Plastic Manufacturing: Common Processes and Materials

Learn how to select the best manufacturing process and material for your custom plastic parts

Imagine there are no plastics

It’s one of those imponderables if you were born any time after the early 20th century. That’s when the first synthetic plastic was developed by Belgian Leo Baekeland. Bakelite was the start of the revolution we live in today.

Unlike 1907, now we have hundreds of different plastics to work with, and they come in powders, solids, pellets, and liquid resins, each of which offer different advantages, depending on what manufacturing technique you use to make your parts. This guide will help you know more about plastics manufacturing, so you can evaluate the processes and learn about the materials you can use as the basis for your parts.

🧴 Clear plastic resin | Plastic Materials: Pellets, Resins, and Powders

Choosing the right material for your parts is critical to their functionality and longevity. Beyond pellets, resins, and powders, it also makes sense to mention solid-form plastics, which come in blocks and cylinders, for use in CNC machining. More about those later.

Thermosets vs Thermoplastics

There are two types of plastics: thermosets and thermoplastics. You can always remember the difference because the end-form of a thermoset part is, well, set. You can’t melt it and use the goo to reform another part. It’s one and done. Generally, thermoset plastics require less heat and pressure to form, but also have high heat and chemical resistance. On the downside, they tend to be non-recyclable.

Thermoplastics are the opposite; while they are built the same way, typically they can be returned to a liquid form and remolded. That said, you do need more heat and pressure to form them into parts. The properties of the parts you get will vary depending on the material you’ve chosen.

Both plastics can be found across the manufacturing ecosystem taking unique journeys to final part based on your chosen service line. If you’re designing medical parts, you have a lot of requirements to adhere to, so you may want to explore some of the more popular plastic materials at a deeper level.

Common Injection Molding Materials

Resin TypeBenefits
POM (Acetal)Tough, stiff, hard, strong. Good lubricity, low creep, fatigue resistance.
PMMA (Acrylic)Good optical properties, high gloss, scratch resistant, low shrink.
ABSTough, impact- and chemical-resistant, low shrink, dimensional stability, inexpensive.
HDPETough, impact- and chemical-resistant, high shrink, floats in water.
PC (Polycarbonate)Strong, extremely impact resistant, heat resistance, high cosmetic finishes.
ABS/PCStrength, heat and low-temperature resistance, improved processing.
PP (Polypropylene)Inexpensive, wear resistant, flexible, resistant to acids and bases.
PEEKHigh-temperature, high-performance, flame retardant, excellent strength.
PEI (Ultem)High-temperature, high-performance, flame retardant, dimensional stability.
PPSUHigh-temperature tolerance, tough, radiation sterilization resistance.

Plastic Manufacturing Processes at a Glance

ProcessDescriptionWorks Best For
Injection MoldingMetal molds filled with liquid resin, cooled to form partsLarge volumes, simple to moderate geometries
CNC MachiningSubtractive process cutting from solid blocks or cylindersPrecision parts, production-grade materials, rapid turnaround
3D PrintingLayer-by-layer additive (SLA, SLS, MJF, PolyJet)Low volume, complex geometries, prototypes
ExtrusionForcing melted material through a dieLong continuous profiles, hollow parts
Blow MoldingAir pressure expands parison inside moldHollow parts like bottles, tanks
Rotational MoldingSpinning mold melts powder insideLarge hollow parts, uniform wall thickness
ThermoformingHeated sheet stretched over moldPackaging, large panels, enclosures

Injection Molding

At its most basic level, injection molding is all about melting plastics and elastomers and squeezing them through passageways to fill a mold in the shape of a part or group of parts. Once the mold has filled, the material cools and parts are ejected.

Potential pitfalls include short shots, insufficient draft, sink, shrink, and minimum thickness limitations. Konlida provides detailed DFM analysis to help customers avoid these issues.

Common Materials (Konlida offers 90+ plastics)

  • Standard/commercial: ABS, PC, ABS/PC, PP, acetal, acrylic, HDPE, LDPE
  • Engineering materials: Polyamides (nylons), LCP, PPS/PPE, PBT blends
  • High temperature: PEEK, Ultem (PEI)
  • LSR & TPEs: Elastosil, Silastic, thermoplastic elastomers

Applications

Electronics/enclosures: ABS/PC, acrylic; Automotive: nylons, LCP, PP, TPEs; Medical: PC, LSR, PEEK, PEI.

💡 Design tips: Use radii, draft angles (1° per inch), and proper shutoff angles for longer mold life. Parting line placement affects cosmetic appearance.

CNC Machining of Plastics

CNC machining is a subtractive process that creates parts by cutting away material from a block or cylinder with incredible accuracy. Konlida’s digital thread turns CAD models into G-code, and we use a fixed set of endmills to speed tool changes.

