Draft

Draft leans the walls of a part in a little as they rise, so it can come out of a mould. A vacuum-formed sheet grips a mould with straight walls, and a casting sticks in a mould with straight sides. With a few degrees of draft, they come off cleanly. The base face (the Neutral plane: the face the part stands on) keeps its size, and every wall square to it leans in.

In Standard, find Draft with Search tools (` or Alt+C), or switch to Advanced at the end of the toolbar.

How to use it#

1. Model the mould with straight walls, for example an extruded block with rounded corners.
2. Click Draft, or press D. The bottom face of the newest part is picked as the Neutral plane.
3. If the Neutral plane is wrong, click the flat face the part stands on.
4. To taper only some walls, choose Pick walls under Faces to draft and click them (click one again to take it away). All walls tapers every wall square to the base.
5. Type the Draft angle. 3° to 5° is usual for vacuum forming.
6. Check the preview, then click ✓ or press Enter.

Step by step#

Here is the whole thing on a vacuum forming mould, from the SchoolCAD video tutorial.

Options#

• Neutral plane: the base face, the flat face the part stands on. It keeps its size. Click another flat face to change it.
• Faces to draft (Onshape: Draft faces · SOLIDWORKS: Faces to Draft): All walls, or Pick walls and click the walls to taper. The walls picked light up. Clear takes them all away. A picked face must stand straight up from the base.
• Draft angle: how far the walls lean in, in degrees. Keep it under 30°.
• ⇅ (Opposite direction): the walls lean out instead, so the top is bigger than the base, as with Reverse direction in SOLIDWORKS. A negative angle does the same.

Draft analysis#

To see which faces will come off the mould before you add a draft, use Draft analysis (in Advanced, in the Measure ▾ menu; Onshape: Draft analysis · SOLIDWORKS: Draft Analysis). It colours every face:

Choose the Pull direction (X, Y or Z, and ⇅ to turn it round; Z is straight up off the base) and the Draft angle you need, such as 3. The panel says how much of the parts is each colour. Close it with ✕, or click Draft analysis again.

Tips#

• Every wall square to the base is tapered: flat walls, curved walls and rounded corners. The line under the angle says how many walls were tapered.
• Draft needs the 3D engine. It starts by itself the first time, which takes a few seconds.
• For vacuum forming, round the top edges with Fillet after the draft, so the sheet forms smoothly over them.
• To change the angle later, double-click the draft in the feature tree.

If it does not work#

• A face picked to draft is not a wall square to the base face. Pick walls that stand straight up from the base, not the top or a sloping face.
• A face to draft has gone. An earlier change took that wall away. Edit the draft and click the walls again.
• Set a draft angle (3° to 5° suits vacuum forming). The angle is 0.
• Keep the draft angle under 30°.
• This part has no walls square to that base face to taper. The base is probably a side face, or the walls already slope. Click the face the part stands on.
• A 5° draft does not work on this part. Try a smaller angle, or check the base face.
• Draft needs the 3D engine, which is not available on this computer. Try another computer or browser, or ask your teacher.
• Pick a flat face for the base. You clicked a curved face.