Showing posts with label jobshopschedulingarticles. Show all posts
Showing posts with label jobshopschedulingarticles. Show all posts
Friday, June 2, 2017
Dr Lisa and Theory of Constraints featured in Wire Forming Technology International
Dr Lisa was featured in the Fall 2011 Wire Forming Technology International magazine with an article titled: Velocity Manufacturing: Stop focusing on efficiency and focus on velocity to reduce lead and queue times, and to increase lead-time predictability, on-time deliveries, quality and cash flow.
The article explains how highly custom job shops and machine shops can schedule and change their thinking using Goldratt's Theory of Constraints to get more jobs done faster with the same people and resources.
You can check it out here: WFTI Fall 2011 Velocity Manufacturing Article
Monday, May 29, 2017
Job Shop Scheduling Problems and Challenges
Job Shop Scheduling - High mix low volume job shops and machine shops can be quite a challenge to schedule.
Why? Here are just a few of the complex problems and challenges that plague the environment:
- Bottlenecks or constraints in job shops can move based on the volume and type of work.
- Work is diverse -- typically low volume high mix but a production job may be run on occasion, or prototypes will be in the mix.
- Jobs are typically made to order, but there are some job shops that may make a stock part, in addition to, custom parts.
- While producing new custom jobs are the norm, some job shops and machine shop will do repair work.
- Shops may do some amount of on-site new work or on-site repairs.
- Emergencies can be fairly common and can take a fair amount of capacity (2% to 30%) and be very disruptive.
- For some shops, customers call and make changes (frequently) - dates, quantity, or change their order completely.
- It's common place to have employees which are not cross trained at all or cross trained very little so the skill needed isn't always available.
- Shop employees don not always show up for work or on they may not show up on time.
- Set-up times can vary and some set-ups can take a substantial amount of time, while others take very little time. And, what's worse, is that both scenarios can occur in the same shop and at the same time.
- The high mix low volume nature of custom job shops leads to a mix of jobs with all different quoted leadtimes.
- The touch time to complete a job can also vary wildly. The same shop can have very short touch time jobs and at the same time have very long touch time jobs and everything in between.
- Due to precision and/or tolerances, certain jobs have to run on particular machines, making scheduling a problem.
- And if those weren't problem enough, some jobs have outside processing to be done and some don't. Some have more than one outside process to be and some have none.
- The leadtime on necessary outside processes will vary by the process and the vendors do not always deliver when they promised.
- Yield rates are not perfect -- they may not be 100% or quality issues can play a role depending on the precision and type of work.
And, regardless of all these problems that can occur in scheduling a job shop and often do, customers still want their job done on time.
Now you know why it's so difficult to schedule a custom job shop. It is the nature of the beast. There is a solution -- it is called the Velocity Scheduling System. It was developed for highly custom job shops and machine shops where these problems and Murphy not only exist, but thrive. Velocity Scheduling is NOT software but a visual scheduling system. It is a manual system that includes a visual planning board, as well as, a visual scheduling board. These boards are customized for your specific situation. Given all the complex challenges discussed above, you can imagine how important it is to customize any solution for your particular environment. To learn more, check out the ebook tab and the webinar tab. The ebook provides more information on the scheduling challenges and the traditional solutions while the 47 minute webinar provides the VSS solution. Best Wishes, Dr Lisa By Dr Lisa Lang This article is copyrighted by Science of Business, Inc. Visit our Re-post guidelines.Job Shop Scheduling Software
Job Shop Scheduling Software | Machine Shop Scheduling Software
I'm like you. I invested in job shop scheduling software (we used to own a job shop). Spent hours and hours getting it setup up only to spend more time continually
updating the schedule. Why does it seem that the moment I print the schedule it's out of date? And the software itself doesn't lead to an improvement, a little time savings but no real improvement.
Job Shop Scheduling Software - it's NOT working!
