How Do Wood Chippers Work? A Detailed Look at the Mechanics Behind These Powerful Machines

Wood chippers are essential equipment for landscaping professionals, rental companies, municipalities, and even homeowners with large properties. But how exactly do these powerful and potentially dangerous machines turn logs, branches, and other debris into tiny chips? Read on for a complete guide to wood chipper mechanics.

What is a Wood Chipper?

A wood chipper is a mechanical device designed to shred wood material into smaller woodchips. Chippers utilize a chipping mechanism that draws material into the machine and pushes it through rotating metal blades or knives mounted on a spinning disk or drum. The chipping action reduces the wood into small pieces or chips.

Chippers come in a range of sizes from small portable models for home use to giant industrial chippers that can process entire trees. They allow for efficient disposal of tree limbs, brush, and other woody material by reducing the volume and turning it into reusable woodchips.

Main Components and Systems

While wood chipper designs can vary, most chippers consist of the same core components:

Feed System

The feed system controls the flow of material into the chipper and often consists of a hopper, feed table, and feed rollers. The slope of the hopper and feed table uses gravity to direct material towards the chipping mechanism. Feed rollers then grip the wood and force it into the blades at a steady controllable rate.

Cutting System

The cutting system is the heart of the chipper and contains the spinning disk or drum fitted with blades that do the actual cutting. The high-speed rotation of the blades generates immense force to efficiently chip or shred the wood. Most cutting systems are powered by a diesel, gas, or electric motor.

Discharge System

Once chipped, wood material is expelled through a discharge chute. The spinning blades create airflow that blows the chips out of the chute into a collection bag or pile. Chutes often have adjustable deflectors to control the direction and spread of the discharged chips.

Safety Features

Given the dangers of getting pulled into a chipper’s cutting blades, wood chippers have many crucial safety features. These can include feed control bars, auto-reverse functions, blade locks, and emergency stop cords. Newer models also integrate advanced electronic safety automation.

How Wood Chippers Work Step-By-Step

Now let’s look at what happens, step-by-step, when a log, branch or other material goes through a typical disc or drum-style wood chipper:

  1. Feeding In – The material is dropped into the top hopper or placed on the feed table. The operator pushes it towards the feed rollers using the feed control bar.
  2. Grabbed by Rollers – Once in range, the serrated feed rollers grab the material and pull it towards the cutting blades. The operator regulates this with the feed control bar.
  3. Cutting Begins – As it engages the cutting disk or drum, the material is cut into chips by the rotating blades. The blades chip material against an anvil or sheer it by passing very close to a stationary blade.
  4. Cut Continues – The feed rollers advance the material through as the rotating blades keep chipping from the bottom up and cutting any remaining larger pieces. Smaller chippers may require wood to be fed perpendicular to the blade while larger ones chip along the grain.
  5. Chip Discharge – Centrifugal force and airflow created by the spinning blades blow the wood chips out of the discharge chute into a pile or chipper bag.
  6. New Material – Once the chipping is complete, the operator repeats the cycle, feeding in new logs, branches, etc to be chipped.

Safely Feeding Material

It’s vital that material is slowly fed perpendicular to the blade, holding the wood firmly against the feed control bar. Pushing material directly into the blades can lead to kickback or uncontrolled chipping. Follow the manufacturer’s instructions for the maximum size of wood that a chipper can handle. Smaller branches can be bundled together. Never reach into the feed hopper while it is running.

Key Components and Technologies

Wood chippers incorporate a range of components and technologies to efficiently convert wood material into chips while maintaining safe operation. Let’s look at some of the most important elements:

Chipping Mechanisms

There are two main types of chipping mechanisms:

  • Disk Chippers – These utilize a large spinning metal disk fitted with 2 or more curved razor-sharp blades. As wood engages the disk, the blades slice it into chips.
  • Drum Chippers – Here the blades are mounted around a cylindrical drum that spins inside a fixed sharpened grate. The shearing action between the drum and grate chips the material.

Engine Types

Gasoline, diesel, and electric motors all power chipper disks and drums. Smaller portable chippers tend to be gas-powered while large industrial models use diesel engines. Electric motors are also becoming more common in certain models.

Feed Systems

The feed system regulates the all-important flow of wood material into the cutting mechanism. Important components include:

  • Feed Rollers – Rubberized rollers with grooved edges that grab and pull material towards the blades. They are typically powered by hydraulic motors.
  • Feed Control Bar – A lever-operated metal bar that adjusts the pressure and grip of the feed rollers on the wood. Also used to force material towards the blades.
  • Feed Hopper – Top opening or tray area that material is placed into and gravity-fed into the feed rollers. Hoppers have sloped metal sides.

