saws, jet skis, propeller aircrafts etc. The IC engine is characterised by an operating cycle having intake, compression, combustion and exhaust. In a two stroke engine the operating cycle is completed in one revolution of the crankshaft (i.e. one up stroke and one down stroke of the piston), contrary to four stroke engines that require two revolutions. This is accomplished by performing simultaneously the down stroke functions (the end of the combustion and the intake) and the up stroke functions (the beginning of the compression and the exhaust). Two stroke engines have the advantage of an increased specific power when compared to four stroke engines, although they are less efficient and produce larger levels of pollution.

3.0. Mode of Operation In this engine model, the piston is connected through the gudgeon pin to the crank drive system, which comprises of a connecting rod and a crankshaft. The piston is restricted to a reciprocating up-and-down movement because it fits in a cylinder, with the same nominal diameter, at the upper part of the block. The crank drive system converts the reciprocating movement of the piston into rotational movement of the crankshaft. The

CAD Assignment

All the models & drawings produced for this assignment must be created using SOLIDWORKS.

crankshaft is equipped with a keyway that may be used to assemble a gear or a propeller. Both the cylinder head and crankcase are attached onto the engine block with M3 hexagon socket head screws. To understand how the two-stroke spark ignition cycle works, we must assume that the engine is already running. During the down stroke, intake occurs before the piston reaches the bottom dead centre (BDC). A mixture of air and petrol comes from the carburettor (which is not shown in this model for simplicity reasons) and flows, through a port, into the combustion chamber. The inertia of the crankshaft and its counterweight keep the engine rotating and the piston is forced to move upward compressing the air/petrol mixture in the chamber (it is also during the up stroke that the combustion gases that still remain in the chamber from the previous cycle are discharged through the exhaust manifold). This produces an increase in pressure (and, consequently, temperature) inside the chamber, which, with the help of a spark plug, and before the piston reaches the top dead centre, (TDC), will ignite the mixture and combustion will occur. This will generate a force pushing the piston downwards, forcing the crankshaft to rotate through the crank drive mechanism. In other words, the force pushing the piston is converted into a torque, and the cycle is repeated again.

Figure 1 and 2 depict the engine assembly components.

Figure 1. Engine assembly components

Figure 2 Engine Assembly Components

Details of the assembly components are shown in appendix A.

4.0 Assignment Requirements The engine assembly comprises of several individual parts, listed below. Detailed descriptions of these parts, including some dimensions, are shown in Appendix A. Note that some of the dimensions are not specified. In some cases, they are readily deducible from the related parts. In other cases the designer (you) should exercise good judgment to define appropriate values. You must model the following parts:-  Engine Block  Piston  Gudgeon Pin  Connecting Rod  Crankshaft  Crankcase  Cylinder Head  Hex socket Head Bolt M3 (or insert them from the SOLIDWORKS library)

Specifically, the assignment requires you to prepare: 1) Solid models of all required Parts. 2) A constrained Engine Assembly – see assembly details in appendix A.

(a) Show the finished assembly with unique colours for each separate part. (b) An assembly drawing in orthographic projection (c) Two configurations of an appropriate view with the assembly at the TDC and

BTC positions (d) A sectional view in the central longitudinal plane of one of these

configurations (e) BOM and exploded view of the assembly

3) A manufacturing detailed drawing (production intent) for the Engine Block only, showing at least 2 appropriate orthographic views, fully dimensioned and with appropriate tolerance values shown. A flatness tolerance of 0.02mm is required on the top mounting areas.

5.0 Guidelines for Modelling and Drawings

5.1. Solid models of parts These should not merely show the correct finished shapes, but as far as possible embody the design intent of the parts. This is typically achieved by ensuring:

 All profiles of 3D operations have appropriate geometric constraints  All profiles are dimensioned as necessary

The modelling should be done efficiently, that is, not using unnecessarily large number of operations and ensuring that operations are in the correct order i.e. fillets and chamfers should be the last operations in the tree.

5.2. Solid Models of Assemblies All of the required parts should be assembled complete with appropriate relationships so that they simulate the real-life application. The finishing touch is to set different colours for each separate part.

5.3. Drawings Only two are required, the Engine Block, and an assembly drawing, laid out in orthographic projection. These should be created from the solid models within the drafting environment. Remember that part drawings must show all necessary manufacturing data,

including tolerances. Appropriate sheet sizes should be chosen for each drawing. All drawings must conform to BS 308 (BS 8888). Refer to the course notes for full details of the standards and conventions for part drawings, assembly drawings, and orthographic projection.

6.0 Timetable for the assignment The assignment is issued on the ----------------------. There are approximately 3 x 2 hour assignment workshops for each group, as shown on the CAD Schedule for this module. It is essential that you do plenty of work prior to each of these so that you can identify any queries and discuss these with staff in the workshops. It is essential that you work over and above the contact hours to achieve acceptable results.

