CAD Report

USER CONSOLE DESIGN

Computer Aided Design

08MMC300

David Coombes

A575990

MMC300 – Computer Aided Design David Coombes – A575990

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Objectives

The overall objective of the activities carried out, along with this accompanying report, was gain a practical

understanding when it comes to using a wide range of software across various design and manufacture

activities of a consumer product. This was completed through the medium of NX Unigraphics and

accompanying additional programs. This leads to a detailed understanding of the important issues

encountered.

Introduction

A control console for a treadmill training machine was chosen as the customer product for the purpose of this

project.

The report will detail the full process taken from initial design all the way to the rendering of the final product.

Firstly the report will concentrate on the design and the shape analysis included in the design. This will include

the analysis of the radii and the surfaces within the design and corrective measures taken as a result of the

analysis. Next the assembly will be assessed, giving details to how it took place and how any problems were

overcome. The next discussion will orientate around the obtaining of the CNC manufacturing information and

the analysis post process. This will be completed through ‘Vericut’, which simulated and verifies the

manufacturing data. The report will then look at how the model was ergonomically tested using a human

modeller from within NX. Finally the report will display the rendering images that can be achieved using NX.

In order to cover all the above sections, the report will be broken down into the following sections;

Design and Analysis

Manufacture Analysis

Ergonomic Analysis

Structural Analysis

Data Transfer

Design Illustration

Design Specification

1. Must fit and attach to the provided treadmill

2. Must have a flat bottomed surface

3. Must be a single casing and designed using freeform features in NX

4. Must include the following features

a. Speed Control

b. Incline Control

c. Start Control

d. Stop Control

e. Emergency Stop

f. Programme Selection

g. LCD Data Display

5. May also include optional extras such as heart rate monitor, drinks holder, ipod/mp3 connection etc

6. Should be aesthetically attractive and ergonomically sound.


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Following the design specification, figure 1 shows the finished model.

Figure 1

The model has combined the stop and emergency stop buttons. Alongside this, the start button has been

combined with the select button within the programme selection controls.

Design and Shape Analysis

1. Demonstrate the casting is consistent and without small radii and/or unwanted inflections

2. Use the dace analysis tools to test the reflective aesthetics of the casing

The first stage in the design was to establish the basic shape; this was completed by using freeform features in

the sketching function of NX. The part was designed in two halves; initially the hand side was fully modelled

and then mirrored to produce the left hand side. This meant there was a need to ensure that the join between

the two parts was smooth, this involved ensuring the curved outer edge was perpendicular to the mirror line

(figure 2).

Figure 2


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After the outer shape was perpendicular to the mirrored line, analysis of the curves was performed. This

involved creating combs on the curves; this gave a visual aid to show any areas where curves occurred that

didn’t flow or any areas where small radii occurred. Figure 3 shows an uneven curve and figure 4 shows the

same curve rectified.

Figure 3

Figure 4


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Following this shape analysis, the first half was extruded and altered using freeform features. Initially a swept

was completed, this is a three dimensional curved surface applied to the component. For this to be completed,

two sketches need to be created, on different planes that dictate the shape of the curve (YC-ZC and XC-ZC

planes, i.e. perpendicular to each other). Figure 5 shows the two sketches, the sketch running away from the

mirror line needs to be perpendicular to vertical again, to ensure that when the components is mirrored there

are no inflections and the part has a smooth surface.

These two curves were then analysed in the same way as the curves which dictated the overall shape. These

two curves provided the swept shown in figures 6 and 7.

Figure 5

Figure 6


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Analysis of the face was then completed, this entailed producing a rendered surface which gives a visual guide

to the radii on the surface and indicates any errors of form which may have been produced. Figure 8 shows

this analysis.

Alongside the image above, other methods of rendering the surface can produce methods of finding any issues

with the surface. Hedgehog method shown in figure 8 and contour lines method shown in figure 9

Figure 7

Figure 7


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After this analysis, the reflections tool can be used to ensure there are no inflections are errors of form. The

model can be rotated with this rendered surface still applied, showing any problems. Different images can be

applied to the surface to aid this analysis, figure 10 shows this reflections tool in use.

