QC inspection vs. operator inspection
If we exclude something like FAI (first article inspection) or a complicated measurement set up that can't be done at the machine and deal with simply measuring what is getting made by the machinist is a QC inspector necessary?
There are the machinists that take great pride in what they do while there are others that consider it "just" a job they have to do to get paid a wage.
I'd think the latter group would think that as long as what they were making was going to get checked/inspected by someone else then it wasn't really their concern as to how good it was. "If it gets approved then I don't give a damn how good it is" attitude. The conscientious machinists will resent having someone looking over their shoulder or constantly feeling they are being checked.
I don't know how many companies still have QC inspectors roaming the shops but here it isn't nearly as common as it was. A machinist that needs a "nanny" to babysit isn't IMO a machinist. He or she is just a button pusher.
The companies that have QC inspectors for "helping" machinists measure what they make should stop up and consider if it might not be cheaper to give those machinists that aren't secure with measuring a training course. Comparable to "teaching a man how to fish" rather than giving him food to stop from starving.
On the same tack I'm often surprised at how many companies have a large receiving inspection. They might find it more worthwhile finding reliable suppliers. The cost of receiving inspection is rarely added to purchasing costs. Don't hold some poor employee responsible for a purchasing employee that doesn't realize exactly what he's buying and paying for. A purchaser with the attitude "I just buy as cheap as possble and it isn't my responsibility if it can't be used" should be castrated to avoid breeding.
Anyone out there actually in favour of large QC departments?
Final inspection for products warranting it is good but if faults are found at this stage then that's where "Corrective Action" comes into play. Somebody somewhere is screwing up but why and how? Mistakes happen. Repeating them is stupidity.
One thing that comes to mind while reading your post is that I am seeing many shops here in NH anyway that have been asking for "machinists" to work for anywhere from $10 an hr and up. One would think if the wheels of progress are turning backwards then I might also see adds for more inspectors.
Originally Posted by Gordon B. Clarke
If that is regarded as a "wage" for a machinist then there should probably be 2 QC inspectors hired for each machinist. One to hold his/her hand and one to help with measuring. I'll ask from curiosity. How much would/does an 18 year old get working at McDonalds? To avoid heart attacks I'm putting further down how much they'd get here. Scroll at your peril.
Originally Posted by AlDrake
At least $17 an hour for an 18 year old at McDonalds + of course a 37 hour week and 5 weeks of fully paid holidays etc.
With a good QC program, you can get rid of those workmen (be they welders, machinists, drafters, whatever) and subcontractors who consistantly perform under par.
OK I'll ask. What is "a good QC program"? Is it something other than the shop manager taking responsibility for dealing with below expectation machinists and the company paying a fair wage?
Originally Posted by Weirsdale George
I'd be more inclined to work at McDonalds for $17. But in the USA, most of their jobs are way, way under $17.
Actually the trend many places I have worked was do do AWAY with inspection of stuff coming in from suppliers. I have seen so much stupid stuff over the years with "inspectors" the first guy I worked with would come over and check a part we made, the elevating cylinder for the main gun on and Abrams tank.
We used a go-nogo gauge for the hole dia, he would engage you in conversation while he worked the go gauge in the hole, in and out, round and round, til the no go would enter a little, then tag it as a defect. The OTHER older guy in that dept, you could take in a first article part and he would check it, tell you to make moves, you could take the part out to the floor, wait 1/2 hour, take it back in, he would say "good to go"....SAME damn part :-).
Some inspectors are quite good, others will drive you nuts, I worked with one guy who would level a part that had a 1.5" turned stub on it from the faced end of the stub, then check everything else more or less from the plane of that surface...when there were a LOT of better areas to "level" from. When the blueprint does not specify datums using the same ones your locating from in the process will tell you a whole lot more IMHO. Once the concept of GDT came along, with datums clearly specified and tolerances given from those datums things got a whole lot easier.
The guys who get their rocks off finding a print error and running with it to mark parts scrap are fun. Say a corner break radius that was dimensioned ".0625" and the print says 4 place decimals are +-.0005...so your .063 radius means the part is scrap, when every other feature on the part is +-.015 :-).
Originally Posted by Gordon B. Clarke
QC isn't about checking up on the lying cheating drunk machinist..... It's about getting good product out the door.
So, a "good QC program" would involve a decent sampling inspection for AOQL, and SPC on at least the most critical dimensions.
SPC if done right will tell you what level of tolerance your process CAN hold, and you can see when the process is NOT holding that level, which may mean a machine problem. Whenever your process is not within the control limits that were established by "historical data" you KNOW something has change, and can find it before making a whole run of scrap.
The operator can do that inspection, but usually is not relied on because either they are already busy enough, or the idea of having "more eyes on the process", and perhaps a little "fox guarding the henhouse" type thought.
It is known that when an inspector *wants* a certain result, they may 'flinch" when getting measurements which don't support that result.... unconsciously adjusting the way they operate the mic, etc. So a more "disinterested" party may be good.
