Fastening and Attaching

HEAT STAKING WITH THE THERMAL PRESS: The thermal press is a tool used to melt plastic together, essentially welding the pieces. First, the press is heated, then it is applied to the plastic, and the piece is cooled.

Characteristics:
-Most notably, the thermal press creates a permanent, fixed joint. Once two pieces are melted together, they cannot be easily taken apart and/or reassembled. This is inconvenient if you are putting together an elaborate piece and make one mistake, or if you are putting together a mock-up and would prefer to be able to make changes along the way. This is advantageous if you want your final piece to be completely rigid and immutable.
-The thermal press can only weld pieces together at perpendicular angles. If you need an oblique angle, then there is no way for the thermal press to accommodate that as it currently is. However, if you need a strong right angle, then the thermal press is ideal.
-The thermal press leaves a distinctive button-shaped melted spot behind. This is a good indicator of how the piece was put together, but it is not necessarily aesthetically pleasing. If you need your piece to have a completely flat surface, then the button is a distinct disadvantage. Also, the size of this button is determined by the tip of the press, and each tip is optimized for a certain peg size. If the dimensions are known, then you can save a lot of trouble having to find out which sizes to use and navigating tolerances, but if the dimensions are not known, then optimizing them requires trial and error.
-There is a size constraint to what can fit under the thermal press. Pieces longer than the height adjustment handle allows cannot be pressed together.
-On occasion, the piece that is pressed will stick to the tip of the press, but this is easily handled with candle wax.

Overall, the process of thermal pressing is fast and simple. Besides burns if handled improperly, it is a low-risk tool to use. The spindle for the windlass project is a boxy shape with four panels set at right angles. I believe thermal pressing them would be a good way to fix them together, because they will be bearing a lot of force, so a push fit or press fit slot and peg may not be strong enough.

PIANO WIRE: The piano wire method involves using a drill press to drill multiple holes through the teeth of two hinge pieces, then fixing a piano wire as a pin through the hinge using an arbor press.

Characteristics:
-This joint is mobile and flexible. It can easily be flipped open and closed, which makes it ideal for temporary designs that are still subject to change. Because it is so mutable, the joint can take on any angle if it is pinned together properly.
-The drill press required the two pieces being joined to have interlocking teeth to drill through and form a hinge. This may not be an aesthetically pleasing design, but it is very functional.
-The drill press has a wide variety of bits, so it can presumably drill through materials that don’t melt as easily, as opposed to the thermal press, which requires the materials being joined to melt at a reasonable temperature.
-Compared to the thermal press, this process took much longer and required more precision.

I think the hinged characteristic is the most unique to a drill press, so if I were to make a small hinged box, this is the tool I would use for the lid (the rest could probably be thermal pressed!)

SLOTS AND PEGS: The delrin joints are cut with corresponding slots and pegs in them, so they can be pieced together like a puzzle.

Characteristics:
-This is a temporary joint, but its strength and rigidity can be altered and customized, depending on how snuggly the pieces fit together.
-Like the thermal press, planes joined in this way must also be joined perpendicular to each other. However, they fit together seamlessly
-This joint requires no other tools to aid it, it can and must be cut directly into the delrin. This is nice, because any piece can have a peg or slot cut into it, but if the joint is cut incorrectly, then the entire piece must be cut again.

The fact that the joint is mostly rigid, but seamless makes it ideal for our windlass project, because we cannot have the windlass tilt on uneven thermal press buttons.

BUSHINGS

Tight bushings allow a rod to be fixed into a position. One way we are using tight bushings on our windlass is so we can use the delrin rod as a support for our structure. Another way we are using them is on the spindle, which we will fix to a piece of the rod that serves as an axel. We want the spindle to rotate with the rod, so it must be a very snug fit. On the other side of the axel, we need loose bushings to allow the rod to rotate within its sockets.

TOLERANCES

The press fit bushings needed to be forced against the table, and refused to slide further up the rod. The snug fit bushings slid along the rod if they were moved, but if the rod was held vertically, they did not slip. The loose bushings moved and slid off the rod if the rod was tipped or shaken slightly.

The loose peg moved within the socket and fell out if it was tilted or picked up. The tighter fit moved less within the socket, but it also fell out when we picked it up. The press fit peg needed to be pushed against the table and forced into the socket

There is a definite discrepancy between the dimensions ins Solidworks and the actual part dimensions. The tolerances differ, because the laser cutter cuts away plastic and melts a wider channel than the theoretically infinitely thin one we model on the computer. This means that when we build with the laser cutter, we need to take into account the plastic that is going to be cut away by the machine itself, in addition to the model.