Figure 8

Figure 9


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Finally, section analysis tool provides curvature comb which indicates any uneven curves. Figure 11 shows the

swept with an uneven curve, this is corrected in figure 12.

Figure 10

Figure 11


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After all this analysis was completed, the part was ready for more features and completing. After this shape

was completed, another extruded curved surface was applied above this initial surface (figure 13). From this

new surface speakers were extruded to provide an extra for the user. Beside the speakers, a LCD screen was

applied to the centre of the console (figure 14). Next, a flat surface was extruded; this will hold all the

necessary buttons and radii were added to numerous corners. Penultimately variable radii were added for

aesthetic reason, drafts added to the vertical faces to aid manufacturing. Finally the single half was mirrored

and recesses added for the buttons (figure 15).

Figure 12

Figure 13


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Once the basic model was created, assembly of the buttons took place. This involved modeling the buttons to

the exact size of the recess created and constraining them into the designated recesses.

Manufacturing Preparation

Once the design was completed, manufacturing processes need to be completed in order to verify the design.

Before any manufacturing can take place, there are numerous stages of preparation that needs to take place.

Actions that need to be completed include;

1. Use the casing design to generate a cavity for a mould tool

2. Adjust the cavity geometry to resolve any problem features

The first stage was to simplify the casing in order to produce the cavity. An over complex cavity would increase

manufacturing time and make the process too expensive and the product not economically viable. Then a

Figure 14

Figure 15


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block is extruded around this simplified model, and the model subtracted from the block. This produces a

negative of the current mould (figure 16).

Then a blank is produced matching this cavity, this will act as the stock material that will be removed in order

to produce the cavity. This is changed to a different colour so it is easy to define between the part and stock

material. Also numerous parameters are set, such as; clearance planes, lower level, start and finish points.

Figure 17 shows the difference in colours and the parameters set up.

Figure 16

Figure 17


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The next step was to ensure that no over small features were in the cavity, making it impossible to

manufacture. This was completed by another analysis tool. Figure 18 shows the analysis of the radii; it shows

that no radii are lower than 5mm which is suitable for manufacturing.

Manufacturing Data

Once all the analysis is completed, the next stage is to produce the manufacturing data.

1. Use appropriate machining methods using NX manufacturing to produce the cavity

2. Tool selection and assignment of speeds and feeds.

3. Process plan and shop floor documentation.

The first stage of this would be set up the tools. With the smallest radii being 5mm, the smallest tool would

need to mimic this radii, it was decided from here the other tool sizes would be 20mm diameter for semi

rough cut and a 30 mm diameter for all rough cuts. Figure 19 shows the set up of the tools and all parameters

that accompany them.

Figure 18

Figure 19


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The first step was to produce an overall rough cut for the part. This was completed using a cavity mill

technique. Figure 20 shows the cutting path the tool will take when run.

Secondly, all steep walls were finished. This included 4 processes; the first was a semi cut for the walls in the x

direction, followed by a semi cut for the walls in the y direction. Then 2 finishing cuts were applied, one for

each set of walls on each the x and y axis. Figure 21 shows one of the finishing cuts. Alongside this, the cutting

paths were altered in the final cut, to ensure that no excess material was left. This was also ensured by

changing the stock levels left. In the rough cut, the process left 0.5mm of stock, the semi rough left 0.25mm of

stock and the finishing cut left 0mm of the stock.

The final step was to repeat the semi and final cut, but this time for non-steep walls; this included the floor.

Similar steps were taken to ensure all the stock was removed; this included changing the tool paths and

removing stock levels left. Figure 22 shows the final non steep wall pass.

Figure 20

Figure 21


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After every process was set-up, it would be beneficial to group all processes that use the same tool together;

this would reduce the tool changes and directly reduce the production time. The meant that the rough cut was

followed by all semi rough cuts and the whole process was finished with all finishing cuts. Finally all the

processes can be generated and run simultaneously to produce the full manufacturing process. Figures 23 to

29 show the results after each process.

Figure 22

Figure 23

Figure 24


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Figure 25

Figure 26

Figure 27


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Once this was completed, it was a case of adjusting all speed and spindle rates. For this the table below gave

all the information required. All rough cuts were completed with a 30mm cutter, all semi cuts with a 20mm

and all finish cuts with a 10 mm cutter.

