Section 5: Machine Overview

Transcription

1 Section 5: Machine Overview Machine Floor Plan Machine Specifications Sequence of Operation Theory of Operation Sensor Location Floor Plan 2007 Douglas Machine Inc. 5.1

2 Machine Floor Plan Figure 5.1: Machine Floor Plan Douglas Machine Inc.

3 Machine Specifications Size Range (Outside product dimension) Direction of Travel Vertical Dimension Across Conveyor Minimum Maximum Machine Specifications Machine Speed Machine Size Plant Voltage Maximum of 30 cycles per minute Estimated Amp Load Length: 25 7 Width: V-3ph-60hz Estimated Air Usage V psi 2007 Douglas Machine Inc. 5.3

4 Sequence of Operation Product is received, in single lanes, from upstream equipment with the long dimension across the machine and a space between each product. Film is automatically cut to the correct length and positioned under the product. The wrapping mechanism is a rotating wand that travels around the product, providing overlapped film under the tray. Each package continues through the shrink tunnel where heat is applied to all sides of the package, including the bottom. The overlap is sealed by hot air passing through the open web conveyor. Controlled airflow within the tunnel ensures a uniform film shrink Douglas Machine Inc.

5 Theory of Operation Wrapper Sequence of Events Refer to Wrapper Primary Components for component descriptions. The wrapper s primary functions are to merge each product group (pack or loaded tray) with a sheet of shrink film, wrap the film sheet around the product, and discharge the film-wrapped product group to the shrink tunnel. The following outline describes the wrapper sequence of events: 1. The infeed conveyor receives product groups from an upstream source and advances them onto the wrapper entry conveyor. The speed differential between the infeed conveyor and the wrapper entry conveyor creates a gap between product groups that is required for successful wrapping. The Infeed Surge Control photosensor monitors the infeed conveyor for product. When this Figure 5.2: Product Arriving at Wrapper sensor s light beam is blocked for a Entry Conveyor preset time, a remote interface signal from the PLC dwells upstream equipment. 2. The wrapper entry conveyor advances product groups toward the wrap conveyor. The Product At Wrapper photosensor monitors the wrapper entry conveyor for product approaching the wrap conveyor. A Wrapper Products Too Close fault occurs when this sensor detects debris between product groups or product groups that are too close together for successful wrapping Douglas Machine Inc. 5.5

6 Wrapper Sequence of Events (continued) 3. The film drive is enabled in machine cycles in which the Product At Wrapper photosensor detects product. The following actions occur while the film drive advances: a. As the wrapper entry conveyor advances a product group onto the wrap conveyor, the film drive delivers the film s leading edge through the wrapper s first wand opening (the gap between the wrapper entry conveyor and wrap conveyor). The film s leading edge merges with the bottom of the product group. b. A wrapper wand rises through the first wand opening as the product group moves past the opening. The film-draped wand moves up past the trailing surface of the product group. The leading edge of the film sheet is held by the product group while the wand lifts the film. c. The film is cut at the film length. 4. The film sheet is wrapped around the product group as the wrapper wand moves in an arc above the product group and down its leading edge. Figure 5.3: Wrapper Wand 5. The wrapper wand carries the film sheet s trailing end through the second wand opening (the gap between the wrap conveyor and the wrapper discharge conveyor). 6. As the product group advances over the opening, the film sheet s trailing end overlaps its leading end, which is held in position under the product group. 7. The wrapper discharge conveyor discharges the film wrapped product group to the shrink tunnel, which seals the overlapped film at the bottom of the product group and shrinks the film tightly around the product Douglas Machine Inc.

