solid modeling project: reverse engineering of a product and documentation of its solid model

7/28/2019 Solid Modeling Project: Reverse Engineering of a Product and Documentation of its Solid Model

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Solid Modeling Project: Reverse Engineering of a Product and Documentation of its Solid Model

By: Yussef Rikli

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Overview:This is a report documenting the modeling of a normal steel hammerhead, acquired at a 99c store. It does not

have a brand name or model, only the words MADE IN CHINA molded into the rubber grip. Fig.1 below showsan isometric free hand drawing of the hammerhead.

This report contains a lot of the gathered information, but not all of it. It is accurate but not enough to be a step-by-step guide to reproduce the work done, but rather a chronicle of how the SolidWorks model was brought toexistence.

Figure 1: the hammer modeled.

Procedure:After finishing some SolidWorks tutorials and sketching the free hand drawing, an idea of both what SolidWorks

is capable of, and of the distinctive features of the model, was gained. However, a clear plan on how to use theformer on the latter was not instantly evident, and so the approach taken was to iteratively take dimensions andtry to model, and then go back to measuring if necessary. The loop will be repeated as many times as necessary.

Basic straight forward measurements:The most obvious dimensions were taken using a Vernier caliper and added to the freehand


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Figure 2:1st version of freehand sketch, final version is attached.

Free hand detailed views were added for the rectangular hole of the handle, and the underside of the tail of thehammer, the original of those is attached.

A contour gauge was used to copy the necking groove between the hammer nose and midsection, luckily, the

contour was the same all around the groove, which is where the contour gauge proved handy. However,reproducing the groove on paper was not easy nor accurate. The contour also seems to be a single arc from acircle, but attempts to determine the center and radius of the circle yielded conflicting results, so this part was

abandoned for now, to be returned to later if necessary.


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Figure 3: the contour is the same all around.

The measurements collected so far seem enough to start modeling, which was initiated as follows.

Modeling:

Midsection:A new sketch was created, the intention is lofting three cross sections vertically to create the midsection of the

hammerhead. A rectangle in the top plane (here used as the bottom plane) was sketched with its center being thecenter point. Two reference geometry planes were created above it. The one in the middle was to account for theslight increase in sides width of the hammerheads vertical profile.Which clearly is due to a draft angle requiredfor casting a part.

A ruler was used to determine the relative horizontal placement of the topmost and bottom cross sections. Their

leading edge project on each other vertically.

Vernier calipers were used to determine the widest part of the midsection, a felt tip pen and a ruler was used todetermine the rectangle which will account for these bumps in the loft.

All were dimensioned accordingly; the topmost (third) plane was inclined such that the leading edge was higher

than the hind one with an angle . Attempts to create an inclined reference plane and projecting the

sketch in the third plane on it consumed so much time and were fruitless. Next 3D sketches were attempted, andworked like a charm. For now.


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Figure 4: inclined 3D sketch instead of rotated reference plane

Finally, the mid-plane was drawn and the loft attempted. At first, the 3D sketch seems unresponsive to anything,whether it is surfaces or solids, a verity of venues were tried but none worked, the internet was not that helpful

either. By chance after trying a solid loft a bubble appeared near the mouse pointer right after selecting the final

plane(the one with the 3d sketch),which didnt show up before. That bubble allows you to select an open orclosed contour, which worked with the 3D curve. However, two corners had to be removed from it so it can loft

without twisting with the other sketches (four corners).

The bottom end constraints were set normal to profile and applied to all. The hind side of the hammerhead

midsection will be taken care of when the tail is modeled. With no idea how to measure the tangent length, thevalue was varied until the preview looked acceptable (settled on 0.5).

As for the top end constraint, the option of normal to profile was not available, most likely because its a 3dsketch. Therefore, a normal vector is sketched at the corner and used as the direction vector for the constraint. As

with the bottom end constraint, the tangent length was set to 0.7.


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Figure 5: midsection loft

The review looks perfect. When OK is clicked, SolidWorks gives a failed to knit surfaces error. Trying again does

not fix anything. Google finds an answer that works; to use surface lofting and not solid lofting. Even though thehammerhead is solid and not a hollow surface, that can be fixed later.

Hammerhead nose:More dimensions were taken of the hammer nose using the calipers, mostly about its relative position to the

midsection, an interesting method to find the horizontal distance between two features is by using the built inruler in the contour gauge, which gives the distance between the pins. So its as simple as pressing the contour

gauge into the features while holding the contour gauge as parallel as possible to the axis the distance ismeasured on (setting them both on a table might help), then subtracting the needles distance readings.

As for the vertical distance between the circle of the nose and the top and bottom planes; the hammer was laid

on the edge of a flat table, with the handle vertically up (later repeated with it down), and the circumferentialcircular surface of the nose was put flat on the table edge. A ruler was then used to extend lines into themidsection with a felt tip pen as shown in Fig.6.


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Figure 6:extension of nose profile into the midsection with a green felt tip pen.

The hammerhead midsection loft was edited by replacing the topmost straight leading edge by an arched onerepresenting the freehand sketch. An important detail which cant be seen in Fig.5.

