Process / design for FFF
Design the part for the way it is built
FFF builds a part as adjacent roads of molten polymer, one layer over another. It is capable of useful, complex forms, but its limits are visible in the geometry: a wall has to be wide enough for a road, a roof needs a place to land, and the direction of the layers changes the way a loaded part fails. Good design makes those facts intentional.
The guide is a starting point for a review of your actual geometry, material and selected nozzle. It is not a generic acceptance promise. Fit-critical interfaces are assessed with their mating context before manufacture.
Start with the nozzle, not a generic drawing rule
The tool width is the starting point for the geometry.
The nozzle is the width of the tool forming the part. A feature that works with the smallest available nozzle may be an awkward or fragile choice for a larger one. The table turns the same design intent into a starting geometry for each supported nozzle diameter. The displayed diameters are derived from the published fleet range, rather than copied into the page.
| Feature | 0.2 mm nozzle | 0.4 mm nozzle | 0.6 mm nozzle | Why it begins here |
|---|---|---|---|---|
| Minimum wall | 0.4 mm | 0.8 mm | 1.2 mm | Two deposited roads give the slicer a deliberate wall to form. |
| Unsupported span | 2 mm | 4 mm | 6 mm | Treat this as the point to add support, an arch, a rib or a different orientation. |
| Bridge | 5 mm | 10 mm | 15 mm | A short bridge is easier to control than a broad unsupported ceiling. |
| Hole diameter | 0.5 mm | 1 mm | 1.5 mm | Below this, choose a smaller nozzle or change the feature. |
| Clearance | 0.1 mm | 0.2 mm | 0.3 mm | Start here for moving or mating printed features, then review the actual interface. |
A wall can be made thicker without difficulty. Making it only just wide enough is the point that demands care. For a hole, the drawing diameter is not the same thing as the surface that emerges after a circular path is approximated by roads. When a bore, slot or clearance is the reason the part exists, send the mating component or its controlling geometry with the file.
Unsupported span and bridge values are conservative prompts to change the geometry, not invitations to test a limit on a customer part. Add ribs, turn a flat ceiling into an arch, split the part, or arrange the layer axis so the surface can be supported where it is not seen.
Layer height trades surface definition for build time
The layer choice follows the surfaces and features that matter.
The available layer range is 0.06 mm to 0.4 mm. A smaller layer catches shallower slopes and gives curved faces finer steps. It also asks the machine to make more passes through the same height, which increases build time and makes a large part more sensitive to the consequences of a long build.
A larger layer produces a more obvious stepped surface on shallow curves, but it is often the sensible choice for a robust fixture, a large hidden body or a part whose important dimensions lie in the plane of a layer. Feature definition also depends on nozzle width, material and local geometry. Fine layers cannot make a wide nozzle behave like a narrow one.
Choose the visible faces and functional features first. We then choose a nozzle and layer height that serve those features together. A part with one cosmetic face and one load-bearing interface may need a different orientation or a different conversation than a part that is only an enclosure.
Orientation decides both surface and failure direction
Layer direction is a structural and visual decision.
Printed parts are weakest across layers. A load that pulls layers apart can separate a part along its build interfaces before a load carried along continuous roads does. That makes the layer axis a structural property of the finished part, not a visual preference added at the end.
Start by locating the force path and the features that locate the part in an assembly. Place the part so the critical force is carried through deposited roads where possible. Then inspect the trade: the orientation that helps a bracket resist a load may put a support contact on the face a user sees. We make that trade visible in review, including when a change in settings could affect visible finish.
Avoid long flat faces held only at one edge. Use fillets, ribs and gradual changes of section to spread a load into the body. At a screw boss or clipped interface, give the load a path into the surrounding wall instead of asking a small stack of layers to carry it alone.
Hollow forms need a way out
Internal geometry has to be considered as part of the route.
Enclosed cavities can collect loose material or leave a region that cannot be inspected after manufacture. A hollow design should include escape and drain geometry at the low points of its intended build orientation, with enough access for support removal where support is necessary. A cavity that is merely sealed on screen may become a permanent blind volume in the part.
Where a fluid path, duct or internal channel is the functional feature, show its entry and exit in the file or drawing. We need to know whether it is a visible opening, a surface that mates to another component, or a void that can be changed. This is particularly important for internal overhangs, where a support strategy could otherwise leave material that has no route to be removed.
Warp begins where cooling is uneven
Geometry can reduce the stress that uneven cooling creates.
As deposited polymer cools, it contracts. Large flat sections, abrupt changes in thickness and long unsupported edges concentrate that contraction into a lifting force at the build surface. Some materials make that effect more demanding than others, which is why material selection and part geometry must be decided together.
Reduce the risk by avoiding broad, uniform slabs where the function permits it. Break up a plane with ribs or a gentle curvature. Keep wall thickness transitions gradual. Put stiffening where it works with the expected layer axis, not just where it looks symmetric. If a shape is still likely to pull, we may recommend a different orientation, a different material route, a split, or a deliberate support strategy.
The largest single-piece envelope is 350 mm by 320 mm by 340 mm. That is an envelope, not a promise that every form inside it is equally suitable. A broad, thin geometry can deserve segmentation even when it physically fits.
When one part does not fit, make the join part of the design
The seam deserves the same care as the part around it.
Segmentation is a limitation of a single-piece build, and it is often a workable engineering technique. A part that exceeds the single-part envelope, or a form that is too warp-prone to make responsibly as one piece, can be divided into sections. The division changes the object. It adds seams, assembly work and another place where force and appearance need to be considered.
Place a seam away from high load, a sealing face, a close-fit interface and the primary visible surface where possible. Use registration features that resist motion in more than one direction: a keyed lap, tongue and groove, stepped overlap or pins with adequate surrounding material. Give bonding surfaces real area and arrange them so assembly pressure does not squeeze the sections out of alignment.
We agree seam placement before manufacture. The current fleet includes Bambu Lab H2S as a reference for the largest available working envelope, but the final route is selected against the entire geometry and material requirement, not a single machine name.
Annealing can change the material and move the part
The material route should account for the part’s mating condition.
Annealing is a controlled heat cycle used for materials that require it. It can change the material’s internal structure and relieve residual stress. It also creates a dimensional consequence: the part can move, shrink or distort as that internal structure changes. The geometry you measure before the cycle is therefore not necessarily the geometry after it.
If annealing is part of the material route, it is considered before the part is made. Keep close fits, long straight runs and thin asymmetric sections in view, and avoid designing a post-anneal critical interface without discussing its mating condition. We use documented drying and annealing where the chosen material calls for them, rather than treating heat treatment as an invisible finishing step.
Start with the actual part
Send the file, or explain the requirement and the environment it must serve. We will read it before we make anything.