Module Title: Advanced CAD/CAM Module Code: 16-7106-00S
Module Tutor(s): Nicholas Pickett Assignment: 1 (of 1)
Hand-out Date: Week 4 (Semester 2) Hand-in Date: See Assessment Scheduler
Coursework Title: Design, Analyse and Preparation for Manufacture of a Retractable Utility/Craft Knife Using an Integrated CAD/CAM Software System
1.0 Coursework Rationale
This coursework aims to provide a variety of practical CAD/CAM related exercises using Creo Parameters 2.0 and its integrated applications. The tasks are intended for an intermediate user and include: solid and surface part and assembly modelling; part optimisation; detailed drawing; injection moulding; computer-aided manufacture; and basic part photo rendering.
1.1 Tutorials Classes
The tutorials for this module are intended to develop and support your practical understanding and use of a typical integrated CAD/CAM system. It is therefore important that your attendance is prompt and regular. Furthermore, it is strongly advised that all assignment work be completed using the University's computer facilities. The software used to complete this coursework is Creo; NO other CAD or CAM software may be used.
1.2 Submission of Work
Please submit a single written report together with all your CAD models via the module’s Blackboard site. The report should evidence, through discussion and selected screenshots, the successful completion of the tasks stated in this assessment. The maximum word limit for the report is 3000 words; please ensure to observe this limit. IMPORTANT, modelling activities undertaken where there is no visible evidence provided by either a screenshot or CAD drawings in your report will not be considered and will therefore not receive a mark. Your submitted CAD files will be checked for ownership and authenticity only.
2.0 Development of CAD/CAM Models/Analysis
Following the activities detailed below your task is to design, analyse and prepare for manufacture a retractable utility/craft knife (see appendix) using an integrated CAD/CAM software system.
2.1 Product and Part Requirements
The product and individual part requirements for your CAD assembly model of a retractable single edge utility/craft knife are given below.
Part Weight (g) Material Dimensions (mm)
(L x W x H)
Body back cover 12.6 ±0.2
(combined) Unspecified – A material of your choice 145 x 5 x 35
Body front cover Unspecified – A material of your choice 145 x 5 x 35
Locking slider (1/2 piece assembly) 1.6 ±0.2 Polypropylene 35 x 10 x 13
Rear end cap 1.8 ±0.2 Acrylonitrile butadiene styrene 23 x 10 x 40
Cutting blade 5.0 ±0.2 Stainless steel 107 x 0.2 x 17
Total 21.0 ±1.0
The design of the body front cover must incorporate the following:
• Recessed locating notches/ features to incrementally position the locking slider and thus extend/ retract the cutting blade;
• Consideration of left and right handed use;
• Ergonomic styling for easy and comfortable use;
• 1mm clearance channel for the blade;
• Cooling features for reducing the cycle time for moulding the part;
• A through hole for a attaching a lanyard;
• Snap-fit features for aligning and assembling the body back cover and rear-end cap;
• A slide channel for the locking slider;
The design of the body back cover must include the following:
• Consideration of left and right handed use to match that of the front cover;
• Ergonomic styling for easy and comfortable use, again to match that of the front cover;
• A through hole continued from the front cover for a attaching a lanyard;
• Snap-fit features for aligning and assembling the body front cover and rear-end cap;
• A 2mm clearance from the underside of the locking slider;
• Cooling features for reducing the cycle time for moulding the part;
• Locating features for accurately positioning the front and back covers ready for adhesive welding;
The design of the removable rear end cap should incorporate the following:
• A recessed cavity, matching the width and height dimensions (±0.2mm) of the blade, in order to insert (up to 8mm) the front end of the blade enabling it to then be snapped off manually;
• Ergonomic styling for simple and comfortable use;
• Consideration of left and right handed use;
• Snap-fit features for aligning and assembling the body front and back covers;
• Able to easily be removed and re-attached to the assembled front and back covers;
The design of the locking slider (1/2 piece part/ assembly) should comprise of the following:
• A working locking mechanism which utilises the recessed locating notches in the front cover;
• Ergonomic styling for obvious and comfortable use;
• Consideration of left and right handed use;
• A means to attach and secure the cutting blade;
• A means to sliding the 1/2 piece part/assembly when not locking the blade in position.