Figure 7: making the leading edge of the middle section curved.

All measurements were added to the freehand sketch. The sketch was started by creating two parallel verticalplanes, one for the circle of smallest radius in the hammer nose and the other is the beginning of the flat portion


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of the nose tip. Since the tip is flat, it will not be included in the loft, but extruded later separately to keep its

angles and flatness.

Lofting the two circles to the loft side is not possible at first, as the front face of the midsection is not really

defined as a profile, after trying several thing it was possible toright click on the face and isolate it, with a buttonto isolate it hovering nearby, the loft was created without any problems, as a solid and not as a surface as well,

the end conditions were not changed as it looked just fine.The nose thickness is extruded next, its draft will be added later.

TailThis part is the hardest part, not only is the shape irregular and lacking an abundance of standard shapes, but the

biggest problem is the horrible finish of the surface, with some bits sticking out and others chipped off,

measurement difference is bigger than usual. Selecting the SolidWorks approach to modeling this part with theminimum amount of measurements for less error, is not easy.

Figure 8: horrible surface finish, tail section.


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General measurements taken before were double-checked and cross-referenced; some were added to the detailed

view of the underside of the tail in the freehand sketch.

Measurement methods included projecting the bottom side edge of the midsection into the tail to easily measure

the depth of the tails tip, using a ruler and a felt tip pen. Also a double sided tapewas used as memory foam tocapture the end profile of the tail. As well as the contour gauge used to capture the upper and lower curves from

the midsection to the tails tip.

Figure 9: one of the measurement method, point of intersection marked with a felt pen later.

Started in SolidWorks with a sketch in a reference plane below the top plane, since the lowest point in the whole

hammerhead is the tails tip profile, which was sketched into the plane and dimensioned accordingly.

Making a 3D sweep over the tails profile captured by the contour gauge would not work, because the cross

sections of the two tail parts are not constant.

Next a reference plane is made from which the tail will protrude from, a horizontal line is drawn with its

respected distance from the top plane which splits the hind surface into an upper and lower part, then split itagain vertically in half, and project the vertical line onto the hind surface.


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Figure 10: sketch for lofting the tail. the nose is hidden from here out.

After this, we split the physical hammer head into four parts for lofting. Part1 will be discarded for the time beingand added later as a fillet, as it connects the two surfaces of the midsection and part2 with a simple curve of

constant radius.

Part2 protrudes from the midsection as a single piece. Part3 is split into two parts connected at a line, and part4

is fully disconnected.


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Figure 11: illustration of the 4 sections of the tail.

The right half is then lofted to the tail end profile, with a start condition of being tangent to the upper lateraledge of the midsection, previously converted into a sketch entity. The results are unsatisfactory, as increasing, the

tangent length would not give the tail its inclined curve, and reducing or removing the tangency removes thecurviness all together.

After using a protractor with an arm to measure some angles to add for the start/end conditions, and adding

angles of and 20 to the tangency vectors were added to the start/end constraints. The tail had an initially

acceptable curve, but when lofted the cross section was all conflicted and twisted.

The cross section of part2 and part3 have the same base width but different heights and both are symmetric withregard to the vertical axis, so drawing the cross section for part3 is easy by tracing the shared outline of part2

while sketching from a vertical view. The measurements are plugged from the freehand and the loft created.

After isolating the midsection loft surfaces and creating the loft, it does not look acceptable as can be seen in(Fig.12)

1

2

3

4


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Figure 12: unacceptable loft of the tail.

Therefore, it seems an extra profile sketch is needed to get a decent loft, so one is added in a reference plane

separating part2 and part3. The profile is added to the existing loft and the results are much more acceptable,even great, compared to the previous one (judgment by eye).

The second half of the tail is quickly done; un-hiding the cross section sketches (they automatically get hidden

after being used in a loft), isolating the hind surface of the middle section, lofting the three profiles, untanglingthe loft, leaving the start and end constraints at default as the third cross section took care of the need for that,

and thats it.

The main features of the hammerhead are finished; we now attend to the small details.

Part1 of the tail, the fillet:Since Laminar edges cannot be filleted as SolidWorks reports as it refuses to add a plane fillet or a solid filletalong the edge or between the surfaces. A work around is to measure the distance between the points tangent tothe fillet circle, draw the points and make a reference plane out of them, sketch the fillet as a part of circle and

sweep it along the edge. That workaround did not work for a multitude of reasons, least of which is unavailabilityof surfaces or their edges to sketch on. An arc sketched on the original front plane and swept through the underedge (which is a sketch and not a surface), is impossible to cover, fill in, trim or cut.

Another approach is to draw lines in the top and side surfaces and project them on the surface then use theirintersection with the curves to sketch single points. Insert a plane on the three points, sketch the fillet arc and

sweep it through the intersection of the curves and not the straight-sketched line used in the profile for part3 inthe tail. Loft it halfway through, now the filled surface works because the three corners and curves are definitely

connected, select the loft and surface and mirror it about the front plane. Done.


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Figure 13: half the fillet before mirroring.

