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Case packing is the process by which packages or products are loaded into cases, boxes or trays. These are usually corrugated board but may also be fluted plastic, heavy non-fluted board or other materials. In some instances, such as milk in bottles and cartons, specialized metal or plastic returnable crates are used. For simplicity, this white paper will use the word “case” generically to cover all variations. With minor variations, case packing is the same regardless of whether it is an RSC case, a tray, a crate or some other box.
Case packing seems like a natural for using operators instead of machines. It is simple work so unskilled, relatively low cost, labor can be used and automation dollars can be saved for other things. In reality, there is no such thing as low cost labor. Compensation is high and rising and qualified employees keep getting harder and harder to find. Case packing is also repetitive, often heavy, work with a lot of ergonomically hazardous lifting and bending. This can add to workers compensation claims.
Automated case packing is relatively simple and generally very easy to justify.
The term “case packing” is frequently used to describe the complete process of getting the package into the case. In reality, there are at least 3 discrete operations:
There can also be placement of internal partitions, slip sheets if more than a single layer of product is packaged, leaflet and instruction insertion.
The entire process may be done on a single machine or multiple machines. This white paper will focus only on the case packing, regardless of where erection and sealing is done.
There are three major methods of automatic case packing: Side loading, vertical placing and vertical drop packing. Some may consider wraparound case forming to be case packing as well. It is beyond the scope of this paper and will be covered in a future paper on caser erection/forming. Each method has a number of variations depending on machine design as well as package and product requirements. The techniques discussed here also apply generally to tray packing. The method chosen will depend largely on the nature of product to be packed.
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The words “case” generally refers to a box made of corrugated board. Occasionally fluted plastic, similar dimensionally and functionally to corrugated board, may be used. The RSC (Regular Slotted Case) case is made from a single piece of board, die-cut, scored, folded and glued at the converter. RSC cases are the most common though there are a number of other styles depending on product need.
It is simple to erect RSC cases by hand and do it fairly quickly provided the workstation is properly designed. There are aids that make it even easier. Ergonomics and lablr availability are 2 good reasons to automate the task. Automation will pay for itself quickly
This case erector from the Frain inventory is about as simple as it gets. Knocked down case blanks are placed in an inclined magazine and feed by gravity to holdback fingers in the pick-off station.
An articulated arm grips major side of the case blank with suction cups and pulls it from the magazine. As it does, an articulated section of the gripper folds the minor side open and tucks the trailing minor flap under. The arms square the case and push it into the takeaway section. There an end guide pushes the leading minor flap closed and side guides fold the major flaps closed.
A glue or tape head may be incorporated into the case erector to seal the bottom closed. In some applications, the bottom is left unsealed until after case packing when top and bottom are sealed simultaneously on a case sealing machine. One issue with this style of case erector can occur with a sloppy glue joint. Excess glue can glue the interior panels of the case and the case erector may not be able to pull it open.
This is never acceptable as it will cause a jam. On higher speed, 15 case/minute and up a different style case erector will be used. This horizontal erector by RA Pearson brings the case blanks into the machine horizontally.
As the case indexes into the erection area, it gripped by suction cups underneath. An arm with suction cups rotates down, grips the top major side of the case. It pulls it forward and up to open it. Gripping both top and bottom of the case allows the erector to pull the case open even if it is glued shut by sloppy gluing.
A kicker folds the trailing minor flap closed. Static guides fold the other 3 sides in while applying glue if desired.
A final step is to compress the case bottom between a backing plate and a ram with a mandrel. After exiting compression, the case falls upright onto a takeway conveyor.
After the case is erected, the packed needs to be placed. There are several automated ways to do this. Where feasible, drop packing is often the simplest and fastest way to do it.
Drop packing drops the product into the case. Sounds simple but there are some caveats.
Products must first be collated in the final pack pattern. This is done by multiple infeed lanes. For a 12 pack, this normally means 3 lanes of product, though 4 is possible.
Backpressure in the accumulation area pushes the bottles (4 in this example) over the drop gate. Once in position, the back pressure on the group is relieved.
While this is happening, an empty case, tray or reusable crate is being positioned under the drop gate.
When bottles and case are in position, the drop gate opens and bottles fall into the case.
The sketch omits 2 critical components in the interest of clarity:
After the drop, the full case is taken away on the conveyor and the process repeats.
A variation on the drop packer, for empty PET bottles in reshippers, multilayer gable top cartons and the like is the drop placer. It is similar to the drop packer but a placing mechanism above the drop gate grips each package and positively lowers it into the case.
