CNC Controller Suggestions  - Page 1
Forum section: electronics / projects

author: Scutarius
author_rank: Regular Contributor
timestamp: September 29, 2013, 01:04:31 am
content: Hello,I just want to hear opinions about CNCs and controllers, a friend of mine is going to build for me the mechanics (4 axis CNC) and I just would be doing the wiring and tweaking, I just want a tool not a project, as Chris G. once said, most of the CNC drivers use the parallel port and I don't want to buy another pc just for the CNC.Does the TinyG would be the best option? What do you use at home?What do you think of this board?http://www.ebay.com/itm/4-Axis-USB-CNC-Controller-Interface-Board-CNCUSB-MK1-USBCNC-2-1-Substitute-MACH3-/360504837775?pt=LH_DefaultDomain_0&hash=item53efc3468fI dont have experience with CNCs besides my makerbot replicator, any comments appreciate it.thank you

author: jaxbird
author_rank: Frequent Contributor
timestamp: September 29, 2013, 11:46:04 am
content: The USB based controller you linked looks interesting, but it doesn't look like it's got any driving capability, you would need to get 4 motor drivers besides that board.Personally I use a parallel port based interface, but I can't say I like it, it's much too easy to loose steps if you go too fast or the cabling isn't sufficient. I've found that good grounding is essential. And I do use a dedicated machine. Just an old PC running LinuxCNC/EMC2. As the parallel control is real time without buffering, it's very important the machine doing the controlling is shaved down to a bare minimum of running processes that could disturb the CNC software.I would like to switch to USB with a more intelligent controller that takes G-CODE and generates the steps with buffering and everything, but the times I've been looking for one, it seems there isn't much software support.Before you get a controller make sure it will work with the software you are planning on using, e.g. LinuxCNC or MACH3.

author: awallin
author_rank: Frequent Contributor
timestamp: September 29, 2013, 12:48:48 pm
content: LinuxCNC with step/dir output on the parallel port is the a cheap and easy way to start. There is recent work with LinuxCNC on beagleboard/bone if you insist on an embedded solution.If you need more dynamic range (faster step rate) then an FPGA (either Pluto-P or from mesanet.com) can be interfaced to LinuxCNC and will provide MHz step rates if needed.Now "real" cnc-machines use servos with encoder feedback and not stepper motors. So if you get seriously bitten by the CNC-bug then you need that FPGA-card and some servo amplifiers at some pointAW

author: jeremy
author_rank: Super Contributor
timestamp: September 29, 2013, 01:16:38 pm
content: Well, my first CNC was supposed to be 'just a tool'... They are a lot more complicated than you thinkI tinker a lot with diy cncs. As mentioned, parallel port is usually a pretty solid choice as most stuff supports it (and it's super cheap/free).If you don't want that, you need to decide if you are going for linux CNC or mach3 as it changes things. The best thing I have seen with linux is the mesa FPGA cards:http://www.mesanet.com/fpgacardinfo.htmland the best with mach3 is the smoothstepper:http://www.warp9td.com/I have one of those usb things you have linked to, never was able to get it working all that well (but I didn't try very hard tbh because the parallel port turned out to be fine)I am building a new 3 axis machine with servos/encoders/geckodrives and a smoothstepper. I've got a rather large CNC router based on roller chain and steppers and you really can't do anything once you lose a step because you don't know until the job is finished. Just gotta cut slower I guessJust a tip: wiring matters a lot. Use cable that can take the current, and get shielded if you can afford it. Don't put signalling cables (limit switches, etc) right next to power cables. Also: cable tie the bejesus out of the thing; no cable should be able to move of its own free will.

author: Scutarius
author_rank: Regular Contributor
timestamp: September 29, 2013, 02:50:05 pm
content: Thank you for all the info, so far I will stick with Mach3 and the smoothstepper, nevertheless I would investigate more about the tinyG option.jeremy, could you share more about your future CNC setup?. Your tip about the wiring, thank youAbout the 4 axis, I what to make aluminium figures, about the size and complexity of a chess piece, what are the tricks on the 4 axis setup?

