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Pulverizer mills act as size reduction equipment. They reduce coarse materials like coal and gypsum at high speeds to tiny granules for a variety of applications. Centrifugal force powers the pulverizers to grind feed materials down to the required size.
Pulverizing is typically defined as reducing to 25 mesh and beyond, but Williams machines provide a variety of finished product sizes. Learn more about the specific particle size options available from our pulverizer equipment.
Williams also offers roller mills that perform multiple functions in one machine. Our roller mills cangrind, dry, and classify materiallike limestone and clay all in one machine for maximized efficiency.
Williams roller mill pulverizers consistently deliver a uniform, fine grind for almost any imaginable application. Cylindrical rollers act as grinding elements to crush and pulverize material, creating this consistency.
Instead of having to endurerepetitive crushing of medications which may cause repetitive strain injuries, our portable, battery-poweredPowderCrush Medication Crusher may help avoid injuries by crushing medications, fast, easy and painless.
We are a 229 bed skilled nursing facility located in southeastern Wisconsin. My nurses are very impressed with your product. We were searching for a portable device that would be easy to use, yet powerful enough to crush multiple medications. From the minute the product was put into use, the nurses noted less soreness and discomfort that comes from using a manual crushing method. This product is also a time saver during busy med pass times. Thank you for coming up with such a useful tool! - Kelli De Ruyter, RN, D.O.N Cedar Lake Health Care Center
Your machine was recommended by our liaison officer at an annual inspection that we had in our Nursing Home. She had noticed that the RN's were doing a lot of pounding and noise with our medication crushing. We had seen the Pill Crusher in one of our magazine we receive monthly. We were very pleased with the fact that we could try it for a month at no cost, that way it gave us a chance to work with it and see the difference that it made with everybody's shoulders and the noise pollution. We knew after 2 weeks that it was a keeper. We liked it so much that we didn't hesitate to buy a second one. - Warren B., Bayside, NY
The necessary force required to crush medication was tested using three pill crushers; the Pharmacrush, the Silent Knight and the Powdercrush. These tests were conducted using large Calcium tablets and the force was measured by a Chatillon Force Gauge. Four trials were conducted where one tablet was crushed at a time by each crusher. By comparing the test results we can see that there are differences in the force levels required to crush medication from one crusher to another. Below is the data.
Please be advised that this was not a controlled study as not all variables were controlled and the sample size was too small.In conclusion, the Pharmacrush required almost twice as much force to crush the tablets as the Silent Knight. The Powdercrush required virtually no force to crush the tablets. Past ergonomic research has suggested that a reduction in force can lead to a reduced risk of injury.Jennifer Kenny BscKinErgonomics Consultant
The literature on the design of cone crushers and analysis of the corresponding crushing processes is mainly based on empirical observations. As a result, it is generally accepted that the crushing action is due solely to compressive forces. Crushers are designed on that basis. Accordingly, many cone crushers today are characterized by common operating principles. Most theoretical work on cone crushers focuses on performance characteristics such as the productivity, degree of crushing, or increase in content of the target fraction or on operational characteristics of individual crusher components such as the life of the armored lining or the increase in life of bearings and drives. To improve those characteristics, a crushing-chamber design with complex armored lining has been developed, while the working components (cones) combine elements of those used in other crushers (of roller or jaw type). However, kinematic efficiency of the working component is only considered in terms of the creation of compressive forces in the material being crushed and minimization of slip. Most of the energy supplied to any crusher is consumed in creating the destructive load. The basic contention of the present work is that, in certain circumstances, it is possible to increase the energy efficiency of the crushing process. One option is to create a complex stress state in the material to be crushed. Some crusher designs are considered, and their applicability is discussed. The creation of a complex stress state in the crusher permitting decrease in its energy consumption is described. Recommendations are made regarding the creation of energy-efficient conditions in the crusher.
Johansson, M., Quist, J., Evertsson, M., and Hulthn, E., Cone crusher performance evaluation using DEM simulations and laboratory experiments for model validation, Miner. Eng., 2017, vols. 103104, pp. 93101.
Vitushkin, A.V., Development of kinematic scheme and calculation methods of parameters of crushing machine with translational motion of jaws, Extended Abstract of Cand. Sci. (Eng.) Dissertation, Novokuznetsk, 2013.
Nikitin, A.G., Laktionov, S.A., and Sakharov, D.F., Mathematical model of process of deterioration of a brittle material in a single-roll crusher, Izv. Vyssh. Uchebn. Zaved., Chern. Metall., 2012, no. 8, pp. 3638.
Nikitin, A.G., Laktionov, S.A., and Kuznetsov, M.A., Position of plane of maximum shear stress at fracture of brittle pieces in roll crushers, Izv. Vyssh. Uchebn. Zaved., Chern. Metall., 2013, no. 7, pp. 4244.
The primary crusher is located in the quarry and consists of a McLanahan 48x72 Shale King Crusher rated at 1,000 TPH (Tons Per Hour). The driving flywheel has a diameter of 2.5 meters and is motor driven through six v-belts. The capacity of the primary crusher had to be increased to 1,250 TPH to produce enough material to serve the wet and both dry lines in the plant. To enable the crusher to operate at the higher capacity, the manufacturer recommended grooving the flywheel for two additional v-belts. To avoid the costs of disassembling, shipping and reassembling, Nesher performed the machining in-place. The operation was performed using portable tools and an auxiliary motor that turned the flywheel for machining the new grooves.
