Everything you need to know to design your own CNC router
mattferraro.dev
mattferraro.dev
For 3D printers they work fine because there is no pushback ('loading') from the extruder. But for anything that cuts servos are the way to go if you want half decent speed and quality cuts, as well as long tool life.
They all boil down to commanded torque greater that the system is capable of delivering. Fix your design. Be suspicious of software trying to accelerate too aggressively under load.
I have cut a lot of metal on a Tormach PCNC 1100 Series 3 machine, with steppers. NEVER had an issue. Correctly designed stepper systems DO NOT miss steps.
That said, servos systems typically are capable of greater accelerations for a motor of a give volume and current load, because of the closed-loop control. Use servos for speed, not because you are afraid of skipped steps from a stepper.
FWIW I designed and built CNC equipment for a living.
As for the Tormach machines, they use 3 phase, not 2 phase steppers, and use current sensing on the stepper outputs to give them a feedback mechanism, and an encoder to close the loop completely these drivers and stepper motors are better than the ordinary two phase kind that you find in regular hobbyist aimed gear.
https://www.damencnc.com/en/nema-34-closed-loop-stepper-syst...
They are properly classed as a hybrid servo system rather than just a stepper on account of that feedback mechanism.
I built a couple of 3d printers from scratch BECAUSE the various components were cheap and approachable. Haven't done CNC because my interests haven't taken me there...but the thing about advancement is: While one fella is saying 'You can't do it that way!' someone comes around and does it that way, and the first person is left in the dust.
You can't really stop Laser printers from dropping to many thousands of dollars to $70...all you can do is ride the wave.
In practice, hobby level machines don’t have near enough rigidity or spindle power to warrant high movement forces in the first place.
Nearly all of the hobby CNC machines on the market use open-loop steppers. They’re definitely not losing steps during normal operation.
The topic of steppers vs servos has been covered over and over on every hobby CNC forum for the past two decades. Closed loop systems are great if someone has extra budget to spare, but they’re unnecessary for machines using hobby-level spindle power.
This technology originated with the Berger-Lahr company in concert with an Italian driver manufacturer for five phase stepper motors, which were the first to be driven past this resonance point, the tech was then perfected and adapted to other, cheaper steppers as well.
So it probably does skip steps, but corrects for it
The encoders will tell you when to increase power because you're about to miss a step, the expected movement is lagging compared to the amount of input current. The current sensing will help you to detect tool strike situations before damage is done to the motors due to overcurrent.
I've been running a small CNC for a while now and though I've had skipped steps, they've never been the cause of a failure. When they've failed, it's been because:
- I stalled the spindle and I'm trying to plow the no-longer-rotating endmill straight through my stock (and if steps weren't skipped, the tool would break)
- I forgot to turn on the spindle and I'm trying to plow the endmill straight through my stock (and if steps weren't skipped, the tool would break)
- I've somehow forced the machine to try to push through its limits and crashed an axis into the chassis (and if steps weren't skipped, the machine would be seriously damaged)
Basically, the only time the steppers have failed is when not doing so would lead to much greater damage, so I'd go so far as to say that skipping steps are a feature, not a bug.
If your steppers are failing in the middle of a job where nothing has gone wrong, either your steppers or your drivers are messed up but it's not because steppers are inherently bad.
I'd recommend servos for applications that are demanding on torque, power, speed and/or accuracy. I wouldn't recommend them for your first DIY machine because of the additional risk, expense and complexity they add.
Is there a classification of a system in terms of 'highly precise pre-defined/pre-programmed' movement vs 'feedback based movement'?
As an outsider, mainly watching youtube demos/videos, I've noticed the old kind of robotics, from ABB, Fanuc, and what not, with massive robotic arms planted to a firm-foundation, is based on precision pre-programmed movement. (I believe) there is no feedback though sensors or cameras or anything.
