[vettespeed]

I've been in the CNC world of exotic metals for 10+ years machining such materials as 625/718 Inconel, 6AL6V Ti, 13-8 Stainless, 4000/300 series steels, etc. Got a new job at a mold/tooling shop and the company is considering bidding on a Joint Strike Fighter carbon fiber package. What's it take to cut this stuff. I couldn't tell you type/grade, just know I got a piece to test and it seems like some dense stuff. What cutters would I use to cut profiles up to .750 deep or so and maybe drill a few holes around 1/4"? Thanks, Mike.

[mxtras]

Are you talking about a laminate, fabric or prepreg? If it's a laminate, do you know what the resin is?

Hate to answer your question with questions, but....

After re-reading your post, it appears that this is already laminated. Standard carbide end mills will work most of the time. I have encountered only a few composites that were extremely difficult to cut and for those, diamond tooling was used to basically sand the part to shape. I have turned end mills into semi-molten blobs trying to cut composite armor plating so I can attest that it can be a challenge. Most of the cutting I did was with either dry fabrics or pre-preg materials but had to rout laminated panels from time to time and I would typically use Micro grain, high helix end mills and adjust as necessary to keep the tool from overheating. Watch the dust.

Scott

[vettespeed]

It must be laminate? It's not fabric. I guess I'l looking at resin and fabric, is that laminate? It's dense and feels rock hard to the touch. I'm not sure I know what prepreg is? We made the molds, now they are laying up the cabon fiber into the molds then we are going to 5 axis trim the profiles, 3-D contour the top side, and drill some holes.

[mxtras]

Drilling can be a challenge depending on the resin and the density, I guess. I have seen issues with the entry and exit de-laminating. If this is a highly stressed part, the holes would likely be molded in or have bushings molded in place, so I am guessing this is not a super-critical component? Edge sealing is an issue with carbon laminates and the trend was heading towards net shape molding when I exited the field a few years ago.

Scott

[vettespeed]

Huh? How do I cut it? Endmill material/style/type, speed/feeds, etc?

[mechanical]

Don't even bother with carbide tooling just go ahead and set up using diamond coating tooling. Trust me you will thank yourself later. You will have great sucess using diamond coated drill bits to drill the composite. The main thing to watch is your feed rate, if you feed to high or with a dull bit you will break out the back side of the composite (aka delamination). The main thing to do early on is monitor your tooling extremely close to determine the point of replacement. Don't try stretching your tooling past this point with composites it will bite you every time. You can get assorted end mills that coated and you can have those end mills recoated a few times to save some money. To answer your questions on feeds and speeds you will have to just go to the machine and start cutting to find out what works best. Also you will probably be using water as your main form of coolant with the allowance of rust inhibitors to protect your machine. Let me know if you have any more questions.

[whirlybomber]

I've worked with cutting cured composite panels (that's what you're doing, btw) for 13 years now.

Without the exact details of what you are cutting (and no, don't post them. the men in the black helicopters would be around to send you on a one-way trip to gitmo vi rendition-air so fast you would not believe it. More seriously, what the JSF is made out of (in detail) is probably an export-controlled secret. posting it here would break all sorts of laws) we would not be able to tell you exactly what type of tool to use to cut the stuff.

contact the people you are bidding with for the contract, and ask them nicely to tell you what they use. Read some composite magazines and get local cutter vendors to visit you and display what they sell. Experiment on your own with all sorts of stuff.

Although to drill holes, we use standard drills for low-tolerance holes one-shot drill/reamers for close tolerance holes, and standard countersink cutters in cages for countersinks. All in comercial product's you understand.

Although if you have made the LM's (layup mandrels) and are producing test pieces/first articles, I would say you already have the contract, as you obviously have the engineering data....

Oh yeah. don't breath the dust. that stuff makes asbesdos look harmless. And be careful which solvents you use to clean up uncured resins. some of those things will do nasty stuff to your kidneys/liver. And lets not get started on mould release agents.....

Why oh why won't they just let us make this sort of stuff out of large monolithic alloy high-speed machined frames and ribs? Al-li is souch a nice alloy when designed and manufactured properly.

[mxtras]

Don't even bother with carbide tooling just go ahead and set up using diamond coating tooling. Trust me you will thank yourself later.

Are you here to tell me that carbon laminates can not be cut with end mills? This is simply not the case. It is done effectively daily.

The main thing to do early on is monitor your tooling extremely close to determine the point of replacement.

Very true. The tools go from cutting fine to too dull to work very rapidly and without much warning. It's best to log cutting distances for each cutter to forcast failure rates and to judge coating performance and tooling geometries. Cutting carbon/epoxy laminates is a very abrasive thing. You may also want to try ceramic tools - a bit more costly but they perform well under heat.

