What is cut length?
Cut length (or cutting length) is the total length of every path a machine cuts to make a part: the outside profile plus every hole, slot and internal cut-out. It is the main input to cut time, which makes it one of the first numbers in any laser, plasma or waterjet quote.
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What does cut length mean in fabrication?
Cut length is the distance the cutting head travels while it is actually cutting, added up across the part. Part size on its own tells you little. A plain 500 mm (20 in) square has 2 m of cut, and a smaller bracket covered in holes and slots can have more.
A worked example, for a 200 x 100 mm (about 8 x 4 in) plate with four 10 mm (3/8 in) holes:
- Outside profile: 2 x (200 + 100) = 600 mm
- Four holes: 4 x 3.14 x 10 = 126 mm
- Total cut length: about 726 mm (28.6 in)
Run 100 of them and the job has about 72.6 m (238 ft) of cutting.
How is cut length used?
Cut length divided by the feed rate gives cut time. At 3 m/min (about 120 in/min), the 72.6 m job above needs roughly 24 minutes of cutting. Pierce time and travel between features go on top to give the cycle time.
Shops also use it to compare parts. Two parts cut from the same size blank can take very different times, and cut length shows why before anything goes near the machine.
A few things change the number:
- Lead-ins and lead-outs, the short paths into and out of each contour, add a few millimetres per feature.
- Etch lines are marked rather than cut, so they're measured separately and priced at the etching speed.
- Common-line cutting, where neighbouring parts share an edge, reduces the total for a nested sheet.
Why does cut length matter?
Cut length sets cut time, and cut time is usually the largest share of machine time on a laser job. If the cut length is 20% out, the cutting part of the price is out by about the same.
The most common source of a wrong number is the drawing. Customer DXF files often contain duplicate lines stacked on top of each other, leftover dimensions, centre lines or a title block. Measure the file as it arrives and all of that counts as cut length. Duplicate lines alone can double the figure, and if they reach the machine, the part gets cut twice.
Cut length and DXF files
Before cut length can be trusted, the drawing has to be clean:
- Remove duplicate and overlapping lines.
- Delete dimensions, notes, centre lines and the title block, but keep a copy, because they often hold the material, thickness and quantity.
- Close open contours so each shape is one continuous path.
- Check the file is drawn at 1:1 scale in the right units. A drawing in inches read as millimetres comes out 25.4 times too small, and so does its cut length.
Our guide to DXF files covers these problems in more detail.
Cut length and quoting
Cut length is one of the first numbers a quote needs, and the one most likely to differ between estimators when it's measured by hand or scaled off a printout. Taken straight from clean geometry, everyone in the shop gets the same number for the same part, and so the same price whoever quotes it.
That's how Tempus Tools quotes: it reads cut length and pierce count from the customer's DXF, DWG or 3D file and applies your feed rates, so the cutting time behind every price comes from the part itself.
Further reading: How fabrication shops calculate laser cutting costs in Excel
Related terms
Clean the drawing, then trust the cut length
Tempus Tools finds duplicate lines, stray dimensions and open shapes in customer drawings and helps you fix them before the part is priced, so the cut length behind your quote matches what the laser will cut.
FAQs
How do you calculate cut length?
Add the perimeter of the outside profile to the perimeter of every hole, slot and cut-out. A 200 x 100 mm plate with four 10 mm holes has 600 mm of outside profile plus 126 mm of holes, about 726 mm in total. In practice, quoting or CAD software measures it from the drawing.
Does cut length include holes and internal features?
Yes. Every internal cut adds to the total, which is why a small part with lots of holes can have a longer cut length than a larger plain one.
How does cut length affect price?
Cut length divided by the feed rate gives cut time, and cut time multiplied by the hourly rate gives most of the machine cost. All else being equal, a longer cut length means a higher price.
Why is the cut length from a customer's DXF sometimes too high?
Usually because the file contains duplicate lines, dimensions, centre lines or a title block that get measured as if they were cuts. Clean the drawing before taking the cut length from it.