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Process Improvement Project
As a secondary deliverable for our MSD team, the process used at the ARCWorks facility within the straw cutting cell needs to be improved. Currently the cell involves,
- 1.The cutting of the plastic straw
- 2.The manual placement of the peg into the enclosure using a T shaped hand tool or a simple hand press. The hand tool presents ergonomic concerns and is an added unnecessary step.
- 3. The final securing of the peg into the Nozzle enclosure is completed on a automated devise which a prior MSD Team completed (P08008). This provides a significant amount of compression force but needs the pegs to be partially inserted in order to operate effectively.
- 4. The Straw and Nozzle assembly are then combined on another automated devise, and the process is complete.
Substantial improvement in the work flow will need to be made to increase productivity within the cell. A basic Value stream map will be created which will help in understanding where the process is most deficient and where there is the most opportunity for improvement.
From first glance it is obvious that eliminating the T shaped hand tool process would be ideal because currently there is double handling occurring which is non-value added. This could be accomplished by a modification of the Current Devise which secures the pegs into the enclosure. Analysis will need to take place to come up with a viable solution.
The Vast amounts of stored inventory will be another challenge. In the current state, straws are produced in mass quantities in anticipation of a large order. This represents a fairly large Push system. Ideally a Pull system should be used but due to the constraints at ARCWorks this might not be possible. Altering the current Pull system might be a more reachable goal especially since the customer seems to not have any concern about the build up of mass amounts of inventory. The components which are being produced are low cost and small, this combined with the fact that ARCWorks enjoys a Large Facility where space is not an issue, might hamper the push for change.
- Current State Value Stream Map
Current State Value Stream Basic map
Process Capability
Currently at ArcWorks a very tight tolerance of +/- .02'' is placed on the cut straws. To determine if the current process was capable of reaching these specs a process capability analysis was performed.
A sample of 200 straws from the 4.33in length cut straw stock was obtained and measured using a set of calipers. After inputting all of the values into excel it was concluded that the Cp for the process was .508 and the Cpk for the process was .486. These values are not ideal for a process and shows that the process is not capable of producing straws reliable within the specifications. A Cpk value of 2.0 would indicate a process is capable of performing to 6 sigma standards. This would mean that no data points fall outside of +/- 3 standard deviations from the mean. The current process has numerous points outside of this range so it is clear to see that the Process is not capable to the desired specifications for length.
However the specs are so unnecessarily tight that the function of the straws within the wash bottle are not compromised. The only way a straw would hinder the function would be if it was too long and actually did not allow the bottle cap to close properly. The straw can not be too short either because if the liquid in the wash bottle is too low a straw might not be able to reach this level.
For our machine we should aim to improve the current capability of the process. Even though ArcWorks is not currently capable of meeting its specs to 6 sigma standards. The straws lengths are fairly reliable and close to the specs. The few outliers within the sample of 200 show that the process is not capable to the specification. However the question must be asked why are the specifications so tight? Is it really necessary to meet this level of compliance for the application which the straws are used in
Histogram 4.33
- Possible Bimodal Distribution. Lengths are either above or below the spec
Run chart 4.33
After discussions with ArcWorks it was discovered that their specification was actually .2'' instead of .02. This creates a huge difference in their calculated capability. They go from having a capability of 0.5 Cpk to 5.0Cpk. It is now not as crucial to reach the outlined Cpk value because the having a cpk value slightly lower will still result in the process being more than capable.
Process Improvement Suggestions for Change
Waste Identified
• Efficiency Loss at Automated Machine Possible Solution-Implementation of a cartridge system
Due to need for straws to be inserted into the 10 holes manually the efficiency which is gained with having the ability to cut these straws at one time is wasted. The idea of implementing a Hooper system was discussed but for the scope of our project this will not be possible. ArcWorks has mentioned that adding an additional process step would be acceptable in this instance. Typically adding a process steps along with operators would not be ideal but in this case it is acceptable because it would give another opportunity for workers at ArcWorks to perform a new, simple task. *This task of loading will simply be transferred to two operators working at a separate station located in close proximity to the cutting device. Multiple hand cartridge loading devices will be pre-loaded at a station next to the cutting device which will utilize two operators. The simple pre-loaded cartridge will then be passed onto the cutting device station where the operator will load the straws and pass back the cartridge to be pre–loading area. Multiple (3-6) cartridges will need to be utilized at this station so that the loading station can stay ahead of the cutting device. If the cutting device gets ahead of the loading task the cutting operator can still load the catting device by hand to allow for more pre-loaded cartridges to be prepared. The efficiency of the system will depend the capabilities of individual operators and how fast they will be able to perform certain tasks. With two operators allocated to loading cartridges. The cutting operation is estimated to take up around half the time that the pre loading operation will take so for the process to not fall continuously behind the loading process must not take more than double the time which the cutting process will take. If the cutting operation took 30 sec the loading operation will need to take less than 60sec, since two operators will be used. It Currently will determine if the cutting operation will get ahead of the loading task.
- Straws which are not cut all the way through
- This causes the operator to be less efficient because time is wasted manually removing the scrap material which is still attached to the blade.