Also you will probably be using water as your main form of coolant with the allowance of rust inhibitors to protect your machine.

Say what? Not a good idea. Ask the designer of this panel if using water on his laminate is OK. Carbon and water do not and have never gotten along. Edge sealing is such a huge issue with carbon parts to prevent delamination that the use of water for cooling would send any composites engineer into convultions. Use a cold air gun and possibly a mist system (and definately a vacuum system for the dust) and get approval from the company you are making these things for. If they are doing any bonding or sealing they are going to want to know exactly what it is that you are using and in what concentration. Do NOT use water as coolant when cutting carbon composites. Ever.

There are a lot of folks cutting carbon laminates with water jet and for this I have no explanation. I can not understand how they get away with this. I have seen dry goods cut with a water jet and I understand that it leaves little moisture on the part but I am not a chemist nor do I have experience with water jet cutting so I can not speak intelligently on this. I am aware of longevity issues caused by (presumably) moisture induced de-lamination involving carbon laminates. Perhaps someone with a bit more experience can enlighten me on this aspect.

Scott

[mxtras]

Without the exact details of what you are cutting (and no, don't post them. .

Uh - very good point! My question was a bit on the un-sensitive side, I guess! I assume he knows not to divulge the sensitive info.

I was first thinking he could be cutting fabric - it was not really clear to me that he was cutting a cured laminate.

Scott

[alucarD]

I helped in a shop that used "WATER" to cool the cutting ... back in the day H2o was a bad thing to use on laminates <forgive my spelling> they were black in color and this was after the 2 weeks in the ovens to cure them.. yes Gov. contracts.. nasty stuff after curing you coulden't put a .38 cal bullet throught a 1/32 inch sheet... stuff scared me to death.... ok the gov. provided stuff they called "water" looks clear and tasts like rusty piping and almost instantly eats plane steal bits you use this "water" on CARBON STEEL only they will tell you this very adamintly <roughly: the guy that told my friend was screaming it at him> the color of the material is a big issue at this point... mind you i have note worked with the stuff since the black,green,gold and yellow days the color will or at least should help you to know what the strength of the stuff is. Black is the toughtest and you can only cut it with a sand cutter or diamond bit but the stuff is very easy to work with once you know what your doing.....
The shop i helped in used 4 pieces about a foot long and did lots of test cutting..
The pieces they were making were dash board type of thing lots of holes and recesses.. One piece took a week to do by one guy.. good luck and i hope that helped

[pvogtcharlotte]

This month's "Manufacturing Engineering"
www.sme.org/manufacturingengineering
has a detailed article about cutting composites.
It seems that waterjet works well.
Paul Vogt,
Charlotte, NC

[mxtras]

Here's another pretty decent article on cutting composites:

http://www.mmsonline.com/articles/120501.html

Scott

[Bill Macfarlane]

I've been in the CNC world of exotic metals for 10+ years machining such materials as 625/718 Inconel, 6AL6V Ti, 13-8 Stainless, 4000/300 series steels, etc. Got a new job at a mold/tooling shop and the company is considering bidding on a Joint Strike Fighter carbon fiber package. What's it take to cut this stuff. I couldn't tell you type/grade, just know I got a piece to test and it seems like some dense stuff. What cutters would I use to cut profiles up to .750 deep or so and maybe drill a few holes around 1/4"? Thanks, Mike.

Mike:
I work for a large aircraft Co. We do a lot of drilling on composets and we use a drill/reamer tool that we call a dreamer. You may want to contact; Quality Carbide Tool. They are the suplier for this drill/reamer. It works very well.

[vettespeed]

OK,
I guess this stuff is "prepreg" carbon fiber composite, probably baked in an oven I suppose after it's layed up. Anyway I lit into a piece today with a new 3 flt aluminum cutting style 1/2" endmill. It cut great, left a smooth nice finish, but created heat and yes did dull very quickly. I cut it dry. You guys keep mentioning diamond tooling, what do you mean? Diamond coated carbide? Diamond incrusted? What manufacturers, flute style, whatever? I used some endmills today that had little diamond bits incrusted to them and it did not leave a nice finish, rather course and porous compared to the fluted endmill. The parts I will be cutting will need about 1.5 flute length to cut the profile then have the top side contour hemstitched. It looks like maybe there won't be any hole drilling after all, so I mainly need advice on endmills. Thanks, Mike.

[crazyneosimpson]

Vettespeed,
Speed? It's a plastic keep the speed up, this is nothing like tooling metals, I find the speed comparable to aluminium. This needs to be tempered with your wear rate, carbon is abrasive, if you only have a few holes to drill it won't change your speed.
Feed? Again it is soft, measure it, same as AL!
To get a neat hole in the B787 we slotdrill 1mm smaller then circular interpolate to finish to size.

