Following whole-grain cleaning operations, those meant to separate seeds, bran and germ from the whole grain, and to remove foreign materials via rotating drums, magnetic separators, aspirators, de-stoners, and varying additional separation methodologies, the wheat, then tempered and soaking for up to 24 hours, conditions the grain for the grinding/milling processes.
Grinding Modern milling processes aim for a gradual reduction of the wheat kernels through a process of grinding and sifting, then blending it to meet the desired formulation of the end products. Typically the process (“Break”) will feed/inject wheat kernels from bins to roller mills (corrugated steel cylinders, paired and rotating inward against each other at different speeds), which separates bran, endosperm (starch) and germ. Typically there will be as many as five additional Breaks, where the rolls will have successively finer corrugated steel cylinders, reducing the wheat particles to granular form (middlings), which are as free from bran as possible.
Sifters Following grinding, broken wheat particles move through a series of vibrating sifters, then shaken through a series of bolting cloths or screens, which separate the particle sizes at the cut point. Larger particles are shaken off from the top (scalped and further processed) while the fine flour sifts to the bottom. The yield will then undergo a purifying process for further removal of the bran and coarse and fine particles separation. Additional procedures, such as bleaching and enrichment, then follow.
The two most common grinding machines used by industry are the pin mill and hammer mill. Both mills have fundamentally unique features that make them suited for a wide range of materials production.
Pin Mill The Pin Mill, unlike the Hammer Mill, consists of a series of pin breakers hinged to discs in the grinding head where it delivers high-energy impact. Pin Mills use shearing and impact methods; however, with a faster tip speed of intermeshing pins when compared to a Hammer Mill. Centrifugal force brings the particle sizes to the grinding chamber’s periphery for collection or further processing. The milling process will produce particle sizes down to ultra-fine micronized sizes +/- 10 µm. Particle sizing generated by the pin mill is the product of rotor tip speed, airflow rate, the feed rate of the material, as well as the morphology of the feed material. The milling process balances additions and reductions of airflow, feed rate, and rotor speed.
Hammer Mill The Hammer Mill, one of the oldest and widely used grinding mills, typically consists of four or more hammers attached on a central shaft enclosed by a metal casing. The mill performs particle size reduction via high-speed impact of hardened steel rotating hammers. Particle size reduction occurs in three actions: repeated hammer impact, particle collisions with the chamber wall, and particle-to-particle impact. Screens (set at a specified cut point) retain coarse particles for further grinding while allowing product sizes below the cut point to pass. Achieving the target particle sizing is a function of rotor speed, feed rate, hit resistance, clearance between grinding plates and hammers, and screen size.
At Classifier Milling Systems, we manufacture both pin mills and hammer mills as well as the leading air classifier mills and a broad range of milling technologies and products designed to give you the fine grind that suits your unique needs. We are a dedicated team with expert knowledge of particle size reduction. We guarantee exceptional service every time. We also guarantee performance!
Toll processing (third-party processing under contract) will offer the many advantages of subcontracting your production, like having the operational expertise without direct hirings and having the essential infrastructure without making the requisite capital commitment. But before awarding a toll processing contract to a toller, be sure that your contract processor can commit reliable capacity, operational expertise, and the high-level Quality Assurance necessary to guard you against potential product liabilities, and also protecting the intellectual property associated with your contracted materials (product formulas, product additives, blend formulations, particle size distributions). Protecting your IP is a quintessential concern.
We look at some ways in which businesses can keep their peace of mind about their intellectual property and derive all the benefits of toll processing:
Due diligence – Know your toll processing services provider. Look into past contracts. Take the trouble to inspect the toller’s process facilities physically. Ask for samples and lab test results before executing a tolling contract.
Handling of raw material – Put safeguards in place to limit non-essential access to your products and processes.
Third-party production – The use of independent contractors by your tolling partner must be defined. Be sure that violations carry meaningful enforceable penalties.
Security of Product – Physical control of the product from inbound raw materials to final products, storage, and delivery, should have security measures in place that are verifiable. Your IP can walk out the door if your contractor is lax about proper security. Classifier Milling Systems remains a party to numerous product confidentiality agreements with industry leaders for their product IP.