PhilipRBrenan@gmail.com on 2022-09-10
Here is a design for a fully automated system for reliably and cost effectively receiving, picking, listing, purging and mailing several thousand books per day chosen from a body of one million books or more. The proposed system is built from cheap and readily available components made of steel.
The proposed system does not rely on humans to work within the process, merely to observe the process from a safe distance and to maintain the process equipment in good working order. Some minimal human effort is required to tip Gaylords full of books into the system and, likewise, transport away Gaylords of books to be recycled or mailed.
Books are tipped out onto a downward sloping ramp. The ramp is vibrated
to spread out the books along the ramp.
Books are picked out of the ramp using a vacuum powered corner grabber. Books that are buys are jacketted in a steel clip. The remainder are transferred to recycling bins. Jacketed buys are moved to the kitting area for loading into storage trays via the lower crane. The storage trays full of books are transported to the dense cube in the storage area by the upper crane.
The storage area is processed periodically in a pick cycle. In a pick cycle, each tray in turn is moved to the kitting area and its contents transferred either to the kitting area or to another tray. The tray is then returned to the storage area by the upper crane.
Here is a movie showing a simulation of the storage area during processing.
The kitting area is used to assemble multi-order orders during each pick cycle. As soon as a multi-order is complete it is moved by the lower crane to the mail area where the books are placed in packages and dropped in to a mail bin ready for daily pickup.
Books can be simultaneously protected from wear and tear, made to occupy a
standardized volume, kept from opening unexpectedly and made manipulable by
jacketing them in a magnetic steel clip.
Three dimensional drawing: Book Clip.
It is conceivable that book clips can be fabricated as a single metal casting or using injection molded plastic with enough iron powder in it to make it magnetic.
The jacket illustrated is designed to be easy to clip around books of differing sizes and, likewise, to be removed when the book is mailed or purged. The pyramid at the bottom is used to guide the clip, and hence the book, into a corresponding pyramid slot in the kitting area and storage trays reducing the need for positional accuracy considerably. The oval clips are made of spring steel which is spot welded to the U-tube frame as is the pyramid at the bottom.
Shapes such as pyramids are easily made by casting.
The book clip shown has the following advantages of:
It is easy to stand books in an egg tray even though egg trays were not designed for this purpose:
Consequently it will be easy to stand books wrapped with such a clip in a tray with appropriate sized slots in its floor. Lowering the book into position with a magnetic or pneumatic grab will engage the pyramid in the corresponding pyramid slot to position the clip, and hence the book, accurately. The grab can then be withdrawn leaving the book standing in position.
The books are stored in a tray acting as a large egg tray:
The outer tray is typically 5.8m by 2.3m and consists of five smaller inner trays bolted to the outer frame. This arrangement allows the inner trays to be removed from the outer tray and reassembled as cubes for easier transportation.
The dimensions of the tray correspond to those of a small Intermodal Shipping Container which enables
us to use equipment developed for such containers to lift and transport them:
There is a significant advantage to using container technology: the spreader bar tensions the sides of the tray when the tray is lifted allowing the sides of the tray to be constructed of less steel than might otherwise be required.
The books are placed in the tray using a three axis crane with an electro-magnetic chuck:
The trays can be stacked in a storage area and then brought to a work area
for processing using a gantry crane.
In the work area books are picked and placed in the AutoKitter which has
enough room to hold the number of books picked in one cycle. For each cycle,
the AutoKitter is preloaded with replacement books to go into the slots vacated
by picked books. At the end of the cycle the three axis crane unloads the
AutoKitter in multi-order order and places the books in the mail area where
they are removed from their steel clips and dropped into mailing sacks. The steel clips are sent back to receiving for reuse on incoming books.
In the receiving area books are tipped out of gaylords onto a descending
ramp. Foam covered weighted rollers hung above the ramp help flatten out the
books. The books slide slowly down the ramp because the ramp is vibrated by a
hydraulically powered plate vibrator which shifts the books into the positions
which minimizes their potential energy by increasing their entropy.
Once the books are sufficiently spread out it is easy to isolate the corners
either by using a 3d camera ($279 from Intel) or manually using offshore labor
with access to gigabit Internet.
Three dimensional drawing: Corner Grabber.
Here is a movie of the corner grabber being printed
Applying a corner grabber with a vacuum to a corner of a book that forms part of the spine of the book enables the book to be lifted off the ramp onto a tray in a known orientation.
A domestic vacuum cleaner id more than capable of lifting a book by a corner of the spine as long as it is placed accurately:
We do not need to lift the book clear of the deck, we just need to lift it enough so that it can slide easily over other books while it is moved to the clipping station and placed there in a known orientation as show in this movie
At this point the book can be examined, cleaned, checked etc. then maneuvered into a steel clip.
