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mike4
04-17-2012, 05:44 AM
I have started this thread so that I am not accused of hijacking another , the one on the used surface plate .

As I have said there is a case at times for parts to have clearance in operation and the parts are made to a tolerance which if it is not monitored can result in a problem caused by in tolerance components actually binding if a little more movement is allowed than the designer thought of .

Take a large mechanical device which is assembled in a factory , all to the specifications in the design .
All parts checked and all well within tolerance.

Now put that machine to work in a dirty uneven area ,drive it at an angle over a high steep mound of rocks several times in an hour push it to the limits for weeks at a time then take it to a workshop for routine maintenance.

You would find that the time in the shop just blew out to a major rebuild .

Not the operators fault , it was purchased to a specified capacity.
The design was not flexible enough to allow it to work in the field.
There were parts broken which the manufacturer said should not break for years as it was not operated on level ground it had twisted they weaseled out of full warranty .
It is a 12 month old D10 sized dozer.

At the moment the frame is being rebuilt after having been split in two and re welded as required .
Several strengthening mods are being done while it is re-assembled .

It should have been a six week job , now blown out to over four months, not in my workshop ,but the owners .

He is doing it to prove that the machine can be fixed and worked as he wants it to , the exercise has cost about $3/4 million so far.
His money and he had paid over $2.8 million for the machine .
So he is pissed at the "service" from the manufacturer and as a result bought two second hand machines which are now doing the work of one as the operators have been told to baby both of them until this one is back in action .
I am waiting for the day that rebuilt machine is back in action as it will out last any new one off the floor.
The work is a team effort with some of us putting our days off in on this project just to prove a point.

By the way its not in a coal mine , just a quarry in the sticks.

And speaking of another kind of "tolerance ", it seems to be dying out , I dont really care what someone thinks or what their opinion is , but others get wound up about what I take as trivial issues , it wont do the blood pressure much good.
Michael

RancherBill
04-17-2012, 08:35 AM
Good points Mike.

What brand is it? You reference a cat, but I think that was because everybody know what they are. It is hard to imagine the force that would tear a machine like that apart.:eek:

gizmo2
04-17-2012, 08:49 AM
That's quite the dodge; seems to me you wouldn't need the equipment in the first place if all you ran it on was level... Sometimes a little extra money up front is well spent. I saved a couple extra years to buy a decent yard tractor, and have watched the neighbors buy and replace theirs all at least once since. Our prairie isn't very level either, and it eats these little machines up. Nt saying your neighbor cheaped out, just sayin'...

Forrest Addy
04-17-2012, 09:40 AM
Patience Tiffie. This was posted in US small hours where resides about 80% of the HSM posters. Even then, most people like to think a bit before offering advise on convoluted issues. Thus a period of time between OP and first responses. And don't be too smug about your serial hijacking of surface plate threads. If you didn't have a talent for making the wrangling fun regulars here would regard you as a malicious troller..

Mike4: Cat, Komatsu and a dozen others make dozers that run for years in quarries taking a hell of a beating pushing aound great big rocks, traversing bumpy shifting surfaces, taking joy rides down scree slopes, getting inverted and mashing the ROP and they keep running. These machines are paragons of design and materials but even so their tracks, track rollers, sprockets, blades, etc have to be considered expensive consumables. The rest of the machine should run for thousands of hours given regular maintenence.

If a dozer fails to meet operational expectations and the maker skates on what should be warranty items there is plenty of commercial experience in competetor's dozers to use as lawsuit fodder. If your dozer fails in your particular service and Brand X and Brand Y in the same service last 250 hours for the hardfacing, 500 hours between track changes, and 5000 hours between engine changes and you can show compliant maintenence records then the maker of your POS should be compelled to remedy - seems to me (I'm not a red mouthed lawyer nor do I play one on TV).

Haven't you lot got the equivalent of US product reliability law down under?

flylo
04-17-2012, 10:23 AM
It's amazing what people can do to machines. After high school I worked as a forklift mechanic for a short time. We had a foundry acct that got new trucks every 6 months. The 6 month old ones looks 30 years old & were good for scrap. We kept 1 mechanic on site at all times & I was there when he was overloaded. I'll never forget fixing one where they ripped off the entore drive wheel.hub, the whole assemble. I still don't know how they did this. I saw them go full bore into cement walls. It was a real eye opener to say the least.
Everthing has limits except maybe people.