7 Film Drive Sequence of Events Refer to Wrapper Primary Components for component descriptions. The film drive s primary functions are to merge the leading edge of the shrink film with each product group (pack or loaded tray) and cut the film at the film length. 1. The film drive is enabled in machine cycles in which the Product At Wrapper photosensor detects product on the wrapper entry conveyor. The film drive advances to deliver the leading edge of the film onto the wrap conveyor at the proper position relative to the bottom of the product group. The film s position is based on the Tray Length (Inches) and Film Position Center Offset (Inches) recipe variables. 2. The sheet transfer air knife guides the film s leading edge onto the film drive s discharge deck. Air pressure to the air knife is controlled by the following solenoid valves: The SHEET_TRANSFER (SV_60524) solenoid valve is actuated while the sheet transfer air is enabled and the film sheet position is not within the Film Drive Air Off PLS On/Off (Inches) PLS window. When the valve is actuated, air from the Wrapper Sheet Transfer regulator flows directly to the air knife. When the valve is not actuated, air from the regulator flows through a flow control valve to the air knife. The SHEET_TRANSFER_MANUAL_CYCLE (SV_60526) solenoid valve is actuated during manual film drive operations. 3. The film drive cuts the film at the film length. When using film registration, the film is cut relative to a registration position on the film. When not using film registration, the film is cut to the Film Length (Inches) recipe variable Douglas Machine Inc. 5.7

8 Shrink Tunnel Sequence of Events For component descriptions, refer to Shrink Tunnel Primary Components. The primary functions of the shrink tunnel are to shrink the film tightly around the product and to bond the lap seal (the film sheets overlap at the bottom of the package). The following steps describe the shrink tunnel sequence of events: 1. The tunnel conveyor receives film-wrapped product groups from the wrapper discharge conveyor. 2. As the film-wrapped product advances through the shrink tunnel, the lap seal is welded by the heated air flowing through the tunnel conveyor s web openings. 3. Air from the side air ducts flows into the open ends of the film-wrapped product. This causes the film sleeve to balloon up and transfers heat to the inside and outside surfaces of the sleeve. The film begins to shrink when the film s temperature reaches its shrink range. 4. The cushion of air between the film and the product supports the film as it shrink against the product. 5. The shape of the heat shroud directs heated air along the sides and top of each package. The flow of heated air Figure 5.4: Heat Tunnel around and through the filmwrapped product causes the film to shrink until it is snug around the product. 6. The suction created by the fan directs the air to the return air plenum, which directs the air to the heat source to be reheated to the desired temperature Douglas Machine Inc.

9 Shrink Tunnel Sequence of Events (continued) 7. As the package exits the shrink tunnel, the film is soft and pliable. The shrink process, which is accelerated by the product cooling fan, continues until the film is cooled to a temperature below the shrink range. Packages should not be moved from the conveying surface during the cooling period. Moving a package results in a loose package and/or distortion of the package graphics Douglas Machine Inc. 5.9

10 Wrapper Infeed Primary Components The wrapper infeed s primary function is to advance product groups (packs or loaded trays) onto the wrapper entry conveyor. The wrapper infeed consists of the following primary components: Infeed conveyor: This VFD-controlled conveyor receives product groups from an upstream source and advances them onto the wrapper entry conveyor. The speed differential between the infeed conveyor and the wrapper entry conveyor creates a gap between product groups that is required for successful wrapping. Product stop gate: This gate, which is located between the infeed conveyor and the wrapper entry conveyor, is plumbed to the machine s controlled air. When controlled air is dumped, the gate rises to prevent product on the infeed conveyor from being advanced onto the wrapper entry conveyor. Sensor: The INFEED_SURGE_CONTROL (PE_25052) photosensor monitors the infeed conveyor for product. When this sensor s light beam is blocked for a preset time, a remote interface signal from the PLC dwells upstream equipment. The Infeed Conveyors Edit 0 Screen allows personnel to view or edit the wrapper infeed s adjustable parameters. Care should be taken when editing the parameters to maximize the machine s reliability Douglas Machine Inc.

11 Wrapper Primary Components The wrapper s primary functions are to merge each product group (pack or loaded tray) with a sheet of shrink film, wrap the film sheet around the product, and discharge the film-wrapped product group to the shrink tunnel. The wrapper consists of the following primary components: Film roll spindle: A film roll is placed on the film roll spindle. When the Roll Grip selector switch is set to On, a rubber bladder in the spindle inflates against the film core to hold the roll in place. The roll must be correctly positioned on the spindle to ensure that the film will track properly for cutting and wrapping around the product. Nip rollers, which are located on the film drive assembly, draw film from the roll as the film drive advances. Film tensioning: The following components work together to keep film tension between acceptable limits: Roll brake (spindle brake): Braking pressure is applied to the spindle when the DANCER_BAR_FULL_OPEN (PRX_60422) proximity sensor detects that the dancer bars are open. Dancer bars: As the nip rollers draw film from a film roll, the film passes around the 45-degree Figure 5.5: Dancer Bars film transfer tube and through a set of dancer bars. The dancer bars dampen the acceleration and deceleration of the film roll during a wrapping cycle. The Dancer Bar Tension air cylinder maintains a constant pressure on the pivoting dancer bar assembly Douglas Machine Inc. 5.11