But the new trend is based on feedback, whether traditional control-theory feedback, or neural network based reinforcement-learning feedback, which I guess eases the rigors of pre-program design and makes the system more flexible in new situations. But of course it's an open research topic, and involves every-increasing sophistication of sensors, high-def cameras, lidars, and what not.
Wondering how the choice of stepper/servo, or some other mechanisms like hydraulics/pneumatics relates to the above categorization.
Thanks in advance.
They can also use machine vision in a limited sense. For example, I worked with one last week that drove screws. There are known numbers and locations where screw pilot holes are expected to be, but they have a variability greater than the radius of the screw. So, the arm moves the camera into position so the field of view is a bit larger than the tolerance on the pilot hole, takes a photo, locates the circular feature of appropriate size, then moves the screw to that location.
However, you're right, these robotic systems are doing fundamentally different things than Boston Dynamics and self-driving cars. They're solving a different problem. The difference is less about stepper/servomotor/hydraulics or other control systems, and more about the degree of control that the users can and want to exert over the robot work environment. If it's easy to mandate that there will never be an obstruction in front of the screw you're trying to install, and the machine must power down the servos if a human is inside the fence, and you can demand of the drill machine a certain tolerance on the hole location, you can have a more reliable, simpler to debug, quicker to build robotic cell. If keeping humans out of the equation and the environment obstacle-free is impossible (as on a battlefield or parking lot), then you have to reach for less reliable, more complex control algorithms.
Like I said in theory. In practice we don't really have the ability to sense that well. While drivers that are that quick exist, they are exotic, or have limited range of motion.
I do think taking into account the feedback from the load as well as the weight of each section of the arm itself, needs to be done. In addition, some aspects of vibration control also need to be incorporated. (I guess the right word is proprioception, as mentioned in another commentor).
There's also systems with steppers and encoders.
A common issue though is that the steppers are driven at too low of a voltage. You also want the right kind of driver that PWMs a high enough voltage to maintain the current at speed. That's because as the speed goes up the motor has higher back-EMF voltage that the driver needs to overcome. Constant voltage drive really suffers as the motor speeds up.
But sure, DC brushless + servos are nice, more expensive, and require more expensive controllers.
The forces involved can be estimated ahead of time with simple math. It's easy to verify stepper motor holding torque with a common kitchen scale. Cutting forces can be estimated with readily-available calculators online.
The closed loop functionality will never come into play with properly sized motors, though.
If the machine gets to the point where the closed loop function is trying to make up for lost steps, it’s almost certainly because something has gone wrong (crashed machine into workpiece, for example). At that point, it’s actually better to halt the machine and alert the operator, which is what a lot of people end up using closed loop stepper feedback for.
New Trinamic stepper drivers have some built in functionality to detect stalled steppers, which can be used for the same effect.
Closed loop steppers definitely aren’t bad, but they’re not a must-have for hobby machines.
This is exactly why 99% of beginners should start with stepper motors.
Building a CNC is an exercise in tradeoffs. It's tempting to want to choose the best option at every juncture, but that's a recipe for blowing your budget. I strongly recommend that beginners start with sufficiently-large stepper motors to get things done, then consider more expensive motors as a later upgrade.
> As long as they don't skip steps. And they always do. So you end up running at 1/10th of the speed your tool could move at to avoid that
They definitely don't always skip steps. I've never skipped steps on my hobby CNC during normal operation. Only crashing the machine causes skipped steps, at which point I have bigger problems to worry about.
It's very easy to measure the maximum force your stepper-based CNC can apply before skipping steps. You can use a common kitchen scale and manually force the CNC axis to compress the scale until it skips.
In my case, the maximum stepper force is about an order of magnitude higher than the calculated cutting forces in aluminum. If someone was trying to push the cutter so hard that it was overwhelming common NEMA 23 steppers, they're going to need an extremely rigid machine. Most hobby-level machines aren't rigid enough to use high cutting forces, and unless you have a 2.2KW water-cooled spindle, you won't have enough power to cut at those speeds anyway.