Safety Features

  • Emergency Stop – A red button or pull cord that immediately shuts down the feed rollers and cutting mechanism if activated. Stops all mechanical motion.
  • Auto-Reverse – Detects sudden increased loads on the cutting mechanism indicating a material jam. When triggered, it reverses the feed rollers to back material out. Prevents kickback injuries.
  • Rotating Blade Lock – A physical metal or plastic lock that can be inserted through slots around the cutting disk or drum to prevent rotation during maintenance.
  • Interlock Switches – When attached to guards and shields, these switches disable the chipper when opened or removed, preventing operation without safety guards in place.

Common Uses of Wood Chippers

Wood chippers provide an invaluable service across numerous industries thanks to their ability to quickly reduce wood material to chips:

  • Landscaping – Tree services, landscapers, and rental stores use chippers to dispose of branches, logs, brush, and organic debris from tree removal, pruning, storm damage, and property maintenance.
  • Forestry – Larger industrial chippers allow logging and forestry operations to process slash, logs, and brush to minimize waste and leftover material after harvesting trees. The chips can be used for landscaping mulch or as feedstock for paper production.
  • Orchards and Nurseries – Fruit orchards and plant nurseries use chippers to grind up and recycle tree trimmings, plant stalks, diseased vegetation, and other organic waste around their facilities.
  • Municipalities – Cities and towns deploy chippers to clear roadside brush, maintain public parks, and handle wood debris from storms. The chips improve organic matter when used by parks departments.
  • Utility Companies – Power and utility companies use chippers to quickly dispose of wood and clear vegetation around power lines, right-of-ways, and infrastructure.

Key Factors When Choosing a Chipper

Those in the market for a wood chipper have several factors to consider that will influence which style and model suits their needs:

  • Intended Use – What material will you need to chip – small branches, larger logs, brush, or a mix? How often will you operate the chipper? Is mobility needed? This helps determine required capabilities.
  • Chipping Mechanism – Drum chippers handle stringy brush well while disk chippers excel with logs. Disks produce more consistently sized chips.
  • Power Source – Gasoline engines offer portable convenience but require maintenance. Diesel engines deliver higher torque for large logs but need fuel. Electric chippers provide quiet, maintenance-free operation but need power outlets.
  • Throughput – Bigger machines process more material hourly based on their engine size, chipper opening size, hopper capacity, and feed rates. Consider your volume needs.
  • Safety Features – Essential for safe operation, newer chippers offer innovative safety tech like electronic monitoring, auto-reverse, and anti-kickback devices.
  • Cost – An important factor, prices range from $150 for basic electric models to over $50,000 for heavy-duty diesel chippers built for high volumes.

Operating a Chipper Safely

While very useful, wood chippers must be operated with caution as they involve powerful mechanisms with fast-spinning blades. Always follow the manufacturer’s instructions and safety procedures, including:

  • Wear close-fitting protective clothing free of strings or loose items that could get grabbed. Use gloves, eye protection, ear protection, and steel-toed boots.
  • Make sure guards are in place and don’t use if any safety devices are disabled. Check for loose bolts, damaged parts, or leaking fluid.
  • Only allow trained, authorized operators who are familiar with the machine to use it. Keep bystanders and animals out of the work area.
  • Feed material slowly, keeping hands and body away from the feed hopper. Use feed control bars instead of pushing with hands.
  • Avoid feeding too much material at once to prevent jamming, and don’t force wood into the blades. Cut logs to size if needed.
  • Support logs as they engage the blades to avoid kickback from unbalanced wood. Maintain full control when feeding.
  • Shut off and disable cutting disk using lockout devices before conducting any repairs, maintenance, or clearing jams near blades.

In Summary

Modern wood chippers are engineering marvels, able to rapidly process material through automated feeding and precisely designed cutting systems. With great utility for handling landscaping debris and other wood waste, chippers have become a must-have tool for certain homeowners and an essential piece of equipment for landscaping professionals, rental stores, municipalities, tree services, and forestry operators.

By understanding key components like the chipping mechanisms, feed rollers, and engine types, operators can select the right wood chipper for their specific needs. Maintaining a chipper properly and always adhering to crucial safety precautions allows users to tap into these machines’ capabilities while avoiding unnecessary hazards.

So whether you operate a chipper regularly for business or just occasionally for home use, keep this overview of how wood chippers work in mind. Knowing the internal workings of chippers helps ensure optimal performance, longevity and above all – safety.

Laura Kassovic

Laura Kassovic, a former engineer at Intel SOC, now dedicates her efforts to mentoring startups in the realms of Wearables and AI. As a co-founder of New Tech Brake, she spearheads a wireless sensing solution enterprise catering to diverse applications including product development, research, location tracking, and people monitoring, as well as asset and cargo supervision. The platform empowers developers to craft an array of innovations such as fitness trackers, temperature-monitored cargo systems, medical trial tools, smart running garments, or even straightforward transmission of unprocessed accelerometer data to cloud-based repositories.

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