CNC Milling Thread - Tips tricks

[Mustachio]

So not to long ago I got myself a CNC machine and have been learning the in's and out's, through lots of reading and trial and error.

The machine I have is a CNC Mogul , I have a 3'x4' model with dual gantry. I built a 4x8' table for it and I'm planning to expand the machine to 8 feet long some time this year I hope.

For pcb's I'm designing with eagle cad and using the plugin called pcb-gcode to produce the tool path. You can find the software and some good write up on the milling process here.

http://pcbgcode.com/

Once I have my board designed and my tool path created I run the tool path file through a program called AutoLeveller. AutoLeveller will create a new file that when loaded into mach3 (the controller software) it will probe down in the Z axis to get the height of the material your cutting every 3/8" of an inch (all settings are editable). To do this you need to connect a few wires to your controller hardware, a ground clip on the tool and a 5v clip on the board. When the tool touches the board it will create a connection and tell the program that depth is 0 for the Z axis. The Program logs all of this information and adjusts the Gcode to compensate for the uneven surface.

You can find the autoleveller software here. I'm currently using 0.7.7

http://www.autoleveller.co.uk/


I've used 30 degree 0.1mm and 0.2mm Vbit's for pcb milling so far. And for drilling I'm using a #69 drill. You should only need to auto level your bottom etch file not the drill file. Also make sure you have something under the pcb that is ok to drill into, You don't want to  start putting holes in the machines table base. MDF works fine.

Here are some bits like what I'm using now

http://www.aliexpress.com/item/10-x-Carbide-PCB-cnc-router-V-bits-Engraving-Bit-Tungsten-tools-Engrave-Wood-Acrylic-PVC/1200677516.html


Now the real tricky part since were working on such small scale for depth and trace width is getting the board held down as flat as possible. Lets say you tape down all the edges or clamp it in all 4 corners, you might still have some flex and areas where the bottom of the board isn't laying flat against the table , and those areas will not mill correctly since they had some give. Some people have said a vacuum table is the way to go and others use double sided tape (carpet tape works well).

Some of my first tests I would cut small squares of carpet tape for each corner of the board I wanted to hold down. But any area that didn't have tape, the board would flex downward when I pressed with my finger just a tinny bit, and that's still enough to ruin the job. There are lots of options and you might have to find what works best for you with what you have on hand. I've taped the sides with packaging tape and used a wooden rolling pin to try to make things *more* flat as well.

I'll post up more info and pictures with settings I used in pcb-gcode later. And anyone else that wants to add more info to this thread feel free to join in!

I have a few videos on youtube showing some of the cnc machine in action but so far its all just been some of my tests nothing to crazy yet.

Turn down your volume ahead of time the dremel is a bit loud.

You can see in this first video the first try was not leveled well and milled too deep ruining it. But the second board leveled worked out great

And another short video of the drilling process

And here is the current very very messy state of my table/work bench. Man I am a mess I really need to tidy up!



Hope some of this info helps and I'll try to update this thread with more info as I learn.

[italianguy63]

That's badazz Jimbo.

It is obvious the Kokopelli's are making the mess at night when you are sleeping.

MC

[italianguy63]

I built a 4x8' table for it and I'm planning to expand the machine to 8 feet long some time this year I hope.

That makes for a damn big PCB.  What will it be?

MC

[Mustachio]

Haha yeah those dang Kokopelli's always causing mischief, gotta get those out in the mail soon. I cut them for a friend he sent me some cool artsy copper sheets that where "aged" and sealed. Might try to use some of the scrap on a pedal.

Holy that would be a big pcb! , Naw I'm planning on using this machine for a lot more then just pedal stuff. Making signs and clock body's hopefully some guitars in the future, and also furniture! So many ideas so little time.

It's fun getting back into the design and 3d modeling I used to do in a past life. 

[italianguy63]

Thank God.  I thought you were getting into the space race with John and the Dead Astro to see who could build the biggest pedal with the most pots.   

[deadastronaut]

john won that with his mutha mfos...


@jim:  nifty setup man, looks like lots of fun..

[duck_arse]

It is obvious the Kokopelli's are making the mess at night when you are sleeping.
MC

sleeping? look at the size of the set-up. how big is his house that he has room to sleep as well?

v. nice, jim. how jealous can you make us? and can you mill me a really big piece of veroboard, just for fun?

[Jdansti]

Thanks Jim for such an informative thread!  I hadn't even thought of issues like having the work piece as flat as possible.  Looking forward to seeing more of your CNC creations!  I need to start saving my pennies for one.   

[italianguy63]

Jimbo-- stuck in my brain somewhere--

I remember that Boeing made this HUGE (IT's HUGE) CNC table to mill wing skins for the 767 or something.  Because bending the aluminum would fatiuge the metalurgy of the aluminum, so they would MILL an entire wing skin.  That's crazy to comprehend!

MC

[Ice-9]

Thanks for the overview of the CNC tooling, it would be great for perfectly milled enclosure drilling and would be great for engraving into the enclosures as well.