As long as your steppers are sized appropriately, it's really not a big deal.
> So you end up running at 1/10th of the speed your tool could move at to avoid that
Again, not really an issue in practice. Use sufficiently-sized stepper motors and the movement speed is just fine.
I strongly suggest that anyone building a CNC focus first and foremost on keeping it simple and cheap. Get it built, learn from the process, and improve on your next iteration. Closed-loop stepper motors are a reasonable upgrade path, but the idea that you're going to be skipping steps with regular steppers just isn't true.
EDIT: Here's a video of a common Shapeoko with significant added weight moving at 1000ipm on the tiny stock steppers without issues: https://www.instagram.com/p/B1wSmXfnm6C/ The stock settings are 200ipm, which leaves ample safety margin for normal operation. 200ipm is plenty fast for rapids unless you're trying to reduce cycle times on large-scale manufacturing, in which case you wouldn't be using a hobby CNC machine.
Doesn't that only happen when the controller either doesn't know (or can't decently handle) the limits for a given machine?
eg if a machine could (say) only accurately (without losing steps) push the spindle at 1000mm/min, with maximum jerk of (say) 0.5
If your controller doesn't know to keep in those limits... it makes sense steps will be lost when going past those limits.
So, seems more like a tuning problem?
That being said, closed loop stepper systems exist, though I haven't (yet) personally tried them.
Skipped steps are only a problem if the machine is tuned wrong, like you said, or the steppers are too undersized to keep up.
People tend to underestimate the strength of common NEMA23 steppers while overestimating the cutting forces they need. Most hobby machines don't have enough rigidity or spindle power to require more than a few pounds of lateral cutting force.
I think your advice is spot-on if someone was designing a 5000lb vertical mill out of steel, but hobbyists building DIY bench top machines face a different set of problems.
Hobby level machines are almost always limited by rigidity, not movement motor torque.
I'm fine with you advocating for steppers for non-contact or drawing work (laser cutters, engraving and so on). But if you care about your tools, you don't want to wait for hours for what should be a small job then add the bit of money for a servo or a hybrid solution, on the total cost of the machine it won't make a lot of difference and the machine will be so much more reliable and faster that you'll end up using it much more frequently.
Right tool for the job and all that, bench top CNC with small servos is a very powerful tool in the hobbyists arsenal, and if you scrounge ebay you'll find they can be quite affordable. Note that anything that cuts has a stand-time, and if you move slower or make many passes because you can't really cut then you will end up spending a fortune in tooling which at some point will easily outweigh the price of the feedback mechanism, which automatically compensates for increased load and toolbit wear.
I wasn't. You'll never make it through your first resonance point without current feedback, and a good stepper driver can easily go into very large multiples of that frequency.
Then there is microstepping.
> Most hobby machines don't have enough rigidity or spindle power to require more than a few pounds of lateral cutting force.
This is true, but a different problem.
Hobbyist CNC machines simply don’t have the same issues as large commercial-grade CNC mills. None of the popular hobby CNCs use closed loop motor control. Skipped steps are simply not an issue at this scale.
I think it’s microstepping. Steppers with microstepping enabled and controlled by an 8-but micro must be assumed to produce zero holding torque and assumed they always miss a step or two.
https://www.tindie.com/products/33366583/grbl_esp32-cnc-deve...
The developer is really responsive, might be worth collaborating since you have put in similar work.
Grbl ESP32 is great. Easily the best of the firmwares I've used so far.
In my case I'm not building a CNC, but controlling the axes of a microscope (X, Y, Z) plus the intensity of the illuminator and likely several other things, so the 6-pack (which I also use on my CNC) had what I wanted.
Oh, you can also use either onboard or external motor drivers with the 6-pack- external motor drivers are good for NEMA23 and other large motors.
