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Sketch it first: planning a 3D print on paper

The prints that work first time are usually the ones worked out on paper. Ten minutes with a pencil settles the sizes that matter, the fit and how the part sits on the bed, before you open CAD.

Measure what it has to fit

shaft 8.00 MUST FIT, mm Ø8shaft 40hole gap 3panel
Measure, write it down, then draw.

Measure what it attaches to, holds or replaces. Those are the sizes it can’t get wrong.

Sketch it in 3D, roughly

Ø8 40 1 block 2 carve 3 key sizes
Box, features, then sizes.

Block it in as a box on isometric paper, carve the features out, then add the must-fit sizes.

Plan the fit

0.2 mm clearance ✓ slides press fit, ≈ 0 ✓ holds
Gaps drawn larger than life.

Holes print a little small, so set each gap on paper: clearance to slide, little or none to press. Print just the fit first.

Choose how it sits on the bed

bed ✗ overhang: support ✓ flat face down
Turned over, no overhang.
over 45°: support 30° ✓ 60° ✗
Overhangs
✓ along ✗ apart
Layer direction
up on its side ✓ round ✗ droops
Holes
✓ wide ✗ narrow
First layer

Sketch it the way it prints, mark the face that goes down, then run these four checks.

Size the walls to the nozzle

0.4 mm nozzle → 0.4 mm lines 0.8 mm2 lines 1.2 mm3 lines 1.6 mm4 lines
Whole lines, no gaps.

Walls print cleanest as whole lines: with a 0.4 mm nozzle, 0.8, 1.2 or 1.6 mm.

Then model it

sketch, beside you Ø8 shaft hole 40 hole gap 1.2 wall 0.2 clearance
Tick each size as it goes in.

Then CAD is mostly typing numbers off the sketch. After the first print, mark what changed on the same page.

3D-print sketches in PencilCAD

Isometric + Line
40 40
Write it; the line takes it
0.2 mm clearance
Text for fits
1:1 DXF SVG
True size, DXF or SVG
  1. In More, choose Isometric paper; on the toolset chip beside the page count, CAD. Block it in with Line.
  2. Size it with Dimension, or write a size beside a line in CAD and the line takes it.
  3. Note fits with Text, under More shapes: “0.2 mm clearance”.
  4. One page per part; a pad holds up to 50.
  5. Share flat views from More as DXF or SVG at true size.

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