Visual Management

Posted on October 25, 2015 by george

Our eyes are heavily linked to the thought
processes of our brains

Seeing is believing. We rely heavily on sight to guide our actions. Accordingly, seeing something for ourselves is a powerful way of having us believe it. When we plan systems to control manufacturing activity, the ones that use things that we can see to guide our decisions work the best. This week I was attempting to solve an accuracy deficiency on a high RPM vertical CNC machining center. This machine is used to cut graphite to make EDM electrodes for mold making. The CAD/CAM cutter path software guided shapes, cut using diamond tipped tools, need to be accurate to better than 0.001 inch (0.04mm) on all surfaces. This shape accuracy is needed to obtain the taper needed to eject parts from the mold. 0.001 inch is a tiny distance that is difficult to see and measure. A experimental method that I call a 6 time repeat study is very effective adding visibility to the task. In this case, we machined a test shape using the CNC. After the graphite was cut we used a yellow paint marker to color all surfaces that were machined. The exact same cutting program was run again. Low and behold, one face showed uncut and completely yellow.

A painted test block shows the backlash in the X CNC axis

My machinist could not understand why I called the test a 6 time repeat study. We had only run the program twice. I indicated that once the machine flunks it is no longer necessary to run the remaining passes. Had the part been black on all sides after the first rerun we would have run the program five more times painting in between every cut to confirm that the machine consistently cuts accurately. I had originally thought that my problem was a worn spindle bearing due to the 15000 RPM cut. The actual test part only has a hint of the zebra stripe that a worn spindle bearing creates. The 6 time repeat test for metal cutting CNC machines is similar. I machine a precision bore as the test. A black Sharpy is used for coloring the bored hole between each repeat.

Segeo Shingo correctly taught that every manufacturing operation needs to leave a visual indication that it has been begun. He was careful to distinguish visually confirming that an operation has been begun from inspecting that it has been properly performed. His experience matches mine. For every part that is made with an operation that has been improperly performed, 9 parts are made with that same operation missed. A good example is a rough boring operation. After the part is finished machined there is no way to visually tell that the roughing bore (or drill) actually happened. A missed rough bore is a problem because the only way to achieve the desired roundness in a precision bore is to set the rough cut size so that it only leaves 0.010 inch (.4 mm) stock for the final cut. I am happy to report that the advent of CNC machining centers gives us a few more options. One of my favorite tools is to use a helix orbit to add a counter bore. I make this cut using the roughing cutter after it finishes its bore so that I can either gage or visually confirm that the cutter has not chipped. (In the pictured example, the helixed counterbore using the robust roughing cutters also protected the fragile finishing cutter from the weld located at the start of the bore.)

Adding a CNC helixed counter bore made by the roughing tool makes visually confirmation possible

Adding a CNC helixed counter bore made by the roughing tool makes visual confirmation possible

A classic example of a manufacturing operation that leaves no visual witness is bolt torquing. This becomes a problem when multiple bolts are needed to secure the joint. On a excavator, the turret is secured with 24 to 36 bolts depending on size. If one of these bolts is not tight, the operation of the unit will work it loose and zipper apart the entire joint. The repair, in one years time, is a $20,000 warranty cost. Confirmation of proper bolt torquing is further complicated by the locktite used to seal rust out of the thread. Checking bolt torque a day later only confirms that the locktite is working. This is where Shingo’s visual management concept fits in. Every operation needs to leave a visual witness that it has occurred. This warranty cost was eliminated by redesigning the bolt tightening wrench so that it left a mark when it was used to tighten a bolt. It became possible to visually see walking by that every bolt was tightened.

Final torque wrenches should leave a visual mark when they are used

Not every application can tolerate a scratch in the paint. I have also modified open end wrenches and sockets so that they leave an imprint on the bolt head or nut when the torquing operation is performed.

