Sheet and machined parts
Design flat plates, bent brackets, and machined features that your fabricator can make and inspect.
Choose the material and manufacturing process before detailing every corner. A flat cut plate, bent sheet bracket, and milled block can solve the same mounting problem with different shapes, costs, and methods.
Talk to the person or service making the part. Find out what stock and tools they have, how small they can make features, how accurate the parts will be, and which files they need.
Flat plates
A flat sheet part often begins as a two-dimensional profile with a constant thickness. Laser cutting, waterjet cutting, routing, and manual fabrication have different material and feature constraints.
For a practice plate, use the 70 × 40 mm, two-hole model from the beginner lessons. Its outline and holes can be exported from a planar face as . The physical thickness comes from the selected stock; a 2D profile alone does not communicate material, thickness, quantity, or revision.
Keep the cutting file clean. It should contain the intended boundaries without duplicate lines, , or . Open the exported file in the receiving tool and measure a known distance before cutting.
is the width of material removed by a cutting process. The fabricator may compensate for kerf or cutter size in their toolpath. Agree on who applies that compensation so it is not applied twice.
Material and thickness
Choose stock for the loads, , impact, environment, and fabrication process. Aluminum alloy and temper affect behavior; “aluminum” is not a complete material specification. Plastics also differ in stiffness, toughness, friction, and heat response.
Use available thicknesses rather than designing around a value nobody can buy locally. Measure stock where the fit depends on it. The stock may be thicker or thinner than its stated size, and a coating or finish can change how it fits other parts.
Keep the in mind when shaping the outline. Leave material around mounting and holes, and use crossmembers or other supports when a broad plate would otherwise flex. See Design for manufacturing for the worked cutout comparison.
Bending sheet
A bent bracket needs a bend radius and a flat blank whose size accounts for the bend. The neutral axis is the layer within the material used to describe length through the bend; its position depends on the bending conditions.
Do not make a flat blank by simply adding the outside flange lengths. Material stretches and compresses through the bend. Use appropriate sheet-metal modeling and the fabricator's bend data.
In Onshape, sheet-metal tools define thickness, bend radius, and features such as flanges, and provide a flat view. A solid L-shaped extrusion is useful as a geometry exercise, but it does not automatically define a manufacturable bent blank.
Keep holes and narrow features far enough from bends according to the process requirements. Include bend relief where needed, and check that the tooling can reach each bend. A closed shape with a seemingly simple final form can be impossible to form in the planned order.
CNC pockets and corners
means computer numerical control: a machine follows a programmed toolpath. For milling or routing, the tool's shape limits the geometry it can leave.
A round end mill leaves a radius in an internal corner. A 6 mm-diameter cutter has a 3 mm radius, so it cannot create a perfectly sharp internal square corner by ordinary three-axis milling. Specify a compatible corner radius, allow a suitable relief, or change the mating part.
A dogbone relief extends an internal corner so a square-ended mating part can seat. It changes the visible outline and removes material, so place it deliberately rather than adding it to every corner.
Check pocket depth against stock thickness. A 2 mm-deep pocket in a 3 mm plate leaves only 1 mm below it. Decide whether that remaining section can carry the load and whether the process can hold the depth consistently.
Holes and threads
Choose drilled, reamed, tapped, countersunk, or counterbored features according to the joint. A reamed hole uses a finishing operation for a more controlled diameter and surface than a rough opening alone.
You may need to drill, ream, or otherwise finish a cut opening to get the fit a bearing or needs. Put that work on the drawing, and ask the fabricator what accuracy the cutting process can achieve on its own.
For threads in thin material, consider the usable engagement after and tool lead-in. Use suitable nuts, inserts, or increased supporting thickness when the joint requires them. The fastened-joint guide explains the stack and access checks.
Hold the part while making it
A machine needs a way to hold the stock and the part. Discuss clamp locations, tabs, sacrificial material, and which face is machined first. A toolpath cannot occupy the same space as a clamp.
Keep thin or narrow regions supported during cutting. Consider the operation that separates the finished part from the surrounding stock. A complicated pocketed shape can require more setup and handling than its final appearance suggests.
Manual parts need an achievable marking, drilling, and finishing process too. Choose edges a student can locate and measure. Avoid requiring a precision fit that the available tools cannot reproduce reliably.
Send a complete package
Include the agreed geometry file, drawing, material, thickness, quantity, units, revision, and functional . Mark any required secondary work, such as tapping or finishing a bearing seat. Ask the fabricator to raise an unclear requirement before making the batch.
When the parts return, inspect the important dimensions, edge condition, and fit with actual hardware. Update and drawings for any agreed correction. Keep the approved files together so someone making a replacement knows which drawing and model to use.