3D printing with PLA has improved in the intervening decade. You can usually get a good print on good modern printers. The first generation of those things had poor extruders, and filament formulation has reportedly improved. There's complicated heat transfer going on in those things. You're welding a hot thing to a cold thing, which is inherently troublesome.
I'm told that works better now.
Machining resin molds is straightforward, because you start with a block of something and machine only its top. So there's no work-holding problem. Trying to figure out how to clamp something that needs to be machined on several sides is usually hard.
Not sure what's going on in tiny mills today. I've used Tormachs, the whole range of Shopbots, and some strange one-off machines that TechShop somehow obtained. (Never did use the beautiful little Pocket 5-axis machine. TheShop had one just before they went bankrupt.)
awesome dump, thanks for sharing. solvespace is cool but until they iron out the chamfer/fillet situation and parametric input I ll have to continue using freecad..
I followed that guide (it is excellent, if a little outdated) to get really good results. I should really write up and share my experiences, there is so much to learn.
In brief:
* It's an excellent method of producing very precise parts with fantastic mechanical properties (the next step up is aluminum, but you don't need it in most cases).
* It is much more difficult than just throwing something at a 3d printer.
* It is not comparable with 3d printing at all. I use both methods: FDM printing for most stuff, resin casting for parts that need to be strong, dimensionally precise, or nice.
* Yes, you can use your resin printer to produce originals or master molds, but you will have two problems: 1) precision, 2) silicone cure inhibition.
* Tips for those in the EU: Sika Biresin F50 is fantastic, Rencast 5146 is slightly worse (higher viscosity), but works very well, too. Both are relatively easily available. For silicones, BLUESIL RTV 3450 is unbeatable.
* For desktop CNC machines, there are good options now: Makera Carvera (either the full model or the "Air" scaled down version) are really nice and precise machines. Software is crappy, but hopefully will get better. I had a Nomad 3, but switched to Carvera.
* Don't buy a cheap CNC. There is simply no way to produce a desktop CNC with good precision for less than, say USD $2000. You will be disappointed. Perhaps if one day a Bambu Lab arrives with experienced engineers and a lot of money, they could mass-produce something cheaper, but right now this is roughly the cutoff.
* Autodesk Fusion, much as I hate it and the company behind it, is pretty much the only game in town if you want integrated CAD+CAM. Again, I hate the software with a passion, but there is simply nothing else that is as well integrated, works well, and is reasonably priced.
* Achievable precision: ±20μm is doable with a little care, things get difficult below that. This is roughly 10x better than what you can get from FDM 3d printing. Note also that this is the limit of what most people can measure: your calipers have an error of ±20μm if they are good. I also noticed that the 3d-printing crowd often has no idea what precision means, so you'll see crazy numbers thrown around.
* Mechanical properties of produced parts are way better than what you can get from FDM printing. I laugh at those "strong filament with carbon fiber" youtube videos.
Not just not comparable, but totally opposite. Subtractive vs Additive. CNC is like chiseling the David out of single block of stone by removing bits. 3d printing is starting with nothing and adding material.
Former MechE for a decade and I owned personal CNC routers and on my 6th 3D printer. The biggest issue with CNC is the cost for consumables and accessories. Need a special bit? $$$ Need stock to cut? $$$ Want a nice ER11 or R2 collet set? $$$. A nice vise? $$$ Cut something wrong with a carbide bit? Shrapnel explosion. 3D printing has a bunch of limitations but is a way better machine for hobbyist. But I have been eyeing the Millennium Machines Milo. A very fair price point for a traditional style CNC. You can also decorate it however you want with your 3D printer.
It is definitely more expensive than 3d printing in terms of consumables but china/aliexpress has really good hobby-quality equipment now - if you don't mind the country of origin. Many of their coated end-mills are decent and < $5 depending on diameter.
Maybe not stuff you would want to run professionally but it works quite well in a hobbyist setting and a mistake won't cost you $50.
I also looked into the Millenium Milo, only downside for me and kinda why I decided to design my own Voron V0-ish sized mini CNC machine was the really large footprint for about 3x the work volume (work _area_ is ~2x afair). An enclosed Milo would take up about the same volume as two 350mm Voron's side-by-side. So footprint of a small desk.
