- Joined
- May 5, 2000
- Messages
- 31
I've spent the last week or so experimenting with various techniques and tooling to machine some Carbon Fiber Samples that were sent to me by Gordon("Carver" from St. Louis).
Basically, I've found that the samples thatI received were very easy to machine and I had very little problem with splintering and whiskers.
Rather than go through some of the "gettign up to speed" failures, I'll just detail the success and hopefully, you all will be able to emulate the techniques and achieve the same results.
First try was with a regular import HSS 4 Flute, Center Cutting TiN coated end mill 1/8" Diameter. ( Cost of this end mill is approximately $5.00) Spindle speed was 2850rpm on a Standard Bridgeport.
The piece was held in a regular Kurt Vise supported on a set of parallels. The Knee was locked and the spindle fed into the work with the handwheel. Initial cut was .010" to establish the cut line. No Coolant. Subsequent cuts were made at a DOC of .015" until the piece was completely milled through (Piece thickness was .180"). The initial cut produced what appeared to be some very tiny whiskers, but after the final cut, they were no longer in evidence.
I tried the same cut with the quill locked and feeding the piece into the endmill with the knee. This produced a cut that was just as clean although in my mind, I felt that it was a little bit better ( Toss up ). Edge finish was excellent with no splintering or burring. A slight "Wire" was observed on the mouth of the cut, although a light pass with 600 wet or dry eliminated it totally.
I noticed during the machining, the the Carbon Fiber machines very similarly to graphite or even Cast Iron, that is, it produces a tremendous amount of dust, this is something that must be eliminated or rapid wear of the cutter occurs. A very simple solution is to hook up either a blower ( bad idea ) or a shop vac ( Eureka! That's IT!) to remove the dust as the piece is being machined.
I then proceeded to machine a pocket with similar good results. Again using the .010" initial and the .015" cuts. Feeding from the knee was, in my observation, the best finish, although we're really splitting hairs here ( no pun intended!).
The only problem with splintering that I encountered, was when I attmepted to pocket with an island. The Island did tend to whisker. I find that the Carbon fiber does NOT LIKE to be Climb Milled. Conventional milling produced the best finish.
I then repeated the above with a Diamond End Mill [4 flute center cutting] (1/8") The approximate cost of this end mill was $200.00. The finish was not perceptibly better than the far less expensive TiN Coated End Mill. Again, removing the dust with a suction.
The Final Experiment was with a Carbide PVD coated End Mill (1/4")[4 flute center cutting] ( Approximate Cost of this end mill was $18.00. Results were very close to the diamond with a slightly noticible edge finish improvement.( I beleive that in order to use Diamond tooling successfully, you need High Speed Spindles ( On the Order of 15,000 rpm). I DON'T recommend using a router as there is far less rigidity in a router than a milling machine.
After 150" of machining to a depth of .150", Examination of the PVD coated end mill showed virtually zero wear under a toolmakers microscope. No edge degradation, no coating removal and no erosion.
Feeds were conservative at 3 - 6 IPM.
I believe that anyone can duplicate these results with conventional machinery.
I hope that this helps.
If anyone has any questions, please feel free to email me.
Jim Harvey
Harvey Racing Engines
Basically, I've found that the samples thatI received were very easy to machine and I had very little problem with splintering and whiskers.
Rather than go through some of the "gettign up to speed" failures, I'll just detail the success and hopefully, you all will be able to emulate the techniques and achieve the same results.
First try was with a regular import HSS 4 Flute, Center Cutting TiN coated end mill 1/8" Diameter. ( Cost of this end mill is approximately $5.00) Spindle speed was 2850rpm on a Standard Bridgeport.
The piece was held in a regular Kurt Vise supported on a set of parallels. The Knee was locked and the spindle fed into the work with the handwheel. Initial cut was .010" to establish the cut line. No Coolant. Subsequent cuts were made at a DOC of .015" until the piece was completely milled through (Piece thickness was .180"). The initial cut produced what appeared to be some very tiny whiskers, but after the final cut, they were no longer in evidence.
I tried the same cut with the quill locked and feeding the piece into the endmill with the knee. This produced a cut that was just as clean although in my mind, I felt that it was a little bit better ( Toss up ). Edge finish was excellent with no splintering or burring. A slight "Wire" was observed on the mouth of the cut, although a light pass with 600 wet or dry eliminated it totally.
I noticed during the machining, the the Carbon Fiber machines very similarly to graphite or even Cast Iron, that is, it produces a tremendous amount of dust, this is something that must be eliminated or rapid wear of the cutter occurs. A very simple solution is to hook up either a blower ( bad idea ) or a shop vac ( Eureka! That's IT!) to remove the dust as the piece is being machined.
I then proceeded to machine a pocket with similar good results. Again using the .010" initial and the .015" cuts. Feeding from the knee was, in my observation, the best finish, although we're really splitting hairs here ( no pun intended!).
The only problem with splintering that I encountered, was when I attmepted to pocket with an island. The Island did tend to whisker. I find that the Carbon fiber does NOT LIKE to be Climb Milled. Conventional milling produced the best finish.
I then repeated the above with a Diamond End Mill [4 flute center cutting] (1/8") The approximate cost of this end mill was $200.00. The finish was not perceptibly better than the far less expensive TiN Coated End Mill. Again, removing the dust with a suction.
The Final Experiment was with a Carbide PVD coated End Mill (1/4")[4 flute center cutting] ( Approximate Cost of this end mill was $18.00. Results were very close to the diamond with a slightly noticible edge finish improvement.( I beleive that in order to use Diamond tooling successfully, you need High Speed Spindles ( On the Order of 15,000 rpm). I DON'T recommend using a router as there is far less rigidity in a router than a milling machine.
After 150" of machining to a depth of .150", Examination of the PVD coated end mill showed virtually zero wear under a toolmakers microscope. No edge degradation, no coating removal and no erosion.
Feeds were conservative at 3 - 6 IPM.
I believe that anyone can duplicate these results with conventional machinery.
I hope that this helps.
If anyone has any questions, please feel free to email me.
Jim Harvey
Harvey Racing Engines
