Overview#
The Work Coordinate System (WCS) is the origin and axis directions that every toolpath in a Setup is measured from. In the machine, the WCS corresponds to the work offset the operator establishes (G54 and its siblings): "this point on the part, or on the vise, is X0 Y0 Z0". In Fusion, you define the same thing on the model. If the two do not agree, the program cuts in the wrong place.
A good WCS is chosen for three reasons at once:
- Machineability: the Z axis points along the tool axis, away from the part, so toolpaths can reach every feature.
- Measurability: the origin is a place the operator can touch off reliably (a corner of the stock, the center of a bore, the top of a vise jaw).
- Repeatability: a flip or second operation can reuse a clear datum so features on both sides line up.
You do not need to understand the whole machine to get this right. You need to know four things: how Z is chosen, how X is chosen, where the origin sits, and how the result looks in the posted code.
Where to find it#
The WCS controls are in the Setup tab of the Setup dialog, in the Work Coordinate System (WCS) group. Open them with Milling > Setup > New Setup or by editing an existing Setup. The WCS is the coordinate system in which the post processed toolpath is output and it defaults to the model orientation.
Fields in the milling group:
- Orientation
- Origin
- Flip Z Axis and Flip X or Y Axis (flip the chosen axis 180 degrees)
- Face or edge selectors for the axes the chosen Orientation needs
- Accessibility Analysis (Preview) to see which areas the tool can reach
Orientation modes#
The Orientation dropdown offers these choices:
| Orientation mode | What it does | When to use |
|---|---|---|
| Model orientation | Uses the model's world axes as the WCS axes | When the Design orientation already matches the machine, with Z up |
| Select Z axis/plane & X axis | You pick a face, plane, or edge for Z, and one for X | The most flexible; use for flips and angled setups |
| Select Z axis/plane & Y axis | As above but with Y | When Y is the clearer datum |
| Select X & Y axes | Face or edge for X and another for Y | When both in-plane directions are clearer than Z |
| Select coordinate system | Uses both origin and orientation of a coordinate system defined in the model | Reuse a datum when the model has no suitable point and plane |
For Z, a perpendicular face or a parallel edge can be selected; for X or Y, a perpendicular face or a parallel line. Z, X and Y can each be flipped 180 degrees.
Choosing Z#
Select a flat face that is perpendicular to the direction the tool will approach. For a top-side setup, pick the top face; Z points out of the face (away from the material). For a flip operation, pick the face that will be up after you turn the part over.
If the arrow points into the material, use Flip Z Axis. Autodesk's guidance is that Z should point away from the face you plan to machine.
Choosing X#
The X axis fixes the part's in-plane rotation. Pick a straight edge or a planar face that is aligned with the direction you want to be X. Then check the red arrow on the canvas. If it points the wrong way, use the flip option for X. Y follows by the right-hand rule unless you choose an orientation mode that selects Y.
Think about the machine: on a vertical mill, X is typically left-right across the table and Y is front-to-back. Align X with the vise jaws (long edge along X) so the program matches how the part is clamped. Mismatched rotation by 90 degrees is a classic error: the part is correct but sideways.
Origin modes#
The Origin dropdown selects where X0 Y0 Z0 lies. The milling options are:
| Origin mode | Description | Typical use |
|---|---|---|
| Model origin | The world origin of the Design | When you modeled with a sensible datum already |
| Selected point | Select a vertex or an edge | A hole center, a corner of the part, a datum point |
| Stock box point | Pick a point on the stock bounding box (lower or upper corner and other box points) | Standard approach: top face corner or center of the stock |
| Model box point | Same, but on the model's bounding box | When you want the origin at a corner of the finished part |
Where to put zero in common cases#
- Vise, vertical mill: the top-front-left corner of the stock is common, with Z0 at the top surface of the stock (or at the finished top, if you face off a known amount). Using a stock box point makes this a single click.
- Fixture plate with a known hole pattern: choose a hole center via Selected point, with Z0 on the plate surface or on the part top.
- Round parts: the center of the top face (a stock box point at the middle of the top).
- Second operation (flip): choose the point corresponding to the same corner of the stock after flipping, so the operator picks up the edge on the same side as in Operation 1 (rotated about X or Y).
- Z at the part top vs. the machine table: top-of-stock zero is the convention for most shops because the operator touches off the top with a tool. Z at the table or vise-jaw top is common for lots of small parts where the stock height varies.
Tip: Place Z0 on the top of the finished part if you face off stock and your datum is the finished surface. Place Z0 on the top of the stock if you will touch off the raw material and the face removes a known amount. Whichever you choose, tell the operator.
Step by step#
- Open New Setup (or edit one) and find the Work Coordinate System group.
- Set Orientation to Select Z axis/plane & X axis.
- Click the Z axis selector, then click the top face of the part. A blue arrow appears. If it points down, enable Flip Z Axis.
- Click the X axis selector, then click a long straight edge of the part. A red arrow appears. Use the X flip option if it points opposite to your machine's X.
