What size should a rib be for a pot that shrinks?

Divide the finished dimensions by one minus the shrinkage rate. A rib for a 90 mm fired mug in a 12 percent stoneware needs a 102 mm profile. If you draw the finished pot in the Jordsmide Mug Designer and open the Rib Creator, this is applied automatically.

What is the best material to 3D print a pottery rib?

PLA is fine for most people and prints easily. PETG is a bit tougher and handles water better if you leave ribs wet. Either works. Print flat on the bed with plenty of infill so the edge does not flex.

Do layer lines on a 3D-printed rib mark the clay?

They can, slightly. A quick pass with fine sandpaper on the working edge sorts it out, or print with a smaller layer height. Some people like the faint texture and leave it.

Jordsmide › Guides › 3D-printed ribs

3D printing a throwing rib for your own mug profile

A rib cut to your exact profile lets you throw the same shape again and again. The one thing that catches people out is size: the rib has to match the wet pot, not the finished one, so it needs to be 8 to 14% bigger than the mug you are aiming for.

Jordsmide · updated 2026

Four 3D-printed throwing ribs and a pulling tool laid on a wooden table — Ribs and a handle pulling tool printed from the Studio. Each rib is cut to a different mug profile.

Why a rib to your own profile

A general purpose rib gives you a general purpose curve. If you want six mugs that actually match, or you want to repeat a shape you got right once, a rib that is the negative of that exact profile does most of the work for you. You press it against the wall on the last pull and the clay takes the shape.

It is not magic. You still have to throw. But it takes the guesswork out of the final form, and it is very good for sets.

The size problem

This is the part worth understanding before you print anything. Clay shrinks between the wheel and the kiln, usually 8 to 14% depending on the body. So a rib traced from your finished mug will make pots that end up too small.

rib size = finished size ÷ (1 − shrinkage) a 90 mm fired mug in 12% stoneware needs a 102 mm rib

If you are drawing the rib yourself in CAD, scale it up by that factor before you export. There is more on the maths in the shrinkage guide.

The Rib Creator does the scaling for you

Draw the mug at its finished size in the Mug Designer, pick your clay, and open the Rib Creator. The profile carries across already scaled to thrown size, so the rib fits the wet pot.

Open the Rib Creator

Flat or tapered edge

Both work. It comes down to what you like in the hand.

Flat. A square edge with a small corner radius. Simple, stiff, easy to print. Good for smoothing and for pushing a wall out from the inside.
Tapered. The working edge thins to a set thickness at a set angle. Gets into tighter curves and leaves a cleaner surface, at the cost of being a little more flexible.

In the Rib Creator you choose one or the other, and only the settings that apply to that style are shown. Flat gets a corner radius. Tapered gets a taper angle and an edge thickness.

A 3D-printed rib held in a hand, showing the finger hole and curved working edge — A finger hole makes a rib much easier to hold when it is covered in slip.

Four freshly thrown pots on a shelf, each with its printed rib beside it — Freshly thrown, each pot next to the rib it was shaped with.

Printing it

Ribs are easy prints. A few things that seem to matter:

Material. PLA is fine. PETG is tougher and copes better if you leave the rib sitting in water. Either is fine for the job.
Orientation. Flat on the bed, working edge along the print surface. That gives the cleanest edge and the strongest part.
Infill. Go high, 50% or more, or the edge flexes under pressure. Ribs are small, so it costs little.
Layer height. 0.2 mm is fine. Smaller gives a smoother edge if the layer lines bother you.
Finishing. A quick pass with fine sandpaper on the working edge stops it leaving faint lines in the clay. Some people like the texture and leave it.

The rib comes out of the tool with a finger hole already in it. You can set the hole size and move it if you want it somewhere else.

Other formats

STL is the one for printing. If you want to change the rib in CAD first, or cut it on a laser or CNC, the Rib Creator also exports STEP and OBJ. STEP keeps the true curves, so it is the better choice for editing.

Doing it without the tool

You can, if you have CAD and the patience. Trace or draw your profile, offset it for wall thickness, scale it up by the shrinkage factor, add a hole, extrude to 3 or 4 mm, export. It is a fair bit of clicking, and the shrinkage step is easy to forget.

The Jordsmide Rib Creator does the whole chain from a drawing. You get a rib matched to the outer profile of your mug, scaled to thrown size for your clay body, with a finger hole and your choice of edge, as an STL ready to slice. There is nothing to install and no signup.

Make a rib for your mug

Free, runs in the browser. Draw the mug, pick the clay, download the STL.

Open the Rib Creator

Common questions

Can you 3D print pottery ribs?

Yes, and they work well. PLA or PETG both hold up to wet clay. The main thing is to size the rib to the wet pot, not the finished one.

What size should the rib be?

Finished size divided by one minus the shrinkage. A 90 mm mug in 12% stoneware needs a 102 mm rib. The Rib Creator applies this for you when you open it from the Mug Designer.

Which material?

PLA is fine and prints easily. PETG handles water a bit better. Print flat with plenty of infill so the edge does not flex.

Do the layer lines mark the clay?

They can, slightly. Fine sandpaper on the edge sorts it out, or a smaller layer height.

Does the rib do the inside or the outside of the pot?

The rib from the tool is the outer profile. It is used from outside on the last pull, with a hand or a sponge inside to support the wall.