7.0 Submission requirements of assignment The assignment will be assessed from a concise report that clearly illustrates all aspects of the work. Additionally, as a backup, the finished models should be submitted to NILE. It is the report that will be marked, so it is essential that this is clear and comprehensive. The report should comprise mostly images of the models, and contain at least:

1. Informative line images of the Engine Block solid part that clearly show all details and all of the modelled-in critical dimensions (use sketch definition to display fully constrained profiles).

2. Appropriate selection of informative colour-shaded and line 3D solid images that effectively show the complete assembly; make appropriate use of the visualisation tools for this (different viewpoints, cutaway section, translucency, exploded views, etc).

3. A screen dump of the history tree of the Engine Block; this reveals how comprehensively and efficiently the part has been modelled. Rename each operation (via RMB) so as to give these informative names. Produce screen dumps for operations / commands you use to show that they have been fully constrained.

4. A screen dump of the Assembly Tree so as to show the overall assembly structure and the relationships for Engine Block. Size it appropriately so as to show clearly all information.

5. A manufacturing drawing (production intent) of the Engine Block in orthographic projection

6. An assembly drawing of the complete Engine showing the views as defined in section 4 above

7. A Bill of Materials (BOM) table for the Assembly (this must use the standard UH format, showing part Names, Quantity, Material etc) and should be part of the assembly drawing.

8. General; Add any additional comments that you think necessary to discuss issues with this assignment, significant problems that occurred, and any other items of interest missing components etc.

The report should be concise but be prepared with care, being effectively structured, with appropriate header/footers that show authors, course code, page numbers, etc. Each image should be appropriately labelled. Effective screen images of the models and the history trees are important, because marks will be lost for CAD images that are poorly presented, irrespective of how good the models may be. Note in particular the benefit of setting White Background for all the CAD solid images.

Note that the report should show the outcomes of your work, not the process of getting these. Therefore, there is no need to provide a storyboard sequence of how items were modelled.

8.0. Assignment Assessment &Submission This assignment assesses skills and application of both the effective use of SOLIDWORKS CAD modelling and engineering drawing. Marks will be allocated for:

% % Part modelling (7 parts) 40

Well modelled Engine block (evidenced from history tree) with all dimensions embedded & clearly displayed on sketches

20

Good shape & detail of all remaining parts (6 Parts) show sketches of command(s)

20

Assembly modelling 20 All parts added & in correct place Appropriate and comprehensive relationships applied (evidenced from history tree constraints) Separate part colours applied

3 15

2 Drawings 25

Assembly drawing (including configurations for TDC and BTC positions)

Manufacturing Drawing of Engine Block 10 15

Report 15

Good choices & standard & clarity of images Overall quality of report

5 10 100%

Note carefully that each of the aspects listed above will be assessed solely from the report, mostly from the images that you export from SOLIDWORKS. If these are lacking in any way then, irrespective of the calibre of the CAD models, marks will be lost. It is essential therefore that sufficient time is allocated to selecting and creating suitable images and preparing the report. For the backup you will need to submit a copy of each file that is involved i.e. each of the part files, each of the drawing files, and the assembly file to NILE.

Ensure that only the files that are your final effort, for assessment, are included – staff will not attempt to sort through a variety of possible files. File names should have your initials at the end. It is good practice in naming convention not to use spaces, and symbols such as “, @ - _ < >? / . ( ) + ^ % = etc. and must include your initials as part of the naming convention. The files must all be in the same directory (which must be the top level) or SOLIDWORKS may be unable to find related files. Ensure that your disc is clearly labelled with your Name & Course Code Use a separate disc for the submission not your original disc, because it may be several weeks before the disc is returned to you.

Ensure that the disc is securely contained in a suitable wallet (or similar) and securely fastened to the report.

The assignment will be assessed from a concise brief report that clearly discusses all aspects of your modelling work and should not exceed 40 pages including your drawings / screen dumps. It is the report that will be marked.

In accordance with university regulations, late submissions are subject to penalty

Include in your submission only the first page of the briefing sheet. ALL STUDENTS SHOULD SIGN THE PLAGIARISM DECLARATION SECTION.

Notes for appendix A

1. Some images are directly taken from CAD solid models. As such, the display of dimensions does not conform to recognised drafting standards.

2. Several dimensions are shown, but some are not shown and these are at your discretion

You are reminded of the university rules on plagiarism. There are various effective techniques for detecting whether a CAD file has been copied from another source. Any attempt to pass off another student’s work as your own will normally result in zero marks for both parties, and possibly further penalties in this module. If plagiarism is proven then a note will also be entered in the student’s record

i. Guidance on avoiding academic assessment offences such as plagiarism and collusion

is given as: http://tundra.northampton.ac.uk/results/showimage.asp?j=Undergraduate Handbook 2012/13&index=21648

Appendix A

Appendix A

Appendix A

Appendix A

Appendix A

Appendix A

Appendix A