Process families: BB, PB, NNPB
Container glass IS machines run one of three forming processes per cavity. BB (blow-and-blow): gob is settled, counter-blown into a parison, transferred and final-blown. PB (press-and-blow, wide-mouth): plunger forms the parison directly. NNPB (narrow-neck press-and-blow): plunger forms the parison through a narrow neck — the dominant lightweighting process for beverage.
When BB wins
BB is the legacy default for premium spirits, complex shapes, decorative bottles, and any SKU where the cosmetic surface matters more than wall-thickness optimisation. The settle-and-counter-blow sequence produces a parison with thicker walls and is forgiving on complex shape geometry.
When NNPB wins
NNPB is the lightweighting workhorse. By plunger-forming the parison through a narrow neck, it produces tighter wall-thickness control and lighter bottles than BB at the same strength. Most beer and CSD glass runs NNPB; lightweighting programmes targeting 10–15% weight reduction live and die in the NNPB process window.
When PB wins
Wide-mouth PB is the dominant process for food jars, dressings, baby food and any container with an opening wider than ~38mm. The plunger forms the parison to size directly; the twist-off finish dimensional standards make this the natural fit.
Lightweighting envelope by process
- BB: 10–20% heavier than NNPB at equivalent strength — but more forgiving on shape
- NNPB: tightest wall-thickness control of the three; lightweighting envelope is broadest
- PB: dimensional precision wins; lightweighting envelope is narrower
Capital and operational implications
Switching processes mid-campaign is expensive — mould investment, plunger systems, training. The choice is typically locked in for 5–10 years per SKU family. A plant designing capacity should run a process-window study against its expected SKU mix; a plant inheriting capacity should run an audit before deciding to convert.
This is exactly the kind of decision where vendor-neutral perspective matters — OEM-tied advisors will tend to recommend processes adjacent to what they sell. We have no equipment to sell, so the process choice is genuinely independent.