Week 10 - Challenge 1- Attachment Feature Creation (Ribs & Screw Boss)
AIM: To design the Door Handle component along with it's ribs and screw bosses through the given Class-A surface. To start with the design, the tooling axis for the given Class-A Surface is created meeting the requirements of the draft angle and at the end perform the Draft analysis on the model.
OBJECTIVE: To design the Door Handle component design from 'Close Surface' through given Class-A surface given in .CATPart. This can be done by designing Class-B and Class-C surfaces then trimming both the surfaces to get the actual closed surface. Then designing the required ribs and screw bosses considering the design rules mentioned in videos. The proper Tree Structure of the model is ensured. Publication is done by using the publication option by publishing the above Tooling Axis, Class A, B, and C surface from the Tree Structure. The sketches are Positioned Sketch and are ISO constriained.
DESCRIPTIONS:
Class A: It is the surface that is created by the concept sketches made by free hand sketchers. The finalised sketch is then fed to the computer and a 2D surface is created out of it by the use of a software like Alias. This computerized design is known as Class A surface.
Class B: It is a reference surface that is created by the design engineer and is a copy of the class A surface that is at a distance equal to the thickness of the part.
Class C: It is again a reference surface that is created by the design engineer to connect Class A and Class B surface also known as the side wall of the surface.
Ribs: These are the solid parts in the molded parts that provide a means to economical stiffness and strength in molded parts without increasing overall wall thickness.
Screw boss: These are the projections designed to accept inserts, self-tapping screws, etc. for use in mounting, fastening or assembling parts.
The technique that is used to create the model is to initially create a class B surface at a distance equal to thickness(3mm taken here) and later a vertical surface class C. Then the three surfaces were trimmed to obtain the required part.
PROCEDURE:
Class A Surface:
1) Open CATIA V5.
2) Open the downloaded 'Door Handle Class A.CATPat' in CATIA.V5 having the CLASS A SURFACE.
3) The CLASS A SURFACE was given it's shape and was saved as a .CATPart.
Tooling Axis:
1) The perpendicular or the below part of the handle or the base is being extracted through extract option.
2) The base area which is not inclined and covers maximum sides among the three axis X,Y and Z.
3) A point was created at the centre of that extracted surface.
4) A point was created between the extract at the middle of the surface.
5) Then a line was drawn along the point perpendicular to extract and on the point along Y-axis.
6) Then that line was was highlighted as the required tooling axis and named as "actual tooling axis".
Class B Surface:
1) One of the outer surface of CLASS A SURFACE was extracted surface by surface.
2) The entire surface was the offsetted below CLASS A SURFACE at 3 mm distance.
3) The surface which was not offseted was later filled with Fill command.
4) The filled and offsetted part was joined with Join command.
5) The joined part was given boundary with help of Boundary command for furthur operations.
6) The boundary part was taken for extrapolation of entire joined surface to 7 mm by Extrapolate command and that extrapolated part was named CLASS B SURFACE.
Class C Surface:
1) The boundary of each opening edges consisting of all four edges at the corners are obtained.
2) Then all those boundaries are subjected to swept operation with Swept command with different draft angle each.
3) Then the sides of all those swept components bounded are later extrapolated sideways.
4) Those extrapolated parts are then trimmed to each other to get a combined swept surface.
5) That combined swept surface is joined with CLASS A SURFACE and then we find something that we named as CLASS C SURFACE.
Final trimming:
1) All the surfaces made i.e. Class A, B and C were made visible for further operations and intersected to see any further non-intersections between those three.
2) Then the surfaces were trimmed to get a model of 3 mm thickness(t).
Ribs:
1) After creating a solid part of the door handle from final trimming, the surface where ribs must be created are selected with Multiple Extract command.
2) A point was created on the middle of the surface obtained from Multiple Extract command.
3) A positioned sketch was drawn on the surface which is a line.
4) With that line, a surface was extruded through Extrude command at a distance of H=3*t=9 mm.
5) That surface was later split with Split command to get the rib surface.
6) The rib surface was later thickened with Thick Surface command towards the point at a distance of the required thickness(w) given in the challenge, i.e. w=40% of t=0.4*t-0.4*3=1.2 mm.
7) Then the rib was inclined/tapered at an angle of 0.5 degrees from the neutral surface.
8) The tapered surfaces then are joined with the door handle solid part.
9) The tapered surfaces then are now given edge fillets at the corners of the ribs and rib root radius is measured.
10) The same thing from top to bottom is done for another rib with same features at a distance explained in video.
Screw boss:
1) The surface where screw boss must be created are selected with Multiple Extract command.
2) The screw hole sketches are made with positioned sketches.
3) The sketches are made solids through Pad commands at an height of 8 mm.
4) With required draft angle and edge fillet radius, the final part was then assembled with the main part.
5) That same part is translated, joined, drafted and filleted and finally assembled with the main part.
Draft Analysis:
1) In plastic design, the draft analysis or angle that is considered in the OEMs (Original Equipment Manufacturer) is 3 degree.
2) First thing to carry out was to select the compass and set it on the tooling axis in upward direction.
3) By clicking on the surface, the whole part turned into green colour. If blue was visible that meant that the analysis was inversely done so just by flipping the direction, draft analysis.
4) Then the hollow part was later created into a solid body by going the part body option and then selecting close body surface.
5) We can see draft analysis on the solid part resulted in green colours.
6) The green region shows the part which is toolable or produceable by the molding machine and the draft angle is 3 degree.
7) Blue colour region states that the part can be allowed in some OEMs but still need to be improved for the other OEMs as the draft angle is more than 3 degrees.
8) Red colour which is there in this case states that the draft angle is less than 3 or 2.7 degree and cannot be produced or if produced would be faulty.
NOTE: The tooling axis was adjusted in such a way so that to mitigate the red colour fault as much as possible and get desired design to get the draft analysis correct.
OUTPUT:
The outputs are given below in the form of screenshots of .CATPart as instructed above in the question for the completed model from Week 10 - Challenge 1- Attachment Feature Creation (Ribs & Screw Boss).CATPart:
a) 3D views:
b) Tree Structure:
INFERENCE:
The design was achieved through the tooling axis and Class A, B and C surfaces and doing the nessesary operations to get the closed surface. Next the thickening surface was solidified through 'Thick Surface' command. After that it's .CATPart was attached below and the entire report is submitted.