Dr Stan
04-17-2012, 10:46 AM
If a dozer fails to meet operational expectations and the maker skates on what should be warranty items there is plenty of commercial experience in competetor's dozers to use as lawsuit fodder. If your dozer fails in your particular service and Brand X and Brand Y in the same service last 250 hours for the hardfacing, 500 hours between track changes, and 5000 hours between engine changes and you can show compliant maintenence records then the maker of your POS should be compelled to remedy - seems to me (I'm not a red mouthed lawyer nor do I play one on TV).

Haven't you lot got the equivalent of US product reliability law down under?

I'm with Forest on this.

It's also an example (previously brought up) that you get what you paid for. Given the OP is from Down Under my guess is that the dozer is of Chinese origin as there is a lot of trade between the two countries, especially in the mining industry.

mike4
04-17-2012, 07:05 PM
It is a CAT and the undercarriage is too light , , cant take the twisting and other forces .
Michael

RussZHC
04-17-2012, 08:43 PM
Way past any experience I have so quick check of YouTube:

http://www.youtube.com/watch?v=WkoDOJxnc_Q&feature=relmfu

Raises some very base yet interesting questions for me, primarily the scale involved...how do things like "warranty" work when talking about very large equipment such as posted by the OP ?
With the dollars involved, my assumption would be its paid for over time with monies made from the work it is doing, what happens if say payments are stopped? Just saying its not like a typical for TV car repo.

Forrest makes some good points, especially the comparison to other competitors' equipment of a similar nature. Is there some leverage if it were to become well known in those circles (local to you quarries say) about the inability for the product to perform as expected? At the per unit costs involved one would think the manufacturer would bend over backward to keep customers happy, its got to be a somewhat limited/elite group of builders and users of the end product.

oldtiffie:
I rather thought or hoped that this thread would be focussed on "limits and fits", surface finish and "shafts and holes" type stuff.
guess hope springs eternal.

Mike: I thought the general topic was pretty interesting, what happens when a whole bunch of parts within tolerance are put together but the result can not perform as expected in the real world.
That was the point, right?

mike4
04-17-2012, 08:59 PM
Way past any experience I have so quick check of YouTube:

http://www.youtube.com/watch?v=WkoDOJxnc_Q&feature=relmfu

Raises some very base yet interesting questions for me, primarily the scale involved...how do things like "warranty" work when talking about very large equipment such as posted by the OP ?
With the dollars involved, my assumption would be its paid for over time with monies made from the work it is doing, what happens if say payments are stopped? Just saying its not like a typical for TV car repo.

Forrest makes some good points, especially the comparison to other competitors' equipment of a similar nature. Is there some leverage if it were to become well known in those circles (local to you quarries say) about the inability for the product to perform as expected? At the per unit costs involved one would think the manufacturer would bend over backward to keep customers happy, its got to be a somewhat limited/elite group of builders and users of the end product.

oldtiffie:
guess hope springs eternal.

Mike: I thought the general topic was pretty interesting, what happens when a whole bunch of parts within tolerance are put together but the result can not perform as expected in the real world.
That was the point, right?
Yes but many have missed the point i was trying to raise , that there is a place for fine tolerances and the clearances in some areas .
However from experience I have found that sometimes a bit of play will save a shaft from scoring or squashing a bronze bush like butter.
As for the equipment manufacturer not wanting to honour warranty , they could have gone to court , but that would have cost as much as the repairs have and the machine would still be sitting in the yard useless.
Michael

RussZHC
04-17-2012, 09:29 PM
OK.

However from experience I have found that sometimes a bit of play will save a shaft from scoring or squashing a bronze bush like butter.

Frankly I thought some of that (bold) was automatic based on size alone and the class of fit needed/required. Using something related perhaps to the D10, a Class F High Limit Forced Fit for 5" is very different than a Low Limit D Driving Fit of the same size and neither are the same as for the same class of fit but for 2" [like I said, way out of my league, I can only go by what is published, from Machinery's 12th Ed 1943]
If those or other specified numbers are not followed, either for shaft/hole in the above example or other clearances, links pivoting past one another to give an example, are not to, shall we say, industry standard...I'd just ask, "why?" or "why not?" I would not expect the same fit on a new, or nearly new Rivett as I would on a new or old pin holding the forks on a forklift...very different use/purpose balanced to need.

I think in some small measure I get and agree with your point, we have a very small piece of equipment at work and I swear there were some shafts and holes you could have put nearly half a second shaft in the space, it was that worn BUT it still work OK. Works a lot better now that I brought it back to within reason for what it is IMO.

