Tracking each piece of material by marking it with a unique serial and barcode is vital for operating a system with a mix of automated and manual handling. The key design objectives and goals are as follows:
Assist the operators with loading and unloading by providing information about what to produce, what material is available, the status of all the in-process material, and load/unload instructions.
Increase quality by allow the inspection operator to learn the history of the exact piece of material under test (the pallet, machine, program, date and time, etc.).
Track unloaded material through manual processes such as final wash or any in-process work between automated machine cycles.
Properly fill workorders, ensuring that all produced material is assigned to a workorder and that enough material is produced to fill workorders on time.
Make it as easy as possible for the operators to keep the data in the computers matching the reality of the material on the shop floor.
When the data in the computers no longer matches the reality on the shop floor, provide an easy way of rectifying this situation by updating the data in the computers.
Provide long-term tracking and part identification for downstream customers.
The key challenge is in points 5 and 6; the system must make the normal, everyday operator tasks easy and straightforward but also be robust to the unknown.
Consider the following method of tracking material not using a computer. On a whiteboard, divide the whiteboard into regions for all the possible places that material could be, so a region for each pallet, a region for each in-process transfer stand, a region for material waiting to be inspected, a region for material waiting to be washed, a region for in-process queues and conveyors, a region for castings, a region for material sent out of the factory for external work, and so on. Any place that material could be has a corresponding region on the whiteboard.
Now for each piece of material, a new sticky note is used. The part name and serial is written on the sticky note and on the back is written a log of activity. At the start of the process, a new sticky note is created and placed on the whiteboard. As the process unfolds, the sticky note moves around on the whiteboard corresponding to the material moving around the factory floor.
For example, a part just completed process 1 and is waiting on pallet 6 at the load station to be unloaded into the transfer stand. The sticky note for the material is currently on the whiteboard in the region for pallet 6. As part of the unload operation, the sticky note is moved on the whiteboard from the pallet 6 region to the transfer-stand region. (Also, if any material is loaded, its corresponding sticky note is moved into the pallet 6 region.) The fact that there is a sticky note existing in the transfer stand position on the whiteboard signals to the operators that the pallet for the second operation should be brought to the load station. When the pallet for the second operation arrives and the material is loaded, the sticky note will then move from the whiteboard region for the transfer-stand to the region of the whiteboard for the pallet.
This whiteboard of sticky notes has several great features:
By centralizing all material on a single whiteboard, it is easy to visualize the entire process and make decisions about what actions to take (what material is available for loading, what material needs to be inspected, what material to wash and assign to a workorder, etc.).
Operators can at a glance determine if the whiteboard matches the reality on the factory floor. If there is a mismatch, the sticky notes can be moved so that the whiteboard matches reality.
Operators at a single station can focus only on a section of the whiteboard to carry out their tasks. For example, at the wash station, only the section of the whiteboard corresponding to the wash stand is relevant.
It is straightforward to accommodate all sorts of material tasks both inside and outside of automation. For example, if a part must be quarantined as potential scrap, its sticky note can be set on the side of the whiteboard. Once examined, if the part is determined to be scrap the sticky note can be thrown in the trash can. If the part needs some remachining, the sticky note can be added back onto the whiteboard once the remachining has completed and the part is ready for the remainder of the process.
By using a metaphor of physical sticky notes, the design provides an intuitive understanding for users. The design is motivated by Google's Material Design, whose founding idea is: "A material metaphor is the unifying theory of a rationalized space and a system of motion. The material is grounded in tactile reality, inspired by the study of paper and ink, yet technologically advanced and open to imagination and magic." In fact, we suggest that operator training start with actual physical sticky notes on a whiteboard before transitioning the training to the computers.
Of course, there is one main downside to using a physical whiteboard; it is tedious for the operators. This is solved by keeping the whiteboard and sticky notes in software and using software monitoring to automatically move around the sticky notes. We believe that when using automation and software as part of process control, you must always start with a design that could be done without software. This produces a design which does not force the process to conform to the software but allows the software to support the process. It also eases user understanding because it provides a straightforward metaphor for the user to understand how the software functions. The software should exist just to support the process by removing the tedious and error-prone tasks.
Software-Based Sticky Notes
The tactile metaphor of moving around sticky notes, with one sticky note per piece of material, is the basis for the FMS Insight Station Monitor page. See the screenshot above, which shows the whiteboard with regions for Raw Material, the two faces on Pallet 1, and Completed Material. Insight allows the operator to view a section of the virtual whiteboard of material sticky notes relevant to the current station, in this case the load station 1.
Insight monitors the machines and automation and moves around the material sticky notes on the virtual whiteboard as parts are loaded, unloaded, and machined. Also, by watching the virtual whiteboard, Insight can control the pallets. For example, Insight will prevent a pallet from arriving at the load station if the transfer stand queue virtual whiteboard region is empty.