12 Wrapper Primary Components (continued) Film drive assembly: The film drive draws film from a film roll, cuts film to the required length, and merges a film sheet with each product group that advances onto the wrap conveyor. The film drive is driven by the film drive servo, which is cammed to the wrapper wrap conveyor servo. The film drive consists of the following primary components: Nip rollers: This pair of rubber-surfaced rollers draws film from a film roll. The nip roller with the larger diameter is driven by the film drive servo. The smaller nip roller is held firmly against the larger nip roller by air cylinder pressure. The air pressure that holds the smaller nip roller against the larger nip roller is adjusted with the Wrapper Raise Nip regulator. This adjustment ensures that the nip rollers consistently pull film from the supply roll without slippage by allowing for films with different thicknesses, stretch properties, and coefficients of friction. To open the nip rollers for film threading, the RAISE_NIP_ROLLER (SV_60528) solenoid valve is actuated to apply air pressure to the opposite side of each air cylinder. This valve is actuated while the Nip Roller selector switch is set to Up and a wrapper guard door is open. Film cutter: Film is cut by a serrated knife on a knife shaft that is driven by the film drive servo and is controlled by the FILM_CUT_KNIFE_CLUTCH (SV_60512) solenoid valve. When this solenoid valve is actuated, the shaft rotates in the direction of film travel and the knife swings in an arc to cut the taut film. Steel deck: This is located upstream of the knife, just outside of the knife arc. This deck provides a sheer point to enhance the cutting action of the knife. Sheet transfer air knife: These air nozzles direct cut film onto the film drive s discharge deck. Wrapper entry conveyor: This conveyor receives product groups from the wrapper s infeed conveyor and advances them onto the wrap conveyor. The film drive merges a film sheet with the bottom of a product group in machine cycles in which the product group is detected approaching the wrap conveyor. This conveyor is driven by the wrapper wrap conveyor servo. Wrap conveyor: This conveyor advances individual product groups toward the wrapper discharge conveyor as a wrapper wand wraps the product with a film sheet. This conveyor is driven by the wrapper wrap conveyor servo Douglas Machine Inc.

13 Wrapper Primary Components (continued) Wrapper wands: Two wrapper wands that are positioned 180 degrees apart travel around the wrap conveyor. A product group is wrapped with a film sheet while a film-draped wand moves in an arc above the product group and down its leading edge. The wrapper wands are driven by the wrapper wand servo, which is cammed to the wrapper wrap conveyor servo. Wrapper discharge conveyor: This conveyor transfers filmwrapped product groups from the wrap conveyor to the shrink tunnel conveyor. Figure 5.6: Wrapper Wand This conveyor is driven by the wrapper wrap conveyor servo. Sensors: The wrapper has the following film and product sensors: The LOWER_FILM_ROLL_LOW_EMPTY (PE_60432) photosensor detects a reflector one time each film roll rotation when the film roll is nearly empty. A Film Roll Empty fault occurs when this sensor detects the number of film roll rotations equal to the # Of Film Roll Revolutions From Low To Empty recipe variable. The PRODUCT_AT_WRAPPER (PE_60100R) photosensor monitors the wrapper entry conveyor for a product group approaching the wrap conveyor. This sensor is used for the following purposes: The film drive merges a film sheet with the bottom of a product group in machine cycles in which this photosensor detects product. This sensor is used to detect a Wrapper Products Too Close fault. The FILM_REGISTRATION_EYE (PE_60101) photosensor is located upstream of the nip rollers. When the active recipe runs printed film, this sensor is used to detect film registration Douglas Machine Inc. 5.13

