Design for Manufacturing: Sheet Metal Parts

What design for manufacturing means for sheet metal

Design for manufacturing (DFM) is the habit of drawing a part so that it can actually be made the way you drew it. For sheet metal that comes down to two processes. The flat profile is laser cut straight from the geometry in your file, and any bends are then formed on a press brake by CNC folding.

Because the laser follows your file exactly, the file is the part. A line in the wrong place is cut in the wrong place. A hole that sits too close to a fold distorts when the flat blank is bent. A shape that is not connected to anything falls out. Good DFM catches these problems on screen, while they are cheap to fix, instead of in the finished part.

It also keeps cost down. With sheet metal fabrication through Partspark you can order laser cut parts online with no tooling, no setup fees and no minimum order, so a design that is right first time goes straight from upload to production.

What Partspark's automatic DFM checks catch

Partspark evaluates your design when you upload it, and again as you adjust a template in the Part Designer. It looks for common manufacturing pitfalls such as warping, floating elements and impossible bends, and where it can, it tells you how to fix them.

• Holes and cut-outs too close to a bend line

  A hole or cut-out near a bend line is at real risk of warping when the part is folded. The fix is to move the feature further from the bend line, or to add relief at the bend.

• Floating elements

  Interior shapes that are not connected to the rest of the part would simply drop out as loose offcuts during cutting. Join them to the part with tabs, or remove them.

• Impossible bends

  Bends that cannot be formed as drawn are flagged before you order, so you can change the design rather than find out after it has been cut.

• Inside bend radius

  The minimum inside radius of a bend cannot be smaller than the material thickness. The uploader enforces this when you set each bend.

Errors and warnings

Issues appear as cards alongside your part. Red cards are errors, and they must be resolved before you can add the part to your cart. Yellow cards are warnings: they are advisory, so read them, change the design if it matters for your part, or accept and continue.

The checks look for common pitfalls. They do not replace your own review of fit and function, and they do not set a tolerance. If a dimension is critical, see when to talk to us first.

Preparing DXF and SVG files for laser cutting

Most DFM warnings start in the file. These points cover the most common file issues when you upload your own flat pattern.

• Use an accepted format

  DXF, SVG and STEP (STP) files are accepted. DXF is the recommended format for flat patterns. If you do not have a CAD file at all, the Part Designer builds the part from a template.

• Work in millimetres

  DXF coordinates are read as millimetres. If your file is drawn in inches or metres, scale it before you upload. For SVG, set the document to millimetres before you start drawing.

• Put cuts and bends on their own layers

  In a DXF, the outer profile, holes and cut-outs go on a CUT layer and bend lines go on a BEND layer. Any layer with BEND or FOLD in its name is read as bend lines. Layers named for dimensions, text, notes, construction or centre lines are skipped.

• Watch layer 0

  Geometry on any other DXF layer, including the default layer 0, is treated as a cut. A bend line left on layer 0 would be cut straight through your part.

• Close every contour

  The outer profile and every hole must form a closed loop. Use your CAD tool's close or join function on open polylines before you export.

• Delete duplicates and extras

  Stacked, overlapping lines inflate area measurements and confuse hole detection. Remove duplicates, bounding boxes, title blocks and anything else that is not part geometry.

• Keep entities simple

  Lines, polylines, circles, arcs and splines are read from a DXF. Blocks, hatch fills, dimensions and text are ignored, so explode blocks into plain geometry before saving.

• Export from the part, not a drawing

  A drawing export can carry the sheet scale, title block and dimensions with it. Export the flat pattern of the part itself.

SVG files

SVG uses layer names in the same way. Put the outer profile and interior cut-outs on CUT, shapes you want cut as holes on layers whose names end in _HOLE, and bend lines on BEND. Everything on any other layer is ignored, so dimensions and notes can stay in the file. Save as plain SVG rather than an editor-specific format.

Step-by-step instructions, including SolidWorks export and layer mapping, are in the DXF and SVG preparation guides. Sample files are on the downloads tab.

Choosing material and thickness

Three metals are stocked, sourced from Australian suppliers, in sheet from 0.9 mm to 10 mm depending on the material and grade. The thicknesses available for each grade are shown in the app when you choose a material, so check there before you commit to a thickness in your design.

• Mild steel

  Grades 250 and 350. The most economical option and it takes powder coat well. It will rust if left uncoated, so consider powder coating for parts that live outdoors.

• Aluminium

  Grades 5052 and 6061. Light and corrosion resistant. 5052 is the go-to for lightweight parts that need corrosion resistance; 6061 offers higher strength but is less formable, so use it where stiffness matters more than tight bends.

• Stainless steel

  Grades 304 and 316. 304 covers most food and hygiene applications; choose 316 for marine or chloride-rich environments.

Compare them side by side on the materials page. If you need a material or thickness that is not listed, get in touch and we will tell you whether we can source it.

Designing bends and folds

A folded part starts as a flat laser cut blank. Draw it as a flat pattern, mark each bend as a straight line on its own BEND layer, then set the angle, radius and direction for each bend in the uploader. A single flat pattern can carry multiple bends, which is how brackets, channels, boxes and enclosures are made.

• Keep holes and cut-outs clear of bend lines. Features close to a bend distort when the part is folded, and the uploader warns you when one is too close.
• Where a cut-out has to sit near a fold, add relief at the bend line rather than relying on the metal to form around it.
• Set an inside radius no smaller than the material thickness. The uploader will not accept a tighter one.
• Pick a formable material for tightly folded parts. Aluminium 6061 is less formable than 5052.
• Use the 3D preview to confirm the folded shape, then check the number of bends reported matches your design.

Each bend adds a folding operation, and the price updates as you add them. If you start from a template in the Part Designer, the bend lines are set up for you. More on the process is on the CNC folding page.

Finishing with powder coat

Parts can be left raw, straight off the laser, or powder coated in standard black or white, or a custom colour. Powder coat is the finish we recommend for mild steel parts that will live outdoors or be handled regularly, and it works on aluminium and stainless steel too.

Design with the coating in mind. It adds a thin layer to every surface, including the inside of holes, so allow a little clearance on tight-fitting holes and slots. Coating happens after cutting and folding, so it adds time to the order, confirmed at checkout. For a custom colour, a RAL reference is the quickest way to tell us what you need, and we confirm availability before production starts. See all options on the finishes page.

Checklist before you upload

Run through this list before you upload, then again when the DFM results come back.

• The file is DXF, SVG or STEP, drawn in millimetres at full size.
• Cut geometry is on CUT and every bend line is on a BEND layer, with nothing left on layer 0.
• The outer profile and every hole are closed loops, with no duplicate lines.
• There are no floating shapes inside the part that would fall out when cut.
• Holes and cut-outs are kept clear of bend lines, or the bend has relief.
• Dimensions, notes, title blocks and bounding boxes are removed or on skipped layers.
• You know which material and grade you want, and have checked the thicknesses offered for it in the app.
• Tight-fitting holes and slots allow a little clearance if the part will be powder coated.
• After upload, the reported width, height and number of bends match your design.
• Every red error card is resolved, and you have read and accepted any yellow warnings.