Forrest Addy
04-17-2012, 09:56 PM
Most manufacturing where a successful assembly requires specific clearances the parts are graded at inspenction grouped for assembly with optilmal mates - its called selective assembly. It's widely practiced in ICE fitting pins to pistons and pistons to cylinders.

If I was going to market equipment requiring close tolerances I would sure as hell selective assemble as tolerances can be relaxed a trifle and the consequent lower costs benefit the bottom line and the competetive position in the marketplace.

Dr Stan
04-17-2012, 11:23 PM
It is a CAT and the undercarriage is too light , , cant take the twisting and other forces .
Michael

Cat is building equipment in China. You may want to check the tag and determine the country of origin.

I'm sorry to hear Cat has not lived up to its reputation. They have built excellent equipment in the past.

rock_breaker
04-18-2012, 01:29 AM
Somewhere a question about boring an aluminum pulley to recieve a needle bearing was put forth. I found some data that might help.

try: htpp.//www.maelabs.ucsd.edu/mae_guides/Tolerance/Tolerancing.htm

With respect to heavy equipment "warranties" there is a lot of room in that arena. Manufacturers can keep computerized records on individual machines that are used for service frequencies and detrimental operation. I was contiually gigged about shifting into reverse while the trucks were moving forward, most instances were at less than 1 mph and the engine at idle. There were no jerks, shudders, banging or stalls but yet this was a situation that the dealer used to minimize warrantee work. This was the same group that could not cure extremely harsh downshifts when going uphill, their solution was to stop at the bottom of the hill on level ground then proceed up the 8 percent grade.

Black_Moons
04-18-2012, 01:58 AM
I still say you are confusing tolerance for clearance.

I can make very tight tolerance parts that have a huge clearance. Indeed it may even need tight tolerance to maintain proper clearance when things shift and twist.

On the other hand, without selective assembly, loose tolerance parts tend not to work very well with low clearances, since the tolerances have to be at least 2x the clearance or some assemblies will end up with an interference fit before anything even moves.

Clearance itself may have a tolerance spec.

Willy
04-18-2012, 02:40 AM
Not the operators fault , it was purchased to a specified capacity.
The design was not flexible enough to allow it to work in the field.


Having operated a wide assortment of road building equipment over the years it sounds as if the machine is too flexible to work in the field, at least the field it's in!

Was the machine perhaps spec'd too light for it's intended application?
It's all too common for the sales team to spec a machine on the, light duty/low cost side in order to garner a sale.
I realize a sale of this magnitude is not taken lightly by the buyer, but quite often capability and price of a machine is pumped up by what should be a knowledgeable sales team in order to make a sale. All too often full disclosure is not prevalent.

In order to make that sale all of the options are not discussed.
The machine is often over-sold. Perhaps the fault is with the dealer/sales team...not the machine.
It's very obviously out of it's element as purchased.

mike4
04-18-2012, 03:33 AM
I still say you are confusing tolerance for clearance.

I can make very tight tolerance parts that have a huge clearance. Indeed it may even need tight tolerance to maintain proper clearance when things shift and twist.

On the other hand, without selective assembly, loose tolerance parts tend not to work very well with low clearances, since the tolerances have to be at least 2x the clearance or some assemblies will end up with an interference fit before anything even moves.

Clearance itself may have a tolerance spec.

The problem is that the parts have been selected to be a little under tolerance but they are still binding in work conditions , assemblies which should operate for at least 100 hours before any maintenance are failing after 30 odd hours.
Currently there is some debate on how it is going to be rectified , possibly tear the whole side down again and maybe make some of the parts ourselves , without any close fitting items which will allow things to have slightly greater movement before any binding can start.

I am talking about going from a 2 thou clearance to about 8 thou and all parts on sixe no + or - . thats what is going to be tried .

If that doesnt work then its curtains for the machine , it will be stripped for parts and the site will continue to change back to older models which were made to work not look pretty.
Michael

Black_Moons
04-18-2012, 04:35 AM
The problem is that the parts have been selected to be a little under tolerance but they are still binding in work conditions , assemblies which should operate for at least 100 hours before any maintenance are failing after 30 odd hours.
Currently there is some debate on how it is going to be rectified , possibly tear the whole side down again and maybe make some of the parts ourselves , without any close fitting items which will allow things to have slightly greater movement before any binding can start.