• A rough textured top surface;
2.2 Development and Demonstration of CAD Modelling Techniques
The CAD modelling of your knife must effectively demonstrate the following techniques, in order to observe the previously defined product and part constraints/ requirements:
• Definition of an overall skeleton model to establish the total volume required for the knife together with the knife’s initial assembly structure;
• Use of extruded, revolved, blended, patterned (at least 3 different types), rounded, chamfered, shelled and holed features;
• A top-down design approach for the body back cover based on the geometry (outer profile) of the front cover;
• Definition of the individual component assembly interfaces for all parts together with the complete assembly of the knife;
• The addition of the flexibility feature to the rear end cap in order to cope with changes to the blade dimensions;
• Definition of an analysis feature in order to complete a dimensional optimisation of the body front cover, so satisfying the combined weight constraint for it and the back cover;
• Interference checking between all parts once assembled to ensure no overlapping geometry;
• Use of basic surfacing and styling features to enhance to the appearance of the body back cover;
• Creation of orthographic drawings (.pdf format) for all parts (except the blade) detailing all dimensions, material, scale, units, part name, date and author;
• Creation of a general assembly drawing (.pdf format) of the knife, shown in exploded and unexploded views and identifying all parts together with a bill of materials, scale, units, date and author;
• Use of basic (i.e. limited scene creation) photo rendering techniques to show your knife assembly on a suitable work surface in a photo realistic manner;
As previously stated in order to evidence the successful completion of the above CAD techniques you must provide both a brief critical written discussion of your workings, justifying your modelling techniques, and the relevant, clear and unambiguous screenshots of your work. IMPORTANT: Please also ensure the above CAD drawings are included as part of your report’s appendices.
NB: The stainless steel cutting blade will be provided as an IGES part to download and use.
(Marks 40)
3.0 Body Back Cover Moulding Analysis and Tool Preparation
3.1 Moulding Analysis
For the first part of this task you are required to determine the mouldability, or the suitable for moulding, of the body back cover part for the purpose of injection moulding. This must be done by using an application called Plastic Advisor (or MouldFlow), which is integrated in Creo Elements/Pro 5 but not Creo 2.0. To get you Creo 2.0 part into Creo Elements/Pro you will need to export (or save as) your part as a STEP file and then open it in Creo Elements/Pro. To analyse and comment on the performance of your part you will need to demonstrate the completion of several steps, which include:
• Identification of a suitable injection point (or points);
• Establishing the best levels of confidence of fill and quality;
• Identify and reduce the location and amount of air traps and weld lines;
• Determine the best shrinkage factor for your chosen material and its effect on part geometry;
Once you have obtain the results of your study you should critically discuss, in no more than 300 words and using suitable screenshots, any issues relating to hesitation and race-tracking (i.e. injection points and part geometry), cooling (i.e. warping & shrinkage), flow disruptions (i.e. weld lines and air traps), part ejection. After which you should address any issues encountered, in order to improve your part’s mouldability (i.e. zero or very few (<10) air traps and weld lines, and high levels confidence of fill and quality) and then conclude, in no more than 200 words, the changes to either the process parameters and/or your part geometry that you have made. Please include Plastic Advisor's initial and final analysis reports of your back cover as part of your appendices.
(Marks 15)
3.2 Mould Tool Preparation
For the next part of the moulding preparation task you are required to develop a suitable mould tool (i.e. core and cavity parts) for the back cover of your knife, using another integrated application within Creo called Pro/Mold. In order to fulfil the completion of this task you need to demonstrate the following:
• Correct application of a shrinkage ratio;
• Definition of a silhouette curve;
• Establishment of a parting surface;
• Generation of both halves (core and cavity) of the back cover’s mould tool;
• Completion of the core and cavity parts by the inclusion of an injection point(s), runner(s), raiser(s) (based upon the previously determined position of the air traps) and clamping bolt holes;
• Creation of orthographic drawings (.pdf format) for the core and cavity parts (except the blade) detailing only the major outer dimensions, injection point(s), runner(s), raiser(s), bolt hols, material, scale, units, part name, date and author;
Again you will need to evidence the successful completion of the above mould tool generation activities. Therefore you should provide both a brief critical written explanation of your workings together with the relevant, clear and unambiguous screenshots of your work. Please also ensure the above CAD drawings are included as part of your report’s appendices.