McDonalds pays $17? What does one of their (abysmal) burgers cost there? I may be getting a better idea of the problems with the Euro if the McD workers are paid 2.5 x as much as in the US.....
I work for a company that mfg a product, filled with foam. One thing QC does is check that foam density, was every 4 hours, now every 2 hours. They also cut a product apart once a shift and verify proper fill. They also measure finished product and verify dimensions on some frequency per shift.
Some of these things are verified by the person(s) actually making the product, but the foam density and "tack time" is NOT checked by anybody but QC. Recently we had a supplier send us the wrong ISO and it took 24 hours of production before it was detected....not sure if it was not apparent in the tests QC does or they just missed it, but 5000 scrap products was the end result. With NO QC the first sign of a problem would be bad product in the field, maybe years later.
I think it has been demonstrated over and over that humans make mistakes, to the degree that people going in for surgery write "NOT THIS ONE" on something being amputated or removed due to so many times the surgical team cutting off the WRONG part. QC should be to catch mistakes not errors due to sloth.
I would have thought that the correct level of QC was mainly a function of the (cost to you) consequences of a particular part being out of spec. If 3 faults in a hundred result in the customer returning the faulty parts for a refund, then that implies the need for a particular level of QC. If 3 faults in a hundred results in 3 crashed aircraft and puts you on the wrong end of a very large lawsuit then that implies a whole different level of QC. It's horses for courses, there isn't one particular answer.
surely in critical situations the QC requirements should be specified by the customer or identified in the sellers offer.
PS: Maybe in all cases it should be the responsibility of he who specifies the tolerances to also specify the QC requirements.
In think any shop that wants to make quality parts and sell quality parts to the customers needs some sort of inspection program. And it has nothing to do with "watching over the shoulder of a machinist" it has to do with keeping your company doors open.
The inspection program I always liked best was the first shop I ever worked in. You were responsible to check your own parts start of the job to the finish of the job. Then when the job was finished the Inspector did a final inspection based on about a 10% basis. Myself and the guy who worked in the department would take turns inspecting each outher parts during the job just to have a different set of eyes looking at the part to help elminate one us missing something.
Every shop I worked in has had a QC person in it. outher than the one i'm in now. We have no QC anywhere along the line, so I do it myself checking every job before it leaves my machine area. and in 5 years 0 I repeat 0 part rejections. Without my inspection and relying on every machist to do his job correctly I can't count have times we would have part rejections. Due to poor inspection from the second shift machinist, or lack of! I have been called "picky, a pain in the a$$, you name it". But the parts I send out the door no one has to question if they are right or not! And my boss loves that witch equals $$$$$$ in my pockets.
On a side note anyone know how to convince a company to not hire "machinists" from a temp agency. That helps your quality problems out alot also!
Here you check it before you use it. You watch it as you work it. You double check the finished product. Then the next operator does the same.
Good, reliable, vendors are hard to find and even they make mistakes.
Shipping and Receiving knows what the stuff on the paperwork looks like and catches some problems by matching the labels on the box with the material labels with the description on the paperwork.
I think a formal QC is necessary to set specifications and to train. I also think everyone should be responsible for the quality of their parts.
The funny thing about human nature is that if you have 10 parts in a run, and one is right on the line of being out of spec (even using up the 10% gimme you almost always have) you can take a PERFECT part and mark it with some layout die, or write something on it, then rub it off, and the inspector will inspect the HELL out of that part, and ignore the other 9 :-).
Originally Posted by racen857
Don't want to hijack it too much, but it bring up a related situation I have.
I work at a company where the machinists have always inspected their own parts.
Inspection tools were somewhat limited, but they used mostly micrometers and vernier calipers.
No gauge blocks or rings or bore gauges or height gauges.
Well now I get some money approved, and I want to set up a little quality inspection lab for the machine shop.
(for the general betterment of the company)
I secured an old blue print storage room for a place to set up a nice surface plate and a height gauge.
I bought a 3 x 4 foot granite plate and a Brown & Sharpe Tesa 600 micro-hite height gauge.
Super nice machine, has the air pump so it will float across the plate to move..
I also got a 6" magnetic cube (squaring block) and some v-blocks, 1-2-3 blocks, and a grinding vise.
Also some gauge blocks and setting rings to check ID caliper jaws.
ANYHOW... I want all the machinists to be able to use this room and Tesa height gauge to do first-article-inspection (and other checks) on their parts. There will be no official QC guy manning the room. Just me (an engineer) to help train and use the equipment. Problem is the machinists are old skool and don't think they need the height gauge and other tools I worked so hard to acquire. They are perfectly happy with their beloved vernier calipers and Starett mics.
Any suggestions to help break down the barriers that exist to being given new and more accurate tools to use for measuring?
Most of my customers have eliminated receiving inspection.
Big, big fines if you ship non-conforming parts. You buy back the bad cars or at least the teardown cost to fix them.
Read this as a bill of 200K to millions here and they are very quick to go after the vendors.
Yes I know of one brand name tooling company who had to write a check for $350,000+ dollars. The small guys just go bankrupt.