Imo besides the price, the other big factor is just how much less forgiving CNC machining is than 3d printing - so many mistakes you can make, zeroing the WCS, wrong WCS, mounting the work different than you had it in CAM, ... bam, at least the work is ruined. That's kind of another longer-term goal with my CNC machine, reducing some of these errors if possible with a web-based UI and maybe some computer vision. But that's far off, I'm currently playing with using a camera for work-probing/WCS-zeroing and it's sloooow progress :')
Have you seen the Carvera Air? Not gonna lie, I'm equally tempted but that price point is tough to swallow. Its about $7-800 more than the Milo but has a bunch of things built in that you would probably would enjoy like touch probe leveling and camera zeroing. Its the "Bambulab" of the CNC world.
I designed a little machine that's smaller than the Carvera with a 300W spindle at a lower price-point but requiring DIY (my build is probably around $550-600 now), I kept it smaller for a couple of reasons but stiffness was one of them.
The Carvera has an excellent work-volume to machine size ratio. Afaict it's not the stiffest machine but quite decent. The spindle power looks about right for it's level of stiffness judging by the YT videos I've seen.
Yeah, the 1.5kW spindle + VFD sounds absolutely amazing. It would be pretty nice to be able to cut some steel but not sure if the structure is stiff enough for it
There seems to be an upgrade path for cutting steel with a slower spindle and extra steel plates for added stiffness. There are other DIY CNCs that are designed for steel and use concrete for stiffness which are probably more appropriate - but they do cost more so it really depends on your needs.
What I think will really change things are the 3-in-1 fiber laser sources that can be used for welding, cutting, and cleaning. Building a CNC gantry that can use the cutter means large pieces can be cut from stock plate, assembled like a 3D puzzle, and very quickly welded together. While much more expensive than a Milo it is be a totally different category for capability. Plus a handheld laser welding, cutting, cleaning are very useful tools in their own right. I think laser welding is soaking up most of the supply at the moment but I also think it's just a matter of time before people figure out how to hook up the cutter to a CNC gantry like many already do with hand held plasma torches.
I have the Carvera (not Air) and it's a very good machine mechanically, the software leaves a lot to be desired.
It isn't even close to being the Bambu Lab of the CNC world, unfortunately, but I'd say only because of the software. If they open-source their controller, things might improve quickly.
Oh bummed to hear that, how’s the ATC? The ATC was always the most fascinating part for me for the original Carvera. The Air does not have this feature but it’s expected given the price difference.
The ATC works really well, better than I expected. Although without software support it is pretty much useless — I have no idea how people can recommend that I renumber my tools to 1-6 in Fusion CAM for every job.
What I did was write a post-post-processor of sorts that takes the .nc output, watches for tool changes, and using the tool library information automatically assigns ATC slots, renumbers tools, and generates pauses if collet changes are required (e.g. changing from a 6mm shank to 4mm or to 3.175mm).
That means I can now look at a list of assigned ATC slots, put in the correct tools, and let the machine rip, only pausing for collet changes. Pretty nice and how it should be.
However, I have to say, while the ATC is nice to have, I would not consider it to be the primary factor when buying a CNC machine. Those tool changes don't take long and are not difficult to do manually. It's much more important to get a rigid machine with limited backlash.
Kinda crazy, I know post processors cost money for CAM software like masterCAM but didn’t expect you needed to write one for a hobby CNC too. I know fusion360 had a post processing functionality but I think they moved that into the paid version. I miss the fusion360 of 5 years ago.
I'd just like to point out how stereotypical of a modern mechanical engineer it is to want to print everything out of plastic and not appreciate the greater versatility of a CNC router.
I can't count the number of times I've converted gasketed joints into O-ringed joints, slotted holes, casting lines and welds I've smoothed out. Yes, there are better machines for performing these tasks in metal but I can just tell the CNC router to go nice and slow and come back hours later. In addition to that there's all buffing and polishing operations you can do with abrasives and the ability to cut cheap wood templates and test parts. The 3d printer can make complex things relatively quickly and easily but it can't work with existing things.