Table 1

Figure 28

Figure 29


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Verification of Manufacturing Data

After the process was completed within the NX program, an add-on program was used to verify the entire

process, “Vericut”. This program allows for accurate verification, as well as highlighting any errors within the

manufacturing.

1. Use Vericut to verify the CNC data

2. Compare machined model with the design model

3. Measure data on machining time and metal removed.

The CNC data was imported into “Vericut” and the process was run. This gave a real 3D of the process taking

place. Table 2 shows progressive images of the “Vericut” simulation. Once completed it was easy to see where,

if any problem occur. Figure 30 shows that the manufacturing had zero errors.

Rough Cut

Semi Rough Steep 1

Semi Steep 2

Semi Non-Steep

Finishing Steep 1


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Table 2

This figure also shows that the process took 2239 seconds, almost 40 minutes. Initially there were two errors

within the process, by consulting the log it was easy to identify the errors and correct them. Both the initial

errors occurred when the semi cut on the steep walls initiated. The tool came in at sharp an angle, this was

corrected within NX and the result was the figure shown above. After all errors are removed, it is possible to

compare volumes between the produced part and the pattern. Figure 31 shows the difference between the

two parts, as nothing is visible on the screen, there is no difference between the two parts (to 0.05mm, which

is what the tolerance is set to).

Finishing Steep 2

Finishing Non-Steep

Figure 30


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Ergonomic Analysis

With this being a consumer product, and directly used by the user. It is vital that all parts are accessible during

use. This was verified by inserting a human model into NX and showing the reach zone of different sized users.

The ergonomic testing included;

1. Add a human model to the treadmill assembly

2. Set an appropriate posture

3. Evaluate the hand reach conditions for the console for a selection of different body types

For this analysis, four models were used. A male at the 5th

percentile, one at the 95th

percentile and two

females using the same percentiles. Figures 32 to 35 show their natural stance.

Figure 31

Figure 32 – 5% Female


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Figure 34 – 5% Male



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This shows the users in their neutral stance on the machine. Figure 36 shows the reach zone for the smallest

user (5% female). This shows that all areas of the console are accessible to this user, and thus, all users while

not using the equipment.

When using the equipment, the user may move away from the console down the treadmill. This movement

may make the console inaccessible. This combined with a different posture for running may make it

considerably harder to access the console controls. Figures 37 to 40 show the reach zone for four models

whilst using the treadmill.

Figure 36



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The four figures above show, that whilst running, all the console controls are fully accessible.

Design Stress Analysis

The next stage was to complete stress analysis on the part. This involved launching the wizard within NX to

produce numerous results regarding stress, yield stress and displacement. The stress analysis involved;

1. Using NX structures assess the handle structure for the default maximum loading given the

appropriate BS.

2. Select a material and tube diameter which will perform satisfactorily with the given maximum load.

The British Standard regarding the strength of treadmill handle dictates that the handrails/front handle bar

must withstand a force of 1000N vertically at the most onerous point without failure or permanent

deformation. This should also be completed using a horizontal force of 500N at the same point, again

producing no permanent deformation and resulting in no failure. Images 41 and 42 show the displacement and

the stresses imparted onto the handles.

Figure 42

Figure 41


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Figure 41 shows the displacement of the handles. This image shows a maximum displacement of 19.05mm. As

figure 42 shows, the stresses on the handles with this vertical force exceed the yield stress of the material; this

will result in permanent deformation of failure. The yield stress of the material is 241.6MPa; the maximum

stress that occurs within the handles is 247.2MPa. This means that the handles do not conform to BS when

receiving load in the vertical direction. The same horizontal analysis is shown in figures 43 and 44.

Figure 43 shows the maximum displacement of 5.73mm, when 500N are exerted horizontally on the handles.

The second image (figure 44) shows that the yield stress is not reached when this horizontal force is applied. A

maximum of 117.4MPa is reached. The horizontal loading conforms to the BS. With the handles failing under

vertical loading, design alterations need to take place in order for the treadmill to conform to BS. The handles

need to be made stronger in order for them to abide by British Standards regulations. The diameter of the

tube was increased from 25mm to 35mm to try and improve the strength of the handles. The same vertical

analysis was completed on these stronger handles and the results are shown below.

