Minimum Batch Sizes and Setup Fee Structures in Custom Silicone Factories

Factories size a minimum batch so changeover, pail, and oven slot get paid. They are not punishing small POs.

A custom silicone cell (LSR press, HCR mill and press, RTV vacuum table) spends hours becoming *your* job: heaters on, last grade purged, first offs thrown, oven recipe loaded, traveler opened. The parts that come after have to pay that motion. Factories either name a setup fee or they hide it as MOQ or they bury it in a high unit price. All three can be honest. Mixing them is how two quotes look different when the physics is the same.

What a “setup” actually is

Walk it once so the fee is not mystical.

LSR injection. Mount tool, connect water/oil and electrics, heat cavities, cool the manifold, vacuum check, load A/B pails, purge the previous platinum grade (color especially), first shots, flash tune, start traveler. At the end: purge again, spray, storage oil if the tool is coming out. Post-cure oven: a recipe and a rack that may be oversized for your 80 parts.

HCR compression/transfer. Mill or preform change, color clean-down, preheat, first compressions, flash. Mill clean-down between dark and light stocks is the silent hours.

RTV vacuum casting. Scale, mix, degas, jacket on the bench. Setup is lighter. Labor per part is heavier. MOQ may be low because the machine is a person.

If two LSR quotes disagree on min batch, they disagree on whether that walk is a line item or a religion.

Compound pack size is a second minimum

Even a zero-setup fairy shop still faces pails and mills.

LSR kits come in vendor sizes. Color paste comes in vendor sizes. If your batch uses 1.2 kg and the kit is 20 kg, leftover is a policy:

• You buy the kit (batch minimum is mass, not count)
• Shop stocks the grade (you pay a carrying story in the unit price)
• Shop runs a shared natural and you lose color/cert control

Medical, self-lube, and conductive grades make this worse because the shop will not “use it up” on a toy bumper. Ask pack size and leftover owner on the RFQ. That *is* a batch constraint.

How fees get structured (and how to read them)

A. Setup fee + true piece price.

Clean. Compare shops. Watch whether FAI, first offs, and tool mount are inside the fee or extra.

B. No fee, high MOQ.

The setup divided by MOQ is inside the unit price. Fine if you will always buy that MOQ. Hostile if you wanted 120 and the MOQ is 1,000.

C. No fee, no MOQ, suspiciously low unit price.

You will meet the fee as a changeover charge, a “color clean” charge, a “small lot” surcharge, or a six-week queue. Prefer A.

D. Sliding batch breaks.

Unit price steps at 200 / 1,000 / 5,000. Useful only if they also show the setup line. Otherwise you cannot tell a material break from a hope.

Cavitation changes the story: an 8-cavity tool has a *higher* honest min batch, because you will not heat that cell for two shots of eight. A 1-cavity aluminum sample cell can run 50 without shame. Do not demand 8-cavity economics at 1-cavity batches.

What should be inside vs outside the setup fee

Put this table in the RFQ and make them tick.

If FAI is inside every reorder’s “setup,” you are paying for a ritual. Reorder setup should be mount + purge + first offs, not a new balloon report, unless the CAD or grade changed.

Batch size vs release size

Your warehouse wants 200 a month. The factory’s min lot is 1,000 because of the pail and the oven. Options:

• Run 1,000, you store 800 (cash, shelf life, color aging)
• Pay setup 5× a year at 200 (conversion expensive, inventory light)
• Change to a stocked grade so 200 is only press setup
• Change cavitation down so small lots are not embarrassing

Shelf life of mixed colors, platinum kits, and customer-specific hardness is part of TCO. A min batch that exceeds what you will use before the compound or the parts age is not a discount.

Overseas vs local cell

Overseas production lots like larger batches: freight, communication, and customs are their own setup. A local sample cell likes smaller batches and will charge the hours. Many programs should *split*: small local LSR lots until freeze, then overseas batches sized to a pail and a crate.

Do not fight an overseas 103 4-cavity shop for a 60-piece monthly. You are arguing with their physics.

The quote that lets you choose

Ask for:

• Setup fee definition (what’s in it)
• Min batch in parts *and* in kg of compound
• Leftover policy
• Unit price at min batch, at 3×, at 10×, same tool
• Reorder setup vs first-lot setup
• How cavitation would change the min batch

Then pick a batch that is a multiple of something real (pail, oven rack, month of demand), not a round number from a homepage.

RFQ sentence: “Split setup fee from piece price. State min batch as a function of changeover, compound pack size, cavitation, and oven slot. First-lot FAI is not a reorder setup. Leftover compound ownership must be explicit.”

FAQ

Is a factory minimum batch a penalty on small POs?

No. The cell spends hours becoming your job: heat, purge, first offs, oven recipe, traveler. Parts after that pay the motion. Shops name a setup fee, hide it as MOQ, or bury it in unit price. All three can be honest; mixing them makes quotes look different when physics is the same.

Why is compound pack size a second minimum even with zero setup?

LSR kits and color paste come in vendor sizes. If the batch uses a kilogram and the kit is much larger, leftover is a policy: you buy the kit, the shop stocks the grade, or they run a shared natural. Medical and conductive grades will not be "used up" on a toy bumper.

Should a ballooned FAI sit inside every reorder setup fee?

No. First-lot FAI belongs in tooling or a first-lot fee. Reorder setup should be mount, purge, and first offs unless CAD or grade changed. Color change is setup again. Tool PM and storage are not your batch fee.

Why might I pay setup several times a year instead of running the pail minimum?

Your warehouse wants small monthly drops; the factory's min lot is a pail and an oven rack. Options are store the extra (cash, shelf life, color aging), pay setup more often, change to a stocked grade, or drop cavitation so small lots are not embarrassing. A min batch that exceeds what you will use before parts age is not a discount.

How do overseas production lots differ from a local sample cell on batch physics?

Overseas lots like larger batches because freight, communication, and customs are their own setup. A local cell likes smaller batches and will charge the hours. Many programs split: small local LSR until freeze, then overseas batches sized to a pail and a crate. Do not fight a 4-cavity 103 shop for a 60-piece monthly.