Planning a cell for a product, quality control, scheduling
In the second half of this article of designing a manufacturing cell for a job shop, we’ll review how to produce cell for a specific product, how to build QC into a cell and the importance of proper scheduling.
Fab Shop: What cells do you have?
DeMoura: We have a flexible manufacturing system (FMS). We also have a flexible manufacturing cell (FMC). The FMS is comprised of three machines surrounding a material storage and retrieval tower system. The FMC is designed to process flat-cut parts using punching, laser cutting and press brakes. It has a TRUMPF TruMatic 5000R punch press that is fully automated with a Sheet Master Material Handling System that can move material to and from the punch. We also have a TRUMPF 6000 laser/punch combination and a TRUMPF Trulaser 3050 laser that are both tied to the tower.
We have a station at the tower that outputs to a machining, marking and bending area. Then on the tail end of the tower is where the raw material is delivered and removed. Our cell is very scalable. I can attach another machine to it. I can also expand it to attach more machines to it, or I can extend the tracks from the tower out to other equipment.
Another cell we have in our job shop consists of two flatbed lasers, a punch press, finishing machines, forming machines, fastener insertion machines along with the processes of welding, marking, finishing and shipping designed along a linear circular line.
It’s designed to do a mix of fabricated products of non-ferrous materials. There are size limits for the cell along with the types of processes that are offered. For instance if a part needs painting we have it to send it out.
Fab Shop: How does a job flow through your cell?
DeMoura: My value stream has me look at the mix of work that I do, and I’m speaking from a job shop standpoint. I will look at this mix and try the best that I can to categorize these jobs and customers into different value streams. I will look at all these value streams and compare them to see which ones I might have overlooked. Once I’ve done all this, I can route my jobs into these value stream manufacturing cells.
Fab Shop: Can you give me an example of this?
DeMoura: Let’s take an electrical enclosure for example. We take flat sheet, process it and end up with an enclosure. The steps that these enclosures take generally are the same, but sometimes there might be an added step where fasteners are installed or some etching is done, but generally they need cutting or punching, bending, welding, finishing and shipping. I also might be doing enclosures of varying shapes, sizes and material types. I might do stainless steel ones, aluminum ones and steel ones, but they all go through these same processes. Therefore, I create a cell that allows this type of work to flow as efficiently as possible. So the cell can handle a product mix, but it’s not designed for a specific product.
Fab Shop: How would you design a cell for these enclosures?
DeMoura: Our production equipment for doing these electrical enclosures uses a straight line flow with machines on both sides. We have our FMC laser with our material storage on one end and finished goods on the other end. Parts are moved through in a linear fashion for the most part. While the laser is running, the operator is taking cut parts and running them through a wide-belt deburring machine, then to a press brake that is within two steps of the deburring machine for bending. Then our welding stations are within five to 10 steps from the bending operation. Our finishing operation is within 10 to 20 steps away from that and beyond this would be the fastener input and assembly area along with inspection and shipping.
Fab Shop: How would scheduling work?
DeMoura: The next thing you have to consider is scheduling that is an important key to producing parts for cellular manufacturing. Let’s say a new customer comes in and wants an enclosure in one week. And this enclosure fits value-stream A perfectly. However, value-stream A is booked. If I put this enclosure into my value-stream A’s flow, it will cause delivery problems for the work that is moving through it.
So I look at value-stream B. It’s not the best choice for this job, but I can get it out on time. Value-stream B might take longer, because the laser is slower, or we have older PEM-fastener machines. So the job might spend more time and labor through this value stream, but it has operators and equipment with open time. Therefore, I will use value-stream B instead of A to make the delivery time. This also allows us to have flexibility between our value streams.
Fab Shop: Can you mix and match products using a cell?
DeMoura: There’s all sorts of ways to mix and match products through cellular manufacturing. For lasers and punches there are many parts that we call process and palletize. Generally speaking these are parts that are flat and profile cut. With a laser I get lots of work that I have a cell designated for that is just for flat parts. These flat parts might include thick steel, thin steel and everything in between. However, our company chooses to separate ferrous and nonferrous steel cutting.
