What is the best type of concrete batch mixer for my application? Regardless of what people have told you, or what you have read, there is a best mixer for each application. Each excels in a different type of concrete:
Twin Shaft concrete mixer - Lots of concrete at high speed, low wear, low maintenance. Designed for rough, tough jobs like dam building, ready-mix and prestressed beams. Handles aggregate sizes to several inches. Does not discharge completely, so not good for mixes of different type or color. End of shift cleanout is slow and difficult (unless our high pressure washout system is used). Performance on dry cast mixes is not as good as the best planetary mixers. Gives the highest throughput of concrete in a given floor space, can double plant output without modification to hoppers, scales, belts etc. Most models have only a full width discharge door; exception is Ocmix RG which has a reduced width door option. "Compulsory mixing" action gives high quality concrete with maximum strength, saving up to 20% on cement compared with non-compulsory mixing action below.
Turbine concrete mixer - also known as the concrete pan mixer. High quality precast, especially wet cast mixes. Medium speed, medium wear, medium maintenance. Designed for precast. Good cleanout but sensitive to blade adjustment and wear. Good for colored mixes. Simple mechanical system. Easy to install moisture sensors in floor. Up to 4 discharge doors. Most models not fast enough to create "DESCRIPTIONCompulsory mixing", so concrete not as high in quality or strength.
Planetary / countercurrent concrete mixer - Highest quality precast, especially dry cast, block, pavers, architectural. Medium to high speed, medium wear, medium maintenance. Designed for precast, block, pavers. Good cleanout, good for colored mixes. More complex mechanically but best models very reliable. Easy to install moisture sensors in floor. Up to 4 discharge doors. "Compulsory mixing" action gives high quality concrete with maximum strength.
Rotating pan concrete mixer - most of these type mixers are obsolete. Good for precast, both wet and dry cast. Mixing action similar to planetary but mechanically complex, high maintenance. Difficult to install moisture sensors. Single discharge door. Most models not fast enough to create "Compulsory mixing", so concrete not as high in quality or strength.
Drum / tilt up and transit concrete mixing trucks - Slow, poor mixing action takes many revolutions to attain good homogeneity. Critical on charging sequence, requiring initial addition of water to wet blades and help remove deposit from previous batch. Cannot be completely discharged, difficult to clean out and maintain.
Ribbon/Spiral blade concrete mixer - The 'old standard' for precast and block plants. Slow, poor, non-compulsory mixing action takes many minutes for good mix. Very little end to end action, so charging method and water entry is critical to avoid variation within discharged batch. Non-compulsory action. Reliable with low maintenance cost. Newer versions with separate angled paddles have improved mixing action and speed. [Top]
Why does the Ocmer planetary mixer have 3-armed stars while other top mixers in its class have only two? Ocmer's designers have studied the action of both 2-armed and 3-armed stars and concluded that 3 are better for most sizes of mixer (one size has three 2-bladed stars). Not only because there are more arms and blades, but because the blades can be positioned to be much more effective. To start with, the arms can sweep the mixing volume more effectively because the more paths there are, the more times each area can be covered in every minute. This gives better mixing. Less obvious, however, is the angle of the blade. The combined rotation of star and individual blade across the mixer floor shows that the blades should be angled not at right angles to the star shaft but at a slight inward angle. This gives better sweeping action and eliminates lengthways slicing through the mix, which is ineffective and causes excessive wear.
Ocmer's blade arrangement is a better design, gives better mixing and lasts longer with less maintenance. [Top]
How does a full mixer still mix almost as effectively and fast as a partial batch? Because in Ocmer mixers, the pan is wider and the depth of mix is less than in most others. Compare width and volumes. This makes it easier to mix a full batch; mixers with higher sides and smaller diameter have more difficulty in achieving top to bottom homogeneity. In addition, the scooped blades create pressure in front and a void behind, drawing material from the top downward behind each arm and mixing material vertically as well as horizontally, which is needed for complete mixing. The high speed creates "Compulsory" mixing action, breaking -up clumps and distributing cement evenly to coat all particles. This creates stronger concrete.
