Glass filled nylon
- Lighter and quieter, molded to final shape
- Color and texture come from the mold, no finishing
- Designed for creep with deeper sections than metal
Industry
Injection Molding for Furniture
A chair base carries a person's weight every working day for years, with a jolt each time someone drops into the seat. Few molded parts see a load that constant, and plastic does not forget it.
From the floor up
The molded parts in an office chair
Each level carries a different kind of load.
- 1
Casters and glides
Small parts that take the whole load at a point. Wheel treads are often a softer material over a hard core so they roll quietly on hard floors.
- 2
Base
The five arm star carries every sit down. Glass filled nylon is the usual choice, because it resists creep and survives impact.
- 3
Mechanism covers
Hide the tilt mechanism and take no real load, so they are chosen for looks and a good fit.
- 4
Arms
Get leaned on and used to push up out of the chair. Thick sections are often cored out or gas assisted to avoid sink.
- 5
Seat and back shells
Large, visible, and flexing slightly with every move. They carry the cushion and the brand's look.
Creep
Plastic under a load that never goes away
The failure that shows up in year three, not in the lab.
Metal carries a steady load and stays put. Plastic under the same load slowly keeps moving, which is called creep. A chair base that passes a drop test can still sag over years of daily use, and a shelf bracket can slowly droop under books.
Glass fibers cut creep sharply, which is why structural furniture parts are mostly glass filled nylon or polypropylene. Designers also keep sections even, since thick spots cool slowly and trap stress, and they avoid sharp inside corners where cracks start under repeated loads.
Chair bases
Molded nylon base or cast aluminum base
Both are on the market at every price point. The choice is partly engineering and partly look.
Cast and polished aluminum
- Slimmer arms for the same strength
- Polished or coated look buyers link with premium chairs
- Casting, machining, and polishing steps add up
Small hardware
The parts that hold flat pack furniture together
Connectors, cam locks, hinge cups, and glides are small, cheap looking, and decide whether the furniture wobbles.
- Connectors are sized against the tolerance of drilled particle board, which is looser than any molded part
- Acetal and nylon take the snap and twist of cam locks and knock down fittings
- Glides with a soft tread protect floors and are often two materials molded together
- These parts run in very large quantities, so a family or multi part tool often makes several at once
FAQ
Questions from furniture makers
How are large seat shells kept free of sink and warp?
Even sections, gates placed to fill the shell evenly, and sometimes gas assist or a foamed core in the thickest areas. Warp on large shells is mostly a cooling and gate layout question settled in DFM.
Can outdoor furniture be molded?
Yes. UV stabilized polypropylene is common for outdoor chairs and tables. It holds color in sun and does not rust or rot.
Can one base design come in several colors?
Yes. Color is set at the press, so black, gray, and white bases can come from one tool.
Who owns the tool?
You do. The customer owns the tool once the tooling charge is paid, and can request it at any time.
Keep reading
Related guides
Parts, processes, and resins behind seated furniture.
Casters
Wheels, forks, and swivels.
CastersHinges
Living and pinned hinges.
HingesGlass filled nylon
Bases that resist creep.
Glass filled nylonPolypropylene
Outdoor and stacking chairs.
PolypropyleneGas assist molding
Hollow arms and handles.
Gas assist moldingSink marks
Why thick spots dip.
Sink marksIndustries hub
Every sector page in one index.
Industries hubNext step
Send the load case with the CAD
Upload CAD with how the part is loaded, for how long, and which faces are visible. DFM checks sections and corners that carry constant load. NetProto manufacturing is ISO 9001 certified.