There's no question that there is an almost unlimited number of job shop scheduling problems and challenges. And the scheduling modules that are available don't seem to fully address these problems. To try and solve these problems and challenges, we tend to add more DETAIL. If what we're doing now is not working, we just need to work harder. Right? We spend more time updating the schedule. We add more information. We update more often. We invest in software or add a module to our ERP systems that provides a way to collect and analyze the data. But, adding more detail is not the answer. Here's an excerpt from a job shop scheduling software article on thefabricator.com.Sources concede that job shop scheduling is just too complex for software to do all the work. “There is always going to be a human element to the decision-making effort,” Lechleitner said. “I think any APS (Advanced Planning and Scheduling software), at its best, will probably get you about 80 percent there.” Liddell agreed. “The software can do 80 percent of the donkey work, which will let the scheduler do 20 percent of the fine-tuning. We’re not trying to create the perfect schedule. We’ve never seen it work.” “I have not seen any magical formula,” said Richard Henning, president, Henning Industrial Software, Hudson, Ohio. “You need to monitor the skills people have for specific operations, what machines people are assigned to work on. These are all complex relationships. You still need a human being to help you see the big picture.”And those guys are job shop scheduling software vendors. But in their defense software just can NOT take into account all the variability that job shops encounter. And yes I know there are some algorithms you can run (and rerun and rerun) that will balance your capacity. But again, it's a continual updating of the schedule. It really doesn't matter if you're running finite capacity scheduling, infinite capacity scheduling, foward scheduling, or backward scheduling -- it takes constant managing and updating. I'm not saying that you shouldn't invest in the an ERP package or even a APS package, just realize that if you just do what you're currently doing a little faster, it's likely that your productivity will not increase, your lead-time will not reduce, and your due date performance will not get better. And isn't that the point?
Job Shop Scheduling Software Solution
Velocity Scheduling System (VSS) is NOT software. It is a visual, manual scheduling system that will work with your existing ERP or no ERP. It is designed specifically for high mix low volume custom job shops and machine shops whose constraint can move week to week or even day to day and who suffer from a number of the job shop scheduling problems and challenges. VSS is implemented during a 14 week coaching program. Each shop is different and the system needs to be customized for your specific shop and challenges -- therefore coaching is extremely important and boxed solutions are not used. Results are realized typically in week 5 but it depends on how fast your team takes action. (more details and our guarantee below is a shorter summary) We need a list of your jobs including their due date, internal process time estimates, and outside process times (if any). And don't worry if your estimates are not accurate. That's to be expected in a custom job shop-- we don't need more detail! We're using the information to come up with a "priority release order". So as long as they are relative to each other, the order is close enough. By visually managing the jobs that are currently in process and on your visual scheduling board - Velocity Board, you eliminate the constant re-scheduling. And the Velocity Board is not like any scheduling board you've ever used. The details of how it works are proprietary, but you get all the specifics in the 14 week coaching program and more importantly we customize it for YOUR custom, complex shop. A good visual scheduling system will help you to see if you have any issues. Nothing can hide and nothing can fall through the cracks. If a problem arises, you see it and can deal with it. There's no rescheduling to do. There's no one walking around with a schedule in their back pocket -- it's a visual SYSTEM. Jobs that are not yet in process are on your To Be Released Board in "priority release order" so that you can visually manage your backlog. One thing we like to view visually on our TBR Board is the status of "full kit" on the jobs waiting for their turn to be released. Another component of Velocity Scheduling System is what we call "Detailed Planning". But detail in this case is much much less. This is where we come up with priority release order (this where we interface with your ERP or whatever you use) that we've already discussed and then we look to see if there are any issues with that release order. For example, if we release in that order might we encounter a constraint? If we release in that order are we likely to meet our due dates? We predict when each job will start and when it will be completed. We do NOT try to predict when each job will be on each machine. That level of detail is very likely to be wrong and cause massive re-scheduling. A macro view of starting and finishing is much more predictable. The order we implement is shown in the graphic below. But before we get to that we need to make sure that you shop is a good fit. So I recommend you watch the scheduling webinar which will provide more detail on Velocity Scheduling System. At the end of that webinar, I'll
explain how we can talk to determine if you shop is a good fit and what results are likely. And if I don't think it would work in your case or your results would not be big enough -- I'll let you know.
THE key measure in Velocity Scheduling System is productivity. The goal is to get more done with the SAME resources (the definition of productivity). And, if you ship more without increasing costs -- your lead-times reduce, your due date performance improves, and of course, you increase profits. All with less chaos and less re-scheduling.
Sincerely,
"Dr Lisa" Lang
P.S. Check out the solution to job shop scheduling software --> How to Get More Jobs Done Faster Webinar!
By Dr Lisa Lang
This article is copyrighted by Science of Business, Inc.
Visit our Re-post guidelines.
Sunday, May 28, 2017
FREE Special Report for Machine Shop Owners
Click the link below to download the free special report for machine shop and job shop owners titled: "The 9 Biggest Challenges to Scheduling YOUR Job Shop and Why Most Schedules are Dead on Arrival!" by Dr Lisa Lang.
https://www.VelocitySchedulingSystem.com/ebook/After you read this free special report, please CLICK on "COMMENTS"above and post your comments. I would love to know if you agree or disagree and your reasons!
Thursday, May 25, 2017
Drum Buffer Rope
Theory of Constraints Drum Buffer Rope
Drum Buffer Rope (DBR) was developed by Eliyahu M. Goldratt (Eli Goldratt), the father of Theory of Constraints. His book The Goal tells a story of a plant manager applying the drum buffer rope concepts.
The drum is the constraint.
The resource that is limiting your output. Most shops typically only have one constraint at any point in time, but the issue is that for many custom job shops and machine shops the constraint can move as the mix changes. A constraint is any resources that had demand greater than it's available capacity. Any time lost on the constraint is output lost by the entire system. Increasing output at the constraint, increases overall output. Improving non-constraints has no effect on overall output. This is why measuring utilization everywhere makes no sense. Trying to 100% utilize non-constraints just results in too much WIP and the many issue associated with that.The buffer is measured in time.
It's the amount of work expressed in time (like days worth) prior to the constraint. We control this amount of work with the rope. By having a buffer of work in front of the constraint, we can ensure the constraint does not run out of work. The constraint is the only place where 100% utilization is a good thing! The buffer's job is to absorb variability. In traditional Drum Buffer Rope there are 2 buffers - one for the constraint and a shipping buffer. The one before the constraints is there to protect the constraint and the shipping buffer protects the due date. Simplified Drum Buffer Rope just has a shipping buffer. Drum is the same. Any buffers are divided into 3 zones - red, yellow, green. If the buffer is red we find out why. The buffer is sized so that it turns red about 5% of the time. For continuous improvement we track the whys so that we can reduce or eliminate our biggest disruptions to flow. These improvements to flow lead to less variability and needing less buffer!The rope is how we control the release of new work.
The idea is that if the constraint sets the pace, the drum beat, for the entire operation, then we should only release work at the rate that the constraint can consume it. If we release work faster than the constraint can consume it, then WIP (work in process) piles up and bad things begin to happen. (See Little's Law.) That's a brief Theory of Constraints summary of Drum Buffer Rope. The real challenge is figuring out how to make it work in YOUR shop. The plant in The Goal is a machine shop. It's not the most complex of cases, but it is a machine shop.Theory of Constraints Goldratt
Velocity Scheduling System was developed for the tough cases:- For the custom job shops and machine shops that run high mix and low volume work or prototypes.
- For the shops where the constraint or bottleneck moves based on the mix of work.
- For the shops that may not run many jobs twice but can also have a production job to fit in with everything else.
- For the shops that do repairs (in house or on-site) or emergency work.
- For the shops that don't have perfect employee or vendor performance.
- For the shops who don't have perfectly cross trained employees, but have jobs that require a particular machine.
- For the shops that produce a wide range of custom parts or products that have a wide range of lead-times, set-up times and outside processes.
- For the shops that may not have 100% quality performance and or yields that are less than 100%.
- And, for the shops who have customers call and change quantities, dates or both.
This article is copyrighted by Science of Business, Inc.
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