A B2B buyer sends over a pretty .3dm render of a signet ring and asks for a 100-piece quote. The factory engineer opens the file, sees a 0.3 mm wall on the shank, a stone seat built to a nominal 6.5 mm round, and no parting line marked, and sends the quote back with a list of eight questions. The buyer thinks the factory is being difficult. The factory knows that a CAD file missing four specific data points will cost three extra rounds of prototyping and push delivery by two weeks. This is the short list of what we ask for on every custom job before we commit a price.

Units, scale, and mesh quality

The single most common defect on incoming files is wrong units. Rhino exports in millimeters by default, but a designer working in inches or scaling for 3D printing will send a ring that measures 17 mm in diameter instead of 17 mm. We ask clients to confirm the file is in millimeters and that the finished ring is sized to the exact finger (US 7, ISO 54, etc.) before we open it. Mesh quality matters too: a triangulated STL with 500,000 facets casts fine, but one with 20,000 facets leaves flat spots on curved surfaces that show up after polishing. We re-mesh anything under 100,000 triangles for a ring, which adds half a day and a small fee if the client did not supply a clean file. Our standard pipeline is described in CAD to production: a custom ring timeline.

Wall thickness, undercuts, and draft

For sterling silver we hold a minimum wall of 0.6 mm on structural rings and 0.5 mm on earrings; below that, casting risk climbs and porosity in 925 silver becomes likely. Under 0.4 mm we will not cast at all. Undercuts are the second tripwire. A prong with an internal hook that cannot be invested or sand-blasted out will lock the ceramic inside and break on burnout. We need the file either opened up or flagged as hand-assembled so we can split the model. Draft angle on any bezel wall should be at least 3 degrees so the wax releases from the injection mold without tearing. If the client wants a production mold, these constraints double in importance because the mold will be pulled 500+ times.

Stone data: girdle, not size

A seat cut to 6.5 mm round is a guess. Every moissanite, diamond, or CZ lot has an actual measured girdle — rounded brilliant stones commonly run 6.45–6.58 mm even when labeled 6.5 mm. We ask clients to send the stone supplier girdle report, or at minimum the gem lot number, so the seat is cut 0.05 mm under the measured girdle. A seat that is 0.1 mm too loose lets the stone rattle; 0.1 mm too tight cracks the girdle during setting. We cover the geometry in detail in stone girdles and seat cuts for moissanite.

Finish tolerance and reference photos

High polish means different things to different buyers. We ask for a target roughness in Ra (our default high polish is Ra under 0.15 micrometers; brushed is Ra 0.4–0.6) and a reference image of a piece whose finish the client likes. Tolerance on ring size is plus/minus 0.15 mm on the inner diameter; on weight it is plus/minus 5 percent for silver and plus/minus 3 percent for gold. Marking position (stamp location for 925, sponsor mark) should be shown on the file, not described in an email. Fineness and marking rules that apply to the finished piece are set out in the FTC Jewelry Guides. We then return a dimensional PDF and a printed wax for approval before any metal is poured. The finishing sequence we follow is broken down in polishing compounds and finishing stages.

What file format do you accept?

.3dm (Rhino), .STEP, .IGES, and clean .STL. We cannot work from a JPG render or a screenshot — we need editable geometry so we can scale, thicken, and split.

Do I need to send physical stones?

For the first prototype, send the girdle measurements, not the stones. Once production seats are confirmed, send 5–10 loose stones for the setters to work with.

How long does the CAD revision loop take?

Most files need one revision round. Expect 2–3 working days per revision if we have to thicken walls or open undercuts.

Can you reverse-engineer a photo?

We can produce a close-approximation CAD from a reference photo, but dimensions, stone sizes, and finish will need a printed wax approval before production. See custom ring wax prototypes before production.

Send us your CAD file this way and we will quote in 24 hours. HOLYCOME runs CAD review, wax printing, casting, setting, and plating under one roof — ask about our small-batch OEM program and upload your .3dm or .STEP with stone girdle specs for a same-day feasibility read.

The 92.5% silver composition and properties of sterling silver are described in the Wikipedia entry on sterling silver.

Frequently Asked Questions

What ring sizes can you supply in bulk?

US sizes 5–12 including half sizes. Send a size breakdown with your order and we cast to that curve; comfort-fit inner bands reduce resize requests.

Can I order a mixed size run instead of one size?

Yes. Mixed runs are standard for wholesale: specify quantity per size and we pack and label by size at no extra labor cost.

What is the MOQ for custom ring designs?

50 pieces per design for existing molds; 100–300 pieces when a new mold or CAD model is required.

How should I price rings for retail margin?

Most partners use a 3–4x markup on FOB cost for sterling and 2.5–3x for moissanite solos, which keeps landed cost under 30% of retail.