I am talking about going from a 2 thou clearance to about 8 thou and all parts on sixe no + or - . thats what is going to be tried .

If that doesnt work then its curtains for the machine , it will be stripped for parts and the site will continue to change back to older models which were made to work not look pretty.
Michael

So the parts are within tolerance for the design, even on the side that gives more clearance then nominal, but the designed clearance is still too small for the application. Its not a matter of needing different tolerances but different nominal sizes.

Also most disappointing that any company would claim 'working on unlevel ground' is a reason to get out of warranty work. Even the roads around here are not very level, Where did they expect the cat to be used? Inside a warehouse with a cement floor?

mike4
04-18-2012, 06:31 AM
So the parts are within tolerance for the design, even on the side that gives more clearance then nominal, but the designed clearance is still too small for the application. Its not a matter of needing different tolerances but different nominal sizes.

Also most disappointing that any company would claim 'working on unlevel ground' is a reason to get out of warranty work. Even the roads around here are not very level, Where did they expect the cat to be used? Inside a warehouse with a cement floor?
The site is a rock quarry and the machine was purchased to rip and push material into a stockpile.

Problem is the undercarriage actually twisted in the first week , after the machine did four days of cleaning up which involved climbing over rills left from previous work , some about six to eight feet high but not very wide at the top.
The owner was told that work should have been done with an excavator, no need to climb over the material just move it .
I have seen and used D7 to D9 sized machine in rougher sites wher if you are not careful the machine will end up on its side or belly up .

All that was done was to right them ,check for damage and oils etc and back to work . the canopies were 20mm plate ,designed to carry the machine if it rolled.
They were the old style machines , very tough and well made, he still has two D9s for clearing new ground.
Michael

whitis
04-19-2012, 08:40 AM
In applications like mining, you can end up with custom machines (in many cases pushing the boundaries of what has been done before) instead of commodity machines; on this scale, the custom machine is almost always its own prototype. You are on the bleeding edge. You can decide who bears the risk. You can pay 3 million if it works the first time and 6 million if it takes a second run, or you can have the builder take the risk - in which case you may end up paying 6 million either way.

Yes, flexure can mess with your clearances. Sometimes the answer isn't just to make the clearances bigger or try to reduce flexure. Sometimes you may have to change the mechanical design so it is more intrinsically impervious to mis-alignment (better kinematics). If a bigger clearance was the answer, then you didn't need tight clearances in the first place and probably should not have specified them even if you thought the stresses were less severe. On the other hand loose clearances can sometimes allow a machine to beat itself to death.

Another thing in these kinds of dirty jobs is it is really crucial to keep the dust out. On the summit of one volcano, we had many makes and models of SUVs driving back and forth on a 6 mile road between the 9000ft altitude and 14000ft altitude. Unpaved washboard road (even though they constantly regrade). All except one model were destroyed with only about 6000 miles on the odometer. It wasn't the bumpyness of the road or the altitude. it was the simple fact that these "off road" vehicles don't come from the factory with off road air filters. Abrasive dust gets in the engine. Almost any moving parts can be affected.

Designers frequently overlook real world conditions. How many buildings have collapsed because they were built on the premise that the ground is stationary?

BTW, Here is a 2 part promotional video that shows some NVIS antennas being designed, built, and torture tested. Warning: there is some actual machining content. NVIS is Near Vertical Incidence Skywave - used by the military and hams for medium distance communication. Of course the test they don't show is forgetting to lower the antenna when driving under a low overhang. Or actually putting luggage in that rack. Not sure if this was already posted here.

flylo
04-19-2012, 09:26 AM
Just curious the 1st post says D10 sized dozer then somewhere it's verified as real Cat brand. Is it a true D10 Cat? Just like in lathes you can get lighter duty machines for farm type duty moving dirt or heavy duty massive for mine/quarry work. Without knowing the facts it sounds like too light a machine for the job but thats an opinion based solely on the few facts presented. Maybe the buyer bought the right size & brand just not the industrial duty. Thats why I like old equipment most of it was overbuilt. They put their reputation & quality 1st, not the shareholders, profits & beancounters.My Dad ran an old D7 cable/winch dozer that would clear land faster than any hyd machine & it was a beast. He taught me if you get it buried pull a log to the tracks chain it to them & it will walk it right out. The machine is standing almost straight on end in the proccess but it works. Massive pucker factor! Good luck as I know how it feels to buy a new machine only to wish you had the old worn out one back as I bought a chinese tractor once. It only broke every time I used it.