Fiber Laser Cutting Design Guide

The rule

Leave 0.50″ on all four sides of the sheet. Maximum part length is the sheet length − 1.00″, and maximum width is the sheet width − 1.00″. A 120″ × 48″ sheet gives a 119″ × 47″ blank.

Why it matters

Mill sheet edges are sheared, can be slightly out of square, and pick up handling damage. The margin keeps your part edge on clean, flat material. It also leaves the skeleton a continuous frame, so the sheet stays rigid and comes off the bed in one piece.

Design it right

• These are flat blank sizes. Measure a formed part by its unfolded flat.
• Check the sheet sizes we stock for your material on its material page.
• For a part near the limit, ask before you design around a larger sheet.

The rule

The smallest blank we cut free is 0.250″ × 0.250″, for every material and thickness.

Why it matters

The sheet sits on the tips of steel slats. Once a part is cut free it has to bridge those tips. A smaller part drops between them and is lost in the scrap. Worse, it can tip up on edge into the path of the cutting head and cause a crash or a scrapped sheet.

Design it right

• Keep each blank at least 0.250″ in both directions.
• Smaller parts are still possible: we cut them on a tabbed skeleton, held by micro-joints, and you snap them out.
• See Min / Max Part Sizes for every stock.

The rule

Each stock has two catalog limits. The Min Recommended Hole Size is the size to design to. The Min Hole Size is the smallest we cut. On 0.125″ 5052 they are 0.063″ and 0.031″. Below the minimum, the quote system converts the hole to a laser-marked center.

Why it matters

Every hole starts with a pierce, a crater wider than the beam, and a lead-in to the contour. In a small hole those fill most of the opening. Heat builds up, the wall tapers and dross collects on the underside. A hole at the recommended size cuts with a clean, straight wall.

Design it right

• Design to the recommended size where you can.
• Between the two limits, expect taper and some roughness. Ream or drill critical fits.
• For a hole below the minimum, leave it in. We mark its center so you can drill it after.

The rule

Make every slot, channel and narrow cutout at least as wide as the sheet is thick, and never under 0.020″.

Why it matters

Assist gas drives the molten metal down and out through the bottom of the cut. In a slot narrower than the sheet is thick, the melt cannot get out fast enough. Dross bridges the bottom of the gap and welds the slug back into the slot, so it has to be knocked out by hand, if it comes out at all.

Design it right

• Measure slot width across the narrow direction. Length can be anything.
• Need a narrower gap? Cut it wider and close it by forming, or machine it after.
• Tab slots follow R-10.

The rule

Keep at least 2× thickness of solid material between two cuts: hole to hole, cutout to cutout, and hole to the part edge. The floor is 0.030″ on the thinnest gauges.

Why it matters

A thin web (the "bridge" of material between two cuts) takes heat from both cuts at once. It has too little metal to carry that heat away. It bows out of plane, its edges burn back, or it breaks while the part is still on the bed. A hole too close to the edge does the same thing to the edge and leaves a visible bulge.

Design it right

• Check the narrowest point, not the average.
• Formed parts also need distance from the bend. See the hole-to-bend distance guide.
• Webs that carry load should be wider than the minimum.

The rule

Every inside corner of a cutout comes out with a small radius equal to the beam's radius. Outside corners of the part stay sharp. To fit a square part into a cut opening, add a relief at each inside corner.

Why it matters

On an outside corner the material is on the inside of the turn, so the beam leaves a sharp point. On an inside corner the material is on the outside of the turn, so the edge follows the round of the beam. A square tab, bracket or bought-in part then rides up on those radii and will not seat flush.

Design it right

• Add a dog-bone (circle centered on the corner) or a mouse-ear (circle pushed into one side), larger than the natural radius for your gauge.
• Only relieve corners that mate with something. Elsewhere the natural radius lowers stress.
• Draw the corner sharp if you like. We cut the radius either way.

The rule

The kerf is the width of material the beam removes. Our CAM offsets the beam by half the kerf, outside the outer profile and inside every hole. Draw the part at its finished size and do not add kerf yourself.