Insight allows the operator to keep the virtual whiteboard in sync with the material on the factory floor. Operators can remove virtual material sticky notes from the whiteboard by clicking a button and add sticky notes by scanning a barcode or manually entering a serial. Each queue or conveyor or place where material is under manual control has a corresponding whiteboard region. By placing a computer or tablet at that place in the factory, the operator can at a glance see if the virtual whiteboard matches the reality on the factory floor, and if not simply edit the virtual whiteboard to match.
An Example Design
The virtual whiteboard implemented by FMS Insight is versatile and can adjust to a huge variety of processes with parts moving in and out of automation and manual handling.
For example, consider a process with two cells: a horizontal machining cell and a lathe cell. Parts are manually loaded and unloaded and transfer between cells via a conveyor. The conveyor between the cells will correspond to a region on the virtual whiteboard. Also, right next to the conveyor, there is a computer or mounted tablet with an attached barcode scanner. The computer uses FMS Insight to display the region of the whiteboard for the conveyor. As parts are unloaded from one cell, FMS Insight automatically moves the corresponding material sticky note from the pallet to the conveyor region. Similarly, FMS Insight is configured to monitor the virtual whiteboard region for the conveyor to know when to bring pallets to the load station to load material out of the conveyor.
During normal operation, the operator does not need to manually edit the virtual whiteboard. As parts are completed in one cell, their sticky notes are moved to the whiteboard region for the conveyor and when the material is loaded into the second cell the sticky notes are removed from the whiteboard region for the conveyor. The operator can at a glance see that the conveyor matches the virtual whiteboard by comparing the conveyor to the computer screen.
Now consider that some parts are removed from the conveyor temporarily. Perhaps the parts are inspected, a part needs some re-machining, or it must travel elsewhere in the factory for a specialized operation. When the material is removed from the conveyor, the operator can click a button in FMS Insight to remove the sticky note from the virtual whiteboard. FMS Insight will then prevent a pallet from arriving to load this missing material. The material eventually returns and when it does, the operator can scan the barcode on the part to add the corresponding virtual sticky note onto the whiteboard. FMS Insight will then activate the pallet to load this piece of material in the second cell.
Whiteboard tracking design
FMS Insight requires that you decide on a list of virtual whiteboard regions and how material will move between regions. The initial design is best done by using an actual whiteboard in a conference room with real sticky notes. Draw regions on the whiteboard, create some sample sticky notes, and step through the proposed process, moving the sticky notes around on the whiteboard. This helps design the whiteboard regions to configure in FMS Insight, but also highlights potential complicated material flow which you might consider changing the process.
At the load station, use a computer or mounted tablet running Insight. Insight will display the section of the virtual whiteboard for the pallet, plus the region for material being loaded and the region to which material is unloaded. Insight will determine based on the whiteboard which specific material to load and display it with its serial. The operator should then load the material with the specific serial requested by Insight. But, if the serial that Insight wants to load is unavailable, the operator can just edit the virtual whiteboard. Insight will automatically adjust with a new instruction for the operator. (Hopefully this doesn't happen and the virtual whiteboard is kept in sync, but if it does happen it is easy to correct.)
At any place where in-process material is queued outside of control of the automation, create a whiteboard region. This could be conveyors between cells or stands for holding parts between processes (e.g. large parts which have process 1 and process 2 on different pallets). At each location, dedicate a computer or mounted tablet with an attached barcode scanner to view and edit the whiteboard region. Insight can be configured to automatically move the virtual sticky notes during normal operations as parts are loaded and unloaded into these queues, but the operator can use the computer and scanner to adjust the whiteboard region as needed.
For in-process manual operations such as manual CMM stations or custom processes outside the automated cell, create two whiteboard regions. One region for the input to the process and one region for the output from the process. For example, at an in-process CMM stand, create a whiteboard region for the unloaded parts not yet measured. FMS Insight can then be configured to automatically move the material sticky note from the pallet to the inbound CMM region. The CMM stand then has a computer or mounted tablet showing Insight; the operator can then see the material not yet measured, perform the CMM measurement, and if successful, use FMS Insight to transfer the virtual sticky note from the inbound region to the outbound region. FMS Insight monitors the outbound region and will bring a pallet to the load station once the CMM has completed. Insight will also transfer the sticky note from the outbound region to the pallet as part of the load operation.
For raw material, Insight supports two options. Insight can just assume raw material is always available in which case Insight will create a new virtual sticky note during the initial loading. In this design, the first time a sticky note appears is on the pallet. Alternatively, Insight can be configured to draw initial material from a virtual whiteboard region. In this case, when material arrives, an operator must scan or add the material into the initial whiteboard region. Once added, FMS Insight will then activate the pallet to load this material.
For completed material, Insight automatically adds the sticky notes to regions for signaled inspections and final wash. Technically, these could just be configured virtual whiteboard regions similar to in-process queues or operations, but inspections and final wash are so common that Insight automatically has special regions for them. Each configured inspection type has two regions: one for completed parts signaled for inspection but not yet inspected and one region for completed inspection. For final wash, Insight also has two regions: one for not yet washed parts and one for washed parts. A computer mounted at the inspection and wash stations can show Insight and allow the operator to move the virtual sticky note as the inspection or final wash is completed.