Roll crushers are generally not used as primary crushers for hard ores. Even for softer ores, such as chalcocite and chalcopyrite, they have been used as secondary crushers. Choke feeding is not advisable as it tends to produce particles of irregular size. Both open and closed circuit crushing is employed. For close circuit the product is screened with a mesh size much less than the set.
Figure6.4 is a typical set-up where ores crushed in primary and secondary crushers are further reduced in size by a rough roll crusher in an open circuit followed by finer size reduction in a closed circuit by a roll crusher. Such circuits are chosen as the feed size to standard roll crushers normally does not exceed 50mm.
Secondary coal crusher: Used when the coal coming from the supplier is large enough to be handled by a single crusher. The primary crusher converts the feed size to one that is acceptable to the secondary crusher.
Detail descriptions of designs are given of large gyratory crushers that are used as primary crushers to reduce the size of large run-of-mine ore pieces to acceptable sizes. Descriptions of secondary and tertiary cone crushers that usually follow gyratory crushers are also given in detail. The practical method of operation of each type of gyratory crusher is indicated and the various methods of computing operating variables such as speed of gyration, capacities and power consumption given are prescribed by different authors. The methods of calculations are illustrated to obtain optimum operating conditions of different variables of each type using practical examples.
Shale, a low-moisture content soft rock, is quarried, transferred to blending stockpiles before it is reduced by primary crushers and dry-milled to a powder of less than 250m. This powder is homogenized and stored ready for pelletization in manner similar to that used for making aggregate from PFA except that no fuel is added. However, after the pellets have been produced to the appropriate size, which depends on the expansion required, they are compacted and coated with finely powdered limestone. The resulting pellets are spherical with a green strength sufficient for conveying to a three-stage kiln consisting of a pre-heater, expander and cooler. Unlike other aggregates produced from argillaceous materials, the feedstock is reduced to a powder and then reconstituted to form a pellet of predetermined size. The expansion (bloating) is controlled during kilning to produce an aggregate of the required particle density. Different particle densities are produced by controlling the firing temperature and the rotational speed of the kiln. The coating of limestone applied to the green pellet increases the degree of surface vitrification which results in a particle of low permeability. This product gives versatility to the designer for pre-selecting an appropriate concrete density. As Figure7.6 shows, while the particle shape and surface texture of the aggregate remain essentially the same, the internal porosity can be varied according to the bloating required for the specified density.
Mined crushed stone is loaded into trucks or onto conveyors and transported to the processing facility. The broken stone is dumped into a primary crusher where the large rock fragments are broken into smaller sizes. Crushing to the proper size usually occurs in stages because rapid size reduction, accomplished by applying large forces, commonly results in the production of excessive fines (Rollings and Rollings 1996). After primary crushing, the material is run through one or more secondary crushers. These crushers use compression, impact, or shear to break the rock into smaller pieces. The material is screened after each crushing cycle to separate properly sized particles (throughs) from those needing additional crushing (overs). Additional washing, screening, or other processing may be required to remove undesirable material. The material is then stockpiled awaiting shipment.
After mining, sand and gravel may be used as is, which is called bank-run or pit-run gravel, or it may be further processed. The procedures for processing sand and gravel are similar to those for processing crushed stone. The amount of processing depends on the characteristics of the sand and gravel deposit and the intended use. If the gravel deposits contain very large cobbles or boulders, that material may be run through a primary crusher. The material may be run through one or more secondary crushers, then washed, screened, or further processed to remove undesirable material. The material is then stockpiled awaiting shipment.
The design of belt and apron feeders is fairly standardized, and most of the producing companies use pre-defined models and calculation methods to get short delivery times with a low-cost approach. The main features of the apron and belt feeders are:
Although the conveying devices are reasonably well defined and standardized, there is still room for improvement of the overall plant layout and construction, e.g. crushing plant, silo discharge system, train unloading system, etc. One of the most obvious ways to improve the overall design of such systems is to develop a better understanding of the equipment itself. Today, most OEMs want to be involved in the process of seeking the solution rather than only the supply of the equipment. This will enable the market to make use of the expertise of the equipment supplier and, at the same time, use their knowledge base for developing a wider scope, including other aspects such as silo design, hopper design, electrical and hydraulic issues, etc.
Highland Valley copper mine experienced a decline in mill throughput after implementing larger holes for blasting, which resulted in coarser fragmentation and a coarser product from the primary crushers . In the quarry at Vrsi, as drilling geometry decreased from 3.0m4.5m to 2.9m3.0m while other parameters such as borehole sizes were constant, a significant savings of 14% was achieved for the quarry . Due to a mine-to-mill implementation at the Red Dog Mine, the mine achieved savings exceeding $30 million per year . This indicates that, at least in some ores, improved internal fragmentation carries through the crushing and grinding circuits. The mine-to-mill project in the same mine identified further benefit, specifically the marked reduction in SAG feed size and throughput variability . A second but important benefit was the reduced wear in the gyratory crusher, resulting in a significantly longer period between relines. When electronic detonators with very short delay time were applied in the Chuquicamata open pit copper mine, the fragmentation was markedly improved . In the Aitik copper mine a raised specific charge from 0.9 to 1.3kg/m3 gave rise to an increase in the throughput by nearly 7% due to more fines produced and shorter grinding time achieved .