Nice, we use CNC microscopes at work for automated feature dimension measurements, they're incredibly useful for validating milled parts and inspecting wear patterns over time.
Thanks for the info, I'm going to have to upgrade again soon it sounds like!
I already have a CNC controller with stepper drivers. Do servos have a stepper interface, and internalize all the servo logic and feedback? IE, can I just buy "servos" that have internal feedback, and send them the same step and dir signals, or SPI signals, needed to drive steppers?
Or, do I have to replace my controller/drivers with a servo-specific driver? The reason I ask is that I have an extremely inexpensive stepper system (grblesp32 6-pack controller with external drivers) and cheap steppers, and definitely am hitting the point where I have to dial back all my parameters to finish cuts without dropping steps.
Servos are great if you're working with huge forces, need a lot of speed, need ridiculously high accuracy, and have a team of engineers to actually build and tune the thing. Ridiculously expensive and complex unless you're looking to go into busines manufacturing CNC systems.
The most reliable build setups we have are kevlar belts coupled with 16:1 reduced stepper motors, and decoupled encoders that index using constant pressure rack and pinions. Even pre-tensioned ball screws give us enough slop to be a problem without encoders, and kevlar belts are an order of magnitude cheaper; going with a reduced stepper vs a servo takes the cost down by half.
Even a cheap encoder, when decoupled from the motor, and directly coupled to the axis it measures, will give better axial positioning than a servo. It boggles my mind why people seem to ignore this in favor of a motor that knows where it is in space, but doesn't know where the axis it is driving is in space.
My experience has been roughly opposite of this. If you overload your motors, you're going to lose positional accuracy and probably wreck your workpiece regardless of whether you use steppers or servos. If you don't overload your motors then the difference is moot, and with steppers there's less to go wrong.
Hobby-scale machines shouldn’t need closed-loop systems for positioning during cutting operations. Especially if they’re using a 300-400W (sustained) consumer router as their spindle as this article suggests.
Cutting forces at this scale are in the single-digit pounds. Nothing a common NEMA23 can’t handle with plenty of margin. Trying to push a low-powered spindle through the workpiece on a low-rigidity hobby machine causes more problems.
Nothing against your advice just providing another option that uses steppers that don’t skip an occasional step (that is to say that if you ask for more torque from a stepper than it can handle, smart or not, it will not produce more torque out of thin air).
If you're using surplus parts, then getting enough documentation to make a servo system work can be touch and go. Steppers are pretty much brain dead simple.
Even with servos, the entire machine has to be pretty stout in order to ride through a bump that would cause a large stepping motor to miss a step. At that point, if it's a homemade machine, something else will end up out of kilter too, such as your clamping or the workpiece itself.
Am thinking they'd not have enough torque, unless you gear them pretty high.
They are basically a stepper motor from the application's point of view, but with some of the advantages of a servo, as far as I can tell.
(No affiliation, just curious if these guys are onto something useful.)
If you are comfortable with soldering, motor sizing, and python, you can pick up an ODrive control board and some sort of position sensor and turn almost any motor into a servo motor.
I ended up not using them because I found it was simpler, cheaper, and fit the mounts better to buy a pack of NEMA34 steppers and a few $15 dollar encoders. Seriously, spent maybe $800 on decent quality steppers/encoders/amps for 3 axes, where the ClearPath servos would have been $1600 for the same 3 axes, but wouldn't have provided position feedback nor allowed position localisation to be decoupled from the motors (which is the best way to do things in most cases).
I think it's hard to justify the costs of these types of motors unless you have some very specific torque/speed/spacial requirements that require them. If you're building a machine that is worth >$4000 per axis, then maybe, but if not, simple steppers are the way to go.
The usual suspects for brands, personal favorite: Panasonic Minas series drivers + associated servos. Cheap, super reliable and available in just about every size that you could possibly want.
