Sandwiching systems: precision engineering for trouble-free operation. By: Steve Fletcher B.Sc, Product Engineer, Sandwiching Systems

Transcription

1 Sandwiching systems: precision engineering for trouble-free operation By: Steve Fletcher B.Sc, Product Engineer, Sandwiching Systems

2 Contents 1. Introduction 2. Synopsis 3. High speed sandwiching systems 4. Process Description 5. OEE: Overall Equipment Effectiveness 6. Cream sandwiching machines 7. Cream feed system 8. Lane multiplier 9. Added innovation and value: the co-deposit stencil 10. Alternative sandwiching systems 11. Contact details Cream Sandwiching Machines Page 2

3 Introduction Although the principles of high speed sandwiching are well understood, the highest levels of output and efficiency can be achieved only by precision engineering of the equipment. This paper examines the critical process areas and how attention to detail in the design and manufacture of the equipment is helping raise standards of Overall Equipment Effectiveness (OEE) to new levels. Synopsis Successful high-speed, high-output biscuit sandwiching systems must be thoughtfully designed and carefully built to very close tolerances for efficient, trouble-free operation. The design of Baker Perkins sandwiching machinery stems from a deep understanding of both process and products derived from more than a century of involvement in automatic biscuit production. Precision engineering of the kind found in high-speed packaging machinery, is utilised to deliver the highest levels of sandwiching system OEE (Overall Equipment Effectiveness) available. The benefits are high output, high efficiency, flexibility and low production costs. The designs incorporate a number of detail features, each of which plays a part in efficient operation; they also ensure that Baker Perkins high-speed sandwiching systems can be engineered around the specific needs of the customer s product. Despite being engineered for high output and high efficiency, flexibility remains a key feature. A wide range of machines is able to produce a variety of different products at outputs from 800 to 4,800 sandwiches/min. (more on mini products) with rapid changeover in between. Cream Sandwiching Machines Page 3

4 High speed sandwiching systems Baker Perkins high speed sandwiching machines are available in two, three, four, five or six lane versions; output is product dependent but usually in the range of sandwiches per lane per minute, but higher outputs can be achieved on mini products. The cream feed system is a critical component in achieving accurate weight control and systems often include a lane multiplier to maximise the efficiency of cooling and handling arrangements. Baker Perkins offers complete systems from biscuit cooling to wrapping machine infeed. Equipment such as cooling tunnels, vibratory infeeds, and wrapper infeeds are supplied by partners with international reputations, and integrated into a complete line. Process description Biscuit shells are delivered into the cream sandwiching machine by magazines fed from vibratory conveyors. The bottom shell rests on two support wires and is stripped from the magazine by two pins, each attached to a chain. An adjustable gate on the magazine ensures that only one shell at a time is stripped out. Cream Sandwiching Machines Page 4

5 The shell is pushed through the sandwiching machine by the pins and is taken underneath the rotary stencil. This features a rotating cylinder with a number of outlets for the cream filling. At the bottom of the cycle an outlet lines up with a hole in a static centre tube and cream flows through the outlet and is deposited on the shell. The support wires are adjusted so that height of the shell beneath the stencil is sufficient to generate some pressure, which spreads the cream out and sticks it to the shell. As the outlet pulls away from the shell, the flow of cream stops and a horizontal cutting wire ensures that the cream is separated from the stencil. The creamed shell then passes under a second magazine where the top shells are fed into the machine. There is a short platform at the bottom of this magazine that supports the shell while it is stripped out. At the end of the platform the top shell drops onto the bottom shell, completing the sandwich. The sandwich is consolidated as it passes under a spring loaded shoe that also ensures all the sandwiches are of uniform thickness. At the end of the machine the sandwiches can be stacked or discharged on the flat to suit the cooling and packaging arrangements Machines are readily configured for a wide variety of product sizes and shapes, including mini and snack size sandwiches. For more unusual products special options and versions are available. Output depends on the product, but is usually in the range of sandwiches per lane per minute on standard products; more for mini and snack sizes. Cream Sandwiching Machines Page 5