Jaw crushers are mainly used as primary crushers to produce material that can be transported by belt conveyors to the next crushing stages. The crushing process takes place between a fixed jaw and a moving jaw. The moving jaw dies are mounted on a pitman that has a reciprocating motion. The jaw dies must be replaced regularly due to wear. Figure 8.1 shows two basic types of jaw crushers: single toggle and double toggle. In the single toggle jaw crusher, an eccentric shaft is installed on the top of the crusher. Shaft rotation causes, along with the toggle plate, a compressive action of the moving jaw. A double toggle crusher has, basically, two shafts and two toggle plates. The first shaft is a pivoting shaft on the top of the crusher, while the other is an eccentric shaft that drives both toggle plates. The moving jaw has a pure reciprocating motion toward the fixed jaw. The crushing force is doubled compared to single toggle crushers and it can crush very hard ores. The jaw crusher is reliable and robust and therefore quite popular in primary crushing plants. The capacity of jaw crushers is limited, so they are typically used for small or medium projects up to approximately 1600t/h. Vibrating screens are often placed ahead of the jaw crushers to remove undersize material, or scalp the feed, and thereby increase the capacity of the primary crushing operation.
Both cone and gyratory crushers, as shown in Figure 8.2, have an oscillating shaft. The material is crushed in a crushing cavity, between an external fixed element (bowl liner) and an internal moving element (mantle) mounted on the oscillating shaft assembly. An eccentric shaft rotated by a gear and pinion produces the oscillating movement of the main shaft. The eccentricity causes the cone head to oscillate between the open side setting (o.s.s.) and closed side setting (c.s.s.). In addition to c.s.s., eccentricity is one of the major factors that determine the capacity of gyratory and cone crushers. The fragmentation of the material results from the continuous compression that takes place between the mantle and bowl liners. An additional crushing effect occurs between the compressed particles, resulting in less wear of the liners. This is also called interparticle crushing. The gyratory crushers are equipped with a hydraulic setting adjustment system, which adjusts c.s.s. and thus affects product size distribution. Depending on cone type, the c.s.s. setting can be adjusted in two ways. The first way is by rotating the bowl against the threads so that the vertical position of the outer wear part (concave) is changed. One advantage of this adjustment type is that the liners wear more evenly. Another principle of setting adjustment is by lifting/lowering the main shaft. An advantage of this is that adjustment can be done continuously under load. To optimize operating costs and improve the product shape, as a rule of thumb, it is recommended that cones always be choke-fed, meaning that the cavity should be as full of rock material as possible. This can be easily achieved by using a stockpile or a silo to regulate the inevitable fluctuation of feed material flow. Level monitoring devices that detect the maximum and minimum levels of the material are used to start and stop the feed of material to the crusher as needed.
Primary gyratory crushers are used in the primary crushing stage. Compared to the cone type crusher, a gyratory crusher has a crushing chamber designed to accept feed material of a relatively large size in relation to the mantle diameter. The primary gyratory crusher offers high capacity thanks to its generously dimensioned circular discharge opening (which provides a much larger area than that of the jaw crusher) and the continuous operation principle (while the reciprocating motion of the jaw crusher produces a batch crushing action). The gyratory crusher has capacities starting from 1200 to above 5000t/h. To have a feed opening corresponding to that of a jaw crusher, the primary gyratory crusher must be much taller and heavier. Therefore, primary gyratories require quite a massive foundation.
The cone crusher is a modified gyratory crusher. The essential difference is that the shorter spindle of the cone crusher is not suspended, as in the gyratory, but is supported in a curved, universal bearing below the gyratory head or cone (Figure 8.2). Power is transmitted from the source to the countershaft to a V-belt or direct drive. The countershaft has a bevel pinion pressed and keyed to it and drives the gear on the eccentric assembly. The eccentric assembly has a tapered, offset bore and provides the means whereby the head and main shaft follow an eccentric path during each cycle of rotation. Cone crushers are used for intermediate and fine crushing after primary crushing. The key factor for the performance of a cone type secondary crusher is the profile of the crushing chamber or cavity. Therefore, there is normally a range of standard cavities available for each crusher, to allow selection of the appropriate cavity for the feed material in question.
Crushers are widely used as a primary stage to produce the particulate product finer than about 50100 mm in size. They are classified as jaw, gyratory and cone crushers based on compression, cutter mill based on shear and hammer crusher based on impact.
A jaw crusher consists essentially of two crushing plates, inclined to each other forming a horizontal opening by their lower borders. Material is crushed between a fixed and a movable plate by reciprocating pressure until the crushed product becomes small enough to pass through the gap between the crushing plates. Jaw crushers find a wide application for brittle materials. For example, they are used for comminution of porous copper cake.
A gyratory crusher includes a solid cone set on a revolving shaft and placed within a hollow body, which has conical or vertical sloping sides. Material is crushed when the crushing surfaces approach each other and the crushed products fall through the discharging opening.
Hammer crushers are used either as a one-step primary crusher or as a secondary crusher for products from a primary crusher. They are widely used for crushing of hard metal scrap for different hard metal recycling processes.
