MIXING ROLLS

MIXING ROLLS

DEFINITION:

                         Mixing roll mixer is a type of mixer in which deformable  material and pastes are dmixed by intense shear by passing them b/w two smooth rolls turning at different speeds

Diagram

                                 

                                                    mixing rolls

  

Mixing and blending units

For equal homogenizing of rubber batches.

The stockblender consist of a pair of rolls. It is mounted above the roll nip and each roll is separately driven. Between the rolls of the mill and those of the stockblender a guide fork is situated, which is moved from side to side by a threaded spindle over the entire width of the mill.

Functioning: as soon as a cohesive slab has formed on the working roll of the mill, it is cut by the operator and fed through the guide forks to the stockblender. The stockblender transports the irregular slab and feeds it vertically downwards again into the mill roll nip. As these processes are effected alternately from the left and from the right side, an extremely good mixing effect is achieved due to the reciprocating motion of the fork.

Further advantages:

• Considerable ease of operation as the usually repeated cutting and rolling operation of the compound does not have to be carried out any longer.
• Favourable cooling conditions due to the increased travel of the compound.
• Increased capacity of the mill.

working

A mill is typically assembled on a steel foundation plate, which is again set on rubber-pads or sound-metals adjustable, to isolate noise-levels to the building also to avoid tensions on the mill structure, precisely levelling out of the mill is very important for smooth operationTwo rigid pillars with removable tops carry the rolls, which are placed either in friction/bush bearings or high quality anti-friction roller bearings. Roller bearings are pretty much standard nowadays, as they allow for 20 – 30 % in power-savings. A lubrication system is no longer requiredAdjustment of the front roll used to be made by hand (manual by ratchet) or later motorized by worm gear.Nowadays hydraulic pistons adjust the rolls and also protect rolls from high forces that can build up in between the rolls (roll safety). They also open roll gap immediately when pushing the safety bar in front or back in case of emergency (required by European Safety standards CE).A mixing mill has 2 horizontal rolls set up back to back. They are made of ground chilled cast iron, with surface hardness ranging from 475 – 520 HV (Vickers hardness) up to 520 – 580 HV (or 68 - 72 HSD). The depth of hardened layer ranges from 10 to 16 mm.Rolls are made with a central bore for cooling through a spray-type lance (low cost type cooling) or peripheral drills, where bores are closer to the surface for better cooling and more equal distribution.The rotary joints connected to the spraying lance are supplied from tempering units to provide constant temperature during the mixing process.At the ends of the roll faces the roll nip is being limited by the compound guide cheeks. The compound guide cheeks of split design with “centre tongue” avoid lateral escape of compound from the working area in any case.

MULLER MIXER

DEFINITION:

                    The Muller Mixer consists of 2 to 4 heavy rollers that move under spring pressure within a pan. A scraping arrangement is also provided. The product dust formed during grinding is confined to within the equipment because of the provision of a hood type cover. The rollers rotate around their own axis and also about the axis of the pan. The number of rollers and their sizes can be customized to the specific applications. The equipment is most suitable for solid particle size reduction.A machine for the mechanical preparation of molding sands and core sands; it mixes silica sands and admixtures, such as molding clay, ground coal, water, and binders. Various types of mixers are used as mullers in the preparation of moldings and core-sand mixtures: standard batch-type mixers, double mixers, oscillating mixers, paddle mixers, and rollerless (vortex) mixers.

DIAGRAM:

                      Muller Mixer

WORKING:

                  Standard batch mixers have a fixed hopper, into which the material to be mixed is fed. Two smooth, vertical rollers move over the layer of material with a circular motion as plows guide the mixed material under the rollers. As the rollers move, the components of the mixture are mixed and become evenly distributed. After 3–12 min of mixing, the prepared mixture is removed through a discharge opening in the bottom of the hopper.

Double mixers have two pairs of vertical rollers and two hoppers interconnected in such a way that their sides form a figure eight. The molding materials are fed continuously into the first hopper, are mixed by the rollers and internal plows, and are then transferred by an external plow to the second hopper, where more mixing takes place. The prepared mixture is then removed from the second hopper by an external plow. Double mixers can produce up to 400 tons/hr, and the mixture can be removed either continuously or in batches.

An oscillating mixer has two or three horizontal rollers suspended on oscillators connected to a vertical shaft. As the shaft revolves, the rollers come close to the rubber-faced wall of the mixer’s hopper. The material to be mixed is fed by scrapers into the gap between the rotating rollers and the wall of the hopper. A batch is mixed in 1.5–3 min. The prepared mixture is removed through a small door in the wall of the hopper.

A paddle mixer may have one or two (parallel) shafts equipped with paddles mounted in a helical line and turning inside a trough. When the shaft turns, the mixture is mixed and simultaneously transported along the trough toward the outlet. Such machines can produce mixtures continuously or in batches.

A rollerless, or vortex, mixer has a vertical rotating shaft and a fixed hopper. The working elements are bent springs with heads at the end that press against the side of the hopper and mix the sand.

