Crushing & Screening 101
Unless it is made of natural wood or solid rock, just about everything we 
use everyday has undergone some sort of crushing and/or screening before it was formed into a finished product. From the roads we drive on to just about everything in our homes, the re-purposing of material typically requires the original material to be reduced, typically by crushing, and sized, by screening.
Screen Machine manufactures crushers and screens for a variety of materials – rock, dirt, construction and demolition recycling and more. Our machines are classified as mobile crushers and screens, because they are on tracks or wheels. This allows them to be transported to worksites by tractor-trailer, and to move around the jobsite once on location. Our machines go to where the work is, rather than having dump trucks haul the material to the crusher or screener. That greatly improves efficiency for the processing company.
Click on the video link at the top to see how we manufacture Screen Machine products. They are built from scratch at our Etna, OH factory, just east of Columbus. After beginning as a flat piece of steel, our finished machines weigh up to 100,000 pounds and be taller and longer than your house!
Here is a breakdown of the machines we make at Screen Machine and how they are used in the field:
CRUSHERS
Crushers do exactly what their name implies – crush big pieces of material into smaller pieces of material. There are 3 types of crushers:
Jaw Crusher – A jaw crusher reduces material through the use of a compressing force and gravity. Material is loaded through a wide top opening while one active jaw repeatedly squeezes it again the other jaw and breaks it apart. As the material pieces are reduced, they drop down farther into the jaw and eventually pass through the bottom when they are the desired size. 
Impact Crusher – An impact crusher reduces material by repeatedly “throwing” it against the wall of the crushing chamber. The crushing energy in an impact crusher is delivered by a large spinning rotor that has four very heavy and durable metal bars attached to it. Two of the bars are known as “blow bars” and they break up material while spinning and also throw it against the chamber wall for additional reduction. The other two “dummy bars” counter-balance the blow bars to keep the rotor spinning smoothly. They also drive material against the crusher wall for additional reducing.
NOTE: Both jaw crushers and impact crushers are “primary” crushers. That means they accept material in its rawest form and reduce it, typically so it can be processed again through a secondary crusher or a screener.
Cone Crusher – A cone is a secondary crusher, and it’s easy to see why. A cone crusher reduces material via a rotating mandel, or cone, that presses material against the cone wall. There is much less open space in a cone crusher chamber than a jaw or impact crusher chamber, so the material has to be pre-sized before it can be run through a cone crusher.
SCREENS
Screening machines come in a variety of shapes, but the principle behind how they work is basically the same. Screens usually have one or more heavy-duty metal screens with steel “wirecloth” that runs in both vertical and horizontal directions, creating a pre-determined gap between the wirecloth strands – such as ½”, 3/8”, ¼”. That is shaken to create movement and separation of the material. The smaller material falls through the screen, while the larger material is moved forward and away. Some screeners have a single screen, others may have up to three screens. With multiple screens, the processor can create up to four different sizes of material.
Spyder Plant – Screen Machine’s most popular product over the years has been spyder plants. These screen plants are called “spyders” because the extended stackers/conveyors attached to them resemble a spider’s legs. Spyder plants can vary in size from very large to compact. Click here to see a spyder plant in action.
Scalper – a scalper is a very basic screening machine, typically without any stackers. Material is dropped on a shaking screen or two sets of screens. The correctly sized product passes through the screen(s) and to the bottom of the machine. Oversize material falls to the side. Click here to see a scalper in action.
Trommel – Typically used with topsoil and/or compost, trommels have a large rotating drum instead of a flat shaking screen. Material is turned over constantly as it travel through the drum, and the properly sized material falls through the bottom. Oversize material runs out the back of the drum. Click here to see a trommel in action.
The operators of all these machines apply many STEM applications to their work. They need to know how much material to put through the machines for maximum productivity. They need to understand the makeup of various materials and how they will respond to what the machine does. They need to constantly monitor the activities on the machine and watch for any blockages or mechanical issues. As you watch the videos here, what other STEM activities do you see engaged?