Sketch to 3D model: draw your part, add the sizes, print it

Some parts are easier to draw than to describe. Draw yours right in the chat (or snap a photo of a paper sketch), write down the sizes you know, and GrandpaCAD builds a printable 3D model from it. Every size you wrote becomes a slider you can change later.

• No CAD skills, no drawing skills
• Mouse, finger or Apple Pencil
• Your lines stay exactly as you draw them
• 3 free generations, no credit card

One real run: a drill bit holder

Here's a real run from start to finish: a block that holds drill bits, one hole per size. You could describe it in words ("120 by 40 mm, five holes from 4 to 12 mm, evenly spaced, and...") but it's quicker to draw, and a drawing leaves less to interpret.

1. Draw it

Start a new chat, open the "…" menu at the left of the message box and pick "Draw a sketch". The pad opens full screen.

A rectangle for the block. Five circles for the holes (hold Shift and the ellipse tool draws a round one). Then the dimension tool for the two sizes that matter: drag across the block, type 120, and it reads as 120 mm. Text for the hole diameters, a blue note for the height and depth, and a red arrow that says "round the corners".

None of it is drawn to scale. The lines show where things go, and the numbers say how big they are.

2. Attach it and say what it is

Press Attach and the drawing lands in the message box as an image. Then one sentence: "Make this drill bit holder. Flat bottom, printable as is." Send.

3. Get the model, with your sizes as sliders

A couple of minutes later the model was in the viewer, with this summary from the agent:

Built to your sketch: 120 × 40 × 30 mm, 4, 6, 8, 10 and 12 mm holes, each 25 mm deep, 5 mm solid bottom, rounded corners with a 3 mm radius.

It read every number off the drawing, the blue note included, and it followed the red one. Nobody gave it a size for the corners, so it picked 3 mm and made that a slider too.

All 11 sizes became sliders: length, width, height, hole depth, corner radius, hole spacing, and one for each hole. Is the 4 mm hole too tight for your bit? Type 4.2 next to its slider and press Save. Sliders never use a generation.

What the AI reads from your sketch

It reads three things:

• The shape: outlines, holes, slots, and where they sit relative to each other.
• The numbers: anything you sized with the dimension tool or wrote as text. These are exact.
• The notes, in any color: "round the corners", "this side faces the wall", "M3 screws". A different color keeps notes apart from the outline.

What it doesn't do is measure your lines. A line without a number is a proportion, not a size. So size the things that have to fit and let the agent pick the rest. If something important is missing, it asks before it builds, with a few answers you can tap.

Tips for a sketch that builds right the first time

• One view per sketch. A top view for plates, trays and blocks, a side view for brackets, hooks and stands. Say which one it is in your message.
• Size what has to fit: the hole for a screw, the slot for a cable, the outside size if it goes in a drawer.
• Don't fuss over neat lines. Hold Shift for straight lines, squares and circles if you like, but a wobbly circle with "Ø8" next to it builds the same as a perfect one.
• Write down the third dimension. A top view can't show height or depth, and a note can ("30 mm tall, holes 25 mm deep").

Three more ways to sketch

A photo of a paper sketch

Paper works. The animation at the top is a pen sketch of a tray with "5cm" and "10cm" written on it, photographed and sent with "make this". Attach the photo like any other picture. The image to 3D post has a napkin sketch run, including the two questions the agent asked before building.

Draw on a photo

If you attached a photo of the part you're replacing, the small pencil button on the attachment opens it in the sketch pad. Circle what matters, add the sizes, and the marked-up photo goes in with your message.

Mark up the 3D model

Once you have a model, the pencil button in the viewer's toolbar ("Mark up this view") opens the current view in the sketch pad, with red ink ready. Circle what you want changed, write what, and attach it.

It's the quickest way to say "this one, not that one".

The sketch pad, tool by tool

There are four ink colors, unlimited undo and redo, and a button that fits the drawing to the screen. Pinch or scroll to zoom. In the chat, it's "Draw a sketch" in the "…" menu at the left of the message box. It opens full screen, on a phone too.

Questions people ask

Draw your first part

Think of the last part you needed and couldn't find: a bracket, a spacer, a holder for the thing that's always rolling off your desk. Draw it, put the sizes on it, and print it tonight.