(Marks 15)
4.0 Machining of the Back Cover’s Cavity Mould Tool
Your final activity is to prepare the machining activities for the bottom half or cavity of your back cover’s mould tool. This must be achieved using another integrated application within Creo called Pro/Manufacture. In order to successfully satisfy this task you need to demonstrate the following:
• Definition of the reference and work-piece CAD models;
• Definition of an operation(s), in order to identify the correct machine tool selection, establish fixturing requirements, machine zero point/ reference, retraction plane and part orientation;
• Creation of an efficient machining sequence(s) to remove material;
• Use of nc-sequences, such as volume, face off, and a drilling, in order to produce individual feature geometry;
• Definition of all required machining parameters (basic), cutting tool geometry and tool paths for each nc-sequence;
• A tabular summary record of each nc-sequence's machining time, % air time and a total machining time for the work-piece;
Once you have completed the above activities you will need to evidence their completion in your written report. Again, provide both a brief written critical explanation of your workings together with relevant, clear and unambiguous screenshots of each activity. Please also ensure the above CAD drawings are included as part of your report’s appendices.
(Marks 30)
5.0 Marking Criteria
2.2 Development and Demonstration of CAD Modelling Techniques Marks (40) Feedback Comments
Correctly applying and demonstrating the product and part design constraints/ requirements in all resulting CAD models. /8 Marks
Definition of an overall skeleton model to establish the total volume required for the knife together with the knife’s initial assembly structure; /2 Marks
Use of extruded, revolved, blended, patterned (at least 3 different types), rounded, chamfered, shelled and holed features; /4 Marks
A top-down design approach for the body back cover based on the geometry (outer profile) of the front cover; /1 Marks
Definition of the individual component assembly interfaces for all parts together with the complete assembly of the knife; /2 Marks
The addition of the flexibility feature to the rear end cap in order to cope with changes to the blade dimensions; /2 Marks
Definition of an analysis feature in order to complete a dimensional optimisation of the body front cover, so satisfying the combined weight constraint for it and the back cover; /3 Marks
Interference checking between all parts once assembled to ensure no overlapping geometry; /1 Marks
Use of basic surfacing and styling features to enhance to the appearance of the body back cover; /5 Marks
Creation of orthographic drawings (.pdf format) for all parts (except the blade) detailing all dimensions, material, scale, units, part name, date and author; /4 Marks
Creation of a general assembly drawing (.pdf format) of the knife, shown in exploded and unexploded views and identifying all parts together with a bill of materials, scale, units, date and author; /2 Marks
Photo rendering of your knife assembly on a suitable work surface; /2 Marks
Written critical explanation of your knife design and justification of CAD modelling techniques; /4 Marks
3.1 Moulding Analysis Marks (15) Feedback Comments
Identification of a suitable injection point (or points); /2 Marks
Establishing the best levels of confidence of fill and quality /4 Marks
Identify and reduce the location and amount of air traps and weld lines; /4 Marks
Determine the best shrinkage factor for your chosen material and its effect on part geometry; /3 Marks
Written critical discussion of your analysis and working; /2 Marks
3.2 Mould Tool Preparation Marks (15) Feedback Comments
Correct application of a shrinkage ratio; /1 Marks
Definition of a silhouette curve; /2 Marks
Establishment of a parting surface; /1 Marks
Generation of both halves (core and cavity) of the back cover’s mould tool; /2 Marks
Completion of the core and cavity parts by the inclusion of an injection point(s), runner(s), raiser(s) (based upon the previously determined position of the air traps) and clamping bolt holes; /3 Marks
Creation of orthographic drawings (.pdf format) for the core and cavity parts (except the blade) detailing only the major outer dimensions, injection point(s), runner(s), raiser(s), bolt hols, material, scale, units, part name, date and author; /4 Marks
Written critical explanation of your workings; /2 Marks
4.0 Machining of the Back Cover’s Cavity Mould Tool Marks (30) Feedback Comments
Definition of the reference and work-piece CAD models; /1 Marks
Definition of an operation(s), in order to identify the correct machine tool selection, establish fixturing requirements, machine zero point/ reference, retraction plane and part orientation; /5 Marks
Creation of an efficient machining sequence(s) to remove material; /2 Marks
Use of nc-sequences, such as volume, face off, and a drilling, in order to produce individual feature geometry; /8 Marks
Definition of all required machining parameters (basic), cutting tool geometry and tool paths for each nc-sequence; /8 Marks
A tabular summary record of each nc-sequence's machining time, % air time and a total machining time for the work-piece; /2 Marks
Written critical explanation of your workings; /4 Marks
Total /100 Marks NB: The minimum pass mark is 50%.
Appendix - Retractable Single Edge Utility/Craft Knife Exemplar (Drawings not scale)