5 Axis CNC Milling Machine - Ramps 1.4 Arduino Mega 2560

Hello all,

I am a recent mechanical engineering graduate and have been working on a design for a 5 axis Opensource CNC milling machine. I have now finished the mechanical design of it all but I am seeking help with the electronic side of it all and am wanting to run it by a few more experienced people before I actually depart with some hard earned cash.

From my research if you don't want to have to use parallel ports and have good free software to drive your board, you run into quite a few problems. Mach3 and LinuxCNC/EMC2 are by far the most common programs and I have used them before, but since I have now left university I don't have access to a computer with a parallel port and have no plans on buying one, this presents a pretty peculiar problem. I then stumbled upon this post - [forum.arduino.cc] - which some clever guys have moded linux cnc to run on an Arduino Mega2560. Great, the best free software with no old out dated ports! This drove my design!

I then looked at 5 axis breakout boards in order to hook up 5 stepper motors and control them. From more research, I found out that the Ramps 1.4 board would be probably work for me. Another box ticked! From the mechanical spec of my design, I reckon I would need to use 5 nema 34 stepper motors (it's a beasty machine) so I reckon it would be best use an external stepper driver that can be hooked up to power supplies to avoid melting the ramps like this one - [www.wantmotor.com]. I found a handy post on how to wire them up here - [forums.reprap.org]. All this probably means I need two pretty meaty power supplies? This paragraph in particular is very new to me and was wondering if someone could confirm that everything I said here is correct? or suggest possible cheaper or neater ways of achieving what I have suggested here?

I haven't fully researched a spindle set up yet, but I am sure I will get to that in due course and I am aware that this can also be controlled from the servo port Ramps 1.4 board. Any suggestions here on what spindles to use would be greatly appreciated. I am planing to use this to cut stuff out of wood hopefully to the precision shown here - [www.youtube.com].

Finally, I do intend on making this design completely available for free on the web once I am done like on instructables or something. It may take a while, but it will happen in due course!

Anyways, I would appreciate your thoughts and advice on all this no matter how small!

Regards,

Euan Foster

Some of my thoughts:

Ramps board does nothing fo you. It has direct connection from arduino to to the step/direction/enable pins so you may as well just run jumpers from the arduino to the stepper drivers as you would need to run the same jumpers from the ramps board to the drivers. On my CNC machine I have a breakout board between the parallel port to protect the compiter.
You do gain three fet driven outputs that you could use for pwm output.

Unless you are building a really big machine I don't think you want nema 34 motors. i would look for low mh nema 23 motors as they will give you faster speeds.

I had not heard of the linuxCNC driving an arduino. Looks like an interesting project and I may hookup my uno to it and try it out. This is similar to what Mach3/4 do to run off usb, but I thought they used much more powerful chips. I would worry about the traction for this software and I worry that support could die but I hope not.

I wonder if you have a budget cost for this machine as even 5 axis software is very expensive.

George

Hey George,

Thanks for the advice on the stepper drivers. I thought there must have been something funky about it but what you said makes perfect sense.

The machine I am hoping to build is going to have a 600 x 600 x 600 cut area, so that's why I was thinking nema 34. Especially so for the weight and torque of a spindle etc on the two other rotational axes which I plan to build into the z axis gantry. I suppose I could use 3 nema 23 motors for the X, Y and Z axes and two nema 34s for the rotation. Do you still think that this is over kill? I did some quick torque calcs and nema 23 and 34 seem to both do the job fine.

I haven't yet budgeted a cost for this machine but I am planning to do this in depth over the weekend when I have more time. I will post it here when I have done. For the software front though, I thought using linuxCNC and an opensourece 5 axis CAM software to drive the g code to drive drive the machine basically reduced that to zero. I know that there have been a few developments here lately. Here is what I have found so far [www.youtube.com] [code.google.com] [www.grasshopper3d.com]

Regards,

Euan

Edited 1 time(s). Last edit at 07/22/2015 07:57AM by euanfoster.

Well....finding free/affordable multiple axis CAM Systems is a pain i.t.a.

Currently, there are two more I know about:
[www.autodesk.com]
[www.cnc-toolkit.com]

I´ve built a 3 axis cnc (1280 x 800 x 660 mm^3 size over all, giving 900x500x390 work space, approx. 250kg weight) using Nema23, which is more than enough. Speed goes up to 7m/min which was too scaring much for this size and therefore I reduced it to 4m/min.
Stepper Motor Driver DQ860MA is cool, I use similar ones too ! :-)
However, most Problems of These machines are riggidity and elasticity And it gets worse with each additional axis !

Next time I built one I will use the following mem: "It can be slow, but it MUST be rigid !"

Do you have a rough drawing how your machine will look like???