[chineguy]

Use Diamond coated endmills. You will not believe the difference in tool life. Spindle speed should be relatively high. When cutting epoxy bonded fiber they usually recommend to use a higher feed to break the fiber. I have heard the diamond coated bits that look like steel grinding wheels with grooves work well. They have to be run at router bit type speeds though. I never could try them. The company I worked for insisted on trying to use antiques (20 yr. old) with slow spindles. You can get some good end mills from Garr. They have some speed feed info in the catalog. Otherwise its just trial and error. The composite articles mentioned would be well worth your time to read.

[mechanical]

Are you here to tell me that carbon laminates can not be cut with end mills? This is simply not the case. It is done effectively daily.

Say what? Not a good idea. Ask the designer of this panel if using water on his laminate is OK. Carbon and water do not and have never gotten along. Edge sealing is such a huge issue with carbon parts to prevent delamination that the use of water for cooling would send any composites engineer into convultions. Use a cold air gun and possibly a mist system (and definately a vacuum system for the dust) and get approval from the company you are making these things for. If they are doing any bonding or sealing they are going to want to know exactly what it is that you are using and in what concentration. Do NOT use water as coolant when cutting carbon composites. Ever.

There are a lot of folks cutting carbon laminates with water jet and for this I have no explanation. I can not understand how they get away with this. I have seen dry goods cut with a water jet and I understand that it leaves little moisture on the part but I am not a chemist nor do I have experience with water jet cutting so I can not speak intelligently on this. I am aware of longevity issues caused by (presumably) moisture induced de-lamination involving carbon laminates. Perhaps someone with a bit more experience can enlighten me on this aspect.

Scott

Scott,

I am a composites design engineer for one of the major aero companies. I was just trying to offer a quick bit of public common knowledge that is available on the web thru any major search engine. Since they are trying to determine if they will bid on the package or not I don't know what engineering has been provided to them. I would first check the engineering package and see what spec's govern what you can and can't do. If there are question's about the spec's contact the buyer for clarification. The spec's must be obeyed unless a deviation is permitted on the engineering dwg itself. In this case I know water is allowed as a coolant while machining on a "cured" composite part. There are also various other coolants allowed but he must read the spec and see what the program has qualified to use at this point. Just a guess i'm sure he will see Boelube, Coolube 21, Water, and Cetyl Alcohol as approved coolants. If the part will be bonded to another part then that will cause a few of the coolants to drop off the list and will require a good cleaning to remove all traces of coolant afterwards.

As far as recomending PCD tooling, it's recommended by experience of living with this stuff daily. Yes you can use HSS or Carbide cutters, but why take the chance of ruining a part with so much labor involved. Remember machining is normally the last step of the labor intensive layup process. I would hate to scrap months of work because I wouldn't spend an extra $100 bucks on a PCD cutter. I just know if he is looking to maximize his machining efforts I would start looking at PCD ball end mills for all profiling efforts.

I will take a stab at your question about using a water jet to cut composites. It seems like you are thinking of cutting uncured composites with a waterjet? If so then that is not allowed to the best of my knowledge on any program I have worked on. Also, there are requirements in place that govern the moisture content of the fiber before it can be accepted for use. Using a waterjet to cut cured composites depends on the final application and what level of inspection (NDI) that the part will recieve when finished. Speaking of NDI most ultrasonic inspection systems use water as the coupler or transfer medium. Most critical composite parts are either submerged or flooded with water during the UT inspection.

[unterhaus]

This is bringing back bad memories from my days as an engineer in the Air Force. I'm pretty sure the manufacturing standards for the aircraft I worked on were called out on the drawing for the part. Assuming you won a bid from the government, they should be able to provide them for you. I don't think that they were usually provided in the bid package that we sent out.

The General Dynamics standards were pretty good, there was a huge book of them.

[vettespeed]

Brand of tooling? Type and style of tooling? Spindle speed or surface footage suggestions? Feedrate or in/rev suggestions. Dry or coolant? I will be cutting on HAAS mills with max 10,000 RPM spindle, maybe less depending on machine the parts go on. Someone mentioned PCD? I tried a cutter that appeared to be tiny diamond chunks bonded to a shank and it did not leave a very nice finish, do you think they were PCD? Maybe my feed was too fast or spindle speed too slow? I ran a 1/2" cutter at S1528 & 15.0 in/min on a finish profile cut. If anyone suggests tooling types please provide brand, type of cutter, spindle speed or surface footage suggestion, feed or in/rev suggestions. I will be cutting it dry or with a typical coolant flood, the machines currently have Hangsterfer's coolant in them, I can't see running water in these machines, everything would rust. Thanks, Mike.

[BptRoadman]

When You say "carbon fiber" is it like cloth or already autoclaved? If it's still cloth then you need something like a Gerber Cutter if its cured then a waterjet ... that stuff is brutal