I think it really depends. 3D printing allows you to be CAD lazy. Things don’t need to make sense as long as the interface is correct. You can also print another part if you mess up. You need to spend some time to make sure CNC parts are engineering sound. But most “experienced” and respectable engineers know their way around the shop. I have zero issues using a manual/CNC mill, grinders, brakes, or drill press. I did it all the time when the schedule is tight, my electrical engineer counter parts would order some off the shelf parts and I’ll modify it for the projects needs.
Any time I see a guide like this, everyone will go on and on about the types of cutters, toolpaths, speeds & feeds, etc. but will always gloss over work holding. For every action, there is an equal and opposite reaction. Without reaction forces, the best cutter in the world is useless. A sizeable chunk of your tooling will just be clamps and indexing tools needed to align and secure the thing you're CNCing, while also trying to keep them out of the work area. 80% of the end mills I've ever broken have been by crashing them into a clamp or vice by accident. This is another thing you tend not to see in 3D printing or laser cutting, or plasma cutting for that matter.
I didn’t know soft jaws were a thing until I started working. Even in college, they just teach you to hold the part up with spacer plates and crank the vise. One of the vendors I worked with was explaining why 4-5 pieces cost the same as 1 piece. The time and effort to make multiple jaws for each operation is the time consuming and expensive part.
There's a much higher barrier to entry with CNC. I have a cheapo CNC - few hundred dollars - and really have only ever made one practical usable "thing" on it.
It's so slow and needs much trial and error to get a decent cut, I feel a more expensive machine would be much more versatile but cost 10x for the machine and consumables as you say.
With the similarly priced 3d printer I feel like I've actually saved a lot of money and hassle printing things. I can quickly download a model and print a perfectly useable "thing" in no time, often with no mistakes. Prusa slicer and a larger $5 nozzle has made things even better, even though I have an off brand 6 year old printer.
Lots of hobbies can get expensive though, especially when high quality tools are involved. I'd actually argue 3d printing is an exception to that.
Decent power tools and consumables rack up and don't even look at the price of hand tools from the likes of Lie Nielsen.
I was in charge of one of these when I was way younger and they are awesome. Downside is that I don't want to house Argon and they're such a pain to maintain. Getting parts ordered is definitely magnitudes more efficient and significantly cheaper nowadays. You can get really nicely machined and anodized parts from China for the same cost as custom part shipping cost here in the states, it's crazy.
The noise from having a router and vacuum dust-collection running all the time can become a problem in residential areas. Most would like a full-sized machine that could directly handle standard sheets of material, but the space is not the only limiting factor (i.e. the insurance provider could pull something nasty with your mortgage creditors etc.)
Peoples situations will differ, and definitely check out reverse-spiral flute carbide-cutters if you handle a lot of sheet-work on a 2.5D setup =3
While everyone wants a machine for full-sheets of plywood, they're expensive, and not used for many projects --- a smaller machine suits most needs and there is always tiling.
My machine is quieter than my neighbor's drum kit --- and I've run mine after 11PM and you can't hear it over traffic and the nearby speedway (on race night) outside in the yard (a quiet vacuum helps a lot), but I have gone over to their house at 11:01 PM to remind them of what time it is.
>Having a CNC Router table in a non-industrial zoned area will not work for most people.
Lolwut? Throw it inside where the narcs can't see it (you'll want it inside or at least in an out building anyway). They're not loud. The venting you'll want isn't loud either.
Are you using a full sized "router" on steel plate, or a mini-engraver made from a hobby-motor on balsa? Even a compressor fed Plasma-cutter rig is usually far quieter by comparison, as cheap import engravers often just make a mess of the surfaces.
My router itself is a 2x2 with the Vevor 3hp spindle (not a repurposed handheld wood router). The router, regardless of material it's being used on, is quieter than just about any woodworking tool with a circular blade. When it's indoors nobody cares. I mostly use mine for making wood mockups of parts before I make them in steel. I have more traditional tools for steel fabrication. The router makes basically no noise compared to the "loud" ones of those.
