CNC Build Thread

fretman_2

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I thought I'd start a thread of my ongoing CNC build. I know it's not a guitar build, but the CNC machine is for guitar building. Some of you guys have CNC machines, and some of you are interested in getting into that.

I also have the MI59 guitar build going on at the same time...lucky me right?!?!? I don't have time to devote to either but that's never stopped me!

I do currently have a CNC machine...an expanded Shapeoko2 - SO2 for short. Original SO2's only had 500mm X and Y axis extruded aluminum rails (called Makerslide) which resulted in around an 11X11 cutting area at max. Not big enough to do much. I rebuilt the machine with 1000mm rails which greatly expanded the cutting area, but introduced a lot more flex in the system. That flex is absolutely a no no!

I'm of the build it yourself rather than buy it mentality...which is why I build guitars I guess. So why not take a stab at designing my own CNC machine! The folks at CNCzone.com DIY CNC Router Table Machines Forum are extremely helpful...just like here. If you're remotely interested in CNC machines, that's a great place to pick up information.

My machine will be constructed mainly from MDF and will use SBR16 supported linear rails. Why MDF? It's strong, easily cut by my current CNC machine (vs aluminum of the same thickness) and readily available. There are lots of MDF CNC machines out there and they have been in use for years.

The gantry (movable part of the machine) will have a torsion box beam for rigidity. I'll used 1/2" - 10 acme 5 start lead screws to turn the rotational motion of the stepper motors into linear motion of the machine.

EDIT...
I'll use 4 NEMA23 270oz (270oz of holding power) stepper motors...one each on the X and Z axis, and 2 on the long Y axis. I haven't decided on the drivers for the motors...still researching that option. But, I'll used an Arduino Uno as the motor controller which will, in effect, take the GRBL CNC commands and turn those into impulses for the drivers to make the motors move. The Uno will be hooked up to an HP Stream 11 laptop running Windows 10 via USB. This is basically the setup on my current SO2.

Here's a couple of drawings...one looking down the Y axis...

fretman_2-albums-cnc-picture78659-newcnc2.jpg


...and a side view of the gantry...

fretman_2-albums-cnc-picture78658-newcnc1.jpg
 

fretman_2

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I've started construction of the gantry torsion box beam. It uses 3/4" MDF. I'm not an engineer so I don't have any analysis of deflection etc., but I have followed a lot of other established MDF designs that have been in use for years, although I did make the design my own.

Here are the main pieces of the torsion box. These were a little too long to be cut on my machine so a friend cut them out on his much larger machine for me at a minimal cost.

fretman_2-albums-cnc-picture78786-20160416-100833.jpg


Here's the box going together...sans ribs...

fretman_2-albums-cnc-picture78788-20160416-133214.jpg


And here are the ribs after being cut on my machine...this job took a long time to complete. I'd never cut so many parts out at one time.

fretman_2-albums-cnc-picture78787-20160417-183752.jpg



Here's a shot at the SBR16 rail for the Y axis...it's 1,150mm long which should give me around 36" of cut. The 16 in SBR16 means the rod is 16mm in diameter. The trucks (square things on the rail) have recirculating ball bearings that ride the rail.

fretman_2-albums-cnc-picture78604-sbr16-linear-rails.jpg


And lastly, I bought a complete Z axis unit off of eBay. I could have made it, but this does save me lots of construction time and allows me to focus on the other major components.

fretman_2-albums-cnc-picture78721-z-axis-unit.jpg
 

fretman_2

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BTW...I'm using Inkscape to do my drawings for the CNC machine. Some of these drawings will actually be cut out on my current machine. Inkscape is an open source vector drawing program. There was a little bit of a learning curve but no more than any other piece of software.
 

Marty M.

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Nice..I'm gonna follow your progress on this. Buying the Z is great! I have a Velox one here for my next build if it ever occurs. I have all the linear guides and acme rod with nuts, but didn't invest in the extrusion yet.
 

fretman_2

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I did look at using extrusions, but thought I could build more rigidity with a lot less money using MDF...especially for the gantry beam.

I've thought about using two extrusions to attach the linear rail for the long Y axis. Those extrusions would be attached to the base and there'll be no opportunity for flex there. But...I could build the same thing out of MDF at a fraction of the cost.


Nice..I'm gonna follow your progress on this. Buying the Z is great! I have a Velox one here for my next build if it ever occurs. I have all the linear guides and acme rod with nuts, but didn't invest in the extrusion yet.
 

pshupe

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What is the width of your machine? I guess that is the X axis?? I find it a little strange that the normal orientation of these machines are what I would consider portrait. I switched my X and Y axis around so it was more intuitive, for me anyway. I've had years of AutoCAD experience so always think of x as the long horizontal axis, and y as the shorter vertical axis.

