Ghost Clip

Summary:

A ghost themed plastic clip that holds papers together. It is 12.9 cm tall, 6 cm wide, 0.1 cm thick, and can hold a stack of paper up to 2 cm in thickness. You can download and print it here, or make any changes you desire, such as changing the engraved initials. Made in collaboration with @charlieb_2915664 and @aoeng_2915687.

Lesson Plan and activity:

Problem Statement:  With a partner, you will recreate your ghost clip using Solidworks.  You and your partner MUST have identical files that you create by collaborating on each step, one at a time.

Sketching Instructions:

Initial Setup:

1. Create a new sketch part in Solidworks
2. Set normal to front plane
3. Create a center rectangle centered on the origin. The rectangle should be construction geometry and have midpoint construction lines.
4. Smart Dimension the constraint box a height of 12.9 cm and a width of 6 cm

Left Eye:

1. Create a circle in the top left of the rectangle, and Smart Dimension the center 2.7 cm down from the top of the constraint box and 1.7 cm to the right side of the constraint box

     2. Smart dimension the diameter to 1.2 cm

Ghost hair:

1. Use the line tool to draw a triangle with one point on the left line of the constraint box, one point on the top line of the constraint box, and one point on the inside of the constraint box. 

        2. Set the base of the triangle parallel to the top line of the constraint box, and make that line construction geometry. Smart dimension the base to 1 cm long and make the other sides equal to the base of the triangle.

        3.  Make a linear sketch pattern of the triangle and smart dimension each copy to be 1 cm to the right. There should be 6 total triangles.

Mouth and Right Eye:

1. Create a vertical construction line with the top point Smart Dimensioned 5cm down from the top and the bottom point Smart Dimensioned 4.1 cm up from the bottom. Smart dimension the vertical construction line 1.5 cm to the right of the constraint box

        2. Select the circle, the vertical construction line, and the center vertical construction line and use the mirror entities tool to mirror them across the vertical midpoint line of the constraint box.

       3. Create a construction geometry tangent arc from the bottom of the two vertical lines just copied.

        4. Select the two vertical construction lines and the arc that connects them, and make a 0.3 cm bidirectional end capped offset using offset entities.

Base of Ghost:

1. Starting from the left edge of the constraint box, make 3 horizontal construction lines across, with the last point being on the right edge of the construction box. Smart dimension the leftmost point to be 1 cm up from the bottom, and set all three segments equal.

      2. Create a three point arc from the left point of each segment to the right edge of each segment, the third point being tangent to the bottom line. Ensure that the bottom of each arc is tangent to the bottom line.

Closing the Contour:

1. Make a line from the bottom of the leftmost triangle to the top of the leftmost arc. Do the same for the right side.

Design choices:

We were originally given a ghost clip, and we sketched it first on paper by taking its dimension with a ruler. This caused some error because the rulers are only accurate to the millimeter, and reading Another source of error is that we measured the physical version, meaning any imperfections with the print would transfer over into our sketch.

When we were sketching the ghost on paper, we also noticed and took advantage of the geometric symmetries of the ghost. The triangles that make up the ghost’s hair are equilateral, so it was not necessary to set the lengths of the other sides or the altitude of the triangle. We were also able to use a linear sketch pattern because all of the triangles were the same. We also noticed that the eyes and vertical portions of the mouth were symmetrical across the center, so we used the mirror tool on them in solidworks.

Mirroring of the eyes and vertical portion of the mouth: 

Duplication of triangles to make the hair:

Our original Solidworks sketch seemed like the eyes and mouth were slightly too high compared to the model ghost clip, so we decided to move the eyes down by 0.1 cm and we moved the mouth down by 0.05 cm. As it turned out however, the changes were unnecessary and the ghost's eyes were in the right place before the change was made.

Change of dimensions in Solidworks:

Final inaccuracy of eyes (blue is ours, orange is model):

We also were off on the total height by 0.1 cm. The model was 13 cm tall, while ours was only 12.9 cm tall. This was likely caused by an inaccurate measurement with the ruler.

Final inaccuracy of height (blue is ours, orange is model):