Slow mold changes? Try a Taco Cart

By Bill Tobin

Editor's note: Consultant William J. Tobin has done and/or supervised hundreds of mold changeovers. Here he takes a lesson learned from the entertainment industry and shows how it can be applied on the shop floor.

I was in a client's shop in the Midwest. The place looked like a basketball-court-sized operating theater with molding machines in it. The machines were spotless, the floor was painted a neutral gray and kept constantly clean, and material was conveyed by a remote loading system. The owner proudly boasted of the tireless housekeeping as well as almost fanatical discipline he employed keeping everything in its place. 

The problem I was brought in to help him with was that his setups and teardowns were simply taking too long. I first went to the tool crib. It looked like a hardware store. The mold clamps and water lines were all organized by size and length and neatly hung on pegboards; bolts, torque wrenches, eyebolts of all sizes, and all manner of tools were readily available to the setup technicians. They certainly weren't lacking for equipment. 

With the agreement of the setup technicians I tried an experiment. I put up a tripod and a video camera to film a mold changeover. I set the camera on slow motion and told the techs we'd turn off the tape and review it before we took it to the company owner. This was a simple changeover. Both molds were conventional-runner, two-plate tools; they did not require new material; and the machine was a conventional 300-ton press. Three hours later, the mold removal/mold hang/startup was complete. The actual startup took only about twenty minutes. 

Reviewing slow motion in real time gives the illusion of a Keystone Cops movie. However, it did show something I would never get a tech to believe if he didn't see it with his own eyes. The obsession with neatness had made them fall off the deep end. As things were removed from the old mold, they were put into their respective spots in the tool crib. When the new mold was hung, several trips, about 200 ft per trip, were made to retrieve ejector rods, the correct length waterlines, the proper machine nozzle, mold clamps, and so forth. All this took time. Because this press is supposed to generate a few hundred dollars per hour in sales, this is lost time and money. 

My son is a lighting and sound technician for rock concerts. On tour, the trailers roll up to the venue, and at 7:00 a.m., they begin to construct the set. The schedules are so tight that when the talent shows up at 3:00 p.m. for the sound check, the set had better be up and the lighting and sound functional. Those who have watched the construction of one of these shows know it is a combination of a large scale erector set, an organized riot, and some incredibly skillful planning. There are two keys. First is that everything is modular. Set construction is really an exercise in fitting, bolting, and plugging together. The second key is the efficiency of movement. In the entertainment industry, this is accomplished by something called a Taco Cart (no kidding, that is what they call it). It is my strong recommendation that every molding operation have at least one. 

The Taco Cart is a simple mechanic's tool chest mounted on 4-inch wheels so it can be rolled to the place it is needed. It has an A frame welded onto its exterior, so it can hold ropes, wires, cables, and everything else. This saves the grip having to walk back to the trailer to get something. 

A Taco Cart in molding should be the same sort of thing: an A frame welded to a mechanic's mobile tool box. Inside the box are the setup tech's personal tools. On the A frame are what is important--waterlines, ejector rods, machine nozzles, mold clamps and bolts, safety hoist rings, and the like. 

In order to make this concept work in my customer's plant, I had to make a few recommendations for changes. We rewrote the setup guides to not only have the settings for the machine, but also specify what length and how many ejector rods were required, how many, what size, and what length(s) waterlines were required, what type machine nozzle was required, and anything else unique to that tool. As one last piece of high-tech wizardry, we used a digital camera and took a picture of the waterline setups on the mold. We put the disk into a computer and came out with a nice 8-by-10 print of all the loops. With a dry marker we then wrote on the print which line was what, re-scanned the entire image back into the computer and reprinted it. Now we had a permanent record (with about 10 minutes work) of how the water was hooked up on each side of the mold. Later, I showed them how to add the text in the computer and dispense with the dry marker. 

With a lot of skepticism, a Taco Cart was built by the time I came back. I also had the new setup guides filled out. I left explicit instructions not to use them until I came back. Again, I set up the video camera. From start to finish, the same mold change we had done before took a little more than an hour and a half with a twenty minute startup. The comments from the setup techs were universal: They had a pick sheet from the setup guide to get everything they needed. Thus there was only one trip to the tool crib. They shopped for all the equipment for the mold change they were about to do before the previous mold's run was over. Thus, the Taco Cart and the new mold were brought to the press at the same time. 

With the digital camera prints there was no reliance on memory or "I think" on the waterline setups. With the exception of a quick run to the soda pop machine, the techs were right there at the press doing what they were paid to do--set the mold. When the new mold was up, they wheeled the Taco Cart back to the tool crib and put everything away from the mold they pulled. Remember, the more you can keep your machines busy the more you can make money. 

Make Taco Carts. They pay for themselves very quickly. Videotape the setup technicians hanging and pulling a mold. Without criticism, ask them what they could do or what you could provide to make the mold changeover easier and faster. When both of you look at it on video, many problems become obvious that you simply accept otherwise. Use digital cameras, scanners, and computers to document your setups. This technology is not expensive. Change your setup documentation. It should be in two pieces. One for setup and one for processing. You can't make good parts unless both are consistent.