Kind regards,
Mike

If you need g code hit me up. i can program and post out some generic fanuc code for 5 axis if you like. just send me a model

here's a good reference for ideas.
kickstarter 5axis

The BlackMill is also a good foundation for an 80/20 based machine.
You could adapt the A/B axis to this easily.
CAD is available also and it's nicely modeled.
BlackMill

this guy did a great job with belt driven cnc mill.
he uses smaller belts than I suggest below.
good speeds, and he cuts aluminum with nice finish results.
belt design

Can you share your design concept with pictures?
What CAD system are you using?

Rookies that share their CAD and thinking usually benefit from the experience of others.
On the otherhand, I'm more of a do-it-my-way guy, and am comfortable with wasting money on the wrong parts and doing things a second and third time to get it right.

My thoughts on creating a CNC mill:

If you stick to cutting foam and soft woods, you can likely get the results you want, but be realistic that you will likely end up with a flexible machine even if you go crazy with stiff design ideas. your cutting forces will be low, so it'll all work out. At the weakest points within your envelop (24x24x24inch!) I'd hope for 1/8inch deflection when a 4 pound push force is applied to the cutting bit. there are cutting force estimates in the attachment BTW.

Use the attached frame stiffness calculator during your design process. It's a kick-ass tool that you should proactively use. If I remember, there was a formula mistake in one area, but you can easily find it and correct that.

I'd avoid arduino for your control interface and stepper driver, and use a USB or ethernet breakout board. Keling has great options and packages and they are the real deal. You won't find critics of them. You need rock solid pulse trains that are coordinated, so use the right tool for the job here. Also, parallel port computers are cheap to acquire, and building a 5 axis machine is going to be a money pit, so don't skimp. I'd budget $2500 at least, and not knowing the tools and machinery you have, budget some for tools etc.

For only a few hundred dollars beyond some sketchy collections of parts, the CS-labs CSMIO-IPS 6 axis would solve a lot of problems and let you focus on other challenges. csmio This would also have some resale value unlike most other solutions, just in case you bail on the whole project.

I'd use Nema 23 as mentioned above for X, Y and Z, and I'd use belted or planatary gear Nema 17 for A and B axis.
If you can, use closed loop steppers, like the Leadshine HBS507 stuff or others, at about $200 per axis setup.

If you select ball screws for motion, pick 1605 or 1610 size for your envelope. the 1610 will give you faster motion, like when cutting foam.
calculate your torque needs here. ball screw torque
You can find many used on Ebay in a lot of lengths, and I trust the ones from Korean and Chinese sellers (look at feedback though).

Along the way, you'll need bearings I'd think, and VXB.com is a great source.

80/20 has great profiles, and on Ebay you can get overstock and cut scrap pieces to save money.
I found a scrap yard in El Paso that had factory scrap from Juarez, and I bought an assembled table/fixture, which gave me a huge collection of strong profiles, t-nuts, bolts and plates. just paid the going rate for aluminum.

For belting and pulleys, there are many sources.
If you choose to use belting for XYZ, then I'd use a strong belt, like Breco products AT5 .
You can select wide belts and put them under a ton a tension, but realize you need a strong frame to hold high belt loads.
For foam and wood, this will be a good solution, and might be cheaper than ball screws. they have some easy to use calculations for load and tension.
Everyone will tell you that belts won't work on a CNC mill, but a 32mm wide Breco will give you adequate control during heavy roughing cuts in wood and easily be enough for light finishing passes with small tools.

For linear guiding, avoid the unsupported round rod/bearing as they will bounce.. The supported round rail is better, but I'd suggest 15mm linear block/rail stuff.
Ebay has deals on used stuff, so look for THK linear in your search terms.


You'll have a hard time finding 5 axis CAM packages for a reasonable price.

save some money for bits and tooling, as it will add up quickly. Foam and wood will be more tolerant for bit TIR, so you might not need precision collets and holders.
collets will give you some idea for precision collets used in wood router spindles, which might be a bit of overkill for foam and wood cutting.

Save some money for tramming indicators and nice precision instruments. Even if you borrow it, you'll need it around a lot.
A magnetic base, dial indicators, calipers and 123 blocks might be enough, and basically cheap on Ebay.

Finally, I'd suggest you make a smaller and stiffer 3 Axis machine. You can get your feet wet with all of this stuff, and with that machine, you can create quality brackets and plates for your ambitious 5 axis beast. Use MIC6 or cast jig plate aluminum, which comes with flatness, is available in many thicknesses etc. MIC6

Do share when you can.

Dave

Edited 6 time(s). Last edit at 10/09/2015 04:23PM by davew_tx.

geez, I just noticed his last posting was July.
I thought it was current. what a waste.
he's probably on cnczone or practical machinist or ?

Don´t mind, I read your post and it´s very informative.
Thanks also for the stiffness calculator.

KR,
Mike

Hey davew_tx ,

Very informative post. Thanks a lot.