Once in a steel clip the book is easy to manipulate using an electromagnet if it is a "buy" else dropped in the recycling bin. "Buys" are placed in the kitting area so that they can be used to replace books picked for mailing. Once a jacketed book has been placed in a tray the book can be safely stored in the storage area from whence it can be picked out as needed in the future.
Here are the key ideas that this design relies on:
There is a strong case to be made for putting the book into some kind of jacket, namely: mechanical manipulators are not as sensitive as human hands and so are likely to subject the book to greater forces when manipulating the book leading to the possibility of damage.
Placing the book in a jacket has the benefit that the book cannot fly open when being manipulated or transferred. While it is easy for a human to see and rectify this condition it is much harder for a machine to do this. But even though a human can rectofy this situation, it is still a waste of valauble time for them to engage in this pointless activity.
A number of different jacketting systems were considered:
Three dimensional drawing: Book Clip.
At the moment using a steel jacket appears to offer the best combination of cost and reliability and so is the solution being most actively investigated.
Humans are capable of removing books placed in a book case albeit at the risk of damaged fingers and skin, bumped heads, bashed knees and wasted space. Trying to get a machine to replicate this coordination of vision and mechanical actions is difficult.
Instead it is proposed to stand books in staggered lines with the books so arranged that there is air space around the outside of the clip around the book that can be entered by a mechanical picker with merely centimeter positional accuracy at a slight loss of packing density.
Vertical book cases are hardly satisfactory for humans as they must reach up and down at awkward heights to get books from the bottom or the top. But for humans, horizontal book cases are not viable due to a lack of the necessary dorsal muscles..
From an automation point of view: vertical book cases require 5 times as much construction material to give them the same moment of inertial as a horizontal book case being tensioned with a spreader bar and are all too likely to drop books when in motion. Picking from and listing to a vertical book case is difficult because gravity frustrates rather than assists these actions.
Horizontal book cases are easy to transport, occupy little head room when being transported and can be constructed from 5 times less material than vertical book cases because they can be pretensioned using a spreader bar. Automated picking and listing is assisted by gravity which is now aligned with the direction of motion used in these actions rather transverse to it.
Vacuum assisted corner grabbing makes it possible to pick up individual books dumped out en-masse from a Gaylord when the books are lying at random angles as we can always be certain that at least one corner will be uppermost and thus available for grabbing.
A plausible corner grabber has been designed in three dimensions and sent for three dimensional printing to test this idea in more detail.
Here is a movie of the corner grabber being printed
Sorting books by size allows similar size books to be stored close together in a structure designed for books of that size to enable greater packing density than would be possible if the structure had to accommodate books of any size. Fortunately most books are sized using the The Golden Section and cluster around a small number of average sizes. It is entirely possible that the existing manual system will have to be retained for books with extremal dimensions.
Fortunately sorting books by size is not difficult using a corner grabber and a three dimensional camera.
This design has numerous advantages:
The cost of the steel used to operate on 100 tons of books can be estimated heuristically at 10% or 10 tons. Bulk steel products cost around $1K per ton or $1 per kilogram. Finished steel products such as book clips cost $10 per kilogram.
The major cost of this project is located in the labor required to design it. We can either hire an expensive engineer to produce the system once using a waterfall development methodology as if we were programming in Java or we can use an agile development methodology as we do with Perl by applying low cost labor to steel to implement a number of prototypes that can be iterated quickly and cheaply to find the optimal design.
A design considered optimal can then be outsourced for construction in bulk to either Mexico or Made In China, the latter in particular having shown great interest in securing this kind of work.
We can build this system incrementally using an agile development methodology.
The smallest component we could build first is the corner grabber illustrated above.
The next smallest component would be the steel jacket used to protect each book.
From there we can progress to a minimal kitting crane followed by a full size one.
Once relationships with suppliers have been established and some capability jdeveloped in basic steel work we can contemplate larger components that will allow us to gradually replace the existing manual wooden system with an automated steel one.
The clips used to protect and manipulate book are made from spring steel welded to a U channel. The clip can easily be placed using the device pictured below:
Clips, recovered from the mailing and purging areas slide along a plastic monorail to the clipping station. The clip at the bitter end is positioned by the blue electromagnet. A book is dragged into the clipping station by a corner grabber suspended from an overhead two girder gantry crane. Once in the clipping station the book is positioned by pneumatic rams and its cover is held down in place to prevent buckling when the clip is applied. A pneumatic ram pushes the next clip onto the book rather in the same way that a staple gun pushes a staple into paper. The book is thus clipped by the face opposing the spine making it easy to pick the book up by its spine using a side grabber which rotates the book into the preferred vertical position used for storage and kitting.
Three dimensional drawing of the: Book clipping Station
Experiments using curved steel kitchen utensils (forks) show that curved steel slides easily over a typical book cover.
Books that are mailed or purged will have to be declipped. The blue
electro-magnet holds the clip in place while the books is moved by a grab and
placed in a mailing sack. The electromagnet holding the clip is then rotated
and the electromagnet released so that the clip falls out onto the grey
monorail below which will transport the clip back to the clipping station.
