The following assignment was centered on understanding the means through which one can attach plastic parts with one another. My partner (Chloe Shi) and I evaluated the advantages and disadvantages of the following methods.
| Method | Description | Advantages | Disadvantages | Situations |
| Thermal Press | The thermal press involves the attachment of parts through the melting of one peg on a part to a complimentary slot on another part. |
· Permanent attachment of parts- would require a large force to break the parts · Strong welding of parts- prevents breaking and increases durability |
· Can only operate and attach items at a 90 degree angle · Permanent attachment- a need to separate the parts will not be possible · Device uses large amounts of heat- can result in burns · Heating device- over time the device will use up high amounts of energy to generate heat. Questions the sustainability (in terms of energy) of the device. · Size of items being welded together is restricted by the size of the heat knob.
|
Given a situation when in which permanent/strong attachment of plastic parts is required, such a method would be ideal. |
| Slots and Pegs | This method involves the creation of pegs and complimentary slots on parts of plastic. Together each peg is attached to its complimentary slot to attach multiple pieces of plastic. |
· Attachment of parts is not permanent— if needed, dimensions of each part can be modified. · Doesn’t require the use of additional materials (i.e.: piano wire, heat) · Provided a snug fit of parts is accomplished, the attached parts will be inflexible. |
· Requires high amount of measurement accuracy, as to prevent a loose or tight fit. · Must take into account the inaccuracies created during laser cutting (i.e.: the dispersion of the laser light as it cuts through plastic) |
Given a real life instance when in which flexible attachment of parts in the absence of external materials is required, such a method would be best. |
| Piano wire | This method requires the use of a drill press to precisely create holes through complimentary pieces of plastic. If done correctly, two pieces of plastic can be attached to one another to create a hinge. |
· Able to create hinges · Able to create devices of high flexibility |
· Hazardous if not trained on how to use · Can permanently damage or alter the shape of plastic sheets · Hard to precisely create straight tunnels for piano wire— in such a case a proper hinge is not formed. |
In cases in which hinges are required, this method would prove to be most beneficial. |
Bushings: Bushings require the attachment of circular plastic pieces around cylindrical plastic rods. Fits of these parts varied in terms of tightness.
Tight bushings might be needed to keep a rod in position within a device or aid in keeping pieces of plastic in place along the rod. Conversely, loose bushings may be required to allow the mobility of items and parts along the rod.
Calipers:
Table showing the measured thickness/diameter of bushings and Delrin rods.
| Item | Measurement 1 (mm) | Measurement 2 (mm) | Fit |
| Delrin rod outer diameter | 6.31 | 6.34 | N.A. |
| Bushings, compartment 1 | 6.38 | 6.23 | Press |
| Bushings, compartment 2 | 6.33 | 6.45 | Snug |
| Bushings, compartment 3 | 6.61 | 6.69 | Loose |
The table showing the measurements of pegs and their respective slots
| Item | Measurement 1 (mm) | Measurement 2 (mm) | Fit |
| Small peg plate thickness | 3.21 | 3.22 | N.A. |
| Height 1 (Solid works measurements: 0.135 in) | 3.71 | 3.80 | Loose |
| Height 2 (Solid works measurements: 0.125 in) | 3.41 | 3.50 | Snug |
| Height 3 (Solid Work measurements: 0.115 in) | 3.16 | 3.27 | Tight |
There is a clear discrepancy between the documented dimensions of each of the plastic items as compared to the solid works measurements. Having any of these pieces be slightly off the intended measurement can pose serious problems when attaching the plastic together. Due to the mismatch of dimensional values between solid works and real life cut outs, a certain uncertainty must be taken into account when cutting parts. Designers must account for some leeway between the intended size of the piece versus the actual size.
The discrepancy between the cut out versus solid works pieces is purely due to the accuracy and precision of the laser cutter. Depending on the thickness of the outlines of parts, the laser cutter can accordingly cut more or less than intended. Therefore, it is important to make sure all outlines for pieces are as thin as can be.
Additionally, the intensity of a laser beam is inversely proportional to the distance from the plastic. As the distance between the laser source and plastic sheet increases, the focus of the laser decreases. Hence, leading to noticeable slants and dimensionally inaccurate cuts.
