Stage 5: Design for Manufacture

Goal#

After this stage you can look at a model and say which manufacturing process can make it, what that process will reject, and how to change the geometry so it passes. You will apply the rules of four processes (FDM 3D printing, sheet metal, injection moulding and laser cutting), choose clearances and kerf compensation from measured data rather than guesses, design a snap-fit closure, and export the correct file for each shop.

This matters for product design because a beautiful model that cannot be made is not a product. Most cost, delay and failure in a consumer product comes from decisions made in CAD: a wall that is too thick, a hole too close to a bend, a lid that will not close because nobody budgeted clearance. In this stage the running capstone (a handheld device) gets its housing: you will build the electronics enclosure that Stage 6 will later wrap in an ergonomic grip.

Everything required here works with the standard licence. Fusion's Plastic tab (Lip, Snap Fit, plastic rules, Boss) belongs to the Design Extension, a paid add-on. Wherever it is useful, this stage shows the standard-licence route (Shell, Draft, Rib, Web, Extrude, Chamfer, Fillet) and puts extension-only tasks under an "Optional (extension required)" heading.

Before you start#

• Stages 1 to 4 or equivalent: sketching with constraints, extrude, shell, fillet and chamfer, mirror and patterns, components versus bodies, and user parameters with equations.
• You can create a named user parameter (for example clearance = 0.2 mm) and drive a sketch dimension from it.
• You can read dimensions off a model with Inspect > Measure and check a section with Section Analysis.
• You have a 3D printer or print service and a laser cutter or cutting service, or you are willing to check your numbers on paper. Checking by calculation is a valid way to pass every task here.

Learn#

Read in this order. The first page gives you the checklist habit, the next four give you process rules, and the last gives you the file handoff.

• Read Design for Manufacture: Sheet Metal and Molding - the checklist habit you will use for every part from now on. Focus on the worked bracket example and the tolerance table.
• Read Sheet Metal Rules - thickness and bend radius are stored in a rule, so you need to know what the rule controls before you unfold anything.
• Read Plastic Rules, Draft and Wall Thickness - uniform walls, draft and rib sizing are the core of moulded design. Focus on the resin table and the draft arithmetic.
• Read FDM Design Guidelines - overhangs, teardrop holes, fillets at cantilever bases and fastener holes. Focus on "Designing a self-supporting part" and "Strength".
• Read Print-in-Place and Tolerance Design - the clearance-by-fit table is the one you will reuse most.
• Read Lip, Groove and Snap Fit - the mating features of a two-part enclosure. Read the warnings about hook strain and undercuts even if you do not own the Design Extension.
• Read Finger Joints, Tabs and Slots - the finger-count formula and the tab-and-slot rules.
• Read Kerf and Tolerances - how to measure kerf with a test square and write it into parameters.
• Read Living Hinges and Flexures - a short read that shows how a flat sheet can behave like a spring.
• Read Exporting for CAM, 3D Printing, Rendering and Web - which format goes to which shop. Keep the Format Cheat Sheet open as a reference rather than reading it end to end.

Practice#

Do the exercises that the pages already contain, then the drills.