Pivoted hammers are pendulous, mounted on the horizontal axes symmetrically located along the perimeter of a rotor and crushing takes place by the impact of material pieces with the high speed moving hammers and by contact with breaker plates. A cylindrical grating or screen is placed beneath the rotor. Materials are reduced to a size small enough pass through the openings of the grating or screen. The size of product can be regulated by changing the spacing of the grate bars or the opening of the screen.
The feature of the hammer crushers is the appearance of elevated pressure of air in the discharging unit of the crusher and underpressure in the zone around of the shaft close to the inside surface of the body side walls. Thus, the hammer crushers also act as high-pressure forced-draught fans. This may lead to environmental pollution and product losses in fine powder fractions.
A design for a hammer crusher (Figure 2.6) allows essentially a decrease of the elevated pressure of air in the crusher discharging unit . The A-zone beneath the screen is communicated through the hollow ribs and openings in the body side walls with the B-zone around the shaft close to the inside surface of body side walls. As a result, circulation of suspended matter in the gas between A- and B-zones is established and high pressure of air in the discharging unit of crusher is reduced.
Reducing the size of material for transport, building, and recycling is critical. Crushers were invented to make the task of breaking down rocks and other materials much easier. Although crusher technology is not particularly sophisticated, selecting the right crusher can take some time. In this article we discuss the different types of crushers and what you need to consider before you buy.
The first viable crusher (known as a mechanical rock breaker) was invented by Eli Whitney Blake in 1858. Another inventor, Philetus W. Gates, patented the first gyratory crusher in 1881. There were crushers patented before Whitneys, but they never made it into production. Since the late 1800s, the size of crushers has greatly increased, but the engineering principles that make them work have remained the same. Both jaw crushers and gyratory crushers are still used today.
The selection of any major piece of equipment entails having a detailed understanding of your job requirements. In choosing the right crusher you must know these key aspects of the material youll be handling:
Dimensions. What is the thickness, length, and width of the material you will feed into the crusher. A large crusher can process rocks up to three feet in diameter. A hydraulic hammer is used to break up larger pieces before they are fed into the crusher.
Obviously, dimension is in essence just measuring the maximum size of the material that will be fed into the crusher. The granulometric requirement is based on how the final product will be used. However, abrasiveness and hardness factor are known through testing and calculation.
The Rock Abrasiveness Index (RAI), introduced in 2002, is often used to categorize abrasiveness. This informs a rocks resistance to crushing as well as its wear and tear on the crusher. Highly abrasive rocks include granite, quartzite, and basalt.
As discussed in our article Get to Know the Common Types of Mining Equipment there are three classifications of crushers: primary, secondary, and tertiary. Crushers are further categorized by how they crush the material.
To understand the difference between the crushing phases, typical examples include reducing topsize from 900 to 300 mm for primary, 300 to 100 mm for secondary, and under 5mm for fine crushing, such as manufactured sand.
A jaw crusher is the most commonly used primary crusher. It uses simple technology to break down large blocks into smaller pieces. Their simplicity requires little engineering expertise to operate. A jaw crusher is reliable and needs less maintenance than other types of crushers.
A jaw crusher has one fixed and one moving surface in a V-shaped configuration. The moving jaw is mounted on an eccentric shaft. The reciprocal motion of this jaw presses the material against the fixed jaw. Rotational movement is achieved via a motor and a belt. The space between the jaws narrows as the material moves downward. Once crushed to the desired size, the material falls through the bottom of the jaw crusher.
An impact crusher (also called a hammer crusher) is quite versatile. It can be used as a primary, secondary, or tertiary crusher. Impact plates and beaters or hammers are used to break down the material. The material is fed through the upper part of the crusher then hit by hammers. Next, the pieces are thrown toward the plates. This further breaks the material. The pieces bounce back to the hammers. The material is thrown back and forth between the plates and hammers until it is reduced to the target size.
Impact crushers can handle an array of materials, including clay, dirt, and metal that may be mixed in with the feed material. An impact crusher can have a horizontal shaft or a vertical axis. This type of crusher may not be as effective for producing smaller pieces. The force needed to break down the material depends, in part, on the energy generated by the broken pieces. The smaller the piece the less energy its impact against the hammer produces. Impact crushers have a high production capacity, low energy consumption, and produce a uniform grain size. However, their operating costs are often higher than jaw crushers.
A cone (or conical) crusher breaks down material with the use of an eccentric rotating head and a bowl. It is often used as a secondary or tertiary crusher. It is best for crushing material 200 mm and less. Advantages of a cone crusher include high productivity and low operating costs. However, a cone crusher does not generate evenly sized pieces that are often required.
A gyratory crusher has a mantle that rotates within a concave bowl. Gyratory crushers and cone crushers are quite similar. A gyratory crusher has a higher angle at the apex of the cone. Its name refers to the constant back and forth motion that compresses the material against the chamber walls. They are often used as primary crushers.
There are mobile crushers that can maneuver around a job site. On some projects it is more cost-effective to not have to transport material to a centralized crusher for processing. Or a site is just too small for a large piece of equipment and requires a crusher with a smaller footprint.
The eccentric throw range is related to how much the crushers mantle veers away from its axis. This determines the rate the material will fall through the chamber. Crushers with a high eccentric thrown will allow particles to fall farther in a single revolution. This results in a coarser product.
