Step By Step Guide To Sheet Metal Bending

Four sheet metal bending examples in four different materials

Table of Contents

From concept to finished product, sheet metal bending requires a deliberate, thought-out design and intentional manufacturing. There are a few major steps to successful bending:

Step 1: Initial Design

Step 2: Preparing Your File 

Step 3: The Bending Process

Step 4: Finishing Processes

We have a variety of helpful resources on bending, but let’s walk through these key steps so you can achieve the best results from SendCutSend. 

Basic Sheet Metal Bending Terms

Before we jump into our step-by-step guide, there are a few basic bending terms that you should know. The video below goes through all those definitions and will help you prepare for creating a successful bent sheet metal product.

Step 1: Initial Design

We’re going to go over some general design principles for bending, but be sure to check out our software tutorials to see specific examples.

Bend deduction

One of the most important things to take into consideration when designing bent sheet metal is bend deduction. Bend deduction is used to account for the “stretching” that happens in a material when it’s being bent. Bend deduction changes based on the material, thickness, and angle of the bend being created, but essentially it’s just making your part slightly smaller to make room for the stretched material around the bend.

The best way to see what dimensions you should be using on your bent parts is to use our online bending calculator.

A laptop showing SendCutSend's sheet metal bending calculator which helps you calculate bend deduction

Flange length

You will also need to know what flange length you’ll need and if that length will work in your chosen material. (The flange is the edge of the part that’s bent from the stationary base.) For sheet metal bending with SendCutSend, the minimum flange length varies by material and thickness.

Flange and base of a metal bend

To see the full list of minimums and maximums for SendCutSend’s bending service, check out our Bending Min/Max Chart.

Bend relief notches

To reduce bulging in the corners of your bent parts and prevent tearing, you can incorporate bend relief notches into your design. Bend relief notches are just narrow notches or circles put into the corners of your design. These notches should be at least 50% of the material’s thickness in width and the depth should equal Bend radius + Material thickness +.020”. These notches allow for less stress on the inner radii of the flanges, and will help keep the corners of the bends from interfering with the base material.

A part with two flanges nearly meeting at a corner, with a bend relief notch laser cut between them

Features spaced away from die line

Finally, make sure that all holes and features are adequately spaced away from the die line. Each material and thickness has its own recommended distance between features and the die line. See our guide to avoiding deformation and reference the specifications for your chosen material to make sure your bent part will not experience any feature warping. 

A bent sheet metal part with an oblong hole crossing the bend line. The hole is warped because it's too close to the bend

Step 2: Preparing Your File for Bending

If you plan to upload a 2D file, be sure to save or export your file in one of these vector formats: DXF, DWG, EPS, or AI (Adobe Illustrator). If you will upload a 3D file, save your design as a STEP or STP format file and ensure it meets our 3D File Guidelines.

Bend line indicators

If you’ll be uploading a 2D vector file, make sure that you are using the correct lines to indicate bends. The bend line indicator we prefer changes depending on what program you are using to design your parts, and we’ve laid it all out in this chart:

SOFTWARE2D FORMAT3D FORMATBEND LINE
Fusion360.dxf.step, .stpSolid line (default)
Adobe Illustrator.aiN/ASolid, separate color from cut lines
SolidWorks.dxf.step, .stpDashed centerline (not Hidden)*
AutoCAD.dxf.step, .stpDashed line
CorelDraw.epsN/ASolid, separate color from cut lines
Inkscape.epsN/ASolid, separate color from cut lines

*SolidWorks may default to the Hidden line style which will not be detected by our system. Please be sure to use a different dashed line style.

While we accept .AI and .EPS files, it’s critical that your bend lines are parallel when uploaded from these software or the file will delay processing. 

If you design your parts in Adobe Illustrator, please send us the original (native) ai file. We’ll take care of the conversion on our end. For the fastest turnaround on your order, we recommend designing your parts in a CAD software.

Pre-flight checklist

Finally, just make sure to follow our pre-flight checklist for file preparation and you’ll be ready to go:

  • File is in a format that we accept (2D: .dxf, .dwg, .ai, .eps; 3D: .step or .stp)
  • All holes and cutouts are at least 50% material thickness and adequately spaced away from the die line
  • Bend lines are shown using the correct indicator for your program
  • File is built at a 1:1 scale, preferably in inch-units
  • All objects are on the same layer
  • All stray points, duplicate lines, empty objects and text areas have been removed
  • No shapes have open contours
  • All shapes have been united, combined or merged
  • All text has been converted to outlines or paths
  • Cut-out text (reversed text) has bridges or has been stencilized

Step 3: The Bending Process

Sheet metal bending is capable of forming many difficult parts and products, but tooling does have its limitations. There are a few bends that we don’t currently offer: 

  • No acute angles greater than 130°
  • No curl, bump, or roll forming
  • No coining
  • No hemming

The tooling bend radius is adjusted depending on the material and its thickness, but you can check what the bend radius will be by once again using our bending calculator. And check out our full bending guidelines to see all the capabilities and limitations of CNC bending.

Bending will also add a little bit of time to your order, so check out SendCutSend’s processing and shipping policies. The estimated ship date for your order will be shown at checkout.

Step 4: Finishing Bent Sheet Metal

Bending may leave die marks on your parts, but these marks are purely cosmetic and will not affect your part in any way. While we don’t offer any protection to prevent die marks, they’re easy to remove with a DA orbital sander after you receive your parts.

Close-up view of die marks leftover on a bent sheet metal part

You can also powder coat bent sheet metal parts, and it’s simple to add powder coating to your SendCutSend order. It’s important to note die marks can show through the powder coating, so while it won’t completely cover up machining imperfections, powder coating will give your parts a protective and aesthetic finish.

Making Sheet Metal Bending Simple

Our goal here at SendCutSend is to make bending a simple, understandable process, and we are continually growing our resource library to make that reality. Take a look at our bending FAQs and reach out to our support team with any additional questions.

After you have finished your design and prepared your file, upload it to our instant pricing tool and get your custom bent sheet metal project started!

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We proudly use hardware by PEM

Flush Standoff, 4-40, .250" Zinc plus Clear Chromate

Aluminum: 5052, 6061, 7075 Steel: Mild, G30

SKUSO-440-8
Thread Size4-40 x .250″
Hole size in sheet (+0.003/-.0.000).168″
Minimum sheet thickness0.040″
Maximum sheet thickness.125″
Fastener materialSteel
Minimum distance hole C/L to edge0.230″
When determining the distance between two or more fasteners, you can calculate the distance by the formula, C/L to edge + 1/2 the diameter of the second mounting hole..345″
Recommended panel materialSteel/Aluminum
Coating typeZinc
Length.250″
Aluminum material ranges (5052, 6061, 7075)0.040″-0.125″
Steel material ranges (CRS, HRPO, HR)0.048″-0.119″

We proudly use hardware by PEM

Flush Standoff, 4-40, .250" Passivated

Stainless Steel: 304, 316

SKUSO4-440-8
Thread Size440
Hole size in sheet (+0.003/-.0.000).166″
Minimum sheet thickness0.04″
Maximum sheet thickness.125″
Fastener material400 Stainless Steel
Minimum distance hole C/L to edge0.230″
When determining the distance between two or more fasteners, you can calculate the distance by the formula, C/L to edge + 1/2 the diameter of the second mounting hole. Example shown with x2 of the same hardware..313″
Recommended panel materialStainless Steel
Coating typePassivated
Length.250″
304 Stainless Steel material ranges0.048″-0.125″
316 Stainless Steel material ranges0.060″-0.125″