• Do the practice exercise on Design for Manufacture: Sheet Metal and Molding (audit a bracket and an enclosure against the limits and write down every violation with its measured value).
• Do the practice exercise on Plastic Rules, Draft and Wall Thickness (80 x 50 x 25 mm enclosure half with draft). If the Plastic tab is locked, follow its fallback with Solid Shell and Draft.
• Do the practice exercise on Print-in-Place and Tolerance Design (clearance parameters and a test coupon).
• Do the kerf test on Kerf and Tolerances (a 20 mm square; if you have no cutter, use the worked figure of 0.18 mm).
• Drill 1 (15 min): fastener holes. In a 10 mm thick block, model four holes for an M3 screw at 3.4 mm, a hexagonal nut pocket 0.2 mm larger across flats than a 5.5 mm nut (5.7 mm), a teardrop hole of 8 mm diameter for a horizontal axis, and a 45 degree chamfer under a 12 mm shelf. Measure each and confirm the values.
• Drill 2 (10 min): draft arithmetic. For a 35 mm tall wall at 1.5 degrees, calculate the top-to-bottom shift: 35 x tan(1.5 degrees) = 0.92 mm. Model it, run Inspect > Draft Analysis with the pull direction on Z, and confirm with Measure.
• Drill 3 (15 min): parameter-driven finger joint. Create thickness, kerf, fit and finger_w parameters. For a 100 mm edge, compute the odd finger count with n = 2*floor(L / (2*finger_w)) + 1 for finger_w = 9 mm (that gives 2 x 5 + 1 = 11 fingers), then recompute finger_w = 100 / 11 = 9.09 mm. Sketch it, change thickness from 3 to 4 mm and confirm the notches follow.
• Drill 4 (10 min): export audit. Export one small body as 3MF, as STL and as STEP, and one flat sketch as DXF. Open each in another program (slicer, viewer, laser software) and note units, scale and anything lost.

Checkpoint project#

Electronics enclosure with a snap-fit lid, then a variation. Estimated time: 3 to 4 hours (about 2 hours for the tutorial, 1 to 2 hours for the variation).

First complete Tutorial 2: Electronics Enclosure with Snap-Fit Lid without skipping steps. It gives you a base, a lid, four PCB standoffs, a connector cutout and two cantilever hooks, all driven by parameters. If you prefer a flat-pack process, do Tutorial 9: Laser-Cut Box with Finger Joints instead and apply the variation below to it with the obvious changes (your measured kerf in place of the print clearance).

Then save a copy and make a variation using parameter changes plus the minimum new geometry:

• A larger board of 75 x 45 mm instead of 60 x 40 mm. The tutorial's outside is 66.6 x 46.6 mm for a 60 x 40 board, so yours should grow by 15 mm and 5 mm to 81.6 x 51.6 mm.
• Two rows of vent slots in the lid, each slot 2 mm wide, kept clear of the rim.
• A change of material from PLA to PETG or ABS: increase the hook root fillet and the clearances (see the fit table), and say in one line why.
• A second USB-style cutout on the opposite short wall.

Deliverables#

• The tutorial file, completed, with every critical clearance a named parameter.
• The variation file, saved as a separate design, where changing only the board length and width parameters (no sketch edits) produces the 81.6 x 51.6 mm outside.
• A one-page "DFM checklist" (any format) listing, for the variation, five checks with the measured value and the limit: overhang angle, minimum wall, hook root fillet, hole-to-edge distance and clearance per side.
• A 3MF of base and lid laid flat, each oriented so the hooks print flat (layers running along the hook), exported in millimetres.
• A short note (3 to 5 lines) saying how the lid would change if it were injection moulded rather than printed: wall near 2.5 mm, draft on all walls, hooks needing a window in the wall.

Challenges#

Challenges have no step-by-step. Use the Learn pages. All dimensions are in millimetres. Values called "typical" are general guidance, not standards: your vendor's published capabilities and your material's data sheet win.

Challenge 1: Laser-cut desk organiser#

Brief. A stationery brand wants a flat-pack organiser tray with two removable dividers. It must be cut from 3 mm plywood on a hobby laser, and a customer must assemble it by hand without glue.

Constraints.

• Plywood measured at 2.95 mm (not the nominal 3 mm). Use your own kerf from a test square, or 0.18 mm if you have none.
• Tray outside 150 x 90 x 40 mm. Corners use finger joints, dividers use tab-and-slot.
• Use slot_w = thickness - kerf + fit and tab_w = thickness + kerf with fit = 0.05 mm for a snug fit. With the values above, slot_w = 2.95 - 0.18 + 0.05 = 2.82 mm and tab_w = 2.95 + 0.18 = 3.13 mm.
• Finger width near 9 mm (about 3 x thickness) with odd finger counts so both ends of every edge are fingers. For the 150 mm edge, 2 x floor(150/18) + 1 = 17 fingers (8.82 mm each). For the 90 mm edge, 2 x floor(90/18) + 1 = 11 fingers (8.18 mm each).
• Sheet size available: 300 x 200 mm. The flat layout must fit with at least 3 mm between parts.

