04-20-2008, 06:48 PM
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| | | Join Date: Sep 2006 Location: Australia
Posts: 2,321
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Hi looks like a parting off burr.
It appears that the part is made with the small diam being the last part to be parted off on as it has less material to go through, hence the burr in the bore.
I would suggest that if it was done on a double spindle CNC then the part should be parted off at the big diam and the second spindle would hold it on one of the smaller diameters for a clean drilling operation from the back, impossible to do if a regular capstan type machining set up is used.
The burr is pretty bad and it would appear that the supplier has not bothered to inspect the product before delivery, or that the specifications did not call for a "burr free" part.
In any case if the suppliers are using regular single spindle machines, they will have to have a secondary operation to clean drill the bore.
The other way the situation could be overcome is if the parting off operation was done in two stages, first down to a diam just a few .01mm's under the bore size, then when the drill goes to depth it will cut through and leave a burrless bore, only problem is to ensure that the drilling force doesn't break the part off the pip, so the drill would want to be done in two stages too, so that the final drilling just breaks through the bore.
Time wise it will add about 20% to the cost price for the extra ops, and if done in this manner with a single spindle CNC, there should be no problem with work stations as on a capstan type machine.
This is a problem for the supplier to worry about and if they are in the turning business and competitive, it should be a "piece of cake", LOL.
Ian.  |
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