Please if you're getting into this look around at second hand machines. You'll be able to do really well if you want to setup an old 90s machine with new electronics. It's not as complex as building one from scratch and you get much better mechanical components.
But maybe that's a bad assumption from working in tech for too long?
The main spindle might have issues with bearings but you should get a lot of life out of one. Ours run 16 hours a day and last 10 years plus. As a hobbyist even if you buy one with 95% of its spindle life left you are not likely to wear it out.
Keep the machine greased and it will last. A good machine will come with a service manual and tell you how often to grease each part. Most will have an auto greaser that will do most for you. Just have to keep it topped up.
All parts are easily replaced. Except the electronics and the computer but if you are wanting to build your own you're replacing them anyway so it's not an issue.
Vacuum pumps need regular servicing and replacement Blades every now and again but again hobbyist use they will last a long time just keep the filters clean. They are almost always 3 phase so that might be an issue.
They have AC servo controllers that you would have to interface with and normally have a can bus for all the peripherals I don't think it would be too much to get all of that going.
I'll have to search for a way to run 3 phase power out of residential. Not sure if that's even possible. I'm curious though!
The type I work with are for wood working. Manufacturing cabinets and furniture. So very big (6m long work surface) but not capable of metal work. But there is a huge range out there.
There is no derating the motor when running on a 3 phase VFD/inverter if you have the correct specs for everything. If you are trying to run a bigger motor than any link in the chain it might work so long as you don't try to draw more power from the motor than the weakest link in the chain.
There is a static phase converter which does derate the motor. They are the cheapest way to run 3 phase from single phase, but otherwise don't have much to recommend them. They are NOT inverters.
Interesting, I've never tried that.
Yes, those cap-and-coil based 3 phase 'convertors' are more of a fake 3 phase than the real thing and they will put a lot of stress on one of the three phase windings of the motor and hardly any on the other two.
They are on most auction sites but your best deals are going to be liquidation auctions. There will be auction houses that specialise in these in your part of the world.
The article said that Teknik Clearpath servos are considered a great value, and they are, but even their smallest fractional HP 24V motors cost more than some name brand Allen Bradley (unofficial slogan "you can get better but you can't pay more!") 3-phase servos at my local supplier: https://www.surplusindustrialsupply.com/motors-mot.html
These places are like a garage sale for industrial lego.
I haven't bought CNC machinery that way, but I've gotten tooling, measuring equipment, etc. for pennies on the dollar buying from auctions.
And like jacquesm said, EBay.
Making large, precise workpieces is an artform, you have to take temperature of the workpiece into account, compensate for that, expansion of the bed and so on. Very tricky to do that repeatedly with any degree of accuracy.
I also don't really need to do any milling, just adjust to the right x-y position and punch a tiny hole and collect the dust. Milling rocks in any case is a no-no from what I understand. Maybe someone could suggest some ideas for my .. unconventional requirements :)
The samples are pretty small (maybe 20cm^2 at the most) and I don't need to do it fast... And I prolly don't have a huge budget
Anyways, for your use case it sounds like that isn't relevant. What positional accuracy do you need? What screws are you planning to use? Start there. Most likely a full or half step setup is more than enough for your purposes and just make sure you set the motion parameters right... The cheapest solution for X/Y positioning is going to be something like fixed voltage (just using some transistors to switch the stepper motor phases) and stepping via software at slow speeds.
What's your budget? What's your more precise requirements? (working area, accuracy, speed etc.?) What can you build yourself vs. buy? Depending on what you need and what you're comfortable building it's either a trip to your local hardware store or just buy a cheap off-the-shelf 3-axis CNC kit.
Its a kit, should be ~$1700 all in. Its repeatability is rather good (0.05mm something like that) the firmware and software are all tuned for that machine (assuming you use a kit)
sure you can just do it all yourself, but if you've never done it before its going to cost months of your time
As long as you are below the maximum pulse frequency that your controller can process, there's no penalty at all to microstepping.