Ocmer's mixers can receive AND MIX their full rated volume - and without any extra mixing time. [Top]
What is the difference between Filling Capacity, Uncompacted Output and Compacted Output? When the mixer is filled to its DRY FILLING CAPACITY, as the stone, sand and cement mix, the air spaces between stone chunks get filled with sand, and the air spaces around the sand grains get filled with cement. The density goes from about 100 lb/cu. ft. to 150 as it is mixed. Even the spaces around the cement powder get filled – with water. The whole volume reduces by 20% or more as a zero slump mix is made. But this zero slump mix still has lots of air spaces in it. If discharged in this state, you get an UNCOMPACTED YIELD of 20% less than the mixer capacity. When the mix is vibrated in the mould or form, all this extra air is expelled and it compacts by a further 15 to 20% to give the COMPACTED YIELD, which is 2/3 of the dry filling capacity.
What does this mean to the user? It depends on the application:
If the user needs 3” slump or less, the container (Tuckerbilt or bucket) capacity must hold the UNCOMPACTED YIELD.
If the user needs 6” slump or more, the container (Tuckerbilt or bucket) capacity must hold the COMPACTED YIELD.
If the user needs something in between, the container (Tuckerbilt or bucket) capacity must hold something IN BETWEEN. Use your judgment. [[Top]
Why does the Ocmer planetary mixer have a shorter scraper blade tail than many? The good mixing action of Ocmer's blades allows faster and more complete cleanout; it simply does not need a wide scraper tail to clean out efficiently. A larger tail causes dead spots in the mixer which increases the mixing time, or reduces homogeneity of the mix. Another manufacturer's attempt to give fast cleanout is to use a descending scraper blade. This is both unnecessary in Ocmer mixers and elaborate, giving higher maintenance costs in those that use them.
Ocmer's planetary is well designed and simple in concept, making it reliable, reducing future headaches and costs. [Top]
Why does Ocmer use Hardox steel liner plates and ni-hard paddles? Most planetary mixers use Hardox liner plates too, and some use Ni-hard cast iron. Both are comparable in price. 18 mm Hardox 500 is thicker and harder than the material that most mixers use, giving excellent life when mixing most materials while Ni-hard 500 cast iron is equal in wear if it is the same thickness but is more brittle, sometimes cracking and breaking. Optionally Hardox 600 costs a little more but wears much longer while remaining tough, not brittle. The paddles are cast, and ni-hard cast iron is the best material for these. Note that Ocmer's ni-hard parts are Italian made and have high (and expensive) nickel content, making them CERTIFIED 600 Brinell, unlike others that use Chinese parts of inferior hardness.
Another example of Ocmer's commitment to total quality. [Top]
Why do we say the gearbox runs cooler? It's a fact that Ocmer's gearbox runs cooler than many others due to its wide, horizontal shape, and as a result it lasts longer. Ocmer's reduction and planetary gears are designed and manufactured specifically for the purpose, and run in a horizontal oil bath for perfect lubrication. Some manufacturers use small commercial reduction gears; the high-speed gears connected to the motor shaft are at the top, where they receive less oil, and are housed in a small bell-shaped cover that does not allow proper ventilation and cooling. The small gears cannot withstand repeated startup under full load and will overheat with prolonged use, destroying the lubricating oils and causing premature breakdown. Others use wide horizontal gears but the planetary drive is designed with very small spur gears that cannot stand repeated heavy loading; they eventually crumble and fail. Ocmer's gears are guaranteed for 5 years/10,000 hours, and that's because we know they are good for it.
Proper design means longer life. [Top]
Do you stock parts in North America? A full stock is kept at our North American Headquarters, ready for same day shipping across the continent. This stock includes all wear parts and most other parts, including gearboxes, for every model sold in North America, including those sold through our dealers. Call us with your model and serial number for prices on any parts that you need.
Can I buy parts on credit? Of course - all it takes is the establishment of a credit account if you don't already have one with us
The customer comes FIRST at Ocmer North America. [Top]
How do you price your products, is shipping included? Some companies price their products in Euros because it is more convenient for them. But you could work out the exchange to Dollars, then find it has changed by the time it is delivered and you end up paying more. Scale-Tron's policy is to price everything in Dollars; you are guaranteed to pay the price we quoted you, even if the Euro goes up.
Your other unknown when buying European products is the shipping cost. Again, we don't ship FOB our European port for the same reason. You only pay the shipping from the east coast port of entry that is most convenient. We can give you a close estimate for this if you wish.
No hidden costs. [Top]
Concrete mixer facts and information © 2006 Robin Shepherdson, Eng.