Why it matters

If the beam ran on your line, every outside edge would come out half a kerf small and every hole half a kerf big. Compensating in your file as well doubles the offset. A pre-compensated part ends up off by a full kerf, 0.008″–0.010″ at this gauge, which is outside the ±0.005″ tolerance.

Design it right

• Send nominal geometry, exactly as the part should measure.
• Expect a slight taper on thick plate: the cut is a little wider at the top.
• More in the kerf guide.

The rule

Laser-cut profiles, hole diameters, hole-to-hole spacing and edge-to-hole distances hold ±0.005″ as standard, with no extra cost or setup.

Why it matters

A ±0.005″ band is 0.010″ wide, and fits have to be designed with that in mind. A 0.250″ hole can measure 0.245″ to 0.255″, so a 0.250″ pin may not go in. Two parts that both come out at the high side of the band can stack into a tight assembly.

Design it right

• Give every fit clearance for the band on both parts.
• For press fits and bearing bores, cut undersize and ream.
• Need tighter than ±0.005″? Mark the critical dimensions on a drawing and we will review them.

The rule

Sheet is bought to a mill standard with its own thickness band: ASTM B209 for aluminum, A568 for carbon steel sheet, A6 for plate, A924 for galvanized and A480 for stainless. For 0.125″ 5052 on a 48″-wide sheet the band is ±0.006″. The laser does not change it.

Why it matters

Anything that fits around the sheet's thickness sees the full band. That includes tab-and-slot openings, stacked assemblies and parts that slide into a channel. A sheet at the top of the band uses up most of a close-fit clearance. Thickness also shifts bend springback and the flat-pattern length slightly.

Design it right

• Size slot openings from the maximum thickness, not the nominal.
• Check the Thickness Tolerance row on your material page; it is wider on 60″ sheet and thicker plate.
• Ask for the mill certificate if the measured thickness matters.

The rule

• Tab width: at least 2× thickness.
• Tab length: the receiving plate's thickness, plus 0.005″–0.010″ proud for welds.
• Slot: tab width and sheet thickness, each plus the fit's total clearance. Use 0.005″–0.010″ for a close fit or 0.010″–0.020″ for a slide fit.

Why it matters

A narrow tab bends or twists when you knock it home. A zero-clearance slot will not assemble once cut tolerance (R-08) and sheet thickness (R-09) are added. A flush tab leaves no metal to fuse, so the weld sinks and shows a gap at the joint line.

Design it right

• Relieve the slot's inside corners (R-06) so square tabs seat.
• Keep slot-to-edge walls at 2T (R-05).
• Close clearance is not an interference fit. Plan on a sample joint for anything critical.

The rule

Through-cut lettering should be at least 0.250″ (6 mm) tall, with strokes and bridges no thinner than the sheet. Engraved text marks the surface only and can go down to about 0.100″ (2.5 mm).

Why it matters

Closed letters such as O, A, B, D, P, Q and R and the numbers 0, 4, 6, 8 and 9 have a center island. Cut through, nothing holds the island, so it drops out and the letter reads as a hole. Thin strokes break the wall rule (R-05) and burn away.

Design it right

• Use a stencil font, or add bridges at least 1× thickness wide.
• Engrave part numbers, revisions and serials. Through-cut is for signage and decorative panels.
• Convert all text to outlines before you export.

The rule

We choose the nest. Where parts have matching straight edges we may cut them with one common line. Small or tippable parts may be held in the skeleton by micro-joints, small uncut bridges that you snap through.

Why it matters

A common line cuts each shared edge once instead of twice, saving cut time and scrap between parts. That lowers your price. A micro-joint keeps a part from tipping into the head (R-02), but it leaves a small nub on the edge where it breaks.

Design it right

• Tell us which edges are cosmetic or mating. We keep joints off them.
• Order several parts in the same material and thickness together so they share one sheet.
• Expect to dress joint nubs with a file or deburr.