Wow, really short section on gears. But there is so much to cover I can't blame it.
If you've ever dabbled in robotics, you've probably found it is an enormous step function from kits like Actobotix [1] to custom parts. It is infinitely easier to use kits or frameworks that have already taken a LOT of the guesswork out of gears, linkages, motors, compatibility, etc. Especially gears, they are an enormous pain in the ass to source online, and even when you find the right gears, you still need hubs and axles, and then you hit min volume issues, non retail sales, overseas... I even have access to a phenomenal machine shop, but what I don't have is a machinist. (There are a few that mill around (pun intended) but they are mostly introverted decent guys that don't really want to help a noob.)
Having spent a million dollars making gears, my ultimate conclusion is it’s the sort of thing you machine from brass gear stock unless you want to spend a million dollars.
For what 99.99% of makers are doing, Actobotix is fine. But if you want to make your own fancy differential or a hypercycloid linear translator, yeah, you're gonna have to do it yourself.
gear stock is basically a gear that's really, really long so you can just cut off whatever width gear you need. Similar to bar stock, which is just rods of metal, but in gear shape.
What dimensional scales, materials, turn-around, volume, and/or processing?
Breaking tools and getting G-code just right seem like the perpetual headaches of modern machinists. Other than occasionally being bitten by a bitchy blade-like chip begging to fillet your grizzled knuckles one last time before banishment from the bench to the backyard becycling bile of betal bits.
If electricity were cheap (or the electric meter rewindable), would multiple beam concurrent FDM be a consideration if the materials and metallurgical characteristics allowed it? I think at some point, it's easier to print complex shapes additively than machine them subtractively, and that needs to be part of structured cost decision-analysis for manufacturing.
I think if you want to make one or two custom gears, you just manually mill them. CNC involves the usual programming tradeoffs -- you spend a ton of time writing and debugging the program, and then you can run the program a million times to make a million parts. For making one part, it's not clear that it's worth the overhead -- just set up your stock on a dividing plate and use a gear cutting tool to cut the teeth. If when you're turning the handwheels the machine makes an unpleasant noise or it feels like you're going to break the tool, stop turning the handwheels and use your brain's built in AI algorithm to develop a new plan ;)
Usually a short run of a new part doesn't take more than half a day to set up on a CNC. If you are making thousands of parts to run unmanned you might have to add another day to it.
Would you know what type of approaches and machinery is needed for relatively loose tolerance / low load helical gears? If going the CNC route, do I need full 5 axis and specialized end mills?
Even with regular involute straight gears, there's a bunch of ways one could manufacture one, and I'm out of my depth here.
It's way easier