Hobby CAD, CNC machining, and resin casting (2015)
lcamtuf.coredump.cx
lcamtuf.coredump.cx
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/
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.)
Instructions to download: https://youtu.be/hqyPzCKGUQc?si=VJ0KRhQOl_-d7Bmm
Download here: https://sites.google.com/view/gatorcam/home
Very user friendly. Tab support, v-bit, ATC, sorts toolpaths for faster carving.
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.
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 :')
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.
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.
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.
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.
And I only briefly looked into it, but most Fusion post-processors are just Javascript! (or at least based on it)
Having a CNC Router table in a non-industrial zoned area will not work for most people. Services like sendcutsend.com makes life so much easier... =3
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
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.
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.
Source: I do this stuff in my house.
Best of luck, =3
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 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.
https://www.goodreads.com/book/show/53168863-jigs-and-fixtur...
https://www.goodreads.com/book/show/5042096-jig-and-fixture-...
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?
* Not necessarily a good reason/excuse
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.
That said, I have an especial interest in archery and multiple machines.
Contact me at: https://community.carbide3d.com/u/willadams and we can at least work out doing a couple of prototypes.
I looked at your site and didn't see a contact option. I'm quite tired and am often worthless by evening, so I'll look again come morning.
My e-mail address is my name here, on AOL.com --- just drop me a line.
My guess form rejection is either:
1. No drawing and vague specs.
2. Too time consuming and they don't want to quote the crazy price it'd take.
Machine shop time is very expensive.
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.
More info on Github: https://github.com/thingsapart/mini_nc
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).
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.
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?
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]
[1] https://www.youtube.com/watch?v=_AYEFjbGaL4
[2] https://www.youtube.com/watch?v=zOqSIRuBgCY
[3] https://www.amainhobbies.com/rc4wd-metric-hex-twrench-tool-4...
https://knifeworks.com/crkt-9100kc-eatn-tool-black-oxide-fin...
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.
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.
[1] https://www.roperwhitney.com/our-products/no-5-jr-hand-punch...
https://sakparts.com/products/can-opener-diy-tool-part-for-8...
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.
Victorinox knife manufacture.[1] Stamp, heat treat, grind, polish. They're not exotic blades, just good manufactured stainless steel parts.
A primer on machining titanium.[2]
[1] https://www.popularmechanics.com/adventure/outdoor-gear/a351...
[2] https://www.harveyperformance.com/in-the-loupe/titanium-mach...
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.
The documentation on your github is a tad lacking however. :)
But good luck on your machine, I like your CPAP fan idea.
The plan was to build a second machine and optimize some of the assembly, take notes and document the build.
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.)
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).
Coolant and plywood do not play well together.
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.
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.
For an example of a knife blade:
https://www.youtube.com/watch?v=G5TYla5x-Nk
small tool:
https://community.carbide3d.com/t/nomad-made-custom-titanium...
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.
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 also definitely make junk single-use guns using either technology, just like the 3D-printable "Liberator".
https://shapeokoenthusiasts.gitbook.io/shapeoko-cnc-a-to-z
(ob. discl., I work for Carbide 3D)
I’d expect that with 3D printing you can even print the spruce and risers.
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.
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.
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)
Jim W. Teknic Servo Systems Engineer