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Offset From Surface

An end condition for Extrude and Cut. Click a face, type a distance, and the feature ends that far short of the face, or that far past it. It is Up To Surface with an offset, and it adds Translate surface, which moves the face itself instead. When an earlier change moves the face, the feature follows.

When to Use It

  • Stop a boss a set gap below a plate above it, such as 1/8 in of clearance
  • Cut a pocket that leaves a floor of a set thickness above the bottom of the part
  • Run a feature a set distance past a face
  • Keep a gap under a tilted or curved face that is the same everywhere along the feature, with Translate surface

Step by Step

  1. Open a sketch on a plane or a face and draw a closed profile. Sketching is part of modeling, which comes with the Pro plans.
  2. Click Extrude (or Cut) on the Features tab.
  3. In End condition, choose Offset From Surface. A Face row, an Offset Distance box, Reverse offset and Translate surface appear.
  4. Choose a Direction toward the face. Both ways is off for this end condition.
  5. Click the face on the part. It lights up in blue, and the message names what kind of face it is.
  6. Type the Offset Distance. You can use any unit, like 1/4 in or 6mm, or a formula (see Equations).
  7. Tick Reverse offset to end past the face instead of short of it. Tick Translate surface if you want it (see below).
  8. Click Extrude (or Cut). The step reads offset from surface 1/4 in in the Model tree, with past it added for Reverse offset and translated for Translate surface, for example offset from surface 1/4 in, translated.

Options

  • End condition: Offset From Surface. The other choices are Blind, Through All (Cut only), Up To Next, Up To Surface, and Up To Vertex and Up To Body.
  • Face: the face to measure from. Flat, cylindrical, conical, spherical and toroidal faces work, carried on past their own edges. Click the button to pick again.
  • Offset Distance: how far from the face the feature ends. It must be more than 0. For no offset, choose Up To Surface.
  • Reverse offset: end that far past the face instead of short of it.
  • Translate surface: unticked (the default), the end keeps the same distance from the face all over, measured square to the face. A tilted face gives an end parallel to it, and a round bar gives an end on a larger round (or a smaller one, past it). Ticked, the face itself is moved straight back along the way the feature runs by the Offset Distance, keeping its tilt and shape, so every point of the end is exactly that distance short of the face along the feature. On a flat face square to the sketch both give the same end.
  • Direction: Forward or Backward, toward the face.
  • Merge result (Extrude only), Draft, Thin Feature and Direction 2 work as they do with Up To Surface.

Translate Surface, an Example

A boss runs up under a face tilted at 45 degrees, with an Offset Distance of 1/4 in (6.35 mm). Unticked, the end is 1/4 in from the face measured square to it, which is about 0.354 in (9.0 mm) lower along the boss (1/4 in times the square root of 2). Ticked, the end is exactly 1/4 in lower along the boss everywhere. Under a round bar, ticked gives the same round shape 1/4 in lower; unticked gives a round 1/4 in larger.

Edit It Later

Right-click the step in the Model tree and choose Edit Feature. You can change the End condition, the Offset Distance, Reverse offset and Translate surface, and click Pick face again. A step made with Up To Surface and an Offset Distance opens as Offset From Surface, because they are the same step. Choose Up To Surface there to end on the face itself. Press Esc to close without a change.

Tips and What to Expect

  • Offset From Surface needs an Offset Distance more than 0. Type one, or choose Up To Surface to end on the face. The box is empty or 0.
  • Up To Surface: the offset is larger than the distance to the face, so the end would fall behind the sketch. Use a smaller offset. With Translate surface the distance is measured along the feature, from the corner of the profile nearest the face.
  • The face is kept by reference, as with Up To Surface. When it is gone the step says so: Up To Surface: the face it ends on is no longer on the part. An earlier step probably changed or removed it. Edit the step and pick the face again.
  • Direction 2 can end Up To Surface with its own face, Offset Distance and Reverse offset. Translate surface is set for the first direction only.
  • A Pattern can repeat the step, and every copy ends the same way from the face. A Mirror cannot copy it yet.
  • A viewer older than this version opens the step as Up To Surface with the offset and does not know Translate surface: it ends the step the same distance from the face all over, which differs on a tilted or curved face. Open such models in this version.
  • For holes that end on a face, see Hole.

Open the viewer

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