• Current automated machine is not capable of meeting the +/- .0’’2 tolerance Possible Solutions- Our proposed machine will improve on the capability to between the given tolerances of +/- .02’’. A new more realistic tolerance which actual reflects the true requirements of the assembly will generate a more acceptable capability value. *The current process is only out of control because the desired tolerances are so tight. For the desired functionality of the straw the dimension only actual has to fit within the bottle enclosure. This is fairly easy to accommodate without meeting the +/- .02’’ tolerance. * A capability analysis was completed on the current process and the Cpk was found to be around .50. Ideally for a 6 sigma process this figure should be equal to 2, and an acceptable process would be greater than 1.00. Our proposed machine should provide a capability which is greater than the current process.
• Inefficient Warehouse System Possible Solutions- Implementing a labeling system which will allow for a more reliable retrieval process.
*Currently the Warehouse locations are only known by 3 individuals. To improve the situation a Labeling/ Number system should be implemented within the warehouse bays. This might be out of the scope of our project but at least for our supplies (mainly the raw material straws and cut straws) designated areas should be identified. This could be accomplished by a simple overhead visual indication where certain boxes of certain straws need to be located. A color code could be used to represent different length straws. This also could be advantageous to determine if a box is comprised of raw material or cut straws. This system could also aid in notifying the straw cutting operation when production is needed. If a designated location is not occupied by a box of straws this would indicate that it needs to be filled. If a warehouse worker recognizes this void a physical Kanban card could be passed along to the production area to complete the straws necessary to fill the unoccupied area.
• Double handling of assemblies during the Pegging process. Possible Solutions- Eliminate the need for the manual insertion of the pegs by the operators. Make adjustments to current automated machine to allow for the process to be completed entirely with no manual feeding required before hand.
• Large Inventory Stock *Solutions-Inventory is currently at 50,000 straws per length. With the addition of the added automatic straw cutter this inventory value will be able to be reduced freeing up more space within the warehouse.• Large Batch Sizes Possible Solutions-Currently very large batch sizes are used to complete the assembly process. Change process to be closer to a single piece flow. This might not be possible to the constraints within the system.
Current Layout
Shows flow of material throughout current process
Current Layout
Possible Future Layout
Shows flow of material through future process
Future Layout
Layout of Storage
PROCESS IMPROVEMENT
- Efficiency and Throughput
The process currently in place at ArcWorks provided many areas for improvement opportunities. Many of the 7 forms of waste (transportation, inventory, motion, waiting, overproduction, over processing, and defects were identified. Much of this waste can be eliminated through the implementation of the new proposed Straw Cutting Device. Currently, operators working on the automated machine at ArcWorks are capable of cutting around 700 straws/ hr. on an average day. This is assuming that with one actuation, 10 straws will be cut. With the new proposed machine, 12 straws could be cut in one actuation. With this added capability, along with a reduced load time, efficiency should increase to around 1000 straws/ hr. ArcWorks plans on using both machines in conjunction with each other in the future. This would mean that the throughput potential from using the two separate machines would equal to more than double the current production capability.
Production Rate Breakdown
A major loss of efficiency is seen when the operator chooses to actuate the system multiple times to make sure all of the straws have been cut. With the new design, the need to actuate the system multiple times should be eliminated. The operators who would be assigned to this station would be highly functional individuals, but it still might be difficult to retrain them to understand that it is no longer needed to actuate the system multiple times.
- Inventory Reduction
With the predicted increase in production and throughput, the need for excessive inventory will be reduced. Currently 50,000 straws / length are required to be on hand in the warehouse. A box is comprised of 5,000 straws. Ten boxes per length is a significant amount of space required in inventory. Due to the fact that there are no forecasts or ERP systems in place (For when the inventory falls below this level) a production signal is sent to the floor to produce more straws of the designated length. With the added capability to produce more straws in a shorter amount of time, the requirements for 50,000 straws on hand will no longer be necessary. A figure closer to 20,000 straws or 4 boxes / length will be more than adequate for the new process.
- Warehouse Management
The reduction of inventory will improve the process at ArcWorks, but, in order for this change to be fully effective, the warehouse needs to have some sort of order to it. Currently there is no warehouse management system and only a few warehouse workers actually know the exact location of particular items within storage. The implementation of a “Warehouse Management System” (WMS) had been discussed in the past, but had never been implemented. A system to track the location of specific items would help the overall efficiency in the system. This implementation is out of the range of our project, but the beginning stages of a WMS could be implemented. An initial step could include labeling designated areas for the specified straw length boxes instead of having the randomized storage.
- Layout Considerations:
In the beginning the layout and flow of material within the assembly area was observed (Figure 14). It was clear that a significant amount of material was traveling back and forth between the storage warehouse and the assembly floor. A U-shaped cellular layout would improve on the material flow within the closure assembly process.
Cellular U-Shape layout Possibility
This layout was designed to be relocated anywhere within the facility. This is important because our contacts at ArcWorks informed us that they were going to receiving some new products. These would require different machinery and layout of the area in which the current straw cutting and closure assembly would take place.
- Process Capability
- New Razor Blade Utilization in Old Machine
An area for improvement which was not originally identified, was the implementation of the new razor blade option into the old automated cutting machine. The size of the blade is roughly the same as the current standard two-blade mock up. The blade mount on the current machine utilizes a recessed area for the blade to sit that is 4 inches in length. Our new Razor blade option is 4 ½ inches long, so either the blade mount could be modified to accept the new blade, or another shorter blade could be acquired to fit within the current mount.
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- Node updated 2011-05-16 12:12 by mme4801