6 OEE: Overall Equipment Effectiveness Baker Perkins utilises the principles of OEE to set the design and operational parameters for high speed sandwiching systems. The calculation of Overall Equipment Effectiveness is based on three factors: Availability, Performance and Quality. The issues that affect these factors are used by Baker Perkins designers to refine equipment and increase effectiveness. Availability takes into account downtime loss caused by reasons such as breakdowns, labour shortages and unavailability of material. It is defined as: Availability = Operation time x 100% Planned production time Performance takes into account speed loss. In other words, how much was produced compared with how much could have been produced, measuring losses such as waste and scrap, and is defined as: Actual run rate Performance = x 100% Ideal run rate Quality takes into account quality loss the difference reflecting the quantity of pieces unusable because of poor quality. It is defined as: Good pieces Quality = Total Pieces x 100% Cream Sandwiching Machines Page 6

7 OEE takes all three factors into account and is calculated as OEE = Availability x Performance x Quality. Some of the above factors that contribute to the OEE of a cream sandwiching machine are not directly related to the machine itself e.g. shell and cream quality, operator training etc. To achieve the highest levels of OEE all of the above have to be performing equally well. From the above it is easy to see that a world-class machine does not guarantee world-class OEE, but by the same token world-class OEE cannot be obtained from a poorly designed or built machine. Cream sandwiching machines The heart of the system, the cream sandwiching machine, plays a key part in adding value to the product. Adding expensive cream to a biscuit shell means that any scrap generated by the sandwiching machine is a lot more costly than scrap generated upstream and it cannot be recycled or reused. Several features covering different aspects of operation combine to maximise efficiency and minimise downtime continuous operation 24 hours a day is the objective Cream Sandwiching Machines Page 7

8 The creamer has to operate in a much harsher environment than most other items of biscuit production and packaging machinery. Sticky cream combined with abrasive sugar particles and biscuit crumb can significantly affect operating efficiency. Pin cleanliness. Dirty pins can create stoppages as biscuit crumbs and other debris adhere to them; Baker Perkins ensures pin cleanliness through two separate operations. On start-up, and when the operator selects it, high-pressure air is blasted over the pins to remove cream and a self-cleaning rotary brush with a helical pattern keeps the pins clean this is much more effective than a static brush. Washdown. Lubrication-free chain technology means that the highest standards of overall cleanliness can be achieved through effective hosedown. Any debris falls into bins for easy removal and disposal; taking away the bins also gives excellent access for maintenance. Eliminating chain stretch. The two sets of pusher pins on each lane are mounted on separate chains. To ensure alignment at the stencils, and thus centralisation of the cream deposit, the chain driveshaft and sprockets are machined from a solid billet. Additionally, on the six-lane machine, the chains are connected through solid plastic blocks in which both pins are mounted making it impossible for them to get out of line. Cream Sandwiching Machines Page 8

9 Shell sensors: no shell, no cream. To minimise selfgenerated stoppages caused by broken or missing shells, clamps are fitted over the chains as they pass under the magazines. This keeps the pins upright as they strip the biscuits from the magazines and avoids shells being missed or broken by the pins being forced backwards. As an additional precaution, each lane is equipped with a sensor to detect magazine jams, and initiate a controlled shutdown. Controlled shutdown. If shutdown is necessary, a controlled stop avoids build-up of pressure in the cream pipes. This avoids a surge of cream on restart that could result in smearing of product contact parts and subsequent stoppages. A gentle stop also avoids disturbing the biscuits, increasing the likelihood of a problem-free clean restart. Depositing position accuracy. To achieve a centralised deposit the position of the bottom shell has to be precisely controlled with respect to both horizontal axes. Firstly, to position the shell in the middle of the lane, a single adjustment is provided that moves the side guides symmetrically. In addition, the chain stretch control features mentioned above help by ensuring that the pins are in line and not skewing the biscuit to one side. Secondly, to ensure that the deposit is placed centrally along the length of the shell, the synchronisation of the stencil outlets with the pin chains is extremely precise. Meticulous engineering of the chain drive mechanism and stencil is the key to consistent accuracy, along with stencils that are easily assembled and positioned right first time. When necessary, phasing adjustment is infinitely variable within its range, and adjustable on the run. Cream Sandwiching Machines Page 9