14 Wrapper Primary Components (continued) The MISSING_FILM (PE_60426) photosensor, which looks across the second wand opening, monitors the wrapper wand for film. A Missing Film fault occurs when this sensor does not detect film while the wand servo s actual position is within the Missing Film Check On/Off (Degrees) PLS window. The PRODUCT_AT_DISCHARGE (PE_60424) photosensor monitors the wrapper discharge conveyor for a wrapped product group approaching the tunnel conveyor. This sensor is used to maintain the wrapper run latch until product is fully advanced onto the shrink tunnel conveyor. The following control panel screens allow personnel to view or edit the wrapper s adjustable parameters. Care should be taken when editing the parameters to maximize the machine s reliability: Wrapper Cam Edit Wrapper Edit 3 Wrapper Edit 0 Wrapper Maintenance Wrapper Edit Douglas Machine Inc.

15 Shrink Tunnel Primary Components The shrink tunnel s primary functions are to shrink the film tightly around the product and to bond the lap seal (the film sheets overlap at the bottom of the package). The shrink tunnel consists of the following primary systems: Air supply unit: Controlled airflow in the tunnel ensures a uniform shrink to the upper film and bull s-eye. The air supply unit, which heats and circulates air, consists of the following components: Heater elements: The heater elements heat the tunnel air. The power to the heater elements is controlled to regulate the tunnel heat to the Setpoint For Tunnel Temperature recipe variable. Heater air blowers: This VFD-controlled blower extends the full width of the heated air plenum to provide uniform airflow across the width of the plenum. The Tunnel Blower Speed (RPM) recipe variable adjusts the volume of air being circulated. BASE_TUNNEL_HEATER_AIR_TEMP (RTD_11022): This resistance temperaturesensing device (RTD) monitors the air temperature downstream of the base tunnel heater. This device provides feedback to the PLC, which modifies the control variable (power level) to the heater elements to maintain the air temperature at the selected setpoint. Heated air plenum: The plenum channels and directs the heated air around the product. Within each chamber, the plenum s cross-sectional area is tapered outward from the fan discharge to equalize airflow through each hole in the plenum surface. These holes are aligned with the openings in the conveyer chain web. Air ducts: Heated air is routed to the side air ducts, which direct air toward the ends of the product. The volume of air passing through the side air ducts can be controlled by opening or closing air knives. Return air plenum: The return air plenum directs air back to the heat source. Heat shroud: The heat shroud covers the top, sides, and ends of the heated air plenum. It contains the air around the product and directs air to the return plenum. To minimize heat loss, the heat shroud is insulated and the entrance and exit openings are covered with a curtain. Tunnel conveyor system: The VFD-controlled tunnel conveyor receives film-wrapped product from the wrapper discharge conveyor and conveys it through the tunnel to the plant s take-away conveyor. The tunnel conveyor system consists of the following components: Conveyor chain: The conveyor chain is a web (open mesh) with openings that allows airflow to the bottom of the packages. The film sheets overlapped ends are welded by heated air passing through the chain s web openings Douglas Machine Inc. 5.15

16 Shrink Tunnel Primary Components (continued) Chain cooling fan: This VFD-controlled fan, which extends the full width of the tunnel conveyor, forces air over and through the tunnel conveyor chain. To prevent film from sticking to the chain, the fan cools the chain to the Setpoint For Chain Return Temp recipe variable. TUNNEL_CHAIN_TEMPERATURE (IR_11034): This infrared temperature sensor monitors the tunnel conveyor chain s surface temperature. This device provides feedback to the PLC, which controls power to the chain cooling fan. Tunnel discharge: The tunnel discharge consists of the following components: Product cooling fan: This fan accelerates the film cooling process by blowing ambient air onto completed packages on the plant s take-away conveyor. The DOWNSTREAM_SURGE (PE_10906) photosensor monitors the plant s take-away conveyor to ensure that packages are advancing. The machine cycle dwells when this sensor s light beam is blocked for a preset time. The following control panel screens allow personnel to view or edit the shrink tunnel s adjustable parameters. Care should be taken when editing the parameters to maximize the machine s reliability: Tunnel Edit 0 Figure 5.7: Tunnel Discharge Tunnel Maintenance Tunnel Edit Douglas Machine Inc.

17 Sensor Location Floor Plan Figure 5.8: Sensor Location Floor Plan 2007 Douglas Machine Inc. 5.17