Fastening and Attaching

Partner: Drew Chasse

Heat Staking:

When using heat staking to join together pieces of plastic, one benefit is how quick and relatively easy it it to do. The joint created is permanent, which is a benefit if done correctly, but a drawback if a mistake is made. A few more drawbacks are that pieces can only be joined together at 90° angles, and after the material is melted, it leaves behind a small mound that protrudes from the piece and which may not be desireable. This technique would be an effective way to make a joint on a toy. The connection would be sturdy enough not to break if pulled on or dropped, and if done successfully it would not have any sharp edges that a child may be able to hurt themselves on.

Piano wire:

Using piano wire is a good way to make a hinged joint between two pieces of plastic. In done correctly, this method can create a hinge that moves 180°. A few drawback to this technique are that it is more difficult and time consuming than the other methods and it may require further altercations, such as filing down edges, in order for it to work smoothly. This method of joining plastic together is ideal for situations where a hinge is required, like a door on a toy.

Slots/pegs:

Slots and pegs are a easy way to make non-permanent joints that have the potential to be very strong. If the pieces are a press fit, it will be a sturdy joint that can be taken apart if that is the intention. One drawback to this method is that it is difficult to get a press fit and may take lots of trial and error in order to do so. If you were designing something that needed to be shipped in pieces, but easy to put together and sturdy once delivered, press fit slots and pegs would be one possibly way to achieve that goal.

Bushings:

A tight bushing would be used if a rod needed to be held in place without any movement. A loose bushing would be useful if the rod needed to rotate or slide along an axis, or if something else needed to be able to slide along the rod.

Table 1: Loose vs. Tight Bushings

Table 2: Loose vs. Tight Slots/Pegs

Discrepancies Between Solidworks and Actual Measurements:

The measurement given by Solidworks for the height of each rectangular hole was about 0.01 inches less than the measured value. This is due to the kerf, or the material that is lost when a cut is made. The amount of material lost is dependent on the precision of the tool being used to make the cut. If a measurement needs to be nearly exact, like it does to achieve a press fit, the extra 0.01 inches needs to be taken into account by making the hole 0.005 inches larger on each side when drawing the piece in solidworks.