With iterations used by humanity for millennia, hammer mills have advanced considerably over time. Today, numerous industries depend on the humble hammer mill. Machines that utilize hammer-like implements continue to develop into the 21st century, providing efficient and reliable particle size reduction for countless applications.

Advances in Hammer Mill Machinery

As one of the most adaptable pieces of particle reduction equipment within bulk material processing systems, hammer mills are used for an array of products and industrial applications. To improve their function, hammer mill components are tweaked to better suit certain applications, from the shape of the hammers to the direction of the feed.

Types of hammer mill machines include: 

  • Full circle screen: With screens that incorporate over 80 percent of the rotor, these hammer mill machines work well for lightweight materials like herbs, spices or grasses.
  • Gravity discharge: Also known as a bottom discharge hammer mill, machines of this type are used for ceramics, dry chemicals, glass or other coarse materials and typically feature heavy-duty hammers that swing from the shaft to which they’re mounted, discharging onto a conveyor or into a bin.
  • Horizontal in-feed: Used to aggressively trim down scrap, wooden pallets and for other forceful grinding applications, this hammer mill design is fed material from the side.
  • Lump breakers: Using fixed hammers, lump breakers condition material into powders or granulates that flow freely, such as cement, dry chemicals and sugar.
  • Pneumatic discharge: Like a gravity discharge hammer mill, components within the machine reduce material more finely and precisely, often featuring configurations with more hammers that’s paired with an external vacuum that pulls ground products like wood, paper, grain or biomass from the mill.

In a hammer mill, each of the machine’s constituent parts perform a specific function.

Hammer Mill Components 

Hammer mill components include a drive system with controls, a feeding mechanism, hammerlike implements, a rotor and screens. While the controls provide power to the drive system operating the rotor, they also enable adjustment of the feeding mechanism. The drive system is either directly connected to the rotor, or else operated via belts that provide more precise control. The feeding mechanism typically consists of a rotary valve or similar device that feeds product into the grinding chamber.

The implements attached to the rotor and used for particle size reduction aren’t always shaped like a hammer. Mill machinery for reducing material sometimes utilizes knifelike hammers attached to the rotor to crush or grind, rotating on the shaft thousands of times per minute. This rotor is driven by an electric motor, with hammers balanced and positioned so as to reduce vibration during operation. Material leaving the grinding chamber must go through screens that classify particles, allowing right-sized particles through and returning larger portions for further processing.

Innovations in Hammer Mill Components

Hammer mill components have evolved substantially over the past century, driven by the need for greater automation, consistency, efficiency and reliability.

Feeding

From gravity-fed and manually operated hoppers that required frequent intervention from operators with inconsistent flow, hammer mill components for feeding materials rely on augers, belts or pneumatic mechanisms to regulate feeding. Modern hammer mill machines utilize variable frequency drives (VFDs) to adjust inputs, while controls and sensors have enabled the ability of operators to adjust in real time.  

Controls

Hammer mills in the early 20th century relied on experienced operators to adjust settings as needed. Today’s hammer mill controls are largely automated, allowing for data gathering, monitoring remotely and real-time adjustments. These systems can automatically adjust feed rates, rotor speed and other parameters while also integrating emergency shutoff systems, hazard monitoring and other safety features.  

Hammers

Often made from cast iron or lower grades of steel, early hammers were fixed in place and tended to wear quickly. These days, hammer mill machinery utilizes reversible hammers that can be either fixed or swinging, and configured so that they last longer. Additionally, hammer tips are often made from more robust advanced materials like carbide or steel alloys that improve wear resistance. Hammer geometry has advanced as well, with grinding implements shaped like chisels, knives, stirrups or other forms.

Rotor

Basic mechanisms prone to vibrations, rotors tended to become unbalanced and wear quickly.  Rotors configurations today are adjustable to enable easier hammer positioning that allows modifications to particle size distribution. With new construction materials and engineering advances, modern hammer mill rotors can operate at higher speeds to grind more finely and process more thoroughly.

Drive System

Inefficient mechanical drives that ran on steam or electricity were common in early 20th century hammer mills. In the 21st century, VFDs have allowed greater energy efficiency while finetuning speed control, while certain drive systems even allow efficiency monitoring to optimize energy use. Additionally, direct drive or gear-coupled systems have been improved, enhancing torque transfer and reducing maintenance.

Screening

Largely made from perforated plates or rudimentary wire mesh, the typical hammer mill screen clogged frequently while limiting accessibility for cleaning, repair or replacement. With a modern hammer mill, machinery is often designed for easy access without the need for tools, making maintenance easier. Additionally, devices that produce airflow or vibrations keep screens clean in many modern types of hammer mill. Components for screening bulk materials in the 21st century are often made with hardened steel or treated with compounds that resist abrasion. Certain hammer mill models even allow for real-time adjustments that enable more precise control over particle size.

Prater Hammer Mill Designs

A century ago, Prater Industries produced its first hammer mill. Machinery for particle size reduction has since evolved from these comparatively rudimentary mills. Today, Prater manufactures two basic models of hammer mill. Machines like our proven full-screen G-series hammer mill offer uniform grinding with a low-maintenance design, while our more compact Mega Hammer Mill fills the gap between these conventional hammer mills and our fine grinders. To learn more about our hammer mill machines and the components that make them sought after, contact the material handling experts at Prater today.