Common variations: 3‑axis and 5‑axis milling, as well as turning (live tooling). 5‑axis adds two rotary axes for complex shapes and efficiency.

Popular Plastic Materials

  • POM (Acetal): Durable, self-lubricating, corrosion resistant – ideal for mechanical applications.
  • ABS & Polycarbonate: Versatile, tough, good aesthetics – enclosures, medical devices.
  • PEEK & Ultem: High-performance, heat/corrosion resistant – aerospace, medical, energy.

Key benefits: Unmatched accuracy, repeatability, automation, reduced waste, and rapid lead times – as fast as one day from CAD to part.

⚙️ Design for machinability: Keep features on same axes, avoid undercuts, maintain 1:3 width-to-height ratio for unsupported walls.

3D Printing (Additive Manufacturing)

Several processes fall under plastic 3D printing:

  • SLA (Stereolithography): UV laser cures liquid thermoset resin – high detail, smooth surfaces.
  • SLS (Selective Laser Sintering): Laser melts nylon powder – stiff, durable parts.
  • MJF (Multi Jet Fusion): Fusing agents + heat – consistent mechanical properties.
  • PolyJet: Sprays photopolymer droplets – flexible, elastomeric parts.

Common 3D Printing Materials

  • ABS-like, Ceramic-like, Digital Photopolymer, PA11/PA12 (nylon), PC-like, Polypropylene, TPU, True Silicone.

Applications: engine components, housings, jigs, fixtures, medical devices, surgical instruments. Ideal for complex geometries and rapid prototyping.

🔹 Design guidelines: min wall thickness 0.003 in, small holes ≥0.020 in. Use lightweight lattice structures to reduce cost and material.

Extrusion

Extrusion creates objects with a consistent cross-section by forcing molten material through a die. Common plastics: PE, PP, PVC, PS, ABS. Used for plumbing pipes, tubing, and profiles.

Benefits: low tooling cost, high-volume consistency, minimal waste. Design tips: uniform wall thickness, rounded corners, draft angles.

Blow Molding

First, extrusion forms a parison (hollow tube). Two mold halves surround the parison, and compressed air expands it against the mold walls. After cooling, the hollow part is ejected.

Common materials: PE (LDPE/HDPE), PP, PET, PVC, PC. Applications: bottles, toys, automotive ducts. Maintain even wall thickness and add draft angles for best results.

Rotational Molding

Plastic powder is placed inside a mold, which is rotated in an oven. Centripetal force distributes the melt uniformly. After cooling, the hollow part is removed. Ideal for large tanks, playground equipment, traffic cones. Materials: PE, HDPE, LLDPE, XLPE, PP, nylon.

Benefits: uniform wall thickness, minimal waste, complex shapes possible.

Thermoforming

A thermoplastic sheet is heated and draped over a mold; vacuum or pressure forms it to the mold shape. Common materials: PS, PE, PVC, PP, ABS, PC, PET, PETG. Widely used for food packaging, disposable containers, automotive panels, and electronics enclosures.

Design for uniform thickness, generous radii, and draft. Consider draw ratio – sheet must be larger than final part.

How is Quality Measured in Plastic Parts?

Konlida employs rigorous quality control across all processes:

  • Material properties: Impact testing, chemical resistance, melt point, tensile testing.
  • Dimensional accuracy: Calipers, vision systems, CMM (coordinate measuring machines) with laser/probes.
  • Visual inspection: Trained inspectors detect warpage, cracks, discoloration.
  • Non-destructive testing: CT scans, X-ray, ultrasonic testing for internal flaws.
  • First article inspection & CTQ: Critical-to-quality parameters flagged in CAD for tolerance assurance.

Konlida’s ISO 9001, AS9100D, and IATF 16949 certified quality systems ensure consistent, reliable plastic parts.

Real-World Applications of Plastic Manufacturing

Across industries, engineers rely on Konlida to solve complex plastic part challenges. Here are typical scenarios where our processes deliver value:

3D Printing for Assistive Devices

An organization developing a learning tool for visually impaired students needed hundreds of tiny plastic springs with precise tension. Using SLA 3D printing with ABS-like photopolymer, Konlida produced functional, accurate prototypes that enabled rapid design validation and user testing.

Injection Molding for Lightweight Drone Components

A surveillance system manufacturer required 19 different plastic parts (casings, structural elements, gaskets) that would not interfere with 5G signals. Konlida recommended a specialized polycarbonate thermoplastic that reduced weight, simplified molding, and met flammability standards.

CNC Machining for Wearable Electronics

A fitness tech startup needed miniature plastic components (as small as 6.35mm) with challenging geometries. Using our automated CNC quoting system and design-for-manufacturability feedback, they received precision parts in days, saving weeks of development time.

These examples illustrate Konlida’s ability to handle diverse plastic manufacturing requirements — from prototyping to production — without compromising quality or speed.