Trim/Extend
Trim/Extend cuts a structural member back, or runs it on, so its end meets another face or body, the way a welded frame's members are cut to fit. A member is a straight body such as a bar, a tube, an angle or a channel, made by Extrude, Sweep or from the Library. The member keeps its name and stays its own body, and the change is one step in the Model tree.
When to Use It
- Run a tube on until it meets a base plate, or cut one back that runs past it
- Cut a member square or at an angle to a face
- Fit a tube to a round post (a cope, the post's curve taken out of the tube's end)
- Mitre two members that meet at a corner, so both are cut to the same angled line
Step by Step
- Make the members first, each as its own body (untick Merge result when you extrude them, or place them from the Library).
- Open the model for modeling, then click Trim/Extend on the Fabrication tab (on the Features tab in the other layout). The Trim/Extend panel opens.
- Choose To a face, To a body or Mitre.
- Click the square end face of the member you want to trim or extend. It lights orange.
- Click what it should meet. For To a face, a flat face (on another body or on this one). For To a body, any face of the other body. For Mitre, the square end face of the second member. It lights blue.
- Click Trim/Extend. The member is cut back or run on, and the volume is shown.
Click a lit face again to drop it and pick another. Press Esc to leave without a change.
Options
- To a face: the member is run on along its length past the plane of the flat face you clicked, then everything beyond that plane is cut off. A face beyond the end extends the member to it. A face across the member trims it there. The face may be square to the member or at an angle, and it may be smaller than the member: its plane is what counts.
- To a body: the member is run on into the other body, and that body's shape is cut out of it. Use it for a tube meeting a round post or pipe, where the end must follow a curve. The body itself is left as it was.
- Mitre: two members whose centre lines meet at a corner are both cut, or run on, to the one plane halfway between them, so they meet edge to edge in a mitre. Square members meeting at 90 degrees get the usual 45 degree mitre.
Tips and What to Expect
- Worked example: a 1 x 1 in square bar 4 in long, with a plate whose face is 1 in past the bar's end. To a face on the plate runs the bar on by 1 in, adding 1 x 1 x 1 = 1 cubic in (16387.064 cubic mm). In millimetres, a 20 x 20 mm bar 100 mm long and a face 30 mm past its end add 20 x 20 x 30 = 12000 cubic mm.
- Trimmed to a face that crosses the bar at 45 degrees through the middle of its end, the bar neither gains nor loses volume: one corner gains what the other loses.
- Mitre: two 1 x 1 in square bars at a square corner, whose centre lines meet 5 in from each far end, are each cut or run on to the 45 degree plane. Each then holds 1 x 1 x 5 = 5 cubic in (81935.32 cubic mm), as if it were cut square 5 in long. In millimetres, 20 x 20 mm bars whose centre lines meet 100 mm from each far end hold 20 x 20 x 100 = 40000 cubic mm each.
- The member end must be square to the member, the end a straight member is cut off at. An end already cut at an angle cannot be run on again; Undo the earlier cut, or pick the other end.
- Trim/Extend never makes a new body. Each member it changes keeps its name, so Cut List and Bodies still list it.
- The Cut List follows a Trim/Extend To a face or Mitre: the member is listed at its new cut length and end angle. A member fitted To a body is listed under Not listed; check that length by hand.
- When an earlier step changes the end or the face, the step stops and says which one is gone. Delete it and make it again on the faces you want.
- Edit Feature (right-click the step in the Model tree) can switch between To a face, To a body and Mitre. The faces stay the ones you clicked.
Common Problems
- "Click the flat end face of the member to trim or extend." Nothing is picked yet, or the first face was dropped.
- "The member end is not square to its member (it may be cut at an angle already, or it is not the end of a straight member)." Pick a square end. Trim/Extend runs a member on from a square end.
- "The face to meet runs along Body 1 (within 5 degrees), so the member never reaches it." The message names your member. Pick a face across the member's path. A face only a little more across than that is still met exactly, however far past the part it is.
- "The face to meet is behind the whole of Body 1, so nothing of it would be left." Pick a face ahead of the end, or across the member.
- "That plane cuts Body 1 into 2 pieces." The member bends back across the plane. Pick a face nearer the end, or use Split.
- "That face is on Body 1, the member itself." For To a body, click a face of the other body.
- "The member would run past Body 2 without meeting it all the way across." The body is not in the member's path, or is narrower than the member. Use To a face instead.
- "That body cuts Body 1 into 2 pieces (the member runs through it)." The member already runs through the body. Use To a face.
- "The two members run side by side or in line, so there is no corner to mitre." Members pointing the same way within 10 degrees, or in line within 5 degrees, have no corner. and "The centre lines of Body 1 and Body 2 pass 0.25 in (6.35 mm) apart, so they do not meet at one corner." A mitre needs members whose centre lines cross. Use To a face to trim each one.
- "You picked the same face twice." Click the end of the member, then what it should meet.
- "The Trim/Extend took longer than 30 seconds, so it was stopped and the part left as it was." Try it on a simpler member.
What It Does Not Do Yet
- There is no dashed preview yet: press Trim/Extend and Undo if it is not what you wanted.
- One member is changed at a time (two for a Mitre). There is no weld gap setting; to leave a gap, use To a face on a face set back by the gap.
- To a body keeps the member whole. A member that runs right through the body is refused rather than cut in two.
- A curved member (a sweep along a bend) works only when the face or body it meets is past the bend.