author: synapsis
author_rank: Regular Contributor
timestamp: September 29, 2013, 04:28:21 pm
content: I'm almost to the point of getting my mill going. I'm using electronics from here:http://www.planet-cnc.com/I had a bad driver board, and Andrej supports his products well. It's pretty much plug and play. I wired it up, loaded the software, and had stepper motors moving after adjusting the current limits.

author: jaxbird
author_rank: Frequent Contributor
timestamp: September 29, 2013, 05:02:28 pm
content: Quote from: synapsis on September 29, 2013, 04:28:21 pmThat does look very interesting, how much is that board? and do you need additional drivers for the motors?Also do you have any feedback on how good the software is? e.g. compared to the standard LinuxCNC and Mach3Thanks

author: mc
author_rank: Regular Contributor
timestamp: September 29, 2013, 05:26:45 pm
content: There are various options.Mach and LinuxCNC are the main two software packages with good support, but there are other options. Planet-CNC as already mentioned, and a couple others I can think off just now, but I've just had a complete mind blank over there names! One is UK based, and one US.I personally use Mach as the support is probably the best without being a total geek or relying on one man. I currently have one lathe setup with a USB smoothstepper (if you go for the SS, pay the extra for the ethernet version to eliminate usb connection issues), and am in the middle of setting up a second lather using a Dynomotion KFlop+Kanalog combo. Dynomotion do provide their own CNC software for use with the KFlop board, but they also have a Mach 3 plugin. I opted for the KFlop due to a few features I'd like to try in the future, however it's not the easiest of boards to set up, but is highly customisable as you can code your own threads in c, without being reliant on any one programmer to add features.There are some cheap USB boards that are compatible with Mach from China, and from what I've seen they are pretty good, although they are bit limited in setup options and support.Other controllers that use Mach I can think of are CS-Labs (EU based, but aimed more middle/high end of the market), PureLogic (Russia based, low-middle market pretty good boards, but all the english pages from their website have disappeared), and CNCDrive's boards (US based, although not seen many mentions of their products).Using seperate stepper drivers is highly recommended, as it gives more choice and the all-in-one cards are quite frankly rubbish with poor reliability.

author: Scutarius
author_rank: Regular Contributor
timestamp: September 29, 2013, 06:55:36 pm
content: CNC USB controller Mk2 (9 axis) seems perfect for the SD support, but 35 euros for the SD card reader... ouchhttp://www.planet-cnc.com/index.php?page=shopI am lost with this, "Controller does NOT need Mach3. This is a stand alone solution and works without Mach3." so I dont need Mach3, but can I use it instead of his own software (another 69 EURO)

author: mc
author_rank: Regular Contributor
timestamp: September 29, 2013, 07:54:49 pm
content: Planet CNC only supports their own software.Do you really need the SD card support?Or to put it another way, would you want to run a machine without some form of display to let you know what it's doing?

author: Scutarius
author_rank: Regular Contributor
timestamp: September 29, 2013, 08:06:10 pm
content: it would be nice to have an SD but no, I dont really need it.I am too used to my Replicator I guess, I never use the USB (only for firmware update) I just copy the file to the SD print and go, some times I take my laptop to the next room because of the smell of hot plastic, that´s all.

author: synapsis
author_rank: Regular Contributor
timestamp: September 29, 2013, 09:03:29 pm
content: The PlanetCNC controller does require separate drivers which they also sell. Pinouts are available to add your own motor drivers. The controller is compatible with EMC2 (uses standard G-Code).The price for the SD card board is steep for what it is, but there isn't any logic on it. You could probably take the card slot off an SD card reader and solder a ribbon cable to it.I tried LinuxCNC in demo mode for a short time before I got my hardware. I might try it again once I got my mill completely running.

author: mc
author_rank: Regular Contributor
timestamp: September 29, 2013, 10:10:04 pm
content: Quote from: synapsis on September 29, 2013, 09:03:29 pmThe controller is not compatible with LinuxCNC (which is what EMC has been called for quite some time now), as LinuxCNC does not support USB controllers, and most likely never will for the forseeable future.What is more likely, is the Planet-CNC software accepts G-code files that are compatible with LinuxCNC.

