Building my own CNC router

smdub · Aug 25, 2016

You could also use MecSoft's FreeMill for a free 'pro' cam solution. http://mecsoft.com/freemill/

If you are new to cnc, for the FCG pocket I would HIGHLY recommend you write the code by hand. Its a skill that should be learned. Its basically 2-3 rectangles which are a dozen lines of code w/ a for loop. Cn't get any easier. If you use cutter radius comp (G41/G42) its REALLY easy. The ray-vin manual will give you the dimensions. IIRC he shows the auto-sear denial 'hump' but I've seen commercial lowers done both ways. If you leave it open like a M16 and your cad model, you are one hole away (and a couple trigger parts) from full-auto. I've never understood how that passes ATF muster for 'not easy to convert'.

ToolAA · Aug 25, 2016

smdub said:
You could also use MecSoft's FreeMill for a free 'pro' cam solution. http://mecsoft.com/freemill/

If you are new to cnc, for the FCG pocket I would HIGHLY recommend you write the code by hand.

If you leave it open like a M16 and your cad model, you are one hole away (and a couple trigger parts) from full-auto. I've never understood how that passes ATF muster for 'not easy to convert'.

Thanks for the advice on both accounts. I have two 20hp CNC machines at work for with proprietary CAM software for stone fabrication so I have the basics but most of our work is 2D. So I will be learning something new here.

Also thanks for pointing out that the cad model included the M16 pocket. I'll be using my AR receiver as a guide.

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ToolAA · Aug 28, 2016

It's alive. Still lots of testing and learning to do.

https://vimeo.com/180532740

But I just couldn't help myself.

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ToolAA · Aug 29, 2016

Ok this is going to work.

https://vimeo.com/180680987

Ghostgunner $1500. Im $850 machine plus $175 for software into this and I've got a machine and software totally usable for other things.

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ToolAA · Sep 7, 2016

smdub said:
If you are new to cnc, for the FCG pocket I would HIGHLY recommend you write the code by hand. Its a skill that should be learned. Its basically 2-3 rectangles which are a dozen lines of code w/ a for loop.

Smdub, I played around doing the block of wood sample by creating one narrow pocket then copying and pasting the rest of the milling code while stepping down the Z each loop. It was not too bad. However I found out about Autodesk Fusion 360 and it has built in 3D design and what seems to be a good CAM. So I've modeled the Lower and two guides and now seem to be able to create a good pocket.

Now that I am at the milling stage I realize I really have no idea what feed speed to use. It seems like when I plug in the materials, mill size and router speed into the Fusion 360 settings that the tool is moving very fast maybe 2000mm/min. I really lack experience in this area.

Is there any good beginners resource that you can recommend.

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PleaseEatSomePoo · Sep 7, 2016

Look up data sheets for the tool you want to use. Should be able to calculate feed/speed/stepover/etc.

smdub · Sep 8, 2016

google feed/speed calculator online. This is the first one that turns up:
http://www.custompartnet.com/calculator/milling-speed-and-feed
for surface speed ballpark 200sfm in aluminum but your machine rigidity is going to be *THE* limit. Grab a block of 6061 and start milling a slot/pocket. 1/4" 2FL @ 0.001"chipload @ 200sfm = 3000rpm spindle & 6ipm feed. The BIG question is then how deep can you cut in one pass? Only you can figure that out. For roughing out the cavity, you probably can't beat plunge roughing for speed on a lightweight machine if you can generate the g code.

ToolAA · Sep 8, 2016

I think you just highlighted another problem I'm going to have. The minimum speed on the router is 15k.

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jcarpenter · Sep 9, 2016

You can cut aluminum at that rpm with a 1/8 in diameter bit. May have to lube it. But then the problem is the overall length of the bit. Cavities on the lowers are pretty deep and getting down in there may be a problem. Also your frame stiffness may be a problem for chatter. One way to see, get a block of scrap aluminum and just try it.