Retrieval

Posted on October 23, 2015 by george

A Victor V phonograph, circa 1907
Norman Bruderhofer – Collection of John Lampert-Hopkins

As a young boy, my family had a old phonograph. This machine came from the Rockefellers because one of my great aunts was a domestic servant. One of my uncles had worked at a radio station so we had a small case of the 78 records to match. As a budding engineer I was fascinated by the wind up mechanism that spun the turntable. Retrieval is what I liked best. I could play my favorite records any time that I wanted to hear them. The phonograph was one of the first data storage devices. It could capture and store music or speech. It was the retrieval as desired that made it popular. A whole orchestra could surround you within your own living room. The quality of that retrieval was inverse to the popularity. The records that were played the most often picked up the scratches. Some of our favorite records deteriorated to the point where we no longer enjoyed listening to them.
One of the more important aspects of retrieval is data integrity. Just like scratches spoil the usefulness of a record, a corrupted bit can spoil a CAD data file. Back when I was directing the designers at Lotus in Norwich England how to create my patented GM engine component, it was necessary to transfer CAD data on magnetic tapes.

We adopted 3D CAD design when we could finally retrieve un-corrupt data files

Even though the internet could transfer data from Canada to England at the time, the transfer usually had corrupt data. This made for a lot of trips by plane. England is a lot farther North and it is dark at 4:00 PM in November. Obviously the data communication protocols that we currently use today automatically correct static. (Skype saves a lot of plane trips) As an aside, we even have programs that can edit the scratches out of music recorded on old-fashioned phonograph records.
A phone call from the IRS strikes fear into most people. We know that this is a time that retrieval is going to be vital. Unfortunately, our accounting friend Darryl Engebregson, who could remember all of his clients data three years back has passed away. We still talk about his answer to an IRS query where he said “That number sounds familiar.”

New York City field office for the IRS by Matthew G Bisanz

This experience caused us to arrange our http://mileagetrakker.com business so that it is possible to retrieve mileage records from three years ago. This is a match to the IRS audit schedule. None of us want to face the penalties that the IRS charges when they disallow a few years of deductions when we cannot retrieve our records.

Batch Process

Posted on October 14, 2015 by george

A batch of fresh baked cookies brings out the kid in me

I was thinking about how to determine the ideal batch size. Cookies came to mind. The ideal batch size is one when you are eating them. As a lover of cookies, I have tried stuffing a bunch of them in my mouth. It doesn’t work as well as eating them one at a time. Further upstream in the manufacturing process, one no longer is the optimum batch size. In my college days the optimum batch size was six. That was the size of my toaster oven tray. Even though the efficiency gurus suggest that we should eliminate all inventory and make cookies one at a time, that is a good theory that does not work in practice. There is something about the smell of baking cookies that attracts and makes friends. Especially on a Sunday night in a guys dorm when there is no food service. Obviously it was necessary to do an ERP (Enterprise Resource Planning) raw material order earlier in the week to pick up a roll of cookie dough from the grocery story when the grocery store was open. Only one because that is all that would fit in the dorm micro fridge that I shared with my roommate. Again the batch size was no longer one and increased to a dozen. Going further upstream the cookie dough rolls arrived at the grocery store in case boxes. These were stocked on the shelf from the distribution center arriving in mixed skids. The food batching plant obviously wanted to send full refrigerated trailer loads to the distribution center but for the slower moving products like cookie dough this shipment usually includes a mix of all pre-made refrigerated dough products to reduce scrapping of stale product. Any batch size is theoretically possible. In reality when we chose a width and load limit for the roads, factors like the size of trailers start to govern the equation. Even further upstream in the supply chain, the concept of “pull” scheduling totally falls apart when we get back to the planting of the wheat to make the flour. Planting wheat in one cookie batches makes no sense at all.

Drones will emerge as a means for avoiding traffic jams as the population concentrates into big cites

It will be interesting to see how new delivery methods such as drones affect batch sizes. In this emerging mass customization era, batch size planning also applies to building heavy equipment like excavators. In this market every purchaser wants a machine that is customized for their use. Theoretically the batch size of a sold excavator is one but in the actual market the end users like to buy units is groups of three or five so that they have some opportunity to reduce the number of spare parts that they need to stock. Many of the large components like diesel engines, hydraulic pumps, cylinders are ordered in one year batches of 1000. This is inconsistent with the customers who would like their machines a week or two after they place an order. The solution is to complete the manufacturing until the point that the parts begin to acquire customer unique features. The historical customer behavior influences the upstream batch size planning. Many of the components arrive in “kits.” Building heavy equipment is the sum of organizing and collecting heavy components onto skids that fit into trailers or sea land containers. In the past we saw more 1 TEU containers in ocean shipping. In the US most sea land containers in use are 2 TEU because they are similar in capacity to truck trailers. Lift trucks and pallets sizes also evolve toward the same dimension constraints. In most cases the workers require lifting assists at every step

