---
title: "Design for the printer"
subtitle: "Design and print · Designing for the printer · Lesson 3"
---

# Design for the printer

**Name:** {{field-24}} **Date:** {{field-15}} **Class:** {{field-15}}

> **Key question:** Two brackets, same file, same printer, same plastic. One holds a shelf of books; the other snaps the first day. The only difference is which way up they were printed.


:::teacher-note

**In one sentence:** Students turn an L-bracket through four print orientations, find the one that needs supports and the one with layers along the load, apply both questions to a hook and other shapes, see Sam's bracket snap across its layers, check orientations in the school's slicer, and justify an orientation for a part of their own.

**Students should be able to say:** I can tell when a part needs supports. I can choose a print orientation so the load runs along the layers.

**Width:** the unmarked parts are the floor every student does (predict, run, investigate and make). Typical adds the modify practice; wider adds the real-world contexts. They add contexts, not difficulty. Students work in the online tutorial alongside this sheet.

:::


## Predict


:::keep-together

**An L-shaped bracket will hold up a shelf. Which way should it be printed to be strongest?**

☐ Upside down

☐ It makes no difference

☐ Flat on its side

☐ Foot down, arm up

My prediction, and why:

{{lines-3}}

:::


:::teacher-note

**What happens:** Flat on its side: no supports, and every layer runs along both arms, so the load pulls along the layers, not across them.

:::


## Run

Try it on the board in the tutorial. Was your prediction right? What was different?

{{lines-2}}

## Worked example: two questions for every part


:::keep-together

### Overhang, then load

1. $\text{overhang} > 45^\circ \Rightarrow \text{supports}$ — Each layer needs something under it.
2. $\text{layers across the load} \Rightarrow \text{weak}$ — Layers bond less well to each other.
3. $\text{bracket: flat on its side}$ — No overhangs, and the layers run along both arms.
4. $\text{check both, every part}$ — Supports cost plastic and finish; weak layers cost the part.

Now try a hook.

**A hook will hang a bag from its curved end. The load pulls down the hook's length. Which way up should it be printed?**

☐ Standing up, curve at the bottom

☐ Flat, so the layers run along the hook

☐ Standing up, curve at the top

☐ It makes no difference

:::


:::teacher-note

**Answer:** Flat, so the layers run along the hook

Flat: no tall overhangs, and the layers run along the load.

:::


:::keep-together

### Find the mistake

**Sam's bracket snaps across the arm the first day. Click the line where Sam's reasoning first goes wrong.**

```
 1  Sam prints the shelf bracket foot down, arm up.
 2  It needs no supports, and it looks perfect.
 3  The plastic is the same all the way through, so it is equally strong every way.
 4  So it will hold the shelf.
```

Line: {{field-15}}

Why is it wrong?

{{lines-2}}

:::


:::teacher-note

**Answer:** line 3

Line 3: a printed part is weakest across its layers. Foot down, the shelf load bends the arm across them.

:::


:::typical

## Make it in the slicer


Work in the tutorial. Plan first: what will you change, and how will you test it?

{{box-4}}

:::


## Which way?


:::keep-together

**Which of these need supports printed as described?**

Groups: Needs supports, No supports

- A letter T standing up, its bar at the top: {{field-15}}
- A letter T lying flat: {{field-15}}
- A pyramid standing on its base: {{field-15}}
- A pyramid standing on its point: {{field-15}}
- A cube with a round hole straight through, top to bottom: {{field-15}}

:::


:::teacher-note

**Answer:** A letter T standing up, its bar at the top → Needs supports; A letter T lying flat → No supports; A pyramid standing on its base → No supports; A pyramid standing on its point → Needs supports; A cube with a round hole straight through, top to bottom → No supports

Anything that sticks out sideways over nothing (the T's bar, an upside-down pyramid) needs supports; sloping in at 45° or less doesn't.

:::


## Make: choose and justify


**A phone stand.** 

**My part.** 

Work in the tutorial. Plan first: what will you change, and how will you test it?

{{box-4}}

## Exit ticket

:::keep-together

**Give two reasons to choose a print orientation.**

{{lines-3}}

:::


:::teacher-note

**Answer:** To avoid overhangs that need supports, and so the load runs along the layers rather than across them.

:::