I'm interested to see how this comes together. I just sold my small phenolic resin machine in favour of an aluminum model with a water cooled spindle.

Looks good so far! ;-)

Cheers Peter.
 

fretman_2

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Width is a little over 34 inches. Yea...what you're talking about is flipping the X and Y axis...making the X the longer axis and the Y the shorter axis. I've seen machines oriented that way. My issue with that is that you're making that part of your machine that's most susceptible to flex the longer axis. The flex may be negligible if the gantry beam is engineered correctly though. But you'd have to be more careful I think and it would depend on the design goals of the machine. Mine's being built to aid in building electric guitars. How accurate do you need to machine a guitar body? How much slop have you seen in a Fender neck joint? How much variability have we seen in Gibson products? EDIT...I meant to say that a tiny amount of flex may be negligible in relation to building electric guitars.




What is the width of your machine? I guess that is the X axis?? I find it a little strange that the normal orientation of these machines are what I would consider portrait. I switched my X and Y axis around so it was more intuitive, for me anyway. I've had years of AutoCAD experience so always think of x as the long horizontal axis, and y as the shorter vertical axis.

I'm interested to see how this comes together. I just sold my small phenolic resin machine in favour of an aluminum model with a water cooled spindle.

Looks good so far! ;-)

Cheers Peter.
 

pshupe

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I'm not changing the physical size of either axis, just naming them different. I would think that the shorter axis should be the one that moves and has the Z axis mounted.

Again I just assume my projects will be oriented more landscape than portrait. Most people if not all that do drawings or sketches have them oriented this way, for various reasons. Some of those reasons are related to the aspect ratio of monitors, and desks for that matter.

Regards Peter.

PS if you're building this for guitars I doubt you would ever need to machine anything bigger, my "Y-axis", than 18"- 20" wide. I think a 24" wide Y axis would be plenty wide while also being stiffer than something than spans another 10". My thoughts anyway. Not to mention the space requirements. Also you may have to get on all 4 sides, if you ever do machine something that wide, or crawl on top.
 

kissTheApex

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Do you plan on sealing/finishing MDF? Would it be affected by seasonal humidity changes? I'd be quite interested in how this turns out.
 

fretman_2

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Yes...I plan on sealing with shellac, then metallic paint on top. It should be sealed very well after that.


Do you plan on sealing/finishing MDF? Would it be affected by seasonal humidity changes? I'd be quite interested in how this turns out.
 

fretman_2

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A few more pics of the completed gantry torsion box beam. This thing is strong!!

fretman_2-albums-cnc-picture78817-20160423-110217.jpg


fretman_2-albums-cnc-picture78819-20160423-112418.jpg


fretman_2-albums-cnc-picture78818-20160424-112721.jpg


And last...a comparison of the beam vs. the Shapeoko2 aluminum extrusions. The Shapeoko has served me well but you can see that it's puny compared to the torsion box.

fretman_2-albums-cnc-picture78820-20160424-145229.jpg


Here's a vid of the movement...

https://youtu.be/G1snj_xbLdc
 

fretman_2

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The beam itself (sans rails) is only 17lbs. But I suspect that the final gantry will weigh at least 50lbs if not a little more. I'm told on the CNCzone forum that weight is your 'friend'. I guess I'll find out about that. The gantry will be moved along the Y axis by two 270oz NEMA23 stepper motors. Lead screws are Acme 1/2-10 5 start.

That gantry must weigh a few pounds, eh?
 

pshupe

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How high is the MDF support for the Z axis above your table? This would be your effective Z axis height. I have seen a lot, and specifically my old machine, that had much more travel in the Z axis, than what that support limited.

If you are going to use this CNC for guitar building there are a few concerns regarding this height. One would be doing any angled neck pocket. This requires the guitar to sit quite high at one end. You need to make sure your support clears the highest point. Another is factoring in the thickness of a spoil board and the height of clamps. I have had issues with these items. Just a heads up. You may already be aware of this as you have a CNC machine currently but it is a good tip for those thinking of jumping into the CNC fray! ;-)

Cheers Peter.
 

fretman_2

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If I make mount my Y rails flush with the top of the working surface, I'll have 4 inches of play between the bottom of the Z axis plate and the working surface. If I mount my Y rails on beams (which I will likely do, I'll have 6 or more inches of Z height.

I get what you are saying about angling the guitar body to cut an angled neck pocket. How high up is the back of a guitar off the working surface on your setup?