Three dimensional drawing: Moving clips back from the mailing area to the jacketting area
The clips recovered from books that have been mailed or purged are returned
to the jacketting area by sliding them along a plastic
monorail. The motion of the clips can be assisted by applying a rotating
arm made of a similar material to push them along a guide rail.
Three dimensional drawing: Moving clips back from the mailing area to the jacketting area The advantages of plastic rails:
Books are pulled out of or placed into the kitting area or storage trays using the Book Puller.
Three dimensional drawing: Book Puller
The book puller is positioned by a scissor jack driven by a worm screw. The design of the clip attached to the book requires only centimeter accuracy to position a book in the kitting area or storage trays, yet a worm screw (unleveraged) can provide 500 times that accuracy at 20cm/s. We do need to position over distances of several meters which would be difficult to do with an unleveraged workscrew but is feasible with a 10 level scissor gate driven by such a worm screw.
The book is lowered (or raised) using two pneumatic pistons. The pistons
grip the book along its spine using a vacuum powered spine grabber. Once the
book has been lifted into the book puller a small gate driven by a stepper
motor closes over the slot through which the book entered the puller to prevent
the book from falling out in the event that vacuum is lost during transit.
Storing books spine up allows a bar code on the spine of the book to be read to confirm the identity of the book stored at that location.
The book puller is mounted on trolleys which run along ibeam(s) scaffolded over the kitting and jacketting areas. The book puller can be positioned in two dimensions using two scissor gates - although only one has been shown in the drawing for the purposes of clarity.
The actual position of the book puller will be measured by a laser
range finder which is accurate to about 3mm: more than enough accuracy to
position the 1cm pyramid at the base of the book clip in the corresponding socket in the tray below.
The laser range finder coordinates for each slot in each tray can be found by shining a strong light under the tray in an otherwise dark room - it will then be easy to center the book puller above each socket in each tray using a light meter and record the coordinates accurately so that the location of each slot can be located subsequently by laser range finder alone without having to locate each socket a new which will save time placing and retrieving books.
The coefficient of thermal expansion of steel is 11e-6 per degree centigrade leading to a change in size of a 10m steel beam experiencing a temperature change of 20C will give rise to a thermal expansion of 2mm which is well within the desired accuracy of 1 cm for positioning books.
Trays holding books are made of square steel tubing with pyramid slots
(yellow) spot welded to their sides. The pyramid on each book clip fits
securely into a pyramid slot. The shape of the pyramid allows the clip to be
placed reliably with just centimeter accuracy.
Three dimensional view of books standing in a tray
The pyramid and the corresponding slot is easy to make by mould casting at $10 per kilogram in bulk. The steel tubes to which the pyramid slots are welded area cost $1K per ton in bulk.
The positioning of the pyramid slots on the square steel tubes only needs to be done with millimeter accuracy or so as we can measure their positions photo electronically then record their actual coordinates for later use.
One proposed solution for separating books dumped out of a Gaylord is to place them on an upward sloping conveyor belt covered with grippy plastic. As the books go up hill any upper books not in direct contact with the conveyor belt slide off any lower books until they settle directly onto the conveyor.
Books coming off the hill climb will need to be oriented in a known way which might require corner grabbing to ensure that the book is correctly positioned in the clipping station. Once corner grabbing is in play we can probably dispense with the hill climb as the separation of books can also be done by corner grabbing once they have been spread out by vibrating them down a ramp which will also be necessary with a hill climb because otherwise the books at the bottom of the dump out pile might get damahed betwen the force applied by the weight of the books above them and the action of the conveyor belt.
There is also the question of whether the grippy plastic can stay grippy enough to be useful after having several tons of books dumped onto it.
Books are poured out of a Gaylord into the large end of a sloping semi-cone which is rocked (and possibly vibrated) so that the books gradually separate into a line of books aligned with their longest axis parallel to that of the semi-cone. The semi-cone is perhaps 5 meters long and 2 meters wide at the wide, high end before narrowing down to perhaps 40 cm at the low, narrow end.
The length and motion of the semi-cone provide space and time for books to
spread out enough that they can be dropped one by one on to the conveyor belt
beneath the narrow low end of the semi-cone.
Three dimensional drawing: Book Sorter
At the low end of the semi-cone the books drop out onto a conveyor belt in front of an array of sized pushers. We can measure the size of each book on the conveyor belt using a bright light placed under the conveyor belt to cast a shadow representing the size of the book onto an overhead camera. When the book passes in front of an appropriately sized pusher, the pusher pushes an alignment rectangle forward to align the book and slide the book off the conveyor belt onto a slide that takes the book to a clipping station capable of clipping books of that size. The clipped book is then moved to the kitting area for loading into a storage tray that can accept books of that size.
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