Custom features
Use FeatureScript tools for repeated CAD work while checking their geometry and references.
Onshape can add tools written in , its language for defining features. A custom feature might generate a pulley, make a spacer, or add a standard mounting pattern. You can use one without writing the program yourself.
Learn the ordinary , extrusion, and pattern tools first. They help you understand the result a custom tool creates and give you a fallback when it does not match your part.
Choose a useful tool
Look for a feature that saves a repeated operation you already understand. A configurable spacer is a good example. It should let you identify the bore, outside shape, length, and any manufacturing allowance.
For a gear or pulley generator, check more than tooth count. The tooth system, pitch or module, profile, width, and shaft connection must match the real mating components. Similar-looking teeth can use incompatible profiles.
Read the tool’s instructions and look at an example part before using it. You should be able to find its source document, understand the inputs, and check the of the part it makes.
Add it to the toolbar
In a , choose Add custom from the feature toolbar. Locate the feature's document by search or its shared document URL. Select the required feature and the document version, then close the dialog.
The new icon belongs to your account's toolbar, rather than being a normal part inserted into this document. Teammates may need to add the tool to their own toolbars. Existing uses of a linked feature remain in the document's feature list.
Start in a separate practice Part Studio. Select the tool, enter the required inputs, inspect the preview, and accept. Rename the feature to describe the geometry it produces, such as Intake pulley — 24 teeth, while keeping the actual dimensions in its parameters.
Inspect the result
For a spacer generator, measure the bore, length, outside dimensions, and end faces. Compare those with the intended shaft and contact. For a pulley, also inspect the pitch definition, flanges, hub, and fastening method.
Check these questions before using the output on the :
- Does it create a new part, alter an existing part, or both?
- Are dimensions entered as radius, diameter, tooth count, or distance across flats?
- Is an allowance added to the nominal bore? If so, in which direction and by how much?
- If you change a setting, do the faces used by your sketches and still exist?
- Can the part be made with your process, including its smallest teeth or walls?
An across-flats dimension measures between two opposite flat sides of a polygonal shaft. It differs from the distance across its corners. This distinction matters for hexagonal and other shaped bores.
Change one setting
For a spacer, generate two lengths with the same bore. Measure them, then change only the bore. The length should remain unchanged. For a mounting-pattern tool, change one pattern size and inspect every hole's location.
Try this before using the feature in several robot parts. If the result is wrong, check the settings and instructions first. Scaling the part or adding cuts to fix it can hide a wrong input and make later edits harder.
If you need a fit trial, print a short test piece before making a complete . Record the material, printer settings, orientation, and dimension that worked. Use Printed parts and Tolerances and fit to interpret the result.
Manage versions
A linked custom feature references a document version. Updating that reference can change generated geometry or introduce new inputs. Review the change before adopting it in parts already sent for manufacturing.
The feature version used in a Part Studio and the version selected by your toolbar can differ. Check both when two students get different results from what appears to be the same tool. Keep the source document and chosen version in the team's CAD instructions.
Before an update that could affect parts you have made, save a named version of your document. After updating, compare the mounting holes, important dimensions, and exported files. Onshape may rebuild the feature without an error even though its shape has changed.
Keep a manual fallback
For a simple spacer or plate, a sketch and extrusion may be easier to maintain than a specialized feature. For repeated complex geometry, a custom feature can save considerable work.
Choose the approach your team can understand and maintain. Either way, keep the editable model, name the features clearly, and include the information needed to make the part. A useful tool saves repetitive work without making the design harder to understand.