From CAD to 3D print: resin, wax, and what your printer actually needs

Direct printing has replaced hand-carved wax for most bespoke work, and it has moved a set of decisions that used to belong to the model maker into the CAD file. If you are commissioning files, these are the ones worth understanding.

Castable resin or printed wax

Two materials dominate, and they behave differently in burnout.

• Castable resin, printed on an LCD or DLP machine. Fine detail, fast, cheap per piece, and now the default for one-off commissions. Burnout needs a proper ramped cycle or you get ash and incomplete fills.
• Printed wax, usually on a wax-jetting machine. Burns out cleanly like any wax, more forgiving for the caster, slower and more expensive to produce.

Ask your caster which they prefer before committing. A bureau set up for wax may not want to run your resin, and their burnout schedule is the thing that decides whether either works.

Resolution is not the same as accuracy

A printer quoted at 22 microns in XY is describing pixel size, not the dimensional accuracy of the finished part. Cure shrinkage, layer lines and resin swelling all sit on top of it.

In practice this means a hole modelled at exactly 1.5mm will print slightly under, and a peg modelled at exactly 1.5mm will print slightly over. Anything that must fit — a mating band, a hinge, a fitted seat — needs clearance modelled in, not assumed.

Wall thickness and the minimums that matter

The file can describe geometry the printer cannot produce or the metal cannot fill. Rough working floors:

• Shank at its thinnest: 1.2mm is a sensible floor for everyday wear, less for a piece that will not be worn hard.
• Bezel and gallery walls: around 0.6 to 0.8mm, depending on how much the setter needs to push.
• Prong tips: 0.8mm and up, remembering the setter will remove some.
• Anything unsupported and long: thicker than you think, because it has to survive investment as well as casting.

These are starting points. Your caster's minimums beat any published table, because they are the ones who have to fill the mould.

Orientation and supports are a real decision

How a piece sits on the build plate changes where layer lines fall, where supports touch, and where you will have to polish. A ring printed flat has lines running across the top surface; the same ring printed at an angle moves them somewhere less visible.

Supports leave marks. Getting them onto the inside of a shank or the back of a gallery, rather than across a polished top, is worth the extra thought before the print starts.

The file itself

A few things make a model printable rather than merely viewable.

• It must be a closed, watertight solid. Open edges and flipped normals are the most common cause of a slicer producing nonsense.
• No self-intersecting geometry, and no coincident faces where two solids meet without being joined.
• Mesh density appropriate to the piece — fine enough that curves read as curves, not so fine the file becomes unmanageable.
• Units and scale confirmed. A model that arrives in centimetres and is read as millimetres is a very expensive misunderstanding.

Ask for print-ready, not just modelled

A file that renders beautifully is not necessarily a file that prints. The checks are quick, but they have to be done deliberately.

We supply print-ready files with closed solids, sensible wall thicknesses and the resolution matched to the job, and we will discuss orientation with your printer if that helps. Quotations are free, so send the design and tell us how it will be produced.