Figure 44

Figure 43


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Figure 45 shows that maximum displacement has been reduced from 19.05mm to 4.71mm. The second image

is where the main improvements in strength lie. This shows that the yield stress is again 241.6MPa, but this

time the maximum stress that the handle undergoes is 85.18MPa. This results, in no failure and zero

deformation, meaning it fits within the BS regulations.

Data Transfer

Data transfer between CAD systems is extremely relevant in the industry today. There is a need to transfer

CAD model between companies, these companies may not be using the same software, and this can cause

numerous problems. From personal experience it is imperative that this transfer of information is completed

as it vital to the success of the project and hence product.

The following images (figures 47 to 54) show the reflective shape analysis applied to the data transferred and

how it compares between software; the software is shown below each figure. Alongside this a small amount of

analysis of the part has been completed below each diagram.

Figure 45

Figure 46


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Parasolid file import. This model was imported easily and provided an editable model, as the figure above

show it gave a surface finish to model also. The volume for this model was 226722.671119592mm2.

IGES file import. Again the surface finish on this file import was relatively good. The difference came in editing

the model. Once the part was imported, the parts list becomes two bodies once the sew faces are selected.

The volume for this part was 226667.586108155mm2

Figure 47

Figure 48


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STEP file import. This created a model that could not be edited as the part list for this model was under one

body. Despite this the surface is good again and the volume is 226753.792005957mm2

JT file import. This produced a part with good surface finish, but with numerous other problems. There were

no parts in the part navigator to edit and it was impossible to determine volume. This makes this model only

suitable for a visual representation and with it impossible to select edges it cannot be added to an assembly

and constrained.

Figure 49

Figure 50


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VRML file import. This import produces a model which has 80 topologies and 10892 facets, this large number

of facets produces a poor surface finish as it comprises of numerous small flat surfaces. This part is also un-

editable and provides no information regarding volume.

Catia file import. This file is imported in the form of one large body. This body is shown in the parts list but

cannot be edited. The volume for this model is 226575.542480758mm2

Figure 51

Figure 52


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Solid Edge file import. This imported model has a good surface finish but is under one body and can’t be edited.

The volume analysis for this shows 226722.6686mm2

STL file import. This produces one topology with 14126 facets. This large number of facets led to a poor

surface finish. There are no parts within the parts navigator making it unable to be edited and the volume

cannot be found.

There are issues that arise from data transfer; the main one being that is very difficult to keep the model up to

date. From personal experience I encountered models, from a third party, that were months out of date. This

is where metadata management comes in to allow better life cycle management of a product.

Design Illustration

The final stage of this project was to produce rendered images that can give an accurate visual representation

of the product in working conditions. Within the visualize shape tool, there are many variable which can be

Figure 53

Figure 54


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altered. These include: materials for the part, colors, lighting, backgrounds, reflections, shadows and sceneries.

The images below show the rendered console with some of these variables changed.

Figure 55

Figure 56


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Figure 58

Figure 57

Figure 59


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Conclusion

This project has shown that are numerous relevant issues when designing a user based product. The analysis

has shown that there are a number of relevant issues within the activities that have been carried out through

the project work applied to the treadmill console design that are naturally transferable to industry. The initial

modelling analysis shows and flaws in the design and problems that may be encountered later on can be

captured here and rectified before the process continues further. The manufacturing stage can give

organisations an idea of the time scale needed to produce the product and will also highlight any problems

that may be encountered during the production. The strength and ergonomic analysis should take place before

the manufacturing stage ideally. This would mean that any fundamental problems within the design can be

rectified before manufacturing simulation is completed. The strength analysis will hopefully eradicate any

problems the product may encounter while in use and the ergonomic analysis will capture any fundamental

design flaws while in use. The rendering is for purely aesthetic purposes but could be used heavily within the

marketing of the product. For each there are advantages and drawbacks; it is evident that it is impossible to

cater for the needs of everybody when creating software for such applications, what is important is that the

tools enable improvements to design activities which in turn allow more accurate cost effective manufacture

to take place, which is the aim of all companies in industry.

Figure 60

CAD Report

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