Finishing strategies (contour, scallop) in CNC Programming - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a contour finishing strategy in CNC programming?

Contour finishing is a method where the tool follows the exact outline or edge of the part to create a smooth, precise surface finish.

beginner

Describe the scallop finishing strategy.

Scallop finishing moves the tool in a pattern that keeps a constant step-over distance, creating small overlapping arcs or 'scallops' to smooth the surface.

intermediate

Why is scallop finishing preferred for complex 3D surfaces?

Because scallop finishing maintains a consistent step-over, it can evenly smooth curved or irregular surfaces, avoiding marks or unevenness.

intermediate

What is the main difference between contour and scallop finishing?

Contour finishing follows the exact edge or profile, while scallop finishing moves in overlapping arcs to maintain a constant surface finish across the whole area.

intermediate

How does step-over affect scallop finishing?

Step-over controls the distance between tool passes; smaller step-over means finer finish but longer machining time, larger step-over means faster but rougher finish.

Which finishing strategy follows the exact outline of the part?

A Contour finishing

B Scallop finishing

C Pocket milling

D Drilling

Contour finishing moves the tool along the exact edge or profile of the part.

What pattern does scallop finishing create on the surface?

A Random paths

B Overlapping arcs or scallops

C Straight lines

D Circular holes

Scallop finishing creates overlapping arcs to maintain a smooth surface.

Why might scallop finishing take longer than contour finishing?

A Because it maintains a constant step-over for a smooth finish

B Because it only follows edges

C Because it drills holes

D Because it uses larger tools

Maintaining a constant step-over means more passes and longer machining time.

Which finishing strategy is better for smoothing complex 3D shapes?

A Contour finishing

B Face milling

C Scallop finishing

D Slotting

Scallop finishing adapts well to curved surfaces by keeping a consistent finish.

What happens if you increase the step-over in scallop finishing?

A Tool path follows edges only

B Machining time increases

C Finish becomes smoother

D Finish becomes rougher

Increasing step-over means fewer passes and a rougher surface finish.

Explain the difference between contour and scallop finishing strategies in CNC programming.

Think about how the tool moves and the surface it creates.

Describe when and why you would choose scallop finishing over contour finishing.

Consider the shape of the part and the finish quality needed.