- Set Origin to Stock box point. Box points appear on the stock. Click the top-front-left corner.
- Verify the triad: Z toward you (out of the top), X along the long edge, Y across.
- Click OK and look at the triad in the canvas. It should sit on the stock corner.
- Rotate the view. Check from the front: does Z0 sit on the top of the stock where you expect?
For a flip operation:
- Create the second Setup.
- Set Z to the bottom face of the part (which will face up after the flip). Because you flip the part about its X axis (or Y axis), the X axis choice matters. Keep X the same edge as in Setup 1 if you flip about X, so the X direction is preserved; if you flip about Y, then X direction reverses and Y is preserved.
- Choose the Origin at the corresponding stock corner.
- Document the flip direction for the operator in a setup comment.
Options reference#
| Option | What it does | Notes/default |
|---|---|---|
| Orientation | Chooses how axes are defined | Defaults to the model orientation |
| Z axis | Face or plane normal defining tool axis | Arrow must point away from stock |
| X axis | Edge or plane defining X direction | Y derived by right-hand rule |
| Flip Z Axis | Reverses Z | Use when the Z arrow points into the part |
| Flip X or Y Axis | Reverses the selected X or Y axis | Corrects the left-right direction |
| Origin | Sets where zero lies | Stock box point is most reproducible |
| Stock box point | A point on the stock bounding box | Moves if the stock changes |
| Model box point | A point on the model bounding box | Useful for finished-part datums |
| Selected point | Origin on a selected vertex or edge | Must be a valid pickable entity |
| WCS Offset (Post Process tab) | Which work offset the post emits | 1 is normally the first zero index (G54) |
How WCS maps to the machine#
The post writes a work offset call (for example G54) at the start of each Setup. The Setup's WCS is what the operator is told to establish on the machine under that offset. If the Setup says "WCS Offset 1" and "origin: top front left of stock", the operator probes or touches that point and enters it into G54. Fusion does not read offsets from the machine; the match between model and machine is a human agreement, which is why your setup sheet and your clear notes matter.
Note: tilted-plane output (for example G68.2 on some Fanuc-style controls) is general industry guidance, not Autodesk data; it depends on the post and controller.
Turning setups#
Turning and Mill/Turn setups use a different WCS group: Z Axis (Rotary Axis) (select a cylinder or sketch line), Flip Z Axis, X Axis (select an edge or sketch line), Flip X Axis, and an Origin of Stock front, Stock back, Model front, Model back, Selected point or Chuck front. Z is almost always on the part centreline and should point away from the chuck. A Safe Z retract (referenced to the WCS origin or stock, with an offset) is also set here and can be overridden on an operation's Passes tab.
4- and 5-axis considerations#
For machines with rotary axes, attach a machine with kinematics to the setup so the WCS and rotary positions are interpreted correctly (see the multi-axis page). For 3+2 operations, a common approach is multiple Setups, each with a WCS Z aligned to the tilted face. See the multi-axis page for details.
Tips and pitfalls#
Tip: Create a visible reference. If you often use a specific location (the vise's fixed-jaw corner), model a tiny sketch point or datum in your fixture component. Using it as a Selected point in every Setup is faster and more repeatable than hand-picking stock grid points.
Tip: Use the view cube to look straight along Z after you set the WCS. If the part looks rotated or mirrored compared with how you hold it, you caught the error before the machine did.
Warning: A Z arrow that points into the stock is the most common cause of "everything cuts upside down" toolpaths. Always confirm it points up and out.
Warning: Changing the WCS after you create operations changes all their positions in machine space, but selected geometry references remain. The toolpaths regenerate; double-check heights and clearance.
Warning: Mixed units. Document units can be inch or metric (Browser > Units > Change Active Units), independently of the machine control. Confirm that your post and control agree (G20/G21) before first cut.
Warning: "Stock box point" depends on the stock size. If you change the stock later, the origin point moves with it. If your physical stock differs from the modeled one, the operator's touch-off point will not match the model. Use model-based origins when stock varies.
Practice exercise#
Model a 60 x 40 x 15 mm block with a 20 mm diameter hole 15 mm from one corner, through the 15 mm thickness. Create three Setups on the same part to compare WCS choices:
- Origin at the top-front-left stock corner, Z up.
- Origin at the center of the hole on the top face.
- A flipped Setup with Z pointing down (bottom face up) and origin at the corresponding stock corner.
For each, add a single 2D Contour around the outside and note how the triad and the posted coordinates differ (use Post Process to view the first lines of the G-code, which will show the work offset and the first positioning moves).
Expected result: the toolpath geometry is identical in shape, but the coordinates in the posted file differ by the offset between origins, and Setup 3 produces a mirrored layout relative to Setup 1.
Related#
- Setups and stock: where the WCS lives
- Post processing: how work offsets are written
- Multi-axis milling: tilted work planes and rotary setups
- Probing: establishing WCS on the machine