Wednesday, April 15, 2015

4 Layout the templates


Template plastic is what bag designers or cloth designers use as templates for fabric products. It is semi translucent with frosty grain, flexible and easy to draw and cut. There are two kind of thickness, in 0.3 mm and 1.0 mm, I use 0.3 mm most of time. They sold in variety of size, mine is 45 x 60 cm, you should find them easily in DIY shops.
Buy some more of these sheets, for we will need them when building bellows.


Tracing and Cutting

Place template sheet onto the drawings we just finished, trace the patterns by pen, then cut them by utility knife.
Be carefully tracing and cutting templates as precisely as possible, for this template will define bellows detail.

I would leave some space for top and bottom of the shape A/B as images show, it would help when outlining extra rib pairs.
So totally there are 3 templates now, shape A, shape S and zigzag ruler for rib pairs.
Below we will build the last template: Bellows layout template.

Bellows Layout

1. with a big sheet of paper (I use roll kraft paper for packing parcel, or majhong table paper), trace first taper A.

2. Place zigzag template by the inner side of shape A, make sure the zigzag tip exactly at the taper bottom corner, trace the zigzag. Be sure the zigzag line extends out the taper, at least two folds.

Do exactly same zigzag line tracing at the other side of shape A, but in opposite direction.

3. Now place the template B, make sue taper edge align the zigzag tips, and taper bottom corner exactly at the zigzag tip, AND ONE STAIR BELOW the shape A, trace the first shape B.

4. Follow the step 2, draw zigzag line at the other side of shape B.

5. Repeat steps mentioned previously, draw another shape A and B, with zigzag lines. What you should get on kraft paper looks like this.

6. Outline the rib pair limits
Leave at least one pair of ribs away from the shape edge, draw the lines at both ends indicating the rib pair limits.
What the shape A/B indicate are the precise bellows size we are building, and those exceeding ribs make sure we leave the space for frame gluing.

As we did to other 3 templates, tracing the layout onto template plastic, then cut it out. Notice that zigzag lines are not necessary to trace.

This concludes the fourth and the last template: bellows layout template.


Extended Study

During template layout, you should notice that shape A and Shape B, thought they have same height 195 mm, but the length of their side are different, it shows when you draw shape B next to shape A sharing the same slant side.
  • Why?
  • Does it matter?
  • Which one should I follow?

The bellows lenght was set as 195 mm, but it seems that zigzag tip does not fall exactly at the end.

  • Does it matter?
  • Both end of slant side, rear or front end is more critical to meet the zigzag tip?
  • Should I make bellows longer or shorter than 195 mm?

When in layout, shape B is one stair below the shape A.
  • Why?
  • Why not place both shapes at the same level?
  • Any different result if shape B is one stair above shape A?

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