APPLICATIONS:

• Ayurvedic & Herbal Products
• Pharmaceutical
• Minerals (Mica Powder Mixing)
• Snuff
• Batteries
• Welding rod flux
• Abrasives
• Soaps
• Putty
• Paints

PUG MILLS

DEFINITION:

                         A pugmill or pug mill is a machine in which materials are simultaneously ground and mixed with a liquid. Industrial applications are found in pottery, bricks, cement and some parts of the concrete and asphalt mixing processes. A pugmill is a fast continuous mixer. A continuous pugmill can achieve a thoroughly mixed, homogeneous mixture in a few seconds. Mixing materials at optimum moisture content requires the forced mixing action of the pugmill paddles, while soupy materials might be mixed in a drum mixer

DIAGRAM:

                                                         PUG MILL

WORKING:

                        Pugmills provide excellent mixing for cement-treated materials because of the violent action of the mixing process. Typically a pugmill will have two horizontal shafts, each with dozens of paddles. The shafts turn in opposite directions, causing one set of paddles to turn clockwise, and the other set to turn counter-clockwise. This motion hurls the particles toward each other in a violent action that allows for uniform mixing.

The pugmill operates on a continuous basis, with an aggregate feed belt, water spray, and cement vane that are all computer controlled to provide accurate metering of the constituents. Pugmills can be set up with more than one silo, so cementitious products (such as portland cement and fly ash) can be blended at the plant.

The mixed material is taken by belt to a surge hopper (or gob hopper) where it will be dumped into a truck to be transported to the job site. The trucks will have tarps to cover the freshly mixed material so that moisture is not lost on the way to the site.

Pugmills on paving projects are typically portable, and can be set up and running in less that a day. Production for pugmills on these projects are normally in the range of 300 – 500 tons per hour.

APPLICATIONS:

• Roller Compacted Concrete (RCC)
• Cement Treated Base (CTB)
• Cold Mix Asphalt
• Hazardous Soil Remediation
• Oil Well Drill Cutting Stabilization
• Flowable Backfill
• Flyash Stabilization
• Lime Addition

Questions to Ask Before You Hire More Employees......

1. What kind of business do you want?

Not everyone wants a big business. Many would rather concentrate on a smaller one and be closely involved on many levels, because there are rewards to business other than just money. As you grow a business, you may have to become disengaged with parts that give you pleasure, because you’ll spend more time on the overall operation and have to delegate more aspects.

Also, you’ll have to channel more cash into expansion, which could mean having to lower your own compensation and standard of living for some time. Some find that a proper tradeoff, while others are unhappy with the transition or ultimate result. Consider what you want from the business and whether you have the necessary patience to personally move backwards for a while to hit the bigger time.

2. Can you throttle back growth if needed?

With some businesses, you have more control over growth. For example, if you offer some sort of personal service, you can restrict your customer base and pass along additional business to colleagues.

In other types of business, you may have less control. Selling a product online puts you more at the mercy of the business that comes in. If your offer becomes hot for some reason, you may become inundated with orders and then be obligated to fulfill them. Depending on the type of business and demand, you might find that you have to expand and hire more people.

3. What is your growth like?

Many entrepreneurs get excited when they see a rush of business. They assume that the proper response is to expand to meet demand. But growth may be momentary rather than continued. Have a product get unexpected publicity and you might see a sudden uncomfortable increase in orders. Once the exposure has run its course, usually in a relatively short period of time, demand could drop back to previous levels.

Before deciding on growing your staff, be fairly sure that the increased workload will last long enough to justify them. If not, consider overtime and temporary help to bridge the temporary gap.

4. Are you suffering from growth?

Entrepreneurs typically have to have healthy egos to believe that they can succeed when others says they will fail. The character feature can become a flaw if it starts to run unchecked. One subtle way it can express itself negatively is in desiring the trappings of a larger business before they are truly necessary. If you’ve grown too quickly, you may notice a rise in the number of customer complaints about service or employee concerns that they cannot keep up with their jobs. The action you choose may be more efficient business processes. But if you still can’t adequately handle problems, it may be a sign that you do need more help.

5. Is there outside help available?

Needing more help is fine, but do you need to hire in-house? You might have business processes that could be outsourced to other companies for a reasonable increase in variable costs you can handle through pricing rather than the fixed business costs of permanent employees. That way, your business can more effectively respond to changes in demand. Some areas to consider might be call centers, fulfillment, or accounting. Moving some tasks outside the company frees internal resources to do the types of work that are core to the business.

6. Do you really need help?

It may be that you can handle some tasks internally more easily than you think. An example: Do you really need a full-time bookkeeper, or are there still a few hours a month where you could personally enter numbers into an accounting system and have an accountant review the work? Are there other tasks you could take on, freeing up current staff to handle orders and customer concerns?

Be most wary of hiring additional executives until the business is really cooking. Even a vice president of sales may be ineffective if the company does not have sufficient revenue.

7. Are you ready for the short-term profit impact?

Growing a business typically has a strong hit on profitability. You ramp up for where you think the business will go within the next few months. That means temporary excess capacity that adds more fixed costs, including benefits, worker’s comp, and additional payroll taxes. These additional costs get distributed over all your sales and cut gross margins until growth catches up and restores a more normal balance.

As you can’t both grow the business and generally cut expenditures at the same time, the hit will be to profitability and possibly your personal income. Do you have the capital to support the growth? Are you prepared, if necessary, to reduce your personal expenses and plans to help underwrite the growth? If not, you will find yourself at war with what you want to do for the business, ultimately hurting everything.

8. Are you set up to handle more employees?

Finally, your startup needs the processes, procedures, and organization to handle a sudden influx of employees. They will all need orientation, training, and management. There might be additional federal or state legal requirements should the staff size expand to certain numbers. You may need additional office space, equipment, and software licenses.

Hiring employees is a big step for a new business. Do your homework, consider the implications, and be ready so your company can continue to be successful.