Crusher technology keeps evolving in terms of automation and safety. Some of todays crushers are equipped with systems that will adjust the CSS (Closed Side Setting) without your having to shut the machine down. The crusher can ensure the bearings are not exceeding normal operating temperature. There are also safety features that will automatically shut down the machine when it encounters out-of-spec material, such as rubber or steel. This protects the shaft or bearing against damage. If youre working on a tight budget, we recommend machine power and brand name over bells and whistles. Larger organizations can usually justify high-cost automation features.
Eagle Crusher claims they sell the number one portable crusher worldwide. Their UltraMax Impactor line offers Horizontal Shaft Impactors (HSIs) that handle primary and secondary crushing in one unit. These units come in stationary, skid-mounted, or portable configurations. Eagle Crusher offers financing and 24/7 service. Made in the USA.
Powerscreen began as Ulster Plant in 1966 in Ireland. Its changed hands through the years but became Powerscreen in 2009. Its parent company is Terex. They manufacturer in several countries, including the US (in Louisville, Kentucky). They offer a wide variety of jaw, cone, and impact crushers. Their Metrotrak model is a compact, mobile unit offering an output of about 200 tph. It weighs around 60 thousand pounds. The Metrotrak is only 12.5 feet wide and a just under 41 feet long. Its low height of 10 foot, 6 inches gives you the ability to handle crushing in tight spaces.
They sell many types of crushers including several stationary cone crushers. Their CS420 is a high-production, compact stationary cone crusher. Sandvik offers their proprietary Automatic Setting Regulation control system (ASRi) This real-time performance management system will automatically adjust based on feed conditions. They also offer crushers that offer safety features and a system to streamline settings adjustment.
You can buy new or used directly from the manufacturer or a local equipment dealer. Financing options may be available. We recommend putting together a requirements document and letting the dealer tell you which crusher (or crushers) will meet your needs. Then you can shop it around for estimates.
Leasing is a great idea to try before you buy. However, depending on the size of your organization, it may make sense to take advantage of contract services that a company like Metso:Outotec offers. Compare it to the total cost of ownership. Its not just the cost of the machine its maintenance and repairs, hiring operators, and storing the equipment.
Buying used is only risky if you dont work with a reputable dealer. Youll want an experienced and knowledgeable operator to perform the inspection. Warranty and service agreements must be in writing. Be sure to understand what the resale value might be. Some brands and models hold their value more than others.
When youre inspecting a used crusher, take a close look at the wear parts. These are parts of the machine that are expected to be replaced periodically. For example, manganese liners protect the mantle and concaves of a cone crusher. The fixed jaw of a jaw crusher is subject to the most wear and tear. (In fact, Hardox offers cheek plates made of a material that they claim can greatly increase the life of your jaw crusher.) Take an inventory of worn parts and get quotes for replacements. There are companies that specialize in spare crusher parts such as Norther Crusher Spares.
Selecting the right crusher is highly dependent on your job requirements. Crushing rock and other hard materials is not a complicated process but selecting the wrong machine for the job can be dangerous. Low production or results of the wrong size grain can have a negative impact on your bottom line. Work with your local equipment dealer to select a machine that will meet your documented requirements. Explore safety and other automation features that will protect your workers and reduce production costs.
Affiliated with PileBuck.com, the leading source of deep foundations and marine construction information for 35+ years, EandCmag.com is the most trusted source for heavy equipment guides pertaining to earthmoving/excavation, concrete/paving, cranes/lifting, trucks/hauling, and mining/tunneling.
I'm building a machine to produce pressed pennies. It's similar in many ways to the ones you might find at a zoo, airport, or museum, with a few important differences. While most penny crushers let you pick between four possible images, this one can make eighteen unique images. It also produces double sided coins, so there are nine front side images and nine reverse side images.
Before I started on this project I built a simpler prototype penny crusher that used interchangeable die plates. That allowed me to validate my some fundamental elements of the design. These elements include the sizing and choice of bearings, die design and fabrication, and the ratio of the drive reduction gearing. For this project, I took the lessons from that prototype, and used them to design a more complex machine that could produce a much wider array of images without manually changing die plates.
If you're curious about why I'm building penny crushers, you might be interested in a talk I gave on that subject or the slides from that talk. My collaborator on this project, Shaun Slifer, put together a great project summary page as well.
The most basic constraints on the design of a penny crusher begin with the process for crushing a penny. The penny is rolled between two wheels with a gap between them that is slightly smaller than the thickness of the penny. This mechanism is an instance of a rolling mill, a common and widely used device for reducing the thickness of metal sheets. In industry, rolling mills can be quite large, and a large body of theoretical and practical knowledge exists to support their design and operation. I applied only the most basic models of rolling mill operation in designing my penny crusher, and added large safety factors where possible to accommodate any inaccuracies in my model.
It turns out that the answers to those questions depend on a few factors, some of which are within the designer's control. The two most important free parameters that determine the force and torque needed to press a penny are the final thickness of the crushed penny and the diameter of the roller wheels. Important fixed parameters outside of my control that are important to the calculation include the material the penny is made of and the thickness of the penny before crushing.