You pretty much have to DIY epoxy granite. You probably get a better machine that aluminum extrusion (which are not meant for machine parts). You can DIY cast iron as well, but the high temperatures scare me away (and I done al casting in my backyard)
Those machines are still really expensive, and I haven't seen any versions that aren't a giant pain in the rear to setup and run.
(spent several years setting up and rubbing prints on metal 3d printers.)
It is to a certain extent. I forgot the exact brand but they give you a spool that’s $100-200 for 500g but that includes an autoclave service. You can ship the part to them to fire up in the furnace. But realistically, it’s cheaper and easier to outsource this whole thing.
With some concerted effort and money spent over several years I was able to more or less reproduce most of this document (but not nearly to the level of detail or variation on process). Eventually I was able to finely CNC engrave a wax block with extremely fine (0.1mm) features, make a mold, and then stamp out as many copies as I wanted. This guide was really helpful in understanding some of the core ideas.
For nearly a year, I've been contacting local machinists for a small[*] project which involves 1) an accurate cut on both ends of a 17" billet of T6061, 2) two crescent cuts, 3) up to 8 threaded holes, but probably, 4) a wee bit o end shaping.
All the aesthetic contours, shaping and weight reduction I'd do manually - I hand machine bronze, aluminum and wood archer's thumb-rings, so can wangle that part.
This project would result in the world's first ILF asiatic (no shelf), ambidextrous aluminum 17" riser.
Though... Every machinist I've spoken to is either friendly at first, implying willingness and ready capabilities, or they simply say no thanks. But all of them ultimately reject the task, typically saying they're too busy.
I also have a design for a bow stringer that can handle longbows, recurves and short Asiatic bows safely and efficiently. No one will fabricate it around here.
Any suggestions as to why this is such a pariah project? Any suggestions on how I might achieve this?
People who aren't trying to expand their business don't want to deal in non-gravy projects from customers who don't seem likely to shovel them a bunch of gravy projects later.
Machining is a slowly dying industry in the west so there's far more people not growing their business at any one time.
Shameless plug if anyone is interested - I'm working on a $600-ish open-source, reasonably capable, but small and somewhat "tidy" hobby CNC machine with BOM cost around $600 that requires some DIYing.
It's meant to be an alternative to the Desktop CNCs like Nomad, Carvera, Bantam, ... moreso than a PCNC or other proper entry-level CNC.
The ultimate goal is to make it hobbyist-friendly, capable of easily cutting alumin(i)um and not taking up a lot space, not being messy or loud enough to require a dedicated workshop. Unfortunately, cutting metal is inherently loud so you probably would not be able to run it in an apartment as I'd hoped.
I've made a couple decisions around being friendly for people coming from the 3DP space around probing, using roborock CPAP as chipvac, running it mostly dry, fully enclosed. I'm also starting to work on computer-vision-based probing and the idea is to later enable a host of more user-friendly and safety-focused features and maybe integration with Kiri:Moto's CNC mode for "guided" CAM and so on - basically a beginner-friendly CNC that guides newbies using an integrated web-interface.
GH is a little outdated but I've been using the little machine to cut alu for a while (mostly parts for itself) and it's working quite well. There's more videos and such on the Discord linked in the GH readme - feel free to ask questions on the Discord, I try to respond as quickly as I can. The full model with all its components is completely open in Onshape (I know it's not ideal but how I learned CAD - link also on GH).
Fully enclosed with a chip vac is good. Chips all over the place is no fun. Especially with coolant.
Don't expect people to precision-cut wood for the frame. The Liteplacer people tried that for their pick and place machine, and most people never got a working machine.
If it needs plates with holes in them, make them in bulk and sell them. Waterjets are good for that. The holes will be where they are supposed to be.
(The Liteplacer was a really good idea - a pick and place machine for assembling prototype PC boards. Camera controlled, with the input parts in partitioned trays rather than reels, it was slow but did the job precisely. The PixiePlacer seems to be the next generation of this. But, as with the Liteplacer, you can't just order the metal parts. You have to make them or have them made. There are commercial machines, of course, but they're for production, feed parts from reels, and are more expensive.)
