Multihead Weighers

Consider the multihead configuration based on the main parts of multihead: top cone, level control, linear pan, buckets and discharge chutes.

• Top cone: Rotary or Vibrate
• Rotary for sticky products, need rotate to spread products to linear pans
• Vibrate for granular or non-sticky products, easy to be vibrated to linear pans
• Level control: Photosensor or weighing load cell
• Photosensor: For light and fluffy product
• Weighing load cell: Heavy
• Linear pans: Different degree & shape
• Flat linear pans: for common dry products
• Inclined linear pans: for sticky products, can be 5,10,15 degrees depends on how sticky the products are.
• V shape linear pans: for round product by either counting or small weights, controls the products to be fed one by one.
• Straight line linear pans: round products, avoid sticking by standard linear pans.
• Belt feeder: for easily damaged products, like oranges
• Screw feeder: for sticky products: ready meal, fresh/cooked poultry

Buckets:

• Single door: 0.8L, 1.6L
• Double door: 0.5L, 1.0L, 1.3L, 2.5L,5.0L
• Flat bottom bucket: 2.5L, for small granules: rice, sugar etc
• Mesh bucket: 1.3L, 2.5L
• Scrapping bucket: 1.0L

Discharge chutes:

• Inclined degree: standard is 85 degree. Sticky products can use 65 degree or 60 degree depends on how sticky the product is.
• Heads numbers: Evaluate by production capacity/speed
• 10 heads, 12 heads, 14 heads, 16 heads, 20 heads/10x2 heads, 24 heads/12x2 heads, 32 heads
• 16 heads=2x8 heads; 20 heads=2x10 heads; 24 heads= 2x12 heads; All these types can be used as two weighers to get high speed or with two packaging machine
• 20 heads/24 heads/32 heads can be used for a mixture of projects.

Control system:

• Standard are MCU control system, can be PLC Siemens or Allen Bradly.
• Touch panel: Standard is Weinview options for Siemens or Allen Bradly.

Extra options:

• Anti-humidity system: Frozen, fresh, low working temperature conditions
• Anti-rotate device: Prevents products being rotated in the discharge chutes.
• Silicon pads: For fragile products or metal parts to avoid noise.
• Touchable surface: Silver Teflon is for regular sticky products. Black coloured Teflon is 380 degree, high grade, anti-sticking.

For irregular / long products: fish, large steak, vegetables like chillies, cucumbers, and carrots...which cannot be processed by regular multiheads we recommend 12 head or 14 head belt scales.

Therefore, to choose the correct MHW for you we have to know the following information:

• Product (actual photos if possible).
• Unit weight or dimensions especially if long/large.
• Target weight.
• Speed.
• Packaging method: Bag or tray or jars...

Packing line:

• Package type, with photo
• Bag/tray/jar/carton dimensions

The principles of a MultiHead Weigher

At a basic level, a multi-head weigher takes bulk product and weighs it into smaller increments according to the weights programmed into its software.

That bulk product is fed into the scale through the infeed funnel at the top, generally via an incline conveyor or a bucket elevator

A multihead weigher is a fast, accurate and reliable weighing machine, used in packing both food and non-food products.

A ‘typical target’ weight per pack might be 100 grams of a product. The product is fed to the top of the multihead weigher where it is dispersed to the pool hoppers. Each pool hopper drops the product into a weigh hopper beneath it as soon as the weigh hopper becomes empty.

The weigher’s computer determines the weight of product in each individual weigh hopper and identifies which combination contains the weight closest to the target weight of 100g.

The multihead weigher opens all the hoppers of this combination and the product falls, via a discharge chute, into a bag or, alternatively, into a distribution system which places the product, for example, into trays.

Dispersion is normally by gravity, vibration or centrifugal force, while feeding can be driven by vibration, gravity, belts, or screw systems.

An extra layer of hoppers can be added to store product which has been weighed in the weigh hoppers but not used thus increasing the number of suitable combinations available to the computer and so increasing speed and accuracy.

Filling bags

The range of bags which can be filled using multihead weighers is immense. At one end of the scale are large catering packs of many kilogrammes. At the other are small bags of crisps which can be handled at high speed and efficiency.

Mix-weighing

Products containing up to eight components can be mixed on a multihead weigher, very accurately at high speeds. The weigher is divided into sections, each with its own infeed. For example, a breakfast cereal containing hazelnuts and dried fruit plus two relatively cheap ingredients, could be weighed on a multihead with say eight heads devoted to each of the more expensive components and four heads to each of the other two. This would ensure high weighing speed while ensuring that overfilling of the expensive ingredients was negligible.

Filling trays

A  distribution system enables you to combine the speed and accuracy of multihead weighing with precise, splash-free delivery of product into trays.

Applications

Multihead weighers were used initially for weighing certain vegetables. Their use expanded exponentially in the 1970s and 1980s when they were applied to the rapid weighing of snacks and confectionery into bags. What cherry tomatoes and crisps had in common was that they flowed easily through the machine and into the pack, with no more encouragement than gravity and a moderate level of vibration of the feeders. Since then, the accuracy and relative speed have been extended to many products which would in the early days of the technology have been seen as difficult to handle.

Sticky products

Fresh meat and fish, whether in a sauce or not, poultry and cheese (including grated cheese) can be moved along by using belts or screw feeders rather than vibration.

Granules and powders

While free-flowing, fine-grained powders can be weighed more cheaply by other means (such as cut-gate or linear weighers, or volumetric feeders), granules such as coffee granules and products such as loose tea can be weighed on today’s multiheads.

Fragile products

Weighers with more shallow angles of descent and various cushioned inserts have made it possible to pack delicate and brittle items such as hand-made chocolates and gourmet biscuits. These are often paired with baggers or other packaging systems designed to handle fragile products.

Complex products

Using mix-weighing combined with a distribution system tailored to deliver separate components into a tray, a ready meal can be assembled with just the right quantities of, say, rice, meat and vegetables in the appropriate compartments.

Linear Weighers

At Total Food Machines we can supply a wide range of Linear Weighers

Various size linear weighers are available from single head to multi-head

A linear weighing machine is used to accurately measure and dispense precise amounts of products into packaging containers whether they are bags, bottles or boxes.

They typically consist of a series of weigh hoppers, or buckets, that are filled with the products to be dispensed.

The hoppers have load cells which measure the weight of the product within the hopper and are connected to control systems which open and close discharge gates or chutes to release the product into packing containers, they will weigh to close precise weights.

Linear weighers is the ideal way to move into weighing instead of using scales and before going into Mulltihead Weighers.

Linear Weighers can be small and compact and simple to use

For further information contact Total Food Machines