The physical process that the penny undergoes when it passes through the rollers is called plastic deformation. Plastic deformation in zinc and copper, the metals US pennies are made from (post and pre 1982, respectively), is defined by two properties called the Compressive Yield Strength and the Strain Hardening Exponent of the metal. Yield Strength is a measurement of the pressure required to cause the metal to flow, rather than bend like a spring. In Zinc alloys, this is about 30,000-40,000 pounds per square inch. The Strain Hardening Exponent defines how the effective yield strength increases as the metal is deformed, and varies between zero and one. This reflects a property of many metals called work hardening - as the metal experiences strain its Yield Strength increases, until eventually the yield strength exceeds the ultimate strength and the metal fractures. Work hardening is why you can bend a piece of metal back and forth several times and then easily break it off. Knowing only the starting and ending thicknesses of the penny, we can calculate the average pressure applied over the contact area to produce the thickness reduction based on these two numbers.
In my case, a penny is about .060 inches thick, and I wanted to reduce it to a little more than .030 inches thick. I arrived at .030 inches after measuring a few pennies in my collection of pressed pennies. Based on these values I calculated the average flow stress over the contact region to be roughly 30 Kpsi.
If you look at the diagram of the rolling mill above, it's clear that only a small section of the penny is actively deformed at any instant. Specifically, the part in contact with the rollers is changing thickness, but the part that's already exited the rollers, and the part that's not yet entered them, are not. This means that we only need to apply that 30,000 PSI of pressure over a small area of the penny.
Ignoring frictional effects, the total force applied by the rollers is equal to this pressure integrated over the surface in contact with the penny. Roughly, this is the area in contact times 30 Kpsi. The total area in contact depends on the geometry shown in the diagram above, specifically, the roller diameter, the gap between the rollers, and the initial thickness of the penny.
Choosing a roller diameter was a complex design problem, that I'll talk about later. For now, it's enough to know that I chose 1.5". Given those parameters I was able to calculate that when the widest part of the penny was being pressed, the area in contact would be at most 0.11 square inches.
I considered three different approaches designing a penny crusher that could produce a significantly larger number of images than the standard commercial design. My primary concerns during this design phase were to ensure that the mechanism was simple enough to build efficiently, that I could use bearings and gearing similar to those I'd used successfully in my prototype, and to ensure that the gap between the rollers could be adjusted easily.
The mechanically simplest solution I could think of was to increase the diameter of each roller to make room for more images. Two large rollers with nine images on each roller would have a diameter of about 3.5 inches. These larger rollers would have doubled the required force per roller and tripled the required torque. Since I was already operating near the maximum load for the bearings and gears I planned to use, I decided not to pursue this design. It was also unclear how to create arbitrary pairings of images without introducing a clutch mechanism to allow one wheel to rotate without the other rotating simultaneously. Preserving alignment between the wheels (so that the images on either side engaged simultaneously) once a clutch was introduced seemed like it would result in additional complexity. In retrospect, it may have been a better idea to switch to larger bearings and gears with a higher load rating rather than pursue a more mechanically complex design to avoid them.
The second solution I considered was to gang three smaller rollers side-by-side into a single wide roller. By sliding past each other and rotating, the rollers could bring any pair of images into opposition. I abandoned this design because of the complexity of allowing the drive gears to remain engaged during lateral motion, and the need to index linear motion.
The third solution was to mount smaller rollers on a revolving carriage that could bring each pair of wheels into opposition. This is the design I eventually built, and that I'll discuss it in detail in the next step.
Of the three designs I considered, the index-able die carriage is the only one that allows any pair of die images to be used without the need for a clutch that temporarily disconnects the drive gears to allow the Die Rollers to move independently.
This is achieved by the use of an epicyclic (planetary) drive gear in the carriage that runs at a 2:3 ratio. If the sun gear in the middle of the carriage is fixed in place, and the carriage is spun around it one full revolution, the dies will have completed two thirds of a full revolution. Since there are three die images on each face, this essentially advances the die image one step without moving the drive gear.
When assembled, the die rollers are placed so that if the first die has its image facing radially outwards from the center of the carriage, the second roller is advanced 2/9 of a rotation from that position, and the third die 2/9 of a rotation from the orientation of the second die. This ensures that each die roller will present its image in the same relative position as the carriage rotates.
The die carriages rest in bearing blocks made from 3/4" thick steel plate. These bearing blocks press against the end plates. The end plates then transfer load to the tie plates that run above and below the die carriages. Because the connection between the end plates and the tie plates is in tension, I used load rated bolt for that connection. I also used the end plate to tie plate connection as the location to insert shims that are used to adjust the die roller gap.
I also used steel shims in the prototype, placing them between the die plates and the roller wheels, and had run into trouble with the shims deforming over time and becoming thinner. My load frame design avoids this problem since the shims only experience the preload tension of the tie plate bolts, but are not under additional force during operation.
The video above shows my first design for this mechanism. I wanted to ensure that the mechanism would provide a strong positive locking engagement, and require only single rotational motion to operate. I started with the idea of using a strong pin passing through both the bearing block and a flange plate connected to the die carriage to lock the die carriage rotation relative to the bearing block.
Because I wanted the mechanism to lock in any of three positions I created three pins and three holes, although it may also have been possible to use a single pin, three holes in the flange plate, and one hole in the bearing block. I didn't like that option because I wanted the mechanism to be symmetric around the die carriage's rotational axis, so that the locking forces wouldn't load the die carriage bearings.