Good point - there is a provision for laser-cut steel or alu plates that sit inside pockets inside the enclosure panels as I figured many would be turned off by a full plywood design.
The metal parts are symmetric so you can cut 2x of each - that is way cheaper on send-cut-send (afair only 25% extra for 2nd part).
The bottom panel is hdpe currently and "trayed", but you wouldn't run this machine with flood coolant anyway. mql might work but the idea was to cut dry, suck away chips and rely on coated end mills.
I've seen people experiment with diesel heater pumps for mql, might try that some time.
coolant always ends up very messy. even mql lubricated chips can be a relative mess compared to dry cutting.
> but the idea was to cut dry, suck away chips and rely on coated end mills.
You can go through a lot of end mills cutting dry. This is less of an issue for hobbyists who aren't turning large volumes of metal into chips and aren't using high-powered milling machines. The main limit on milling speed is getting rid of the heat. If you're willing to run slow, dry cutting works. Or if you only cut materials softer than steel.
At some point, you get Machinery's Handbook.[1] For most of a century, machinists' toolboxes had a built-in space for a copy of that book. Now it's available as an app.
I like to think of wood CNC as a step in the kit to something better. If you do your operations rights errors can cancel each other out and so you get better results by having a few extra steps. Make the wood CNC, then use that to cut the molds to make a epoxy-granite frame, then transfer the electronics to the new frame.
Documentation is definitely lacking - I just got the design to a point where I'm pretty happy with it. So far only 1 machine exists and the build has a few bits that are... less than ideal.
The plan was to build a second machine and optimize some of the assembly, take notes and document the build.
What's the advantage of this over a 3018 or 3030 machine? With some basic upgrades (you mentioned needing to diy anyway) you can easily cut aluminum on those for $500 or less.
I tried [1] - replaced the sides with 2040s, blind-jointed every extrusion, replaced X with MGN12H + 4 carriages, replaced the whole Z with 4080U and even bolted it into an MDF box to stiffen it up. The 3018 could cut alu, but not well. Maybe it was the 4080U but it just didn't work for me, it could cut alu but had lot of chatter.
For $600-800 it is fully enclosed, includes a decent spindle, wifi-enabled +offline RRF-based controller with folding/rotating LCD screen, 2 power supplies (24V + 48V for the spindle), a chip vacuum and probably some more I forget.
This machine was designed [3] specifically to cut alu rather well for < $1000, can run adaptive clearing toolpaths at 0.5mm optimal load and 3mm doc at 1800 mm/min with a 6mm end mill and produce decent chips. It can probably do more, my standard settings are 1200mm/min, 0.5 woc, 3mm doc. Mind you, this is all still hobby-level though you could still push the feeds and speeds a bunch I reckon.
This would be a lot more interesting if it could cut steel and titanium. I guess that is more difficult.
Added: a dumb question, if the main cutting device is a router with a spinning bit, how do you cut angles? One thing I'd like to make is a 4mm hexagonal hole in a piece of steel, to turn little hex drive screwdriver bits and the like. Is it even possible to make that with a mill, or do you need a different machine?
That's usually done with something called a rotary broach.[1] This is a clever trick. You first make a round hole. The rotary broach is a hex-shaped cutting tool. Both workpiece and tool are clamped in a lathe. But the center of the tool is slightly offset from the rotational center of the workpiece. Both spin, but the eccentricity makes it cut a hexagonal hole. Here's the process.[1]
A milling machine can cut a hexagonal hole, but the inside radius at each corner cannot be smaller than the radius of the cutter. A 4mm hex hole would require a tiny cutter to do a good job. Here's that process for a larger hole.[2]
If the hole goes all the way through, just get a hexagonal punch. Might need to drill a round hole first.
Or just buy a 4mm socket with a T-handle. Cost US$4.99.[3]
Thanks, yeah, a separate 4mm socket with a handle is certainly a possibility, but I liked the idea of a 4mm hex hole in something like this, to accompany the holes that are already there:
I'll look at the rotary broach video. Yes the hole would go all the way through, so a punch sounds ok. Anyway it's not about making this one hole. It's more an example of the kind of stuff I'd like to do with metalworking gear if I had access to it and knew how to use it.