This kind of incentive makes sure you have your ducks in a row.
We run SPC on everything and the operators get trained on how to use it. All of it is done in the computer and it will bitch if it sees something strange.
I have built SPC systems since the 80's so our stuff is different than most off the shelf solutions.
50 part runs for us are small, 500 is more typical, so I'm a little different than the job shop doing one offs.
One thing I've learned is to not trust the production gauge. We audit check the parts against the SPC systems numbers to make sure everybody agrees on the same "zero". This is a biggie.
Yes, on occasion we find the gauge at the machine off by .0003. This results in a big hoopla and you can bet your butt that everybody in the building knows about it. (We post it on the wall and it comes up in the next employee meeting, you do not want to be the guy who messed up zeroing your gauge).
I am a big fan of measure the darn thing once. Checking twice is crazy expensive.
This means gauging at the process that can handle the tolerances so at +/-.001 in my shop micrometers are "rough" gauges and never used to inspect final dimensions.
I have one customer that does incoming inspection.
After rushing out a job we spotted that it was made wrong.
I called the customer as fast as I could. He told me that I was wrong, his inspection department had accepted the parts and they had gone to production.
I was sure it was not to print, everything in my system said it was made backwards and that the top rake was left hand when it should be right.
I started a new batch and kept calling and e-mailing him.
Eventually he called and thanked me for catching it as his shop would have done their side (PCD tipping) and sent them to the final customer whom I sure would not have been happy with a tool where the top rake was reversed.
Many here run one off repair shops. A whole, totally different world than where I live.
I can certainly see that if it works the customer is happy and making the customer happy is the key to making money.
The quality control guy needs to make sure only good parts make it out the door.
If he feels he must measure everything something is wrong in your process measuring.
I'm not sure how you break down an institutional ignorance like that. But I was taught on important things to use three methods of measurement. I did not hear mention of gage pins ?? The nicest place to check parts I ever worked in had full libraries of Vermont gage pins all over the place. .001 and .0005 in plus and minus. Maybe you do not need ALL of that, but just the .001 minus pins are darn handy, they add a "method" and are a great help in measuring a hole location with the height gauge.
Originally Posted by Doozer
One nice thing that place did was give you $25 a month for not making any out of tolerance parts, and another $25 for the quarter. Does not sound like a LOT, but they gave you a little business card sized certificate, you could stash them in your toolbox til you had a pile then turn them in for some cash for something or other you wanted. An extra $400 around Christmas can be nice :-).
I learned a lot from the one guy who made it every month and every quarter, some fast and easy way to double check things, such as taking a quick "scratch cut" of a mill profile in dry run, measure with digital calipers, find a silly mistake you made before you scrap a part, break a cutter, or worse. Or the one thing he did that probably helped the most, he had a whole set of highlighters, and each feature on a part the dims got a different color highlight, really helps to sort out a complicated drawing with a lot of features. But the point was that making it every quarter WAS recognized, and in the group we could learn from things others found to help avoid mistakes, or to make things go smoother.
The premise of this thread almost seems naive, which I know the OP is not. I'll certainly agree that machinists should be responsible for their work but there is a lot more to QC than verifying dimensions. QC needs to ensure that all of the requirements of the b/p or contract have been fulfilled. The correct material, outside processing etc and that all the documentation is correct. I'm also fairly confident that if you were audited by your customer or regulator that telling them that the dimensional inspection was done by the machinist would not go over very well. Would it even conform to ISO or AS requirements?
Also, obviously the reason for receiving inspection is to catch any problems ASAP, rather than waiting to discover a problem after the invoice has been paid and a bunch of time wasted. An example might be that you received a part from your heat treater, didn't do receiving inspection, did a bunch of work on the part, at final inspection it was found that the hardness was out. Now what do you do?
I'm not sure what world you're in but in the commercial aerospace world that I spent my career in the role of QC is doing nothing but getting bigger and more onerous
Knowing human nature is fun, and can be useful :-). The upshot of the whole deal really was to make sure that any parts going out, or on to another dept did NOT have any such markings on them. And we all know that a bolt hole that is dimension ed .281 +- .005, or .28 +-.01 if it is a few .0001 out of that tolerance, it's gonna ship, and the bolt will never know.
Originally Posted by racen857
Reminds of me a part we made for a co called "Wine Railway" it was the whole gearbox for the bottom of a railroad hopper car, cast gears with teeth cast on, the box, the shafts, the whole assembly. Well the bore in that thing had a +.01 - 0 tolerance on it. We held to that for years...til the foreman was messing around one day with a finished assembly and noted that the 1.625 bore had a 1.500 shaft running through it, 1/8" of clearance. So they dug all the ones out of the steel scrap that the bore was slightly out of tolerance and used them. "Out of spec" sure thing :-).
Measuring tools are supposed to resolve to 10% of the required tolerance, and I was always told that was why for many purposes you can count on an extra 10% on a tolerance. GDT has done a LOT to lower cost of mfg I am sure when it at least TRIES to define the actual required accuracy.