It's more complicated than that [0,1] and characterising it as a myth is dismissive and wrong.
[0]: https://www.faulhaber.com/fileadmin/user_upload_global/suppo...
[1]: https://www.njr.com/electronic_device/PDF/application_notes/...
But a full-stepping motor also has bad incremental torque for small displacements; by disabling microstepping you're just forfeiting the option to command them.
If anything, microstepping lets you run even closer to the motor's torque envelope, because you're less likely to induce a dynamic stall by either exciting a resonance or letting the stator's magnetic field get too far away from the rotor angle.
I can now find this article, but I think the one I remember reading also tested the torque in microstepping vs full step mode: https://hackaday.com/2016/08/29/how-accurate-is-microsteppin...
I not only don't want to replace it, but I bought a diode laser CNC in addition to it. I could wish that the laser had a larger bed or was more powerful, but it really can do the vast majority of what I want. I maybe eventually buy a better one, but I doubt it.
Going budget on both of these was a good move. It gave me what I wanted while not wasting money.
Couple of questions:
1. Why did you chose to mount the Y axis servos in that orientation instead of where the axis of the servo is perpendicular to the floor?
2. Since you welded the frame, how did you manage the mount the linear rails square? Shims? Post weld machining the frame via bridge gantry?
3. What was the total cost of this vs buying an OTS machine? I'm guessing around $12k.
1. How the Y-axis Servos are mounted isn’t the ideal orientation. Some of my initial decisions, ie for linear rails, limited my options based of what I was able to fabricate in-house. There were a lot of lessons learned and if I was to do it all over, I would actually go with mag driven linear servos if I can afford them or have the same existing Servos mounted in vertical orientation with the gear rack facing outwards engaged with the pinion
2. Good question! One of the biggest challenges of starting to make your own machine are the real life unknowns, which might yield one answer theoretically, and another in practice. Trying to balance between a realistic budget and wanting a unicorn setup, I realized that it was out of my budget to machine the entire base frame for this machine. So, the Y-axis gear rack was basically mounted to base frame using self tapped holes, some shims from McMasterCarr and very long hours with a Mitutoyo dial riding back and forth. Since the gantry was much smaller compared to the base frame, I was able to get the X and Z axis machined from a local shop. Here’s pix of that: https://imgur.com/a/RLEETAm. Due to the DIY nature of my project, I was also not able to stress relieve the weldments but was still able to achieve 0.001” tolerance for my use case materials (with the exception of aluminum which is probably around 0.01”).
3. Having made some mistakes along the way and doing this for the first time, my actual expense was around $23k over 1.5 years. However, that also includes a very nice 2x high volume Busch 20kW vacuum setup for the vacuum table (which I got for a steal deal on eBay). They would normally run $20k/ea but I was able to find and fix DOA units with minimal work for around $1600 for both.
I hope this helps!
In the German community Estlcam [0] seems to be used a lot. With a 50€ price tag it seems quite reasonable and it might be a nice piece of software to try out.
End mills, work holding, dust collection, and other accessories will quickly add up.
I actually got two for that price, but on closer inspection one has a fatal break in the casting and so it is scrap - I expect to make $2500 once I get all the valuable parts off of it
Here’s some tips and tricks: https://www.chiefdelphi.com/search
EDIT: Random tidbit is that I control it from an old PC's parallel port. The PC runs DOS (the best real time OS ;) ) and uses some old free software called TurboCNC that can read G code and drive step and direction drivers. It has it's limitation but if you have an old PC around...
Btw, if anyone is interested that build is documented here: https://www.cnczone.com/forums/diy-cnc-router-table-machines...
I think this forum post pointed me in the right direction: https://www.forum.linuxcnc.org/18-computer/36879-raspberry-p...
It's a 1000mmx600mm gantry design I made in fusion 360. I've been mostly copying a commercial design (omio cnc). It uses 20mm aluminum plates, ground rails, and ball screws.