Based on the initial idea of three pins that repeatedly insert and withdraw from indexed holes, I designed a mechanism to automatically withdraw the pins under a spring load, then use the pins to transmit a rotational force from the input shaft to the die carriage, and then automatically re-lock the die carriage after it had completed its rotation.
Ultimately, however, I decided this mechanism was overly complicated, and built a pair of 3-position Geneva mechanisms to perform the indexing. Unfortunately, because of the small torque arm during the middle of the index-advance movement and the unexpectedly high friction in the die carriage bearings the Genevas, as built, require manual assistance to advance the carriages, although they do an excellent job of locking them at their indexed positions. Eventually I plan to separate the drive-power for advancing the die carriages from the indexing mechanisms, using reduction spur gears to drive the carriages and an indexed ratchet to hold them in position.
Before beginning to fabricate the penny crusher in steel, I made a quick prototype using laminated plywood and a laser cutter. I built two die carriages, including the gearing the die wheels, the load frame, and a mockup of the indexing geneva.
This prototype identified two issues that would have been difficult to correct if I hadn't identified them before beginning work on the steel assembly. First, I'd left zero clearance between the drive gears and the middle plates on the opposite drive carriage. This interfered with rotation of the die carriages, so I added a 1/16" clearance by making the die carriage plate spacing asymmetric.
I began by fabricating both die carriages. The three-lobed carriage plates and the rectangular tie-plates that join them together were cut from plate steel on the waterjet, as shown in the video. The end plates are designed to have a short shaft protruding from them that rests on the load frame's bearing blocks. I created this shaft by first finishing the rough hole cut on the waterjet in the vertical mill, enlarging it to a precise diameter and adding a chamfer to both sides of it. Then I turned mating pieces on the lathe that were about .001" larger than the holes. These pieces also had matching chamfers.
I used a hydraulic arbor press to insert the shaft "spuds" into the end plates using about 5000 lbs of force. Then I TIG welded the plates and spuds together, using the matching chamfers to ensure good penetration of the plate steel. I cleaned up the back-side welds with a face mill, then turned down the spuds to the final diameter on the lathe.
Using the turned spuds as my reference datum I was able to create the bores through the spuds that the drive shafts pass through, and bore out the three smaller recessed areas for the die roller shaft bearings. Because it's essential that the die rollers be a consistent radius from the center of the die carriage rotation, using the turned shaft as my reference was important.
I used the water jet to cut a small jig that let me hold the carriage plates on end in the vice so that I could use the vertical mill to drill and roll-tap the holes for the tie-plate bolts. This was a slow process at three setups per plates and six plates, if I'd had access to the TR-160 5-axis trunnion at this time the work could have been done in one setup per plate.
I also made the mistake of tapping the holes for the tie plates before welding the spuds. The heat from the welding warmed the threads enough to make the thread fit noticeably tighter. I chased all 36 holes by hand to fix this.
The load frame was a simple but time consuming machining process. The bearing block's primary features are the bores for the bearings and the tapped holes used to attach them to the end plates. In addition to these features each block required three setups to clean up the edges after the rough cut on the waterjet.
The smaller epicyclic gears are stock gears available from manufacturers like Martin or Boston Gear. The larger ones, however, were custom cut on the waterjet. Because the waterjet cuts a beveled profile and is unable to cut with better than .030" accuracy (YMMV, but that's my experience) I designed the gears in Autodesk Inventor to include about .020 of backlash. I was also able to design gears with non-standard diametral pitch, which let me achieve specific shaft-to-shaft distances at particular gear ratios with theoretically perfect tooth engagement, rather than design the ratios or the shaft distances around a stock diametral pitch.
I found that water jet cut gears worked best with diametral pitches of eight and below. After cutting the teeth and a rough undersized bore on the waterjet, I used a vertical mill to bring the bore up to size, then used an arbor press and broach to cut a keyway to lock the gear to the shaft.
I used a two setup flip-milling process for both parts of the Geneva mechanisms using soft jaws to hold the work after flipping it. The simple setups and soft metal made this one of the fastest parts of the project, despite the relatively complex geometry.
The photos above shown one of the driven elements during machining, and the full process for machining one of the driver elements. The process begins with a block of aluminum, from which the basic shape is roughed in one pass. Then the drive pin feature is cut down to the height of the drive pin. Next the pin is cut away from the surrounding material. After this, several finishing passes countour and chamfer the edges of the piece.
After this the soft jaws are machined to match the profile of the cut part, and the part is held in them while the remaining stock is removed from the back of the piece with a roughing mill and then finished with a combination of a face mill and chamfer mill.
The dies are cut from solid rod stock of A2 tool steel. I begin by drilling and boring the inner diameter on the manual lathe. Since I'm working with ground shaft stock I aim for an ID of 1.000 +.0005/-0. I made a custom mandrel that fits in the jaws of the 4th and 5th axis trunnion. This mandrel has a 1" OD that fits the die blank, and positions the blank inside the very small working envelope of the mill. Once bed travel limits and tool holder clearances are taken into account, there's only about 1.2" of Y-axis travel, so the placement of the die blank relative to the trunnion chuck needs to be carefully planned.