author: synapsis
author_rank: Regular Contributor
timestamp: September 30, 2013, 07:12:16 am
content: Quote from: mc on September 29, 2013, 10:10:04 pmPossibly. I was just going off the Planet CNC website, I haven't tried it myself yet.

author: jeremy
author_rank: Super Contributor
timestamp: October 01, 2013, 01:15:55 am
content: Quote from: ee.jcesar on September 29, 2013, 02:50:05 pmSure. I'm planning on a 3 axis mill, hoping to do light steel work eventually. I have some random chinese brushless DC motors about the size of my two fists put together.Encoders are the AMT102V (you can grab them at digikey), they are bloody amazing for the price and they come with a ton of different shaft adapters. I've used a few before, you really need a hardware/FPGA quadrature decoder for them as you can get up to 2048*4 quadrature edges per revolution.Servo drives are Geckodrive G320X. Gecko is basically the agilent of small stepper/servo drivers imo; in the optics lab that I work in, everything runs off zabers or geckodrives. Just don't forget to heatsink them.Smooth stepper for the motion controller was my first choice as I have heard some rave reviews. I somewhat disagree with the linuxcnc folks; a pc is not a real-time system (nor should it be), better to leave the motion control to a hard real-time device. For $150 or so you can't really go wrong.The most expensive part by far will be the ballscrews. I'm still trying to spec some good ones, which really just means I am trying to decide if I should get real THK/Thompson precision screws or just buy the cheap Chinese onesAlso, 4 race THK linear guides would be awesome, but I don't know if I can afford them/find them. 2nd hand ones are plastered all over US ebay, but none for me out in AU; shipping long hardened steel tracks over here isn't all that cheapI plan to make the frame out of aluminium/steel. Unfortunately I have been quite busy lately so haven't worked on it. Also been spending my little spare time with the 3d printer....Just a quick side note: encoders on steppers are a no-no. Mach3 doesn't support closed loop steppers (servos are fine), and steppers have a non-constant torque throughout their rotation iirc which messes with many control algorithms.

author: Scutarius
author_rank: Regular Contributor
timestamp: October 01, 2013, 03:16:28 am
content: Thank you Jeremy that's a bunch of info, this is going to be more than a "tool".Smoothie is on Kick starter!http://www.kickstarter.com/projects/logxen/smoothieboard-the-future-of-cnc-motion-control

author: johansen
author_rank: Super Contributor
timestamp: October 01, 2013, 07:52:12 am
content: Quote from: jeremy on October 01, 2013, 01:15:55 amhaving started out as a total noob, and bought a TAIG 3 axis mill, with a 75$ 3 axis driver, and upgrading to G240 drivers, but limiting the steppers to 2/3rds of what they are capable..i would say:you need to understand a few things first:absolute accuracy is second to machine stiffness for many but not all machine operations.it is better to repeat a machine operation a few times to get that last .001 inches of steel removed than attempt to remove it the first time with stiffer end mills, and better accuracy.one example, as i've recently modified my TAIG mill significantly.I can drop a 3/8th 4 flute end mill at 1 inch per minute into an aluminium block with a 1/4th hp belt driven spindle.note that: that is nothing compared to what is possible with perfectly sharp HHS or carbide, at three cubic inches per minute per horsepower of metal removed.I cannot exceed that unless i play games with the RPM to avoid resonance, which is specific to the diameter of the end mill, and the number of flutes, and the material.cast iron is easier to machine than aluminium without lubrication in my experience, but this depends on a number of things.my milling machine cannot generate enough force to snap a .25 inch end mill. (which is great, because i can't break most of my tooling.there were many times where a 3/8th inch end mill stalled the X/Y axis without stalling the spindle. ( this means you can save the work by pressing the stop button quick enough.in any case, unless you're trying to machine a custom scroll compressor...you're better investing the $$$ in a stiffer and bigger machine than in ballscrews.