It does sound like hard materials are an obstacle as well. Aluminum is a start though.
Ah. Here's the tool for that job - a Roper-Whitney hand punch.[1]
This is like a hand paper punch, but stronger. Costs $85.
Made in USA.
With a punch and die, you get clean edges on the hole on the exit side.
Scroll down for how to order the specific punch and die you need. Hex punches are not common, but are available. If you fill out their form, and tell them you need to punch 3CR13 stainless, they'll tell you what to order. Might need something with more leverage than the small hand punch. Lubrication helps.
Most machine shops will have such a punch, but they won't have a 4mm hex die in stock.
Or you could drill an undersized round hole and file it out to a hex hole. Maybe use the existing round carabiner hole.
There are touch-up kits for guns, called "gun bluing", to make your shiny new hole black.
This is all do-able but way more trouble than it is worth.
The idea isn't to duplicate an existing can opener, but rather to make custom specialized tools to fit into a SAK, or replacement knife blades out of specialty knife steels (i.e. very hard, so probably difficult to machine). It wouldn't just be for SAK's but also for other folding knives, each with its own special cutting pattern to work with its pivot and locking system.
Titanium is another material of interest, for ultralight gear.
All of this is probably impractical at the hobbyist level with limited work space, though. Oh well.
DIY knife forging is common. Search "knife forging". Look around for classes and forges with training. There's a huge amount of info on knife making and metallurgy. People obsess on this stuff. A good knife is a trick of metallurgy. The blade must be hard at the edge to be sharp but ductile in the body so as not to be brittle. How to do this is well understood today, but there was much mystery around it for centuries. If you're fascinated by metalworking, but don't have to make machine parts, that's a hobby direction.
Victorinox knife manufacture.[1] Stamp, heat treat, grind, polish. They're not exotic blades, just good manufactured stainless steel parts.
Sure, knife forging is one thing, but the idea of making replacement blades for folding knives sounds like it takes machining, because of the weird shapes needed at the pivot end, especially for weird locking mechanisms. It would be nice to be able to do that at a semi-commercial level if one were to get into it at all. Victorinox is on a completely different scale, making millions of units of whatever. But forging is for making one or two of something, while CNC machining is interesting for making a few hundred.
In practice I don't have it in me to pursue something like that for real. It's just interesting to find out about.
If I simply wanted to make knives, then no machining would be needed, just some cutting discs and belt sanders. It's the specific thought of making replacement blades for existing folders that seems to want more automation. I guess there are existing shops that can do that type of thing from a CAD drawing though.
Knifes are done with heat treating. you need to get the steel red hot and follow the proper cooling process. You machine soft iron to close then make it too hard to machine, finally grindit to the perfect size.
Steel is sooooooooooooo much harder than al, it’s not even in the same ballpark. Aluminum is about as hard to cut as wood. For non round holes, you are looking at approximations or broaching. Look up manual hex broaching
that looks like a nice project, reminds me of the ghost gunner 3 machine.
I like the safety note too. might hop into discord sometime next week. thanks for sharing!
oh my! I found this exact page in ~2017. I m something of a tab hoarder and I had around 2k open tabs back then. I loved the page and content and wanted to get back to it, but you know how it goes. Somewhere in early 2018 my browser crashed and I lost the tab. I distinctively remembered losing that page and I tried to find it, over and over again. I actually had one of the pictures saved (blue-red-white wheel), so I opened it in new tab as placeholder until I find the page. 6 years later here we are!!! tnx hughgrunt xd
I'm not too excited by the idea of making little plastic precision gearboxes for robots, so when PLA printing isn't good enough, I mostly want to machine metal. Not car parts or firearms but flashlight bodies, knife blades, small tools, that sort of thing. Nothing wrong with robotics but there are other interesting areas too. I think the article skips over that a little too easily. That said, it's a good article.