Before I can engrave the dies I need to reduce their OD to the final size. It is essential to the engraving process that the surface of the die blank be concentric with the trunnion's B axis to within 0.001" or less, since any variation in that distance will change the depth of the engraving. Since the engraving is only .0075" deep at mosta variance of even .001" is significant. Rather that turning the OD on the lathe I rotate the B axis while keeping an end mill rotating in a fixed position near it. By varying the distance from the B axis to the end mill axis I can get very consistent diameters and excellent concentricity. The final photo shows a dial test indicator measuring the runout in the die blank after this operation. There was no observable runout.
I used carbide engraving cutters at 10,000 RPM spindle speed to cut the images into the dies. The deep boundary dots in the pattern are cut with a 90 degree drill/mill. Then, the larger areas of the images are removed using a 0.010" 45 degree flat-tip engraver. More detail is added using a 0.005" 45 degree engraver, and final touch-up is done, depending on the image, using a pointed 45 degree engraver.
The toolpaths for the engraving started as black and white raster images provided by the artists. I used ArtCAM to convert those images to vector outlines, then did my layout on a rectangular work area that would 'wrap' onto the surface of the die blank. I used V-cutting and smart-engraving tool pathing to generate the toolpaths, adjusting the vectors slightly as needed. I customized the default ArtCAM post processor to use the Haas mill's G107 mode, which substitutes B axis motion for X axis motion, effectively wrapping the design onto the cylindrical die.
I assembled the components I've built to date and produced and was able to produce several pressed pennies. However, much work remains to be done. I still need to fabricate the image selection mechanism, that lets the user pick what pictures they want on their penny and control the rotation of the die carriages and timing of the coin drop. After that I'll make a case to keep the moving parts safely away from users, and create a more ornate handle.
Is there any way I could purchase some of your pressed pennies? I am getting into making them as jewelry and even the fishing lures to sell locally. I would like matching sets for earrings and then jut some in both horizontal and vertical orientation for necklaces, keyrings, bracelets, etc. Email me at justondean at gmail dot com if you want to sell some off.
I'm still sitting here in awe after viewing your fabulous Instructable. I hope you don't mind, but I've added a link to your Instructable to my latest project, making Pressed Penny Wind Chimes. Your Penny Crusher is beyond cool.I'd like to give you a free one year PRO membership for the use of your impressive project link on my Instructable. Just acknowledge this message to let me know you're still with us, and I'll send the code for the free membership your way via private message. Kudos, bravo, and all the well-deserved applause!
If the sole point is to produce medallions starting with a penny, there is a simpler solution, one that a vendor at a Renaissance Faire I used to attend had in operation for years. It used a tower with a ratchet mechanism to raise a striking die. The die weighed a few pounds, and the striking surfaces could easily be interchanged to get different patterns. You could even create movable type, if you wanted to go to the trouble of making hardened steel type small enough.
Cool! I thought about building something like this but was worried the dies would shatter on impact and had difficulty modeling the required energy. I'll have to look for pictures of what you're describing, or just try jury rigging something together.
Don't know anything about the types of steel in the dies, but I know he would haul the striking die up maybe 15' or so with a hand-cranked ratchet, it would slam into the other die and the planchet, bounce a couple of times before stopping. I think the two steel pieces were abut 6" overall in diameter, tapering to around a half inch where they came together. The striking part was probably about a foot long, maybe as much as 10-15 pounds. I think he only struck copper or maybe bronze, not silver, but wouldn't swear to it. It generally only took the one strike to make the new image. Not sure he used pennies, i think he might have had his own blanks. I'd think something tempered more like a hammer or anvil, rather than real hard would reduce the chance of shattering, and still be enough harder than copper to do the job. Have fun!
This reminds me of the way one can make grommets. So depending on how thick and malleable the material is, it may not take as much strength, but enough weight of the die block to a waiting slug below. Just making sure the guide along the path to the slug is direct and relatively friction-free would be good.
Great project! Patting yourself on your back by using machines unavailable to almost all individuals reading your post is also great! Try letting some know where they can obtain dies at a reasonable cost and you might impress someone!
I was looking in on penny crushers for camp thinking you could make a fishing lure with one. A simple spoon or a small fish that a ring and hook could be attached later. What do you think? Penny lures. how much is this costing to make.
Perhaps you should ask mblem to make a die for your logo(s) and just run a few thousand blanks of suitable material and make the lures yourself, to sell directly to the bait shops for resale at the counter. Otherwise, you need to be able to punch holes, add hooks and swivels, all while in front of the penny press. Not a kid friendly task let me tell you.
I like the penny lure idea, but if you only need a handful of them I'd probably just hammer them out with a small ball peen hammer. If you want to make a larger number, you can get a hand-power rolling mill for jewelry making for ~$200 on ebay, which is probably less than you'd pay in materials to build a penny crusher.
I always loved the old coin press at things like the Rail Road Museum in Sacramento, or Ren Faires etc. A neat little "mystical" feel. Probably why as an adult Im a sucker for Silver Dollar collector coins. I was just thinking the other day how the penny has been removed from our currency that press machines may make a return, adding that old mystical feel to that "rare" penny you find... All of a sudden that jar of pennies I have as a door weight might easily be turned into magical dabloons to my kids and the neighbors kids....