My initial plan is to only build guitars of my own design with Fender style bolt on-flat neck pockets. Don't get me wrong...I love my Les Pauls, but in terms of ease of design, machining and building, the Fender flat neck pocket/hard tail bridge combination is very hard to beat!

Tnx!!!


How high is the MDF support for the Z axis above your table? This would be your effective Z axis height. I have seen a lot, and specifically my old machine, that had much more travel in the Z axis, than what that support limited.

If you are going to use this CNC for guitar building there are a few concerns regarding this height. One would be doing any angled neck pocket. This requires the guitar to sit quite high at one end. You need to make sure your support clears the highest point. Another is factoring in the thickness of a spoil board and the height of clamps. I have had issues with these items. Just a heads up. You may already be aware of this as you have a CNC machine currently but it is a good tip for those thinking of jumping into the CNC fray! ;-)

Cheers Peter.
 

Marty M.

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I'm not sure why you would want to tilt the body, since the gcode can cause an angled neck pocket with a straight bit. I'd just write the code, and actually have done that.
 

pshupe

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Frankly the software I use is not easy to do something that is not flat, especially when it is a small area like a neck pocket. Also an angled pocket with a ballnose or regular endmill will result in a stepped pocket. It's much easier just to angle the body in the CNC and the result is a perfectly smooth pocket.

Regards Peter.
 

Marty M.

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Frankly the software I use is not easy to do something that is not flat, especially when it is a small area like a neck pocket. Also an angled pocket with a ballnose or regular endmill will result in a stepped pocket. It's much easier just to angle the body in the CNC and the result is a perfectly smooth pocket.

Regards Peter.

This sample example will drop down .5 inches and then proceed 3 inches while incrementally dropping another inch. No steps...just a ramp. You could then return to Z.25, change the x in both directions and have a neck cavity, depending on cutter diameter. The depth would obviously need to be adjusted for your specs. If you have a simulator, try it out. I have found that most guitar body stuff goes faster in 2D than 3d if there are no contours involved.

(ANGLED SLOT )
G17
G90
F( pick a number that you like for a feed rate)
G01Z.25
G01X0Y0
G01Z-.5F( pick a number)
G01Y3.00Z-1.50F( pick a number)
M30
 

pshupe

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That's cool. I use Vectric software, currently. Vcarve Pro and Cut3d. I can definitely see the advantage for something like the sloped neck pocket. Would you have to copy this for every step, or is there a way to type in the overall Z travel and input a DOC (depth of cut)? That would help greatly. If I'm using a 3/8" endmill, I'd probably cut 3/16" or less per pass, so that would be 8 passes, meaning 8 x 8 (50% stepover), 64 passes that you would have to enter 3 or 4 lines of code, correct? I guess once you do it once you are done, though.

Probably work OK for neck pocket but the perpendicular face to the slope would not be 90 degrees.

Can you recommend a free simulator, if one exists? Would be cool to play around with that.

Cheers Peter.
 

Marty M.

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That's cool. I use Vectric software, currently. Vcarve Pro and Cut3d. I can definitely see the advantage for something like the sloped neck pocket. Would you have to copy this for every step, or is there a way to type in the overall Z travel and input a DOC (depth of cut)? That would help greatly. If I'm using a 3/8" endmill, I'd probably cut 3/16" or less per pass, so that would be 8 passes, meaning 8 x 8 (50% stepover), 64 passes that you would have to enter 3 or 4 lines of code, correct? I guess once you do it once you are done, though.

Probably work OK for neck pocket but the perpendicular face to the slope would not be 90 degrees.

Can you recommend a free simulator, if one exists? Would be cool to play around with that.

Cheers Peter.


I don't have a simulator. I've heard cutviewer works well. I usually just watch how it works in Mach before I actually stick a bit in the router.

There are a couple ways to approach a ramped rout. Maybe the easiest thing would be to use a 1/2 bit and make fewer cuts with more stepover. I'd recommend you play with writing some code in Notepad and try it out. When two axes are on the same line, they move simultaneously, like the example I showed. You could copy and paste and change the X and Z values respectively to do a wider and deeper portion. It would take a few passes to do it, but it's do-able. I usually go down in 1/4" increments but I'm using a PC 690 router too. I do know there is a nesting G code, which is like the old Gosub routine files of old school Basic programing. If you look at a list of Gcode commands, you'll likely see it. I think it may be the G65 shown here:

http://www.cnccookbook.com/CCCNCGCodeRef.html

http://www.cnccookbook.com/CCCNCGCodeSubprograms.htm
 

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