[Jdansti]

> Once I have my board designed and my tool path created I run the tool path file through a program called AutoLeveller. AutoLeveller will create a new file that when loaded into mach3 (the controller software) it will probe down in the Z axis to get the height of the material your cutting every 3/8" of an inch (all settings are editable). To do this you need to connect a few wires to your controller hardware, a ground clip on the tool and a 5v clip on the board. When the tool touches the board it will create a connection and tell the program that depth is 0 for the Z axis. The Program logs all of this information and adjusts the Gcode to compensate for the uneven surface.

Cool, so for milling a metallic object, you can instruct the machine to know where the top of surface is in the Z axis by using the conductivity of the metal.

[Gus]

It looks like larger 8020 like extrusion might make it more rigid
http://www.8020.net/

How much side loading can the cutting tool bearings withstand?

[boogietone]

Every few months I take a look at diy cnc. This is awesome.

[Mustachio]

Yeah that 8020 is nice stuff I think you could build a nice machine with it. The machine I have is basically maker slide with a rack and pinion system. The gantry Is a quad rail so its pretty ridged. The rails it rides on seem pretty ridged as well But there is always room for improvement I'm sure. I've seen the same machine as mine engrave on concrete and run a plasma cutter system as well so it has some nice options and upgrade-ability. For the price its not bad at all. There are nice machines out there though like the Romaxx but they are a bit more expensive then what I have. I think what I got was a bargain.

All in all I'm real happy with it, its well made and coming from Wisconsin, I've talked with the owner on the phone a few times and he was a really nice and helpful fella. Would be nice to use something like the 8020 to make a portable frame for the machine to do concrete engravings and things outside of my basement.

Gus I dont know any specific numbers on the tools side load , I think the craftsman digital router I have connected to second Z axis is pretty strong and should handle a good amount of side load, The dremels on the other hand I expect to eventually give out. I was using a dremel 3000, but I picked up a 2 amp black and decker rotary tool for under 20 bucks with some accessories, and am using that now. As for deflection I haven't measured or noticed anything bad yet. The machine has stayed ridged while cutting wood for me so far. As far as milling a hard material like steel I haven't tried yet. I think for engraving it should be fine since were not putting much strain in a shallow path.

Duck I sleep under the table obviously At one time this basement was wrecked from flooding and I got my first taste of remodeling on my own. I'm still in the process of remodeling though , I'm pretty slow haha.
How big of a vero are we talking ? Maybe a halftone image vero board ?   

I'll try to take some video of the autoleveller process and get some screen shots and settings of the pcb-gcode set up soon.

[Mustachio]

Well, I did take some new video of the autolevel process and some new engravings on sheet steel... but I haven't uploaded it yet I really should combine and edit them and take out the loud tool audio (no one wants to hear a rotary tool spinning).

But I have some pictures! I've been getting the pcb etching a little better the last few nights. I started mounting the pcb better and maybe chucking the bit better. Or maybe I just am getting lucky.



The circuit on the upper right is the Craig Anderton Super Tone Control, there are a few spots on there that didn't get cut away ill have to touch up, but its not bad, will be easy with an exacto knife. That one and the smallest circuit(LPB) where done with a single pass. I think the upper left circuit was 2 pass and the other 2 on the bottom should be 3 or 4 pass. You can see some of the traces got pretty thin but I think they will hold up.

Last week I made these little boards to use surface mount fets as through hole. They should work out pretty good. I got 100 Fairchild mmbf5485(2n5485) at 10 cents each. Gonna have to get some of those sot-23 mmbf201 (J201) next. I made another layout with all 3 holes on the bottom side I just havent engraved the boards out yet.




Oh and I engraved some steel for an enclosure It's finished and I love the circuit! Thanks Rob! This Thing Sings!


I sorta messed up on the engraving of the steel and ran it twice so it got deep and funky in a few spots and left those ripple spots (very apparent on the circles on the left)
But I really like how it turned out overall.I'll post the finished pics of it in the pictures thread soon. And ill get on uploading some more video of the process.

[deadastronaut]

uber cool man.....nice

been playing with my spitty a lot lately, add a crybaby and your set..

[Gus]

When I machine anything like PCB material I use a HEPA vacuum to collect the dust.

[duck_arse]

I know the spitfire was made of balsa, but how thick is that spitfire's steel? how is the bend along the engrave going to turn out? geeze, that thing would make even sheet steel bending easy.

[Mustachio]

@Rob Oh yeah I love the Spitfire with a wah in front ! Whomp Whomp

@Gus for sure a HEPA is a good Idea. I need to run my Vac on a diff breaker, when I kick it on it makes the dremel drop in rpm.

@Duck it's 22 gauge (about 0.029")  so not very thick. Bends real nice and easy along the lines This ones already bent and assembled I'll take new pics of it soon!

[Mac Walker]

That sheet metal looks great, did you use a v-cut bit for that as well?  How does it hold up to machining mild steel?