Modelling a run of pipe, a stair handrail, a rib following the edge of a roof. All three are the same shape of problem: there is a cross section and there is a route, and the two have to become a solid.
The sweep command in AutoCAD does exactly that in one pass. This article copies the prompt sequence verbatim, measures the volume of the solid and checks it against hand arithmetic, and sets out four options almost nobody opens. For the full modelling toolkit see our AutoCAD for Construction course.
Where to start it
Read straight out of the acad.cuix interface file of the 2027 release.
| Way in | What to use |
|---|---|
| Full command | SWEEP |
| Alias | none |
| Ribbon | none |
| Classic menu | Draw → Modeling → Sweep |
| Toolbar | Modeling → Sweep |
Two empty rows explain why people can use AutoCAD for years without meeting this command. It has no alias, and the ribbon of the default workspace carries no button for it. To get a button you have to switch on the Modeling toolbar, or use the classic menus — bringing those back is covered in our article on the AutoCAD interface.
Two relatives, from the same file:
| Command | Alias | Menu |
|---|---|---|
EXTRUDE | EXT | Draw → Modeling → Extrude |
REVOLVE | REV | Draw → Modeling → Revolve |
The steps on the command line
Copied verbatim from AutoCAD 2027.
Command: SWEEP
Current wire frame density: ISOLINES=8, Closed profiles creation mode = Solid
Select objects to sweep or [MOde]: 1 found
Select objects to sweep or [MOde]:
Select sweep path or [Alignment Base point Scale Twist]:| Step | What it asks | What you do |
|---|---|---|
| 1 | Select objects to sweep or [MOde]: | Pick the profile, then Enter |
| 2 | Select sweep path or [Alignment Base point Scale Twist]: | Pick the path |
Two steps only, but the first line rewards reading. The program prints Closed profiles creation mode = Solid, which means a closed profile gives a solid. An open profile gives a surface instead, and that is far and away the commonest reason somebody reports "it swept but there is no solid".
The volume matches the formula exactly
This is the surest way to check the result, and it produces a satisfying number.
Take a circle of radius 100 as the profile and a 1000-long vertical line as the path. After the sweep, read the volume of the solid:
| Value | |
|---|---|
| Volume read off the solid | 31,415,926.54 |
| By hand, π × 100² × 1000 | 31,415,926.54 |
| Difference | 0.000000% |
Not one part in a million out. So the command does the arithmetic properly, and what it makes is a genuine solid rather than a hollow shell — a shell would have given a quite different figure. This is also the quickest check on a model that arrives from elsewhere: select the solid, open the Properties palette, read the volume and compare it with your own sum. A match means the model was built properly; a mismatch means something is hollow or overlapping where the eye cannot see it.
One more thing measured in the same run: after the sweep the drawing holds one object. Both the profile and the path were consumed. To keep them, set the DELOBJ variable to 0 beforehand.
The four options at step two
This is the part tutorials skip, and it is what separates a plain tube from a usable component.
Alignment decides whether the profile turns itself square to the path. Autodesk's SWEEP page puts it this way: "If the profile is not perpendicular (normal) to the tangent of the start point of the path, then the profile automatically aligns. Enter No at the alignment prompt to prevent this." Answer No and the profile keeps its original orientation all the way along — right for a flat band following a curve rather than a tube.
Base point says which point of the profile rides on the path. By default the program takes the centre. With an off-centre profile — an angle section running along a slab edge, say — picking the right base point is the difference between correct placement and being tens of millimetres out.
Scale lets the profile grow or shrink along the route. This is how a tapered tube or a handrail that thins towards one end gets built.
The twist option turns the profile around the path. The same page states: "The twist angle specifies the amount of rotation along the entire length of the sweep path." So the angle you declare is the rotation over the whole route, not per unit of length. Declare 360 degrees and the result turns exactly once — the way threads, springs and spiral balustrades are made.
Drawing pipework with a sweep
This is what the command gets used for most in construction work, so it is worth the detail.
For round pipe the profile is a circle and a sweep path is the pipe run itself. A run like that is hardly ever straight, so it has to be a polyline with filleted corners, not a handful of separate segments. A polyline keeps the continuity the sweep needs to run through in one pass; separate segments mean sweeping each one and leaving gaps at the joints. Joining loose linework into a polyline is covered in our article on polylines in AutoCAD.
Notice the option offered at the very first prompt: Select objects to sweep or [MOde]:. That MOde switch is what decides between a solid and a surface, and it is worth opening once so you know it is there. Left alone it follows the setting printed on the line above, Closed profiles creation mode = Solid, which is why a closed profile normally gives a solid without anyone having to ask for one.
Pipe with a wall thickness takes two passes: sweep the outer circle into a solid, sweep the inner circle into a second one, then subtract the inner from the outer with SUBTRACT. The selection order there catches people out: pick the solid to keep first, press Enter, and only then pick the solid to remove. The other way round loses the part you wanted. Working with regions and boolean operations is covered in our article on the region command in AutoCAD.
When the profile is not a circle
A circular profile is the easy case. Real drawing work throws up others: steel sections, mouldings, drainage channels, flat handrails.
Those ask two more things. First, the profile has to be one single closed object — a few separate lines may look closed but the program does not treat them as closed, so they must be joined into a polyline or turned into a region first. Second, watch the base point, because an off-centre profile left to the program's default centre drifts off the route.
A quick way to tell whether a profile is closed: select it and open the Properties palette. If there is an Area row it is closed; if not, it is open. That palette is covered in our article on the Properties palette in AutoCAD.
A solid model: sweep against extrude and revolve
Three commands in the same family, and picking the wrong one makes work.
| Command | What it needs | What it makes |
|---|---|---|
EXTRUDE | a profile and a height | A straight solid of constant section |
REVOLVE | a profile and an axis | A solid of revolution |
SWEEP | a profile and any path | A solid following that exact route |
In short: a straight run calls for EXTRUDE, a run around an axis calls for REVOLVE, and only a route with a shape of its own needs the sweep command in AutoCAD. Revolution is covered in our article on the revolve command in AutoCAD.
The reason for choosing carefully is not tidiness. Each of the three writes a different kind of object into the drawing, and the one you pick governs how easy the model is to change later. A straight length of duct modelled with EXTRUDE can have its height edited in the Properties palette in a couple of seconds. The same duct swept along a line takes a rebuild if the run changes. So reach for the simplest command the geometry allows, and keep the sweep for routes that genuinely bend.
Three things people say that are not true
| What people say | What the 2027 release actually does |
|---|---|
| The command has a ribbon button | No button and no alias; only the menu and the Modeling toolbar |
| Open or closed, the profile gives a solid | The first line reads Closed profiles creation mode = Solid; an open profile gives a surface |
| The profile survives for reuse | The drawing holds one object; profile and path are both consumed |
Frequently asked questions
Is there an alias?
No. Type the whole word SWEEP, or use Draw → Modeling → Sweep.
It swept but there is no solid?
Usually the profile is not closed. The first line says Closed profiles creation mode = Solid: closed gives a solid, open gives a surface.
How do I keep the profile and the path?
Set DELOBJ to 0 before running. Left at its default both are consumed and the drawing holds one solid.
How do I make a tapering tube?
At step two type Scale and declare a factor. The profile then grows or shrinks along the route.
Can it model a spring?
Yes, with the twist option and a helix as the path. Declare 360 degrees and the profile turns exactly once along the run.