Gathering heavy items takes a lifting device

I also market a connected car device http://www.mileagetrakker.com that helps people who drive for business save about $1000 to $2000 per year on their tax bill. We give the user the option of recording trip purpose in batch sizes of one using their cell phone or in weekly bunches using the internet. One size does not fit all. Users choose a batch size which fits their work pattern. People that have an unpredictable travel pattern like recording in smaller batches. People with a more stable work pattern tend to like recording trip purpose in weekly batches using the internet because is saves time.

Ed Kocsis

Posted on October 13, 2015 by george

In a die casting era before we had lean gurus, Ed Kocsis lived lean die casting with every ounce of his engineering thought. Part of his legacy is the NADCA die material cleanliness standards for premium H13. This is just one tool that enables the 500,000 shot life he achieved on dies like torque converter stators where heat check is a issue. A really high bar when 100,000 shot life is declared good even now.

Molten Aluminum causes major tip and sleeve wear

He bought shot tips at 4.5 inch OD and threw them out at 2.75 inches using them 20 times at .060 inches smaller in OD per renewal. The single design common shot sleeve for the plant (20 machines from 800T to 1200T) was the reverse it started at 2.75 inch ID and went out of service at 4.5 inch ID.

Prince Die Casting machine cartridge
closing manifold

He invented the cartridge valve manifold that became embedded within the Prince closing circuit, not for simplicity, but because it allowed the use of a 25% smaller electric motor and we stayed within available plant main transformer amps. Most of the dies he designed were loaded into the casting machine and were run continuously (even breaks were relieved) for a month. The 81% of theoretical yield (fastest that you can make a part divided into good parts sold) that was achieved during the 5 years I work with him (only shut down Christmas days) has not been approached at any other good casting house that I have been associated with since.

Inversion

Posted on October 7, 2015 by george

Classic illusion flips from faces to vase by Brocken Inaglory

As we focus in on our immediate objectives, the lesson we learn from classic illusions is that occasionally we need to step back and see the bigger picture. The most famous example of a figure–ground illusion is probably the faces–vase drawing that Danish psychologist Edgar Rubin described. Your mind can’t decide whether to focus on the white vase or the black faces.
Shigeo Shingo invented the concept of SMED (Single Minute Exchange of Die) He correctly asserted that if a die change occurred fast enough, the manufacturing planners would not be tempted to build extra production to put into inventory to save die changes. People who only saw the black faces simply tried to increase the die change speed. Shingo correctly guided his followers to focus on the white vase. In most cases much of the die change can be done while the equipment is in production.
Demand charges for electricity work the same way. The size of the wires in the power grid and within the plant are related to the peak draw on the system. Significant savings occurs when the high power draw actions do not occur simultaneously. This is especially true in situations where the usage is approaching the maximum that the existing infrastructure can deliver. I happen to like coloring Excel spread sheets so that a quick glance confirms that all high power users are not active at the same time.

Colored charts add understanding to simple
tables of numbers

Attention to detail made it possible to divert 100 of 450 amps to added hot oil heating units.
The same focus on only the black faces applies to my mileage trakker business. In start up mode our effort was aimed at tabulating the trips in IRS format so that our trakkers could qualify for the deduction which puts about $2000 in their pockets. It took a request by one of our users to help us see the white in addition to the black. Some business owners need to tabulate how long they are at the customer on a service call. Surprise – Surprise! This matches how long their car is in the customer parking lot. We are now beta testing a feature that logs the time at the customer.

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Lean Engineering Solutions to Improve Profitability in the Areas of Manufacturing, Material Handling and 3D

Monthly Archives: October 2015

Visual Management

Retrieval

Batch Process

Ed Kocsis

Inversion