Deliverables.

• Parametric 3D model with panels as separate bodies.
• Flat layout sketch with all panels, and a DXF.
• Parameter list showing thickness, kerf, fit and the equations above.

Self-check.

• The 150 mm edge has 17 fingers and the 90 mm edge has 11, and no joined panels interfere (Inspect > Interference).
• The slot reads 2.82 mm and the tab 3.13 mm in the sketch.
• Changing thickness to 4 mm rebuilds all slots, tabs and finger depths without broken sketches.
• The DXF opens in your laser software at the right scale (the 150 mm edge measures 150 mm).
• The layout fits in 300 x 200 mm with the 3 mm spacing, checked with Measure.

Stretch. Add a hinged lid with a living hinge strip, or a T-slot (screw and nut) joint for a rigid divider. Hint: see Living Hinges and Flexures and the T-slot section of Finger Joints, Tabs and Slots.

Challenge 2: Sheet-metal sensor bracket#

Brief. A maker-space customer needs a bracket that holds a sensor board to a wall, laser-cut and bent from steel, ordered in batches of 100.

Constraints.

• 2 mm mild steel, inside bend radius 2 mm, one 90 degree bend, base 60 x 40 mm, flange 15 mm measured on the flat pattern from the bend line.
• Two 4.5 mm diameter mounting holes in the base, centres 9 mm from the bend line.
• Typical limits from the DFM page: minimum flange = 4 x 2 + 2 = 10 mm; hole edge to the bend at least 2 x 2 + 2 = 6 mm (lower end of the 2 to 2.5 x thickness guideline); hole diameter at least the thickness (2 mm).

Deliverables.

• Sheet metal model with a rule that stores thickness and bend radius.
• Flat pattern and DXF.
• A written table of the checks with measured value and limit.

Self-check.

• Hole edge to bend: 9 - 2.25 = 6.75 mm, at least 6 mm. State what happens at a 7 mm centre distance (edge at 4.75 mm, which fails).
• The flange is 15 mm, above the 10 mm minimum.
• Unfolding and refolding returns the same 90 degree angle.
• The flat pattern DXF has closed contours and the expected bounding box (Measure on the unfolded body).
• Changing the rule thickness from 2 mm to 3 mm updates the flat pattern, and you can name which check in your table now has a different limit.

Stretch. Add a second bend to make a Z-bracket and compute the stack at plus or minus 0.3 mm per bend (plus or minus 0.6 mm for two). Dimension the second hole from a single datum edge rather than chaining. Hint: see Design for Manufacture: Sheet Metal and Molding.

Challenge 3: Moulded-style housing half#

Brief. A client intends to injection mould a handheld device housing in ABS in 20,000 units. Provide a manufacturable bottom half for a vendor to review.

Constraints.

• Outside 80 x 50 x 25 mm, nominal wall 2.5 mm, 1.5 degrees of draft on every wall, pull direction Z, inside radii 1.5 mm.
• Two floor ribs at 60 percent of the wall (1.5 mm thick) and at most three times the wall high (7.5 mm).
• Four screw bosses for M3 thread-forming screws, outer diameter 6.5 mm (about 2.2 x the 3 mm screw, within the 2 to 2.5 x guideline), hole 2.5 mm, cored out.
• Cooling time scales roughly with wall squared, so a 2.5 mm wall cools in about 39 percent of the time of a 4 mm wall ((2.5/4) squared).

Deliverables.

• Solid model using Shell, Draft, Rib and Fillet.
• Draft Analysis and Section Analysis results.
• A short list of every wall thickness measured.

Self-check.