Therefore I can use my FMC with a laser that has a 5 ft. by 10 ft. bed. As long as the part fits on this bed, I can cut it, no matter if it’s one or 1000 parts. This cell has a fully automated material storage and retrieval system. It brings out the raw material, processes the parts, brings away the finished parts, and takes away the skeleton or the dropped material and then brings up the finished part to its next step, which in this case, would be palletizing and shipping.
I can take this fully automated cell and create a production plan for the coming week. The plan would cover work such as customer A needs one part cut out of 0.25 in. steel. Customer B needs 15 parts out of 0.25 in. steel, while customer C needs 120 parts out of 0.25 in. steel. I will run this through our ERP software, look at the scheduling, and tell the program to find me everything that needs 0.25 in. steel cut, using the same grade of material and due within a specified time range. The program will find these jobs, and I will dynamically post them to a laser machine. I will nest these jobs as efficiently as I can, and then through the software or barcoding, I will know where each part goes.
To take this another step further, let’s take customers A, B and C again, but this time we’re looking at four different types of material. I can’t produce a full sheet nest on any of the material. However, I’m still able to bring a sheet to my machine, cut the part, remove the part, send the remainder of the sheet back into my storage and retrieval system and bring up the next job and the next material all fully automated. So while I’m cutting a job, my storage and retrieval system is queuing up the next material. However, the jobs are getting done automatically, but not necessarily in the most efficient manner, because of the way the parts are nested and handled.
Obviously these jobs cost me more than if I could dynamically nest them and reduce my material handling and material quantity. This whole scenario cycles all the way back to the front end, and what I call the central nervous system or the organizational intelligence center.
Fab Shop: Explain organizational intelligence and intellectual capital.
DeMoura: Every organization has intellectual capital. This would be what each of us offers as far as our intelligence and experience is concerned for processing work.
By using our intellectual capital, we use this information to look at how jobs are being taken in based on all the attributes that they must be processed through such as: Will I be able to nest these parts dynamically or not? Therefore the knowledge worker is sitting at their desk and a customer walks in and says, “I only need one piece of 0.25 in. steel cut to this geometry.” This knowledge worker knows I have a blank spot on my schedule for next week that will work for this part. And can accept the job and make money doing it.
Now the dynamics of how you accept a job, when it gets done, and how it’s scheduled, all play into these factors, and they become much more contingent on your use of ERP software. Then they must be coupled with your organizational intelligence to be competitive. It requires the central nervous system personnel to be very in tune with the organization’s heartbeat.
Fab Shop: Is their software available that will help with all this?
DeMoura: Yes, absolutely, unfortunately a total solution is very hard to find in a software package I’ve found. Although software companies claim that they do have the perfect solution.
eFab Shop: When you’re creating a cell especially for a job shop are you looking at primarily what you have available for machinery, or is it a matter of being customer driven? For instance if you have a plasma cutting system, but not a laser, and someone needs a laser cut part, would you take the job on or send it out?
DeMoura: Job shops will have to look at what equipment they have, but they should also have a keen eye on what new equipment is available, because a particular part might justify purchasing equipment (given the volume and profit margin, etc.). For instance, if we put a new laser inline with our other one, the throughput is going to be unbelievable. This would allow me to justify the expense.
For instance, if you walk into a shop, and see that the lasers are running at over 90-percent capacity with most of the work laser cut, formed and welded, and the shop has mountains of parts piling up in front of the press brake, because there’s only one, the shop could justify additional press brakes if they have long-term contracts for using their lasers at 90-percent capacity.
Fab Shop: Does it make sense to have quality control checks within the cell?
DeMoura: Absolutely yes, and no. Quality has to be built into the process during the value being added. But I also feel that a company shouldn’t have a quality department, quality inspector or a quality assurance department. Basically in today’s manufacturing world whether you are an OEM or a job shop, your quality must be introduced where the value is added to the part. This would mean that every single operator who touches the part looks at its quality and must have the knowledge to make sure it’s meeting its specifications.
Cellular manufacturing can help a company become more productive, even if it’s as simple as making sure all the equipment that is most often used is within close proximity to save on operator and part travel.