10 Stable shell support. The shell support wires are moved in pairs with a single adjustment handwheel to ensure that the product remains flat throughout its passage through the machine. An additional stability feature on the six-lane machine is that the solid platform under the top shell magazine that sits between the pins has been replaced by a forked platform sitting outside the pins to give much broader and more stable support. Stencil purge facility. This facility allows cream to be purged through the stencil outlet prior to start up. Air is discharged from the cream pipes so that cream delivery is synchronised with the availability of biscuit shells to avoid wastage of cream and shells. Pin pitch. Baker Perkins cream sandwiching machines are designed around the customer s product. Standard pin chain pitch is 3.5, but this can be reduced for smaller products to give either increased output, or standard output at a slower, more comfortable linear speed. Cream Sandwiching Machines Page 10

11 Cream feed system Special purpose hoppers feed cream to the sandwiching machines, and ensure accurate deposit weight over extended periods of operation. Precise weight control. Hoppers are specified with one pump per lane; each pump has its own variable speed drive to enable the deposit weight on each lane to be controlled with pinpoint accuracy. Pump speed is set to follow the creamer speed and, in some circumstances, may be adjusted by feedback from a checkweigher, to maintain accuracy throughout long production runs. Lane multiplier Lane multiplication is usually necessary with sandwiches that are chocolate enrobed or pass through a cooling tunnel before packaging: this can be achieved in ratios of two, three, four or five times the number of creamer lanes. Cream Sandwiching Machines Page 11

12 Choice of presentation. Sandwiches are transferred from the creamer on the flat, and discharged from the multiplier either on the flat or stacked the choice is determined by the preferred presentation to the wrappers. Easy to use and clean. The sandwiches are transported on a conveyor belt and multiplied using a simple overhead mechanism to push the product sideways. The multiplier assembly can be lifted away from the belt for easy cleaning. Added innovation and value: the co-deposit stencil This Baker Perkins innovation allows simultaneous depositing of two fillings either concentrically or adjacent to each other, enabling a wide variety of appealing, added-value products to be developed. The perfect register obtained contrasts markedly with alternative dual deposit techniques that use sequential stencils to place separate deposits on the shell. The alignment problems this creates are avoided with the co-deposit principle. Additionally, an array of different of fillings can be handled for instance a soft cream encircled with a harder cream, or a cream with a jam/jelly centre. A range of products containing two different types of cream, jam, cheese or peanut butter can be developed colours and consistency can easily be varied. The co-deposit system can be retrofitted without any major modifications being needed to existing sandwiching machines. Cream Sandwiching Machines Page 12

13 Alternative sandwiching systems In addition to the high-speed creamer, Baker Perkins offers two alternative sandwiching systems. Pile Pack creamer. To cater principally for a rising demand for vend packs, the Pile Pack creamer incorporates a patented system to form piles of two sandwiches that are collated into pack lengths of one to six piles. The unique feature is that the two sandwiches are formed one on top of the other during the creaming process and fed straight to the wrapping machine. Pile Pack creamer and wrapper are thus integrated into a seamless unit with no need for a cooling tunnel, reducing cost and complexity. The unit uses the same process as high speed creamers, and therefore offers the same benefits in terms of efficiency and accuracy. Full width creaming. This method eliminates the cost of lane reduction systems - the number of lanes matches that emerging from the oven. It is ideal for highly automated plants where delicate products, soft or aerated creams, or secondary processing such as chocolate enrobing, are employed. Low linear speed through the creamer enables delicate products to be handled gently; after sandwiching, products are ideally placed for subsequent coating or enrobing with no lane multiplication. The stencil is a rotating drum with retracting pistons that draw cream from a hopper; this very gentle method of handling lends itself well to aerated, soft or high fat creams. Cream Sandwiching Machines Page 13

14 Contact details Further information is available from Keith Graham, Baker Perkins Limited, Manor Drive, Paston Parkway, Peterborough, PE4 7AP, United Kingdom Tel Cream Sandwiching Machines Page 14