Prototype Lead Time Reduction Strategies for Hardware Startups

Prototype lead time is usually waiting, not machining.

Hardware startups lose weeks on custom silicone by running a production ritual (steel, 4-cavity, full cert pack, brand color) in front of a question that was only “does this lip invert.” The spindle is innocent. The queue you built is not.

Cut calendar by cutting decisions, not by shouting expedite into a toolroom.

Rank the time-killers

In the order they actually eat a startup’s month:

1. CAD that never freezes because three lips still live in Figma.
2. Process mix-up: RTV vacuum-cast samples used as if they were LSR, then a surprise recut.
3. Compound specials: custom color, medical file, self-lube grade with a two-week pail.
4. Steel as first tool while undercuts and gates are still theoretical.
5. FAI/regulatory paperwork added after tryout.
6. Queue: sample press booked, overseas crate, Chinese New Year, your own incoming lab.
7. Actual CNC. Often the shortest bar on the chart.

If your plan attacks (7) with overnight CNC and ignores (1)-(4), you will get a fast wrong tool.

A sequence that is actually shorter

Do not run these in parallel until you know which question is alive.

Day 0 question: shape only?

Print the part. Or RTV vacuum-cast off a printed master in a convenient Shore A. No LSR pail. No heaters. Kill assembly and industrial design here. Inhibition: post-cure the master or barrier-coat if platinum RTV is the jacket.

Question: is the *silicone* right?

Soft LSR tool: printed insert only if heat/flash limits are acceptable for a handful of shots; otherwise 1-cavity aluminum, open-and-shut if the geometry allows. Use the intended family (platinum LSR, target Shore), even if color is natural. Color paste is a later queue.

Question: will production flash and shrink?

Stay on aluminum until yes. Measure after post-cure. Balloon the five dims that mate. Skip the 40-balloon FAI until the five pass.

Question: volume is real and CAD is dead?

Now steel, class matched to lifetime, cavitation matched to batch. This is not a prototype step. Putting it first is how a seed-stage team buys a 16-week brick.

Undercuts: if the startup part is a glove-mold shape, stay RTV or redesign for slides *before* anyone quotes Class 103. Slides are not a lead-time reduction.

Moves that remove days without magic

Send STEP + a 1-page 2D on day 1 with flash max, gate keep-out, Shore, process. Incomplete RFQs bounce.

Name a sample cell, not a factory. A shop with an R&D press will beat a famous production floor that will not dirty a 300-ton for 20 shots.

Stock grades. Pick a catalog LSR the shop already has on the shelf. Your unique translucent peach is a purchasing lead time.

One DFM call, then freeze. Written. After freeze, changes are a new clock.

Parallel the master, not the steel. While aluminum is programmed, print a master and an RTV jacket for assembly fixtures. Do not parallel two metals.

Skip multi-cavity. 1-cavity is the prototype. Cavitation is TCO.

Expedite only named gates. Pay to jump CNC queue *after* freeze. Paying to jump a queue while CAD is open buys the same wait with a fee.

Local vs overseas. Overseas aluminum can be cheap and still lose if crate + communication + time zone adds a week per loop. For first LSR shots, a closer sample cell often wins calendar even if the hourly rate looks worse. Production steel can still go overseas after the aluminum taught you the part.

What startups should stop doing

• Asking five vendors for Class 103 8-cavity quotes to “save time later.” You will wait on five DFMs and still cut aluminum.
• Requiring ISO 10993 reports on the first 10 shots of an unfrozen lip.
• Changing hardness after the tool is cut “because the investor liked softer.”
• Using tin-cure RTV parts in a life test and then blaming LSR.
• Overnighting a master that is still sticky, then losing a week to inhibition.

A 30-day shape (illustrative, not a promise)

If CAD is frozen on day 1, grade is a stock LSR, geometry is open-and-shut:

• Week 1: DFM freeze, aluminum in cut or a heat-capable print for a fill check.
• Week 2-3: tryout, post-cure, five-dim report.
• Week 4: one recut if needed, sample pack to testers.

If you need slides, medical color, and a full balloon FAI, this is not a 30-day object. Split the questions or admit the calendar.

The test to run this week: write the single question the next sample must answer. If the sentence contains both “investor demo” and “FDA file” and “unit cost at 50,000,” you have three prototypes. Sequence them. That is the lead-time reduction.

FAQ

Why is overnight CNC often the wrong lead-time attack?

Prototype time is usually waiting: CAD that never freezes, RTV samples treated as LSR, special-order compound, steel as first tool, paperwork added after tryout, and queues. Actual CNC is often the shortest bar. A fast wrong tool is still a wrong tool.

Should a seed-stage team cut Class 103 steel first to save time later?

No. Sequence questions: shape (print or RTV), then intended-family LSR in 1-cavity aluminum, then steel when volume is real and CAD is dead. Putting steel first is how you buy a long brick. Asking five vendors for 8-cavity 103 quotes still ends in aluminum.

Why pick a catalog LSR the shop already stocks instead of brand color on shot one?

Custom color, medical files, and self-lube pails are purchasing lead times. Natural in the intended family answers flash and shrink. Color paste is a later queue. Incomplete RFQs also bounce; send STEP plus a one-page 2D on day one.

When does a closer sample cell beat cheaper overseas aluminum?

When crate, time zone, and a week per loop dominate. For first LSR shots, calendar often wins even if the hourly rate looks worse. Production steel can still go overseas after aluminum taught you the part. Expedite only named gates after freeze.

What single sentence sequences three prototypes instead of one overloaded sample?

Write the question the next sample must answer. If it contains investor demo, FDA file, and unit cost at high volume, you have three prototypes. Split them. That is the lead-time reduction, not shouting expedite into a toolroom.