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What Do I Inspect? - RANT

acgarcia
Hello Everyone,

For the most part, I've had unbelievable freedom when it came to creating a CMM inspection program. Number of points, which dimensions to inspect, which to leave out, what to name the features, number of probes needed, types to styli, etc... Managers and operators only asked my to to specific things that would help them with their jobs.

Example 1 is that I might get asked to check certain features first so they get quicker feedback for CNC offsets. That may be a slightly longer program or I might have to load a probe more than once but that's how they wanted it. Ok, I can do that.

Example 2 I'm checking a feature with a loose tolerance that is always out of tolerance but it doesn't affect the fit, form, or function of the part. Operators have to enter in non conformance reports which hold up the part from getting further processed and engineering has to get involved in the decision to accept or scrap to that part sits and waits which is a waste.

Example 3 is let say there is a reference dimension that the operators do by hand that is not on the drawing. No problem.

Example 4 is when non conformance reports on consistently entered to engineering and they finally tell me not to check that feature anymore because either its not important or production just can't hold it and therefore not important enough to check.

Example 5 is when the CMM inspection is longer than the CNC run time so now managers get involved, we have a meeting and review what is being checked and they ask me to remove what ever measurement that aren't needed to save time.

So about a year ago, our engineering department started using numbered bubbles on our drawings. We had a meeting and they said to only check what was bubbled and also to name the feature after the number inside the bubble for clarity and standardization. Great. That was so helpful to me. CMM programs and program creation got much faster.

Then we had a meeting a few months ago about only checking the numbered bubbles was NOT their intent. We need to check all the features at some point not just the numbered bubbles. Since there was some confusion, engineering decided to no longer use the numbered bubbles anymore ( I think they are just trying to save time on their part) so I'm back to square 1. Whiskey Tango Foxtrot.

So now that I've been programing for a few years, I understand that I don't want the CMM to be the bottleneck and give the operator as much dimensional information as they need to get their job done. Now I'm approving drawings and the new versions have no numbered bubbles and tolerances are changing and I'm at the point to where I'm asking myself, what do I inspect?

How do you all get your instructions for creating inspection programs? Does every inspection program need to be a meeting?
  • You could create a "Bubbled CMM Prints Folder".

    Bubble your drawings, store 'em in that folder, name your CMM prg stuff after the bubbles, give the operators a copy of the CMM print with their CMM data.

    I don't get instructions for "what" needs to be on the CMM program..

    I'll receive a job and they'll just tell me "this needs to be measured yesterday" so I will program what makes sense for the CMM and then check the rest with other tools.
  • ya what Dan said. Bubble your own drawings.
  • I've been in both situations. I prefer being able to use my discretion, but don't really mind, provided I don't get thrown under the bus.
  • Bubbled prints from engineering is the way to go, for me that means that the bubbled requirements is a must to check but I am free to add/remove whatever non-bubbled requirement I wish as I go along programming the part (and you should). Seems to me that you have seen the promised land (bubbled prints from engineering) and you should do anything in your power to get that back...
  • I was in a similar situation. I got a hold of xact measure balloon software and would create my own bubbled prints (only!). It was like a guide map for my CMM programming, the time spent creating the bubbled prints gave me the time to really familiarize myself with the drawing, and my CMM output followed the balloons. Saved me a lot of time. The only thing I hate is having to maintain yet another file but revisions rolls weren't terribly bad.

    After I left the industry I did a bit of consulting work. I used a circle stamp and pencil'ed the numbers in and provided those bubbled prints to the customers, only if they wanted them, and most did take them.
  • I think the question really lies within your company's function.
    --Are you a job-shop? High part variability and low volume? IE you're making new routines EVERY day or week, and generally never use them again?
    --Are you a small batch production shop? inbetween the two
    --Are you a production facility? IE you make x types of parts with x different variations all known and you have to control/sustain the inspection process for each high volume part?

    If you are a job-shop, it's best to do process your work as such. conduct your 100% inspection, using all tools to your avail, as the print mandates.
    If you're in between, you can batch process stuff, and you might want to internally develop a template FAIR form or something of the like to at least sustain what tool you're going to use to measure what dim.
    If you're a production site: setup meetings for each part, develop plans to make sure the measurement methods are set in stone and in accordance with whatever your engineering team or customer desires.
  • We are a production facility and most of my CMMs are in cells that run just one part over and over. Once I set them up, I usually don't need to touch those CMMs unless there are issues related mostly to hardware like probe got loose or fixture is wearing out. Some of my CMMs do run a small mix of parts. As a manufacturing plant, we are trying to stay flexible when it comes to our CNCs. We are constantly offloading parts from 1 CNC to another to accommodate new products coming through which means I need to move CMM programs around which can be a pain sometimes.

    Another issue my CMMs don't have the same heads so moving programs around can take some time.

    I'm on the fence about a meeting for every part. I do think that would be beneficial so every department will be on the same page but I think it can be a waste of peoples time as well. Have my own bubble drawings would be great but it would go against our policy to keep duplicate drawings and I wouldn't keep up with revision control.

    There are only like 2 guys here that are the brains of the entire operation. I think I'll have a chat with them about what to inspect. I'll initiate the meeting by getting the current drawing and inspected everything that particular CMM can inspect. Tell them this is what I plan on checking on this part, speak now to remove inspections or this will proceed as is.
  • The customer determines what to inspect and the frequency. If you make your own product then the customer is internal, most likely the design engineer. If you're a contract manufacturer then your customer is external. Your manufacturing engineer decides what needs to be checked throughout the process.
  • I'm in aerospace, every print is ballooned, every dimension, and they ALL get inspected, every single time, at machine set-up and at final inspection.

    Do you want to get a plane where no one inspected 20% of the dimensions on the parts making that plane?

    Now, there are some balloons we inspect MORE of than others. I said they all get inspected, but we don't 100% the parts, we do lot sampling. Dimension is +/- .030" we check 8 out of the lot. Dimension is +/- .001" we check 13 out of the lot. Dimension is KEY or FLIGHT SAFETY we check 100% of the parts for that dimension.

    My guess was, the intent was to get people to focus on these important things while paying limited attention (not NO attention) to the non-ballooned things. But I wasn't there.

    There are ways to statistically validate processes to reduce inspection, but inspection is never going to drop to zero, don't bother. And again, would you want to get on the airplane that had zero inspection. I wouldn't.



    That all said, having management give me different instructions that are conflicting and vague pisses me right off, so I empathize with you there. If you have options for employment (that's a big IF), I'd tell them to get their crap together or pay me to be a manager and figure it out myself. Why am I doing their job for free because they are bad at it.
    Keep that "IF" in mind on this, they could show you the door. And be respectful when you phrase what I just said lol.



    Beyond that. I'm always the bottle-neck.

    I've got manifolds that take 40-60 hours to inspect one machine operation of. The machining is 6.5 - 10 hours. People thought it was me, gave it to another inspector manually, MUCH slower. Two other machine shops, same time or slower. Inspection is slower than manufacturing, most of the time, with today's CNC machines, anyway. Don't revel in it and be slow as molasses, but accept that it is what it is.
  • in reply to Caemgen
    It's baffling to me how many companies still view inspection as overhead and don't factor inspection time when promising delivery dates to customers.
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