For electronics I'm using a teensy 4.1 based grbl board (grbl-teensy-4) with external stepper drivers, 34mm steppers, and a 500w brushless spindle. I'd go bigger on the spindle but I'm limited by wattage.
The hardest part for me is the hardware. My design is simple based around plates with holes in them, but a couple plates require threaded holes in the end.
If you are a software guy, drilling a 12mm horizontal hole 30mm deep into the edge of a 20mm x 400mm plate is surprisingly difficult. It won't fit in my drill press that's for sure.
Welcome to the wonderful world of jig-making. "Making" jigs has about the same amount of "making" like "coding" in programming. You have to invent or search for a jig which will make that task doable. I suggest clamping lightly two planks to sides of your plate, make a thick block with your desired hole, then screw that block onto planks so that your hole is centered between them. Now you have a guide for drill.
Punch to center the first hole, then a center drill to start, then pilot holes at 3mm, 6mm and 12mm, use duck tape on the drill bit to keep the depth right.
If you really need the holes to be dead straight use a handheld router those are a great thing to have anyway and pretty much all of them have 100mm of or so of travel.
If you're drilling into something very hard skip the 3mm.
A good video on how to tap so you break fewer of them: https://www.youtube.com/watch?v=33wfSMsUbuc
Some years ago I actually tried building my own desktop CNC. A lot of the warnings and "don't do this" mentioned in the article have gone into my design, which is why it never ever worked or did anything and is now laying disassembled in a box.
The most niche thing I actually care about is probably Cold War espionage, and even if the exact thing I mention doesn't ring any bells with any commenters, someone will usually chime in with at least familiarity with the people involved.
Edit: it is open source, and easily replicated by design! https://sienci.com/dmx-longmill/open-source-and-modification...
I think the date at the top has the wrong year (2020 / 2021)
- For an Aluminium frame, you could also use solid Aluminium bar or plate. Depending on your location, it might be cheaper/easier to acquire. One benefit is that plate especially can be purchased pre-milled, so you can get it very flat, which is good for things like mounting linear rails, which require high-tolerances from their mounting surfaces.
- Missing from the "Linear guides" section is the varying tolerances and rigidity specifications of the various options. Linear rails can have some crazy high ratings for stiffness (e.g. page 27 of [0]) and high degrees of parallelism and overall precision. Shafts are often unspecified. However a tradeoff here is that linear rails also require high tolerances from the surfaces they're mounting, otherwise they're out of spec and can wear out quicker. It also misses that rails can be quite expensive. I'd also add that though the rails are low-profile, if you want more clearance you can always elevate them.
- Missing from the "Linear actuation" section is how much stuff and expense goes into a proper ballscrew setup. In addition to the ballscrew and nut (which usually have to be purchased pre-assembled together), you also need a fixed support to hold the motor-end of the screw (this keeps the axial load off the motor), a floating support at the opposite end of the screw, some kind of mount to hold the stepper motor concentric with the screw and a coupler to connect the screw to the motor shaft. Ballscrews can also be expensive.
- I'd actually add a whole section for the stepper drivers. 3D printing in particular has led to some interesting options that can be applicable to smaller DIY CNCs. Trinamic stepper drivers for example are able to drive stepper motors silently, even with high current.
- I'd add accuracy to the pros of servos. They're typically limited by the resolution of the attached encoder, which can be obscenely high.
- The controller section is focused on Arduino-based or derived controllers which aren't much seen in much of the DIY CNC community. The most popular options by far are [1] Mach 3 and LinuxCNC/PathPilot. Personally, I really like EdingCNC [2] but it seems to see limited success outside the German-speaking parts of Europe.
[0]: https://www.hiwin.com/pdf/linear_guideways_1.pdf
[1]: https://www.cnccookbook.com/choose-best-cnc-control-2017-cnc...
Well done!
Favorited!