Filling the inside of the midsection of the hammerhead:Selecting the midsection surface and thickening it by .2cm as pre the freehand sketch. The result is unacceptable

as the hole where the handle goes in is not uniform, and the thickness is not the same for all sides.

Therefore, the thickness is removed while extruding the original cross section that was sketched horizontally in

the beginning for the midsection, vertically downward. The edges are then selected separately as open loops usingthe selection manager. The two are lofted, with the bottom sketch having a constraint of normal to profile to

account for the steepness of the hole sides, and set to the maximum possible value.

Figure 14: filling the midsection; extrude surface and loft open loop.


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Drafting the flat surface in the hammerhead nose:SolidWorks draft feature was not easy to use or quick to learn. Extruding a plane from the draft edge and lofting

it did not work either. This detail has been abandoned due to lack of time.

Finally, the open surfaces in the tail were closed with planar surfaces. As was the bottom of the midsection. Theextruded surface from the top of the midsection was sticking out through the loft, and was fixed.

Results:Soft copy of the modeled SolidWorks part is available for 3D view and

download on:http://grabcad.com/library/hammerhead--1

Discussion:When coming across conflicting measurements, it was important to define a criteria to differentiate between

measurement differences which were meant in the original design and those which were not, but rather an errorof manufacturing or assembly. The following affected the judgment of whether to neglect the difference or take itinto consideration:

- Does the peculiar reading serve a purpose? An oval is easier to pull out a mold than a circle.- Magnitude, usually if it was 0.3 mm or less it is ignored.- Symmetry of some parts, which gives a context to the error.- If the cause of the error is apparent to the naked eye, like bumps or inclinations.- There is no 90 edge in real life, wear of edges should be taken into consideration.

Things I would have Done Differently:In selecting the object to model, I would definitely have gone for a higher quality product than the oneI did; which was dirty, unfinished and chipped in different locations. Drops of the glue used to hold thehammerhead with the handle had spilled on the hammerhead and were an eye sore and a hindrance to

measurement. Removing them with a screwdriver is not as easy as it sounds and has cost me some skin.Irregularities in the design are hard to discern from manufacturing flaws, although symmetries came in handythere. In conclusion, a hammer that serves its practical purpose is not necessarily suitable for reverse engineering.

In the Midsection;- Forget inclined top and add it later via extrusion. Dealing with a 2D sketch on a normal plane is much

easier than with a 3D sketch. Especially with complex features/surfaces.- Instead of removing two corners from the six corner 3D sketch to match the rectangular 2D sketches

and loft properly, I would have just added 2 dummy point corners to the 2D sketches instead.

- I learned how to make a tilted inclined plane but a bit late, use the 3D sketch to create 3 points or twolines then use them as the references to your new reference plane.

In the tail:- Make the underside groove (part3), by adding a curve and making it a guide curve to the two parts of

the tail.


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- Make more accurate measurements and modeling of the fillet (part1) and the surface covering its ends.- Would evaluate the contour of the tail with more than eye judgment and reference geometry calculation.

Other remarks:- The item designed is a rugged power tool of simple design and functionality, it seems sturdy enough to

fulfill its purpose, any further insight requires experience with hammers, which I do not have.- However, imperfections in the design were noticed, regardless of whether they effect the functionality or

not, those include; a clearly sideways tilted hammerhead with respect to the handle. Solid glue and waxhere and there, the rough surfaces mentioned previously, and irregularities in the surface that strikes thenail.

- Vernier calipers are very good for testing two surfaces for flatness/parallelism.- Solidworks usually crashes when you try to display a print preview of a drawing, and the margins are not

set correctly.

- Surfaces are more versatile than solids, but less stable and predictable.- Double sided tape makes for good memory foam:

Figure 15: profile impression on double-sided tape.

- My skill level in SolidWorks is listed as having advanced command of the software. After this project Irealized I barely know the basics.

Internet links I found useful: by order they were looked uphttp://www.tresnainstrument.com/how_to_read_a_vernier_caliper.html

http://www.youtube.com/watch?v=qqyey1MHjV0https://forum.SolidWorks.com/message/288263

https://forum.SolidWorks.com/message/302653

https://forum.solidworks.com/message/282065
http://www.tresnainstrument.com/how_to_read_a_vernier_caliper.htmlhttp://www.tresnainstrument.com/how_to_read_a_vernier_caliper.htmlhttp://www.youtube.com/watch?v=qqyey1MHjV0http://www.youtube.com/watch?v=qqyey1MHjV0https://forum.solidworks.com/message/288263https://forum.solidworks.com/message/288263https://forum.solidworks.com/message/302653https://forum.solidworks.com/message/302653https://forum.solidworks.com/message/282065https://forum.solidworks.com/message/282065https://forum.solidworks.com/message/282065https://forum.solidworks.com/message/302653https://forum.solidworks.com/message/288263http://www.youtube.com/watch?v=qqyey1MHjV0http://www.tresnainstrument.com/how_to_read_a_vernier_caliper.html


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solid modeling project: reverse engineering of a product and documentation of its solid model

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