A colleague of mine sent me a rather hilarious video entitled “Why We Hate Engineers.” The basic premise of the video is that engineers and machinists often don’t communicate well. Sometimes the cultures become so divided that the engineering department is seen as the “inner sanctum” that only the select few may enter. Communication between Design and Manufacturing teams is important for success. As someone with a background as a Machinist and Designer I’d like to offer my two cents and my experiences with dealing with engineers, the positive, the negative, and what I have found in my twenty-seven years in manufacturing to work the best.
Lack of communication between teams leads to expensive parts
When I was just starting out in this field, I was doing mostly manual machining. I was good at it. One day I was handed a cylinder of stainless steel, a print with very tight tolerances, and told to make a part similar to the one you see below.
Concentricity around the internal boss with the outside profile, and the drilled hole was about .001. There were profile tolerances along that spline just as tight. The walls were thin enough that I had to worry about them springing out of round with clamping pressures. It was an expensive part to make as a one-off but that’s what I was told to do. Without a CNC and my first years in the trade skill levels it took nearly 30 hours of actual machine time to make.
One of the problems was I had no idea what it was for. For all I know it went on the space shuttle! I just did my job; it took a lot longer than expected and I am sure we lost money on it. When it was finished and inspected, I was told to deliver the part to the client, which was a large industrial kitchen. I walked in the door and the client asked, “Want to see what it’s for?”.
“Of course.” I said, thinking it was integral to some piece of equipment.
It wasn’t…It caught juice as it came out of a juicer. They were using a dixie cup while waiting for the replacement part and I honestly felt a bit dejected at that moment.
I returned to the shop, went to engineering and asked if they knew what the part was for.
“Nope, they just brought in this cracked part and asked for one out of stainless.” The engineer said showing me a cracked piece of plastic he had carefully measured, drew, toleranced as he saw fit, quoted, and handed off to manufacturing.
To share some of the blame here, if he had asked what the part did, we probably wouldn’t have wasted nearly a week of everyone’s time, but if I had asked “do these tolerances really need to be this tight?” We could have made the part for the cost we quoted if not cheaper.
Now why didn’t I? This place was not the kind of place the guys on the shop floor were in direct communication with the engineers. The culture had grown up to the point that if someone had even the simplest question it had to go up the chain to engineering. I would have needed to talk to my supervisor who had a disdain for the “stupid engineers,” and I felt that any concerns I had would have fallen on sympathetic, yet deaf ears. The Engineering department had no machinists, tool makers, or anyone that had worked on the shop floor. The quoting skills were basic, along the lines of “It takes about an hour to remove XYZ amount of material.” As a result, I felt like as a young new guy, that I wasn’t empowered to ask questions to Engineering.
How the right communication can speed up processes
Fast forward a few years to a different manufacturer. We were primarily an Injection Molding Shop, but because of our abilities to hold some very tight tolerances we were occasionally asked to do some aerospace work. I was officially titled “CNC Coordinator” but my duties were programming and setting up the CNC’s, Splitting and prepping product models for the mold designers, and some mold design. I was a busy guy and if I wasn’t dealing with a machinist or toolmaker, I was dealing with engineering.
One of those Aerospace jobs, which can best be described as a three-sided angle iron, had some very tight, but not unusual tolerances for that type of work. The part looked like the one below with the holes I marked in red true position +-0.001 and a diameter tolerance +-0.0005 inch. But they were also an odd size hole to be toleranced like that. A diameter of 1.313 looks an awful lot like 1-5/16 or converted to decimal units 1.3125.
To hold that location tolerance, we’d need to use our jig bore and deal with the set-up and the time and expense of a skilled toolmaker we would rather have been doing something else.
The culture here was very different…I was empowered enough to simply walk over to an engineer and say “We are going to need to jig bore these holes, but something isn’t right about it. Can you call the client and ask what’s up with these holes?”
He found it odd also and did just that. I went about at least roughing out these massive blocks of Inconel. The next day he came over to me with a grin. “Guess what those holes are for? They’re clearance for a bolt, just cut them however you want they sent us a variance.”
Turns out whoever made the original prints had just used the default tolerance on the last parts he made, but if I had not asked that question those blocks would have taken hours longer to manufacture because “they need to be that tolerance.”
Learning from these experiences
So, what’s my point in these two stories and how does it affect you? For one thing, to be an effective manufacturer you need to be a team. The best teams have excellent communication between design and manufacturing. Imagine a baseball team where the pitcher is not allowed to talk to the shortstop without going through the third base coach? Someone hits a pop up and they are both running for it, but the pitcher can’t shout “I’ve got it!” without running over to the coach, telling him, and then the coach running over to the shortstop. By the time that happens you’d have an infield grand slam. Another analogue might be to think of your manufacturing team as your NCO’s. My father who, was a veteran, said the best lieutenants he dealt with were the ones who said, “What do you think Sargent?” and wanted real input from him because at that point he was on the ground longer than they were, even if the answer might still be “tough, we need to do it this way.” The ones who never did that, and or never listened to their NCO’s tended to never advance that far in their careers.
Ideally, you’d have someone with a machining background on your design team that can spot things that look out of place and ask questions. Sometimes the answer is that +-0.0001 needs to be there, and sometimes the answer might be “Well, it’s a cup holder so no, maybe it doesn’t” At the very least encouraging questions from the shop floor can go very far. While we all claim we’d never be that guy to accidentally leave a dimension tolerance default set to +-.001 true position, we’ve all done it. Having someone who understands what tolerance means for manufacturing in your back pocket can save you the embarrassing phone call where you need to admit you made that mistake.
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