CAD Design Tips

Fractory gives instant prices for STP and DXF files. STP CAD models can be used for both cutting and bending. DXF drawings only work for instant cutting price quotations.

For creating your CAD models, we have compiled a list of free CAD software.

STP Files

Convert your CAD models to STP before uploading them onto Fractory’s platform for instant manufacturing quotes.

Recommended Minimum Flange Length and Inner Radius

Sheet metal bending chart
Metal folding chart (units in mm)

According to every sheet thickness, there’s a suitable inner radius and flange length when bending sheet metal.

Flange too short for bending

It is visibly clear that it is not possible to bend the part on the right. The flange is too short.

Sheet metal bending inside radius

The radius for the part on the left has been chosen according to the bending table. Therefore, we can give an automated quote for that.

The part on the right is not producible. The inside radius is too small compared to the material thickness.

Chamfered Flange

Bending a chamfered flange

If the flange has a chamfer, the shortest side should be considered as flange length. See metal folding chart.

The danger with such parts is that the shorter part of the flange may get deformed during the bending operation.

Hole Distance

Hole distance to bend

Holes close to the bend may get deformed. Holes should be farther than the minimum recommended flange length. See metal folding chart.

Bending metal with holes

The flange on the left is designed according to the rules in the bending table. Thus, the hole is far enough from the bend for an optimal result.

The part on the right has the hole too close to the bend and will get deformed.

Successive Bends

2 bends in succession

When you have successive bends, the minimum distance is the minimum flange length. See metal folding chart.

Bend Relief

Sheet metal bend relief

Use cut-outs next to flanges to avoid tearing the material during bending.

Max Dimensions 2980×1480 mm

Cut metal sheet

Although the standard sheet size is 3000×1500 mm, we have to cut off the edges to secure proper positioning of the cutouts.

Tolerances on a Separate PDF

Hole tolerance in sheet metal


Any specifications about metal surface treatment should be included in the commenting section.

Cutting Letters and Signs

Laser cut letter and signs
The versions of the letter “O”. Version 3 will end up like version 1. It just has an unnecessary extra cut.

The insides of letters will fall out unless connected to the part. A common mistake we see.

Cut to Normal

Cut to normal in CAD

When making cuts in the sheet metal environment, use the cut to normal function.

Threaded and Chamfered Holes

We can also do threading and countersinking. Indicate the number of threaded/countersunk holes on the ordering form to get an instant price.


The 3D models should include pilot holes for each threaded hole according to the table below but not the threads. Please attach a production file with relevant information about the threads.

Hole size for threading
Pilot hole sizes for thread size


Your 3D models should include the main hole but not the chamfers. Please attach a production file with relevant information about the chamfers.

Hole Distance

Hole distance sheet metal
2 mm sheet metal

The distance between cuts should be equal to or more than the material thickness.

Hole Size

Hole size in sheet metal
Hole size in 2 mm sheet

Holes should have a diameter equal to or more than the material’s thickness.

DXF Files

1:1 Scale

DXF Drawing scale

All drawings must be 1:1. Overwriting dimensions will not help. The scale command is your only tool. You can check if the dimensions are correct after uploading your drawing.

Create Your Drawing from Scratch

Save as files often bring unnecessary hidden layers or unnoticed faraway views with them. Create a new drawing instead of using an old as a template.

One Part per Drawing

Correct DXF

Cutting Lines Only

CAD drawing without dimensions

There must be nothing else in the cutting file besides the cutting lines. No title block, dimensions, tolerances, center lines, bending lines or hatching.

Breaking the Views

Broken view in CAD

Don’t do it. The system does not recognize it and has no way of knowing the actual dimensions of the part.

Connected Lines

Connected lines in CAD

Avoid Splines

Splines can cause plenty of problems. Laser cutters have their own software that tends to interpret splines in a way that produces an unsatisfying result. Use arcs and lines instead. They are easily readable for laser cutting software.

No Overlapping Lines

It may be hard to notice with the human eye but the computer recognizes them and calculates them as extra cuts.

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