Bore size variation on ductile iron castings

[Len Wilk]

I'm boring 5 different hole diameters in a ductile iron casting (rough and finish) from cored holes. Hole sizes vary from 1.50" to 3.75". Once in a while about 1 in 100 parts 1 or 2 bores jump in size up to .005" from the previous part. Without any adjustment the next parts are back to proper diameters. I don't have an explanation for this problem and these parts cost about $500 each. Does anyone else experience this?

Thanks

Len

[GoetzInd]

Chips getting in the spindle taper during tool change would be my first guess.

 

Mike

[specv]

chips in the spindle, like mike said.

[powerfulp]

Yes, this is a problem at my shop as well. We have some older equipment. We end up cleaning the spindle and tool shanks before boring, which remedies the problem. We also use gage cuts if we don't want to clean the spindle every time. Bore enough to be able to check it, and if ok, finish the bore.

[Len Wilk]

These are high quantity production parts (200 per run), so we can't be cleaning the spindle for every part. Also it seems to be mostly one bore size that jumps. There is an air blast from the spindle at every tool change so I'm hoping that the shavings are blown away. These parts are machined on a HMC. Do you think that the material could be a problem (hard spots)?

[Joe788]

These are high quantity production parts (200 per run), so we can't be cleaning the spindle for every part. Also it seems to be mostly one bore size that jumps. There is an air blast from the spindle at every tool change so I'm hoping that the shavings are blown away. These parts are machined on a HMC. Do you think that the material could be a problem (hard spots)?

 

What is the cutting operation that's going on with the tool that immediately precedes the bore that's jumping oversize? Maybe add an extra dummy toolchange in before that boring tool next time you run the job, and see if your variations go away.

 

Are you using overhead shower coolant to make sure chips are never able to accumulate on the top of the spindle housing?

[mkd]

some horz have an auxiliary air blast controlled via m code. perhaps plumb it to shoot at the tool/spindle interface.

properly programmed, it could blast the tool after m09 and before m05.

this is what i used to do.

[Len Wilk]

There is an overhead shower so no chips on the spindle housing. Shouldn't the normal air blast be sufficient to remove chips?

[mkd]

There is an overhead shower so no chips on the spindle housing. Shouldn't the normal air blast be sufficient to remove chips?

joker in me want to ask how that's workin for ya?

 

by your description, chips seem to be the only common mishap. when the next part runs fine with no other changes........

welcome to the best forum...

[GoetzInd]

Clean out the tool magazine pockets. Good place for chips to hide.

 

Mike

[specv]

We have a spindle taper cleaner by every machine (horizontals) and clean the spindle at the start of each shift. Depending on the job length we will clean the pots once a week if needed.

[Len Wilk]

thanks for the replies guys, will pass this info to the higher ups.

[mkd]

MMS's december issue has a good write-up on using Big Kaiser series 310 ewn tooling for "random" boring issues.

 

rigidity could be a culprit with slamming of a tool changer. but with this failure mode the diameter would stay at the oversize/undersize setting for subsequent parts, not really part of your solution.

 

is there a laser setter that could measure the diameter of a boring bar, where you could setup a Macro to throw and alarm if it was not within size parameters???

[taperlength]

Probably a variation in some of the castings, like a core out of place.