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Guide

How Many Cavities Does a PET Blow Molding Machine Need?

Calculate a preliminary cavity count from target good bottles per hour, cycle time, availability and acceptance yield using explicitly hypothetical inputs.

Direct answer

How Many Cavities Does a PET Blow Molding Machine Need?: key points

Use N = ceil(target good bottles/hour * cycleSeconds / (3600 * availability * acceptanceYield)). Here, ceil means round up to the next whole number, availability is the running fraction of scheduled production time, and acceptanceYield is the fraction of produced bottles that pass acceptance. This estimates a minimum cavity count under the stated assumptions; it does not identify an available machine configuration or guarantee output.

  • Define the target as accepted bottles per scheduled production hour so demand and availability use the same time basis.
  • Use cycle time for the actual bottle and configuration; bottle volume alone does not supply a validated cycle time.
  • Apply availability and acceptance yield once, keep full precision during calculation, and round only the final cavity result upward.
  • Treat the calculated integer as a minimum under assumptions, then check available machine configurations, tooling fit and utilities.
Review status

What this page is reviewed against.

ClusterBlow machine selection
Last reviewed2026-07-15
Use this page forShortlisting, RFQ preparation and evidence-aware route selection
Factory and route evidence

Public references linked to this buying decision.

These links point to public route pages, reference media or downloadable worksheets that buyers can review before requesting a project-confirmed quote.

KRC machine route pages Configuration review starting points; these pages do not validate the hypothetical example inputs. Automatic vs semi-automatic comparison Review handling tasks when defining running time and downtime assumptions. Machine cost factors Compare commercial scope after checking the calculated configuration with engineering.
Decision table

Use this guide to avoid vague machine or mold quotes.

Each row converts a common buying question into the exact data engineering needs before final route selection.

Sizing equation N = ceil(target good bottles/hour * cycleSeconds / (3600 * availability * acceptanceYield))
Hypothetical target 3000 accepted bottles per scheduled production hour; an assumed demand, not a model output claim
Hypothetical cycle time 3 seconds per cycle while running; assumed only for this example
Hypothetical availability 0.85 of scheduled production time spent running; assumed only for this example
Hypothetical acceptance yield 0.98 of produced bottles accepted; assumed only for this example
Substitution and rounding ceil(3000 * 3 / (3600 * 0.85 * 0.98)) = ceil(3.00120048...) = 4 cavities
Check the lower integer At the same hypothetical inputs, 3 cavities yield 2998.8 good bottles/hour, below the 3000 target
Check the rounded result At the same hypothetical inputs, 4 cavities yield 3998.4 good bottles/hour; this is a calculated scenario, not equipment performance
Engineering confirmation Confirm the actual cycle time, loss assumptions, available configuration, mold fit and utility requirements before selecting equipment
Workflow

Prepare the buyer-side data package.

01 Step 1

Convert accepted-bottle demand into a target per scheduled production hour. Define the scheduled hours and count downtime in availability only once.

02 Step 2

Obtain or explicitly assume cycleSeconds, availability and acceptanceYield for each bottle and configuration. Cycle time must be positive; availability and yield must each be greater than zero and no greater than one.

03 Step 3

Substitute the inputs into the equation, retain full precision and round the final result up. Check it using good bottles/hour = N * 3600 / cycleSeconds * availability * acceptanceYield.

04 Step 4

Send the assumptions, bottle drawing, preform data and production schedule for engineering review. Confirm an available machine and mold configuration rather than assuming the calculated cavity count is offered.

FAQ

Questions this guide answers.

How do I convert bottles per hour into a cavity count?

Multiply the target good bottles per scheduled hour by cycle time in seconds, divide by 3600 times availability times acceptance yield, then round up. With hypothetical inputs of 3000 good bottles/hour, 3 seconds, 0.85 availability and 0.98 acceptance yield, the result is ceil(3.00120048...) = 4. Do not round the intermediate value to 3.

Can I infer cycle time from bottle volume alone?

No validated cycle time is supplied by bottle volume alone. Request a cycle assumption for the actual bottle, preform, machine and cooling configuration, and recalculate for each format rather than applying an unsupported output band.

Is more cavities always better?

No. The formula gives a minimum under the entered assumptions, not an automatic recommendation for a larger platform. Compare available configurations against the production schedule, tooling fit, utility requirements and quotation; no fixed 8-versus-6-cavity rule follows without those inputs.

Does cavity count on the blow machine have to match the preform mold?

They are separate tooling scopes and do not have to match. Calculate preform supply and bottle demand using their respective cycle times, schedules and acceptance assumptions, then check that the preform supply supports the blowing plan.

Can the hypothetical worked example be used in a purchase contract?

No. Its numerical inputs are assumed solely to demonstrate the equation. Contractual output needs project-specific confirmation against the bottle drawing, preform specification, machine configuration, utilities and agreed acceptance criteria.