author: Galenbo
author_rank: Super Contributor
timestamp: October 01, 2013, 08:29:15 am
content: Quote from: ee.jcesar on September 29, 2013, 01:04:31 amWhat will the CNC do? Welding, cutting, painting...? The big difference between a toy and a tool is about automatic greasing, dust/waste collection, material feeding, auto tool change,...Quote from: ee.jcesar on September 29, 2013, 01:04:31 amAs a machine builder, I can assure you every machine has it's own controller for the critical and lowlevel tasks. It doesn't matter (everytime, always) if it's a PLC, PC, Arduino, RspbPi,... but the controller is dedicated and doesn't contain Microsoft Office, Email and Facebook.USB serial is one of the worst options for this, even if it looks more fancy than the "old" parallel port, witch is the most dedicated port on a standard PC machine.

author: mc
author_rank: Regular Contributor
timestamp: October 01, 2013, 10:41:29 am
content: Quote from: jeremy on October 01, 2013, 01:15:55 amTha't a bit misleading. You are correct in that Mach 3 doesn't support closed loop, but that applies evenly to steppers and servos. If you want to close the loop, then it has to be done in the drive. Servo drives that accept step/direction (or CW/CCW) signals are capable of this, but so are the new closed loop stepper systems.The new closed loop stepper systems are pretty good, however you still have the issue of torque dropping of as speed increases.

author: arvidj
author_rank: Contributor
timestamp: October 01, 2013, 02:04:47 pm
content: I will add this to the "controller list"http://dynomotion.com/.I have it and do not use Mach3 ... though there is a Mach3 plug in available ... or LinuxCNC. I just use the KMotionCNC that comes with it.

author: Falcon69
author_rank: Super Contributor
timestamp: October 01, 2013, 09:32:11 pm
content: This is the board you wanthttp://www.pmdx.com/PMDX-126you can plug a Ethernet Smoothstepper directly to it and also buy another board from PMDX that has the spindle control. Both of those plug right into the PMDX-126.This is the board I got, and allthough I have not hooked it up yet, The quality is superb. I've read from others that this board is great with all it's inputs/outputs, etc.

author: jeremy
author_rank: Super Contributor
timestamp: October 02, 2013, 12:10:40 am
content: Quote from: johansen on October 01, 2013, 07:52:12 amActually, the two things I am interested in are a) precise drilling and b) gas-tight parts. Acme threads just have too much backlash for this sort of work imo. And I plan to make the thing stiff as hell. My CNC router can already do aluminium and various other bits with reasonable accuracy, no need to build another one of those

author: jeremy
author_rank: Super Contributor
timestamp: October 02, 2013, 12:15:19 am
content: Quote from: mc on October 01, 2013, 10:41:29 amInteresting, I have never heard of a good quality closed loop stepper system. Care to link? And iirc you can get servo PCI cards that plug straight into mach3, although I guess technically the control loop is still in the hardware on the card.

author: mc
author_rank: Regular Contributor
timestamp: October 02, 2013, 09:29:38 am
content: Quote from: jeremy on October 02, 2013, 12:15:19 amLeadshine are doing them. The small size pretty much runs blind, but the larger size has the option of a signal to let you know it's on position. Both will fault if they go out of position by a set amount. There are a few arguments that if you need to close the loop using a stepper, then you are pushing the stepper to hard, however they're a good compromise as they're cheaper than servos, and provide some feedback if you want to leave the machine running unattented.There are various controllers that let you close the loop. Dynomotion KFlop will let you do it with any kind of motor, and even let you have a dual closed loop (i.e. encoders on the motor, and linear encoders on the axis). It all depends on how much money you're willing to spend.

author: johansen
author_rank: Super Contributor
timestamp: October 02, 2013, 07:56:27 pm
content: Quote from: jeremy on October 02, 2013, 12:10:40 amthe Taig uses 1/2-20 tpi lead screws which are hardened and ground, so there is no non linearity to take out.practical backlash is on the order of .001 even on a well used machine.but that is really not low enough for gas tight parts, and small shrink fit components. so it looks like you are stuck buying ballscrews.http://www.cnczone.com/forums/linear_rotary_motion/8813-ballscrew_basics.htmlA quick check on ebay indicates at least 200$ per axis for ground ballscrews.