John C

smdub · Sep 9, 2016

I don't see how you can do it w/ a 1/8" bit. That's like a 10D deep hole. If you attempt that, don't even think about using a HSS bit. And take a *TINY* depth of cut each pass. You'll spend enough on electricity running it that long to just buy a lower

ToolAA · Nov 5, 2016

Finally had some time today to get back to this project. I ended up buying a true router spindle and VF Drive on eBay. Got it all hooked up last week.

Today was a test run to make the lower receiver holding fixtures.

So far so good.

Im going to run a test of the FCG pocket in solid bar of aluminum later this week. If all goes well I hope to have a finished lower soon. Then I can start my 300BO pistol build.

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Boss94 · Nov 6, 2016

It would help you to drill out as much as you can before you start milling. Even if its just a entry pocket for a plunge area . If you have to plunge in Z helix is your best option , Ramping would be second best. Since your just starting out 4 degree in Z would be a good place to start. There is 2 basic trains of thought when it comes to milling. 1st is shallow Z steps and side step overs up to half Dia. of cutter ( you can do full engagement , But you need a good coolant flood and a rigid machine and fixture).2nd is 1 to 2 times Dia. Z depth with a .02 to .04 side step over path. By doing this you can increase your feed considerable and the mill wears more evenly along the flute giving you longer tool life. Also climb cutting is the way to go with CNC as you do less recutting of the same chips.

ToolAA · Nov 6, 2016

Boss94 said:
It would help you to drill out as much as you can before you start milling. Even if its just a entry pocket for a plunge area . If you have to plunge in Z helix is your best option , Ramping would be second best. Since your just starting out 4 degree in Z would be a good place to start. There is 2 basic trains of thought when it comes to milling. 1st is shallow Z steps and side step overs up to half Dia. of cutter ( you can do full engagement , But you need a good coolant flood and a rigid machine and fixture).2nd is 1 to 2 times Dia. Z depth with a .02 to .04 side step over path. By doing this you can increase your feed considerable and the mill wears more evenly along the flute giving you longer tool life. Also climb cutting is the way to go with CNC as you do less recutting of the same chips.

Thanks for the technical details. I am using Autodesk Fusion for CAM and there are loads of built in options for tool setup. Your idea to pre drill the pocket is a good one that had not occurred to me. I could simply put a high quality 3/16 bit in the spindle and let it pre-drill 30-40 holes. It would be easier to lubricate and make a lot less mess. Then when I do mill the pocket the chip load will be a lot lighter.

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Adolph Oliver Bush · Nov 6, 2016

If you go the drill route, use "peck drill" if that is an option in ur CAM program. Using 0.050" per peck or something similarly small will keep the chips small and therefore more manageable, and help keep fluid on the cutting edge, thus helping to avoid built up edge.

PleaseEatSomePoo · Nov 6, 2016

Full volume milling!
https://youtu.be/H4_TY6EMMOM

Boss94 · Nov 12, 2016

We use Volumemill at work ( we have Gibbs ) And it works great !! but you do have to wag the dog some to get what you want sometimes. Since Gibbs was bought out recently we seem to average about 2 upgrades a week . When it was Gibbs owned we had very little issues . But lately its had some serious issues. I hope they resolve them soon !!

on a different subject if you decide to use a drill to remove most of the meat . Make sure the holes don't overlap as it can cause issues. Try and leave .01 to .02 wall between them.

FrankOceanXray · Nov 12, 2016

Seems all too involved ATM but I am certain once you have this runninng, dialed in... it will be a gem.

Good luck! Keep up the good work. A lot of knowledge on the forums.

ToolAA · Jan 4, 2017

Finally getting a chance to test milling the FCG pocket in aluminum. So far so good.

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ToolAA · Jan 13, 2017

I had a chance today to continue testing. Following the suggestions of others I decided to drill a pattern of 1/8" holes then mill the pocket. This worked much better with less tool chatter. The final pass was 32mm deep

Sunday I'll run finishing passes and mill the trigger hole.

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Boss94 · Jan 14, 2017

Looking good !!!

Building my own CNC router

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