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How I created my own CNC machine – part1

How I created my own CNC machine – part1

It has always been a dream; making my own guitar. But being distracted by work, Atmel microprocessors (and later arduino’s, raspberry pi’s and the like) and designing in 3D,  I never really got to the point of actually building my guitar. As years flew by, CNC machines got my attention; it perfectly combines mcu’s, engineering, 3D designing and my ultimate dream. So now the goal became: get yourself a CNC machine. To later find out that these machine are not at all cheap to begin with. I need to build my own CNC machine.

This article (and perhaps more in the future..) is about my journey up to the point where I am now, building my 4th machine. Every version is an upgrade of the previous one.

Version 1: the small worker.

Schermafbeelding 2016-06-03 om 14.33.31

I started out with a good internet search and found a cheap CNC machine on DealExtreme. It turned out to cheap, to expensive for what you get, inaccurate and the workarea was way too small and not capable of cutting wood at all.. So I copied the idea of construction but scaled it up a bit. I drew the design in 3D-Max for good idea of where the rails, motors and other parts should go. The working dimensions on the first: 30cm x 15cm (w x l). It had some drawbacks, some of which I was not aware of at the time. But mainly machine was not stable enough (in particular the sideways movement of the bridg) and the working dimensions where not even close to the sizes I need for my guitar. But hey, it was my first machine.

IMG_7441

 

The motors are fed by drivers on protoneer’s CNC Shield for Arduino. It has a emergency button, 4  steppers (z, x and double y) and limit switches.
All rails were supported rails, bit on the heavy side, but stable. Eventually I built a case around it, to limit the dustcloud and added a vacuumcleaner to it.

The powersupply, arduino and buttons all ended up in a case. The frontpanel was actually made by the CNC! Hurray, the machine creates itself! Also, the spindle was also held by a self designed and constructed holder. And again, made by the machine!

Schermafbeelding 2018-06-28 om 19.12.14

Some specifics on why I chose some things and how I set them up:

NEMA 17 steppers:42BYGHW811-AG5.18 NEMA 17
These motors came in an affordable deal: 4 steppers for around 50 euros. And the could easily been driven by the drivers DRV8825. True: not the strongest in their league but sufficient at the time.

Drivers: DRV8825
Cheap and easy to get drivers. The only trick was to get them adjusted to the right currentlimits. There’s not really a good guide anywhere on how to set this. This is what made it a bit of atime consuming job. In short: hook up all the gear, power up the arduino and the power for the motors. Measure between the ‘ref’pin and ground.

Current Limit = VREF × 2
So, for example, if you have a stepper motor rated for 1 A, you can set the current limit to 1 A by setting the reference voltage to 0.5 V.
Arduino CNC Shield  by protoneer
This little nifty thing really made my choice to build a machine myself reality. This thing was shipped from New Zeeland to me, well designed and made, with good support from the maker. But really, it doesn’t get any easier: just plug it onto the Arduino, load up the GRBL firmware (get it from Github) and you’re good to go! It has limit inputs (with noise cancelation on it so unshielded wires can also be used), a probe input, emergency button, spindle control and so on. A big thumps up to protoneer for his work, my advice: do NOT buy the ripoffs on these chinese websites, he deserves his fair share!
 IMG_1769
Spinde: Kress 1050FM
A good, strong and fast machine with variable speed, at fastest mode it runs at 24000 RPM. What can I say..
Rails: SBR16
I chose these rails for their  weight and stability. These rails are supported throughout and so do not bend under the carried weight. Sideplus: there’s a little gap in the middle under the rails where I could run 2 small wires for the limitswitches. Clean wiring, I like it!

CAD/CAM software: Fusion360 and UGS

As my background in designing comes from Autodesk 3d MAX I was very pleased to find out they make Fusion360 which combines CAD, the CAM proces as well as generating GCODE! For sending the GCODE to the Arduino the software of Universal GCODE Sender did a pretty decent job, not to much fancy options, just run the code. Good enough. All software was running on my MacBook Pro, which was ok for then but soon it locked my computer so I could not do anything else but wait while the job was running on my machine. Hmm, had to come up with something better.

More to come…

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