Blow Molded Cases: When a One-Piece Shell Fits
                     Blow Molded Cases: When a 
One-Piece Shell Fits
How the process works, where it beats other case technologies, and where it falls 
short
A practical primer on choosing a blow molded case for high-volume equipment programs
2026 | Protective Case Manufacturing Insights
A mature process built for volume
Blow molding has been producing hollow plastic parts commercially for almost 90 years, which is why it 
remains a default for cases made in thousands.
1938 ~10B 3 #2
First commercial US plastic soft drink Main process types: Resin ID code for 
blow molding containers in 1999, extrusion, injection HDPE, a common 
machine sold up from zero in and injection stretch case material (ID, 
1977 not a recycling 
promise)
Sources: Wikipedia, "Blow molding"; ASTM D7611 as summarized by ANSI
2 / 5
How a blow molded case is formed
Form the parison
1 Plastic, usually polyethylene, is melted into a hollow Where it fits best
tube. High-volume runs, leased or shared equipment, 
simple shapes and frequent wipe-down cleaning. 
Clamp and inflate Case makers such as Shell-Case have used it for a 
2 A cooled steel mold closes and compressed air hospital-grade breast pump case where 
pushes the plastic outward. cleanability and cost-efficiency mattered most.
Cool and eject
3 Water channels cool the shell, which is ejected in 
one piece.
When a design needs finer detail, tighter precision or a premium finish, custom plastic cases made by injection molding are 
usually the alternative to weigh against blow molding.
3 / 5
What blow molding misses
Where it falls short What a better spec does
• Intricate contours and form-fitted interiors • Compares unit cost, tooling, development 
are hard to mold time, cleanability and production time
• Surface finish cannot match injection • Chooses a technology per component, not 
molding or EVA per case
• Lower mechanical precision for delicate • Pairs a molded shell with a custom foam 
instruments interior
• Openings must be cut, burned or punched, • Confirms ports and windows early in design
adding a step
4 / 5
Five steps to a better case decision
1 Estimate annual volume before choosing a technology
In short
Blow molding delivers low unit cost, 
2 Define cleaning routines and the setting the case lives in one-piece construction and easy 
cleaning at volume. Choose it for 
rugged, simple, frequently cleaned 
3 cases, and look elsewhere when Map required openings, ports and recesses early precision or premium finish drives 
the brief.
4 Ask which blow molding variant a quote assumes
5 Treat resin codes as identification, not recyclability
5 / 5