Custom jewellery development fails on timelines more often than on quality. Buyers budget two weeks for sampling because that is what a supplier promised, then lose a season when it takes five. This is the sequence with realistic durations, and the points where schedules actually slip.

The full sequence with realistic durations

Stage	Duration	What you receive	Common delay cause
Brief and feasibility	1 to 2 days	Feasibility note, stone options, indicative price	Vague reference images
Quotation	2 to 3 days	Costed quote with stone, metal, labour and mould broken out	Specification changes mid-quote
CAD and 3D render	3 to 5 days	Render from three angles plus top view	Buyer requests many small changes
Revision rounds	2 to 3 days each	Updated render	Underestimating rounds needed; budget two
Mould and wax	3 to 5 days	Wax photograph before casting	Design complexity
Cast, set and polish sample	5 to 8 days	Physical sample with stone set	Stone sourcing for unusual sizes
Sample shipment	3 to 7 days	Insured express parcel	Customs documentation
Sample approval	1 to 3 days	Signed approval sheet	Buyer-side decision time
Bulk production	12 to 20 days	Production run	Queue position behind larger clients
QC and certification	3 to 5 days	QC report, certificates	Third-party grading turnaround
Packing and dispatch	2 to 3 days	Carton photographs, documents	Custom packaging printing run

Realistic total: six to nine weeks from brief to goods in hand for a new design. If you are launching for a season, start twelve weeks out. A supplier promising three weeks is describing stock adaptation, not a new mould.

Writing a brief that does not require three revisions

Give dimensions, not adjectives. A 7 mm wide band, 2.2 mm thick, with a 1.0 ct centre, rather than chunky but elegant.
Give a reference with a purpose. Say what you like about it: the prong style from image A, the shank profile from image B.
State the stone and grade up front. Changing stone size after CAD invalidates the render.
State the metal and target weight. Metal weight drives both cost and how the piece feels in the hand.
State your retail price point. It lets the factory propose a workable specification rather than quoting something unsellable.
Send vector or high-resolution source files for any logo or engraving.

Budget for two revision rounds

Round	Typical change	Cost implication
Round 1	Proportions, prong style, shank thickness	Usually free, because CAD is parametric at this stage
Round 2	Stone size, setting height, gallery detail	Sometimes free; may require a new mould drawing
Round 3 and beyond	Fundamental redesign	Normally charged as a new development

Ask at the quotation stage how many revision rounds are included. Two is a fair standard. Unlimited revisions usually means the cost is hidden elsewhere.

Approving a sample properly

Check on the sample	Acceptance criterion
Stone grade and size	Matches the specification sheet; request the certificate with the sample
Prong security and symmetry	No gap, no rocking, gaps equal within 0.2 mm
Weight	Within plus or minus 5% of the agreed target weight
Dimensions	Band width and thickness within 0.2 mm
Plating and finish	Even colour, no edge thinning, mirror polish inside the shank
Comfort	No sharp edge on the inner band; the piece sits level on the finger
Setting height	Matches the render; not raised or lowered without agreement

Approve in writing against the specification sheet, and attach photographs of the approved sample. That sample becomes the master reference for the bulk run, which is the single most useful document in the whole order, because it converts it looks different into a measurable comparison.

Where suppliers and buyers actually lose time

Buyer-side decision latency. The most common cause by far. Every day you sit on a render adds a day to delivery.
Stone sourcing for non-standard sizes. A 1.35 ct pear is not a stock size. Add five to eight days if your specification is unusual.
Custom packaging. Printed boxes and care cards have their own production lead time of 10 to 15 days. Order them in parallel, not after approval.
Third-party grading. IGI grading adds turnaround outside the factory control. Certify a subset rather than the whole run if the deadline is tight.
Change orders after production starts. Acceptance of a mid-run change resets the schedule and is correctly charged.

Running development in parallel with sales

Week	Development activity	Commercial activity
1 to 2	Brief, quote, CAD	Pre-sell the render to gauge demand
3 to 4	Revisions, mould, sample	Prepare listing copy and sizing content
5 to 6	Sample in hand, approved	Shoot the physical sample; open pre-orders
7 to 9	Bulk production	Finalise packaging and launch assets
10 to 12	QC, packing, shipping	Schedule the launch for arrival week

Buyers who run development and commercial preparation in parallel launch within days of arrival. Buyers who do them sequentially lose two to three weeks of selling time on every new design, which across a season is the real cost of OEM development.

Authoritative References

For buyers who need to verify the technical and regulatory basis of this guide, the following independent institutions publish authoritative reference data:

ISO 9001 Quality Management - the international standard for consistent production quality.
Wikipedia: Jewellery - manufacturing processes, materials and global trade background.