One area of concern when drop packing into cases is the case flaps. Guides or a funnel must be provided to assure that they are kept back and out of the way. If not, they can prevent the bottles falling smoothly. If one bottle is out of place, all the others will get out of place.
Manually packing product into cases is ergonomically hazardous. Drop packers are a simple and effective alternative.
The term case packing is often misused to cover 3 distinct operations, erection, packing and sealing. This is often done on 3 separate machines, especially on higher speed lines.
When the case is a standard RSC and the product is straightforward, all 3 machines may be combined into a single, all-in-one case erector-packer-caser. There are several advantages to this:
The case erector may be located below the case packer infeed. Case blanks are placed in a magazine and held in position for opening. An articulated arm with vacuum cups grips the flat case on both sides of the score line and pulls it out of the magazine. As it does so, the section of the arm gripping the rear portion of the case folds 90 degrees opening and squaring the case.
The case is now a square tube. As the vacuum cups release, a pusher moves forward kicking the bottom trailing minor flap closed. As the case is pushed forward, a guide pushes the leading minor flap closed and side guides push the major flaps closed. In some applications the major flaps are left open to allow air to escape when packing a conformal product like cartons.
The case moves to the packing area. Product may be dropped into the case with a drop packer or placed using a robot or other pick and place mechanism.
As the case exits the packing station, glue is applied to the lower major flaps and guides close them (if needed) The trailing top minor flap is kicked closed and guides close the leading minor and majors. Glue may be applied before closing if needed. Top and bottom belts normally compress the case to assure good glue adhesion.
If tape is to be used, side belts will pull the case through the upper and lower taping heads. Tape is normally self-adhesive but gummed tape may also be used.
Casers are machines that automatically, sometimes semi-automatically, load products into corrugated RSC cases. There are a number of styles depending on product and speed, but most are vertical, loading into the open top of the case. This allows gravity to help the process.
Some cases, such as a 24-pack of cans, are designed so that loading flaps are on the ends rather than the top and bottom. Other products, such as cartons do not lend themselves to vertical loading even though the case has a top and bottom.
Side load casers load horizontally rather than vertically.
Products are collated into the proper pack pattern in a separate system or as part of the machine infeed. These collated products are staged in the loading section of the caser.
Case erection may be done manually, on a separate case erector or on the same caser. If formed vertically, it will be necessary to tip the case on its side prior to the loading area.
Guides will typically be used to hold the front flaps out of the way to avoid interference during loading.
However erected, the case is presented horizontally to the caser infeed. If the product fits tightly into the case, for example cartons, the rear flaps may be left open. The reason for this is that the tight fit causes a piston (product) in cylinder (case) effect. If the opposing flaps were closed before loading, the product would form an air cushion and it could be difficult to push them in.
Once the case and product are aligned, the product is pushed into the case. In some patterns there may be double layers of product. These may be handled by either stacking the product double deep and pushing with a single push or making two separate pushes. Machine design, case and package will determine which is to be done.
Once loaded, the flaps are closed and the case is moved to a sealing station. This can be integrated to the caser or can be a separate machine.
Case packing, placing a carton, bag, bottle or other package in a corrugated case, is a natural for robots. SCARA and delta style robots may be used in some applications but 6-Axis or articulated arm robots are more common. Their low cost, reach, freedom of movement, and size makes them a natural.
A common configuration for the robotic case packer uses 2 conveyors. Cases are erected, either by hand or machine, and conveyed to a staging station near the robot. Meanwhile, the product is staged in a nearby station. The closer together all 3, robot and 2 staging stations, can be, the shorter will be the robot travel. Shorter travel means faster cycle time, less wear and tear on the robot and smaller overall footprint.
Where possible, product should be staged in its final packing format. If bottles are to be packed in a 4X3 pattern, the conveyor can be divided into 3 lanes before the staging station. A backpressure relief mechanism isolates the 4 bottles at the end of each lane. The robot, with an appropriate gripper, picks up 12 bottles at a time and places them in the case. The case is released to the case closer/sealer.
Additional speed can be achieved in some applications by using a larger robot to pick 24 bottles at once. An articulated gripper spaces them so they can be placed in 2 cases simultaneously.
It is possible to pick 4 bottles at a time from a single lane but this will require 3 cycles of the robot and each placing position will be slightly different.
An advantage of the 6-Axis robot is that one robot may be able to pack for 2 separate lines. The case and bottle staging area of each line remain the same with the robot in the center. As the robot is loading one case, the case and product for the other line is staging.
Some lines may be too fast for 6-Axis robots. Delta and SCARA robots can run much faster and may be a solution in these applications. A drawback may be their limited reach compared to a 6-Axis robot.
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