• Draft Analysis shows all walls at or above 1.5 degrees.
• The 25 mm wall shifts 25 x tan(1.5 degrees) = 0.65 mm top to bottom, and Measure agrees within 0.05 mm.
• Section Analysis shows every wall between 2.0 and 3.0 mm.
• Rib thickness reads 1.5 mm and rib height is no more than 7.5 mm.
• If you linked rib thickness to the wall parameter by equation, changing the wall from 2.5 to 2.0 mm gives a 1.2 mm rib.

Optional (extension required). Rebuild the same half with a plastic rule ABS_2.5mm, the Boss command and Design Advice, and compare the flagged faces with your manual checks. Hint: see Plastic Rules, Draft and Wall Thickness and Lip, Groove and Snap Fit.

Stretch. Add a lip and groove between the halves with standard Extrude: lip height equal to the wall (2.5 mm), width half the wall (1.25 mm), 0.12 mm clearance per side, groove about 2.7 mm deep.

Challenge 4: Print-in-place cable clip#

Brief. A product needs a cable clip that comes off the printer already assembled and snaps shut around a 6 mm cable.

Constraints.

• FDM, 0.4 mm nozzle, 0.2 mm layers, PETG.
• A hinge with a 3 mm diameter pin in a hole with 0.3 mm clearance per side (hole 3.6 mm), vertical axis, 45 degree chamfers on pin and hole entries.
• Clip body 20 mm long, 12 mm wide, 8 mm tall, with a 6.4 mm cable bore.
• A cantilever latch printed flat to the bed, root fillet at least 1.5 mm.

Deliverables.

• A design with the moving bodies and a clr_pip parameter.
• A 3MF containing everything on one plate.
• A clearance coupon: five 3.0 mm pegs and holes at 0.1, 0.2, 0.3, 0.4 and 0.5 mm per side.

Self-check.

• Minimum distance between pin and hole reads 0.30 mm (Measure).
• Inspect > Interference reports no overlap between the bodies.
• Every downward face is within 45 degrees of vertical or sits on the bed.
• Coupon hole diameters are 3.2, 3.4, 3.6, 3.8 and 4.0 mm.
• Changing clr_pip from 0.3 to 0.4 mm updates every gap.

Stretch. Rotate the hinge to a horizontal axis and use a diamond or teardrop section so it needs no supports. Hint: see Print-in-Place and Tolerance Design.

Challenge 5: The vendor pack#

Brief. You must send a design to three suppliers on the same afternoon: a print service, a laser cutter and a machine shop. Each will reject a bad file.

Constraints.

• One design with at least three bodies: a printed part, a flat laser-cut part and a machined-style part.
• Printing: 3MF in millimetres. Laser: DXF with closed contours only. Machining: STEP plus a drawing noting material, tolerance and thread.
• No stray surface bodies and no hidden construction geometry in the exports.

Deliverables.

• Three export files plus a three-line cover note per supplier.
• A re-import test: open each file in a clean Fusion design.

Self-check.

• The 3MF re-imports at the original bounding box (read off with Measure).
• The DXF has no duplicate lines or open loops.
• The STEP re-opens with holes and arcs intact, not faceted.
• You can name one thing each format lost (for example, STEP carries no tolerances).

Stretch. Write a one-page format decision table for your own studio. Hint: see Format Cheat Sheet.

You have finished this stage when#

• I can check a part against sheet metal, moulding, printing and laser limits using measured values, not by eye.
• I can pick a clearance per side from the fit table and justify it for a given process.
• I can measure kerf and write it into parameters that drive tabs, slots and fingers.
• I can design a cantilever snap fit with a filleted root that prints flat.
• I can add draft and uniform walls to a body and verify them with Draft Analysis and Section Analysis.
• I can unfold a sheet metal part, read the flat pattern and export a clean DXF.
• I can pick 3MF, STL, STEP or DXF for a given supplier and test the file by re-importing it.
• I have an enclosure design and a DFM checklist I can reuse in the capstone.

Next stage#

Continue with Stage 6: Form and Surfaces.