Has anyone here tried using CNC machines for gunsmithing as a hobbyist? Is that even feasible? What about 3-D printing metals instead of plastic? To be clear, I know little about either firearms or metal working, but it seems like it would be an interesting engineering challenge for a hobbyist.
Current hobby 3d printing of metals usually requires a clay-metal type of filament and sintering, usually by heat or laser to harden the metal, and often needing compensation for shrinking and a lot of other inconveniences.
The resultant pieces are "metal" but not strong enough for most internal firearms parts that need to be metal but not necessarily pressure-bearing like a barrel: most notably bolts and carrier groups, fire control group parts like triggers, hammers, sears, disconnectors.
You can't easily make a high-quality firearm a hobby mill, chiefly because the barrel needs to be made out of good steel and needs to be rifled. But the quirk in the US is that federally, only the receiver is the regulated part, and many types of receivers can be made out of plastic or aluminum. You can certainly use cheap three-axis CNC with some fixturing to make AR-15 receivers, for example, and many people did. Cody Wilson / Defense Distributed had this whole thing where they were selling CNC mills for cranking out guns.
You can also definitely make junk single-use guns using either technology, just like the 3D-printable "Liberator".
Routers don't have enough rigidity (this is why you don't see gantry mills except in huge sizes) for the kind of work you'll want to do. So much of your stuff will be one off that you're not going to have any speed advantage over a guy with a Bridgeport.
For one thing, IME with cheap hobbyist 3d printers (e.g., Ender printing PLA), the article is dead on about accuracy... people say 3d printers are good for 0.1mm but I don't know how long they spend tuning the machine. I mean, they are... kind of... just not reliably. CNC accuracy of 0.025mm is much easier to achieve (IME).
If you mean to tell me that I should just have a resin printer to start with, well I agree but I think we should be specific about what kind of 3D printing we are discussing.
Remember, the guide was written over a decade ago. Certainly 3d printing has gotten better, cheaper, and a lot more reliable. Resin is really strong, though.
It is possible to get good results with 3D printers, but that requires you to go to below than 0.1mm layer heights with 0.1mm nozzles and nobody has time for that. You can make a hundred resin parts in the time it takes for the printer to finish making one.
It depends on the accuracy you are trying to achieve, and with what technology.
If you mean FDM, it's absolutely true.
If you mean SLA/MSLA these days, i think you could get there.
On the first - i have an entirely ballscrew + linear rails driven FDM printer with closed loop servos and proper absolute encoders - I got bored and do lots of CNC retrofits/etc, so had lots of parts around. Think of it as insane version of the Pantheon HS30, if you didn't care at all about costs or practicality.
It can position, at speed (IE 300mm/s+), and repeat, the nozzle placement to within 0.0005 inches on all axes, easy.
But even with input shaping/etc, you will not get a better surface finish than CNC, and definitely not one good enough for casting.
Filaments are just too finicky, even with really really good hotends, sensors everywhere to monitor response and optimize, etc.
Now, i did this for giggles, and yeah, i never get misplaced layers, my parts are consistent, etc.
But 0.4mm is still a pretty big feature size, and that's the minimum if i don't want prints to take until the heat death of the sun.
So I could still machine the same thing on my metal mill and achieve castable surface finish, etc, in much less time and effort.
This sounds fun, have you written anything up about this project? I’ve been considering switching to ball screws and closed loop servos on my next project. I’d be especially curious for component recommendations for hobbyists, as it seems like ball screws and servos are often super expensive or suspiciously cheap.
For hobbyists, i think components are tricky. You have two basic options:
1. Linear motors - these are ideal (because it's a high acceleration, low intertia application. the extruders basically weigh nothing), but harder to find. Peopoly has a kit but my experience has not been the best there.
They do seem to be coming down in price, but i haven't yet seen the equivalent of what teknic did with the clearpath steppers, but for linear motors.
2. For closed-loop steppers, you'd be best off with something close to the pantheon - closed loop teknic steppers.
They have a good history at this point (well known in the CNC community), and are now even commonly used in mid-grade CNC machines these days. I've heard nothing but good things about them.
