machining aluminum forgings

[KMI]

Good Morning,

 

I'm curious if anyone out there has had problems with carbide endmills breaking when cutting forgings. The material is 6061. We use kennametal hpfa coated endmills and in billet plate we have never had a problem. We have recently started using forgings in our product line and have broke alot of endmills. I have tried lower feeds,lower spindle speeds. The only thing that seems to work is to drop below about .003 per tooth loads. In billet plate we run the same endmill at .010 per tooth with no problems. We have tried roughers as well and they last about 1 hour. Any suggestions?

 

Thanks in advance.

 

Kodiak Motorsports Inc.

[Philcott]

The biggest problems, I have had, with forgings are hard spots and sand in the material. Sand will take a sharp edge off your cutter quicker than almost anything. You will probably need to go with inserted tooling at least for roughing the skin off the outside.

If you listen carefully you will hear when the cutter hits a sand pocket in the casting.

 

Good luck,

 

Phil

 

Nice wheels. How about a tour of the shop next time I make it to Abbotsford?

[Keithm]

Do you know how they are cooling the forgings. If they don't have a way to controll the cooling process you will have a lot of vairation in the hardness of they. That is what will give you a lot of problems with the outside hardness.

[Phil Orenstein]

I've cut 6061, not forgings but flat plate and extrusioned stock and I have had the typical problems associated with 6061 due to its gummy nature. I've had tools gum up and break mostly when cutting deep slots and contours without multipasses leaving no room for the chips and coolant to flow. I don't know if this helps in your situation.

 

Phil

[KMI]

Thanks for the info. I have changed the step over settings to 60% and have decreased the DOC to only .300 with a .625 endmill. The forgings are 6061-t6. I will contact the supplier to see about the heat treat. No problem with the tour of the shop. Give me a call and come on over. Bye for now.

 

Kodiak Motorsports Inc.

[MetalMarvels]

A 6061 forging is typically about a T4 temper after forging, but before heat treating. It requires a heat treatment of 8 hours at 340 to 360 degrees F to achieve T6 temper. There are a whole series of Txxx numbers for aluminum that have a huge set of different conditions associated with them. For example, I just learned that the 6061-T651 that I use was stretched after heat treating to a T6 condition - hence the "51" on the end.

 

These were pulled from "Handbook For The Metalworking Industries" - pages 530-531.

 

I can go home now - I learned my new thing for the day!

[KMI]

Hi again,

 

I talked to the forging producer and they assure me that the material has been heat treated to t6. I talked with the tooling engineer from Kennametal and he suggested not plunging at all. I took the advise and was able to make some parts without loading the cutter. It is a fair bit slower than what we usually do in billet. He also suggested using some powdered metal endmills instead of the solid carbide. I will try some of those tomorrow and let you know. Thanks for the tips.

 

Daryle

Kodiak Motorsports Inc.

[SledGeek]

Used to use ti coated cobalt corn cobs on on copper and alum. "crap castings" with no shortage of sand pockets. 1' dia.75 % step 1 inch deep around 1000-1200 rpm. Doesn't sound good but works great .Don't know how well it would work on production level, but for orders of 10 or less it actually saved us time compared to changing inserts.

Climb cut only.

[specv]

I think everyone needs to realize that he is talking about Forgings, not sand castings. Pro-max makes very good roughing endmills. They make rough and finish endmills and they make 3,4,5 and 6 flute. they are spendy but the last a long time and resharpen very well.

[Guest CNC Apps Guy 1]

Plunging in 6061 regardless of condition is bad IMHO. Either do helical or ramp entry. This way you get better chip evacuation and coolant flow. Also set your ramp/helix angle to about 2 deg.

 

You do have good coolant flow right?

 

HTH