Calling all ENGINEERS

Togowack said:
It would be nice if it was a simple center drill issue. Thinking of pre drilling or step drilling the alignment pins to full size gradually so we can be sure of the position of the holes before they reach full size.
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If they are pre cored then use a multi flute core drill - 3 to 5 flutes
Use as short a drill as possible and not HSS. Not all of them end cut though so you might need to pre drill to get depth. They have a lot more rigidity and won't tend to wander or follow a previous hole.

Finish ream should be OK then. Or use a burnishing drill but that adds $$$

If you still have position issues then single point bore to true the hole up before reaming.
 
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We have a massive contract with the Chinese, spent the last 6 months dealing with them because we have a few problems meeting their completely unrealistic expectations . They are fucking impossible. GL dude, you'll need it.
 
we lost a lot of customers to china a few years ago, got most of them back within a year or so because of quality issues they had with them.

If Your goal is crap, no one can do it cheaper than china.
 
Yes Arak, at this size 3-4 flute carbide/cobalt drills should be ok with reamers. I expect in the first day to know also providing brand new spot drills if we are hitting target position. CMM software apparently has the ability to do temperature compensation. So I will test the parts soon as we get them in the room and then after 24 hours at 21 degrees also. Temps in China right now are supposed to be 25-35 degrees which is a major factor.

Funny thing is visited the customer this morning to get a stronger feel for their CMM operations and got offered a job. Jewish guy... pays to be a Zionist :)

he actually operated CMM originally for the IDF.
 
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Also thinking of using a small end mill to force the position of the hole if a spotdrill/drill/reamer combination isn't good enough.
 
Cik said:
He is speaking truth. An engineer doesn't see the operation.
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I would beg to differ


Togowack said:
CMM software apparently has the ability to do temperature compensation.
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Just be careful with that - it probably only compensated for the temperature the cmm is at not the part that it is measuring (which means you can stick them out on the shop floor). Unless it has a little thermocouple probe that you stick onto the part then it wont compensate for part temp. Never trusted them anyway tbh as the part is cooling while measuring so it can change during the measuring cycle if it is a long one.
 
Togowack said:
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you can rough and finish mill all the ID's. However you need to finish at .010" undersize on all diameters(take faces to proper depth). have boring bars set to finish size( first part you will obviously sneak up to size) and run them all last.

bore all in line bores one after the other so machine doesnt move in x or y axis.

then move down PAST the bottom alignment pin hole, then back up to it for location and bore it, then move up only to top alignment pin and bore it.
 
Togowack said:
Nothing is standard in China, one person has this idea, another that, and money is so important to them you can never trust tool wear. They work in a very low pressure environment with machines scraping and screeching and to them its business as usual - their way of putting in the extra effort is putting plants and flowers all over the machine shop.



I went through this entire line of thought today, thanks for the pointer I forgot to check for linear interpolation. That was a big no in school too. However the bores align fine on most parts.

Yes Chia I know engineers all too well.

Lots of good reasoning here, I told the boss line boring might be an option.

But had a conference call today and he basically wrote off the challenge of temperature deviations, and the local boss (even though he doesn't have a clue) said he would allow me that much (what much?) as though I was being held to some unknown standard in his head.

Big boss wants to pour a grey iron fixture and use quick change tooling and for me to overhaul the entire production process instead of just producing 6 good parts, which is good. Foundry and pattern labor are basically free and he wants to really impress.

I think the final critical part here is once the part is machined, to insert a dowel pin and use a dial to center the spindle on that location to double check the distance from the bore.

.005" deviation on a diameter of 19" is more than a temperature problem. I also checked the reports this morning and there was no pattern or consistency to the hole locations, they appear completely random.
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machine ball screws are shot, if its cnc.

if you are using a horizontal boring mill, use the left to right, bottom to top method, always stop on location going in the same direction.


also the bores are probably inline simply because they arent moving the machine while doing them all together.

My bet.

they are machining the faces
then drilling all the holes.
then reaming the dowel holes
then machining the bores.

thus, the holes are everywhere, the dowel holes are fubar , but the bnores are straight, relatively speaking, but they may not be perfectly round, checking out ok-ish at 0,90,180,270.
 
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oh, and temperature compensation isnt really an issue.. if you hold tolerance on positioning you should be ok. only thing it will affect is diameter size, and if they have the issues i just explained previously, that will make a difference but is not the core issue.
 
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