As for real servos, if you want real servos, the problem you hit (relative to the current requirements of the average 3d printer) is not just cost, but the space requirement. You need real servo controllers, and they are all basically built to be in cabinets. So having 6 servo drives is not an insignificant amount of space + power.
It is also severe overkill in some sense. Servos are meant to bring more efficient power usage to bear on the problem of generating torque (for the most part). But you don't need that much torque to drive a 3d printing axis, it weighs basically nothing and the mechanisms used rarely have any meaningful inertia or friction. So while I haven't tried it, i suspect you would be a lot better off with steppers + absolute encoders to ensure positioning (absolute so you don't have to home, and because incremental vs absolute cost is a complete wash at this point).
The servo drives are just basically PID controllers + rotary encoders on the motors anyway. If you instead used steppers, linear absolute encoders, and controlled them by pid, i would bet you could do very well (assuming you can dynamically increase the step resolution as you approach position).
The ball screws and linear rails are easy - you can get cheap c5 ballscrews (which, over this distance, are fine), and pretty much any linear rail will do (a 25mm linear rail can easily work on a 1000lb gantry).
Don't overdo the ballscrews.
The thing about ballscrews that people miss is that while the grades tell you the rough positioning error (which is caused by deviation in the ball track), they have little affect on repeatability, which is still very high. So even C7/rolled/whatever ballscrews are very very repeatable. The ball tracks just aren't ground as precisely, so the deviation from expected distance is higher.
What this means is that if you just map the position error, once, even on a low grade ballscrew, you can correct for it very easily, because it doesn't really change.
(this isn't perfectly true, but is true enough for this purpose).
This is commonly done to get better accuracy out of lower grade ballscrews.
If you do use linear encoders, you don't have to worry about any of this - they will be much more accurate than the ballscrew, especially over this small a distance (ie 300-400mm) and you use their position as the source of truth. In that case, you could easily use c7 or rolled ballscrews.
The thing you won't be able to fix in the end without changing how we think about these printers is the mass. Wood/Metal CNC use mass to reduce vibration because it's very effective. While input shaping is great, in the end, you will hit the limit of the acceleration/movement speed you can practically achieve unless you are willing to add like 1000 pounds to your printer to absorb vibration. This is not fixable. you can't make the vibration 0 and the energy has to go somewhere. You can see this on linear motor based printers. Even without belts and lots of moving parts, they still can't do more than about 300mm/s print speed without vibrating too much.
I would bet with better isolation/etc we'll get towards 500mm/s, but we will hit a limit that will require increasing mass in practice (IE whether you bolt the printer to the floor or built a concrete base or whatever)
Hi DannyBee - I’m a Teknic application engineer and I just came across your post. I appreciate your kind words about Teknic! I wanted to clarify that Teknic ClearPath motors are actually fully closed-loop servo motors with integrated servo drives, not stepper motors or hybrid steppers. If you have any questions, please feel free to contact Teknic at 585-784-7454, or submit a contact request any time at https://teknic.com/contact/ and someone will get back to you shortly. Thanks!
That was written before resin printers were affordably available or input shaping and so forth had made such a leap in print quality for fused filament printers --- that said, I get much better surface finishes on my CNC machines than my 3D printers, and casting will reproduce even the tiniest imperfection.
https://news.ycombinator.com/item?id=41467268
https://news.ycombinator.com/item?id=27645605
This was a resource which was mentioned on the Shapeoko wiki --- while it's off-line, it's still on the Wayback Machine: https://web.archive.org/web/20211127090321/https://wiki.shap...
Since then, some of those pages have been made available on Reddit:
https://old.reddit.com/r/hobbycnc/wiki/index
https://old.reddit.com/r/shapeoko/wiki (ob. discl., I work for Carbide 3D)
And there have been a number of other developments
- FreeCAD has hugely improved since that was written.
- Solvespace as greatly improved, adding some basic CAM functionality
- Blender has had the Solvespace sketcher ported to it as https://www.cadsketcher.com/ and BlenderCAM has gotten quite a bit more workable
- Dune3D was created and is remarkably capable: https://dune3d.org/
Also a fair number of forums discussing CNC were gathered at: https://forum.makerforums.info/