Design Guidelines for Bent Sheet Metal Parts

In addition to blank cutting, OSH Cut now offers sheet metal bending services!

Usually, obtaining a quote for a fabricated metal part requires that you prepare and send a print that describes your part, including bend radii, part dimensions, tolerances and so on.  This can make quoting tricky, because actual bend properties (radius, bend allowance, etc.) depends on material properties and tooling availability.  Often, getting a quote for fabricated parts involves a lot of back-and-forth with shops to finalize your design so that it is manufacturable.  That quoting complexity and expensive overhead drives the very high costs that usually characterize short-run and prototype fabrication jobs.

At OSH Cut, our bend parameters are standardized and published online, so that you can know right away how you should design your part to make it as close to your target size/shape as possible.  Check out our material catalog for bend information on all our materials.

As you prepare your designs for bending, please keep the following in mind:

1. Understand how k-factor and bend radius will affect the size of your fabricated part

Instead of working from a print, OSH Cut allows you to upload a DXF flat pattern of your part and select bend lines, as shown below:

A bend line just has to be a straight line, of any length.  Our web app will automatically extend the the bend line to the part edge as needed to make the bend manufacturable.  Your bend line can also overlap the part edge. 


The bend parameters used for our material and tooling are shown on the bottom left when you've selected a bend line (as shown above).  This will let you know the inner radius, k-factor, and other properties you can use to ensure that your part is designed correctly.

You can also get bend properties from our material catalog, without having to upload a part first.

When bending your part, we will place the punch EXACTLY on the bend line in your drawing. 


To obtain a fabricated metal part that is the size you expect, your part should be designed to match the bend radius and k-factor for our material and our tooling, as described in our material catalog, and in the bend properties that our system reports when you create a bend in your part.

We recommend that you determine what bend parameters to use through our catalog, and then design your part in CAD using those parameters, to ensure that your part is as accurate as possible.  If you are manually adjusting the size of your flat pattern in 2D instead of unfolding a 3D model in CAD, you can use the bend allowance reported by our web app to adjust the flat properly for your selected bend angle.

While our bend parameters are specific to our materials and tooling, we selected tooling that is close to "optimal" in terms of v-gap size and resulting bend radii, so our guidelines should get you close no matter what shop you choose to use.

2. We will review your order for manufacturability after it is submitted

Our system does not (yet!) perform manufacturability checks on your part, so it is possible for you to submit a design that we can't make for you.  After you submit your order, we will review it.  We'll contact you if there are any problems, so if you don't hear from us, you are good to go! 

To ensure that your part can be manufactured, follow the design rules under the "Bend Parameters" section for your material in our material catalog, as shown in the highlighted area below:

See the graphic below for an illustration of the meaning of the bend parameters listed in our catalog:

3. We currently only offer air bending

We currently do not offer any operations beyond air bending.  This means we cannot create seams, hems, hinges, etc. on your fabricated part.  We are also currently unable to perform finishing operations on your flat before bending, including edge rounding or surface graining.

As a result, your part may contain shallow, cosmetic scratching and small edge burrs, particularly on the bottom side of the cut edge.  We are working on expanding our finishing capabilities, but for now, this is not something we are capable of doing for you.  If your part needs to be ready to paint or ready to ship to a customer when you receive it, we recommend for now that you find a full-service fabrication shop that has the equipment to finish your parts as needed.

4. Lead-times and shipping prices are provided during checkout

Our system is smart about figuring out how to package and ship your parts, whether via parcel or freight.  Sign in and click "Checkout" button to enter your address to get shipping prices and lead-time options.

3D box packing shown above.  You won't see this during checkout, but this is what our system is doing under the hood to figure out how to package and ship your parts.