How do you transition to Lean when you’re running a job shop?
It’s not the same as repetitive manufacturing!
While the philosophy of “lean” is universally applicable, the techniques and emphasis will vary from industry to industry. A job shop has its own set of uniqueness’s. We’ll broadly address some of them here. We welcome your comments and additions.
Use flow cell equipment arrangement when / where applicable. Move partial lots between operations where possible.
In most job shops there is a portion of the product line that allows for the use of “Group Technology” and “Cellular Production.” Products are grouped into “families” based on the similarity of their processing steps / production machines (Group Technology).
Cellular manufacturing means to physically identify and relocate this equipment into a “cell” such that this family of parts can easily flow from machine to machine: i.e. create a factory within a factory.
The big gains come not from the reduction of travel distance as much as the reduction of set-up times (the products have similar physical attributes and therefore generally reduce the set-up effort), and from the ability, at times, to “partial” the lot and move items to the next sequential operation before the entire lot is completed on the prior operation.
There are obvious significant advantages to cellular operations: Less inventory, shorter lead times, reduced material handling (and the associated damage), reduced set-up effort which can allow for smaller batch sizes, etc. There can also be savings in the non-value adding administrative activities such as job tracking and labor collection: The cell is treated as an individual work center. Creating cellular operations is a significant part of our “Just Do It” approach.
Not all products will lend themselves to cellular manufacturing. And, often, the typical routing will involve one or more “monuments,” i.e. one-of-a-kind equipment that can not readily be replicated or moved. This generally relegates the cells to contain only a portion of the entire routing.
When this is the case, our approach is similar to that of any other type of manufacturing: Cut the lead times, Cut the lot sizes, and Demand on-time completions.
Cutting the lead times is typically done via the scheduling system. Cutting the lot sizes will obviously drive a concerted effort to reduce set-up costs. And the “on-time all the time” initiative will require several parallel initiatives: refined shop loading, and the “rubber factory”.
Some job shops have scheduling systems that allow for easy “what if” analysis. The scheduler loads in each new order, and the system shows the new load profile for the impacted pieces of equipment. The scheduler then has the ability to move operations, as required, to provide a “reasonable” schedule. Note that the system will also reschedule all downstream operations when an upstream operation is moved.
The illustration above shows a typical load profile for a category of interchangeable equipment. The scheduler uses this information to assure valid order promising and to generate an achievable schedule for the people in operations. This is a crucial first step in making a job shop function reliably, minimize the cost of expediting, and reduce the need for a “daily production meeting.” There is not much reason for a daily meeting if the schedules are reasonable, and operations consistently and reliably accomplishes them.
Where such a system capability is not available, we have worked with clients to create a more manual, but serviceable, system to take its stead.
The “Rubber Factory” concept provides for capacity flexibility. This is an entire subject in itself. Suffice it to say that it involves more flexible work hours, extensive cross training, etc. The rubber factory provides for considerably more ease in scheduling: producing what the customer wants, when he/she wants it.
We now have a “doable” schedule, utilizing reduced lead times, and hopefully reduced lot sizes as well. The “On-Time” requirement is, in most shops, a matter of management deciding to do it!
We use a simple mantra: “The day ends when the schedule is done. NOT the other way around.” Rocks will be exposed during this process. And the resolution of those rocks will improve customer service and eliminate waste.
It is worth noting that cutting lead times and lot sizes WILL likely increase accounting production costs, at least in the short term. However, it will generally have a positive impact on cash flow, via inventory reduction, both in WIP and in finished goods. We used the term “accounting costs” because they typically exlude the hidden overhead and indirect costs that long lead times and large lot sizes necessitate. We advocate that this cash windfall caused by inventory reduction be used to overcome any cost inhibitors: set-up costs, scheduling capabilities, cross training, et al.
Many job shops have issues with fully loaded equipment. If you are a 24 x 7 operation, you may be able to pay for needed additional capacity via permanent inventory reduction. If you are not 24 x 7, you might gain capacity and flexibility by increasing your “available hours”.
This has been, by design, a brief overview of job shop lean. There is a wealth of additional circumstantial information. If you would like to discuss your specifics, write or call. There’s no charge, and we’ll try to be helpful.
Also, if you have comments, send them along. We’d love to hear from you.
The Hands-On Group