T.I.R. probs drilling

[jhauschild]

I'm haveing problems drilling concentric to the O.D. The work is being done in a Hydromat Indexing machine in which the tooling is rotated and moved into the material. I have tried gundrills and reaming and fluted drill to size, with or with out a previous hole, and we always end up with a fairly good entrance hole, but the exit is off around .003 to .005 or more. The machine is squared up and lined up as well. The part is compacted metal, cuts like a gray cast iron. Also the feeds and speeds have been brought up and down with little to no difference. Does anyone have any ideas?

 

Reverse the sequence of operations. and try to drill the part first and turn it between centers or on a mandrel. This whould take care of the concentricity problems.

 

[jhauschild]

Well, the parts are centerless ground before they get to machining. It would be nice if it could be that way. Tried some coolant fed twist drills today. One from Sumitoma and the other from Tirex. They didn't do too bad but we still ended up with the exit sides big. Had my QA do a density check on the parts tonight. Trying to see if there is an issue there. The parts are long and being that they are powder metal, a variance is possible. Have a few things to try yet. I have to thank everyone for there ideas and input. Every bit of info is a help even if it has been tried or thought of already. It all goes to show that different people can think alike, it's all good.

 

[knobhead]

I'm with Ornery Norsk on this one. Get on the phone and get Laundromat, or whoever they are, to prove out what they said the machine could do.

Excessive accuaracy is a sign of poor breeding. -Socrates.

 

[bill1898]

Someone has to make a decision regarding whether you want to achieve the 8 second cycle time or achieve the quality level stated. The two are incompatible on the machine and tooling you describe. You have already used up thousands of seconds experimenting, with little to show for it. Drills are good for removing material and little else. Reamers follow what has gone before them. Your problem has to do with deflection of the cutting tools as they attempt to cut material in an extended mode. Single point boring is the only way you will achieve the concentricity results you are looking for on a consistent basis. You need to achieve the maximum rigity at the cutting tip as possible. Talk to Kennametal about their special boring bar material and make the bars the largest diameter and shortest length that you can.
Make the cored hole as large as possible as long as you are removing material with each pass of the cutting tool.
Secure the bars as close to the spindle bearings as possible. Maybe Hydromat could help with this, it is unlikely that they will be much help regarding the tooling. They may need to upgrade the class of bearings at the station where you are making the final pass.
Instead of zeroing in on the cycle time, look at the total cost, including machine maintenance; tooling cost; downtime cost etc. If you do that properly my guess is that the cycle time will increase, but the number of acceptable parts produced per shift will increase.
Sorry for being so long winded, but I have been in your position in the past and can appreciate what you are going through. Good luck.

 

[elpedro45]

Shefcut reamers are made by Cogsdill Tool.

http://WWW.cogsdill.com