Manufacturing techniques

Explain the difference between manual manufacturing and mechanical manufacturing (using machine tools), and give an example of a product made with each.

Name the appropriate tool for each operation: sawing a wooden strip, drilling a sheet of metal, sanding an edge and screwing two parts together.

Explain what a template in manufacturing is and why it saves time and prevents errors when making several identical parts.

Explain what "additive" manufacturing means and how it differs from "subtractive" manufacturing (saw, drill, milling machine), giving an example of each.

The figure summarises the manufacturing process of a part by 3D printing, but one step is missing. State which step it is and what is done in it.

In 3D printing, explain what "layer height" and "infill" are, and how each parameter affects the printing time and the strength of the part.

Choose the most suitable manufacturing technique for each case and justify it: (a) a single prototype of a complex-shaped part, (b) one thousand identical metal washers, (c) a hand-carved wooden sign.

To manufacture the flat parts of a scale model, your team is torn between 3D printing and laser cutting. Compare both techniques for that specific job and explain which one you would choose.

In the workshop, you want to make 20 metal reinforcing brackets ($50\times 50\times 3\text{ mm}$) and a cylindrical shaft of revolution with two stepped diameters for a pulley. A classmate suggests 3D printing both parts in PLA to "avoid getting tired with hand tools". Refute their proposal technically: predict what mechanical or functional failures each printed part will present compared to one made with traditional techniques (sheet metal forming/machining and lathe) and justify which traditional technique is appropriate in each case.

When cutting parts that must fit together, you work with a margin or tolerance. Explain what that means and what happens if one part is cut at the upper limit of the tolerance range and the other at the lower limit.

In the workshop, you must produce a batch of 40 wooden keychains in a 90-minute session. The process consists of four successive stations with one student per station: Marking and cutting ($3\text{ min/unit}$), Drilling ($1\text{ min/unit}$), Sanding ($4\text{ min/unit}$), and Varnishing ($1,5\text{ min/unit}$).

1. a) Identify the current bottleneck and calculate how many complete units you will actually be able to finish in the available time.
2. b) Design a redistribution of tasks or resources to balance the line so that you reach the 40 units without causing intermediate accumulation of parts, justifying the new cycle times.

During the quality control of a batch of 50 3D-printed parts with a hole that must measure exactly $20,0\text{ mm}$ (permissible tolerance $\pm 0,15\text{ mm}$), you measure the first 5 and obtain: $19,65\text{ mm}$, $19,70\text{ mm}$, $19,65\text{ mm}$, $19,68\text{ mm}$, and $19,67\text{ mm}$.

1. a) Interpret the data: is it a random or a systematic error? Diagnose two possible causes linked to the thermal shrinkage of the plastic or to the slicer (slicer) configuration.
2. b) Design an action plan: what adjustment must you apply before resuming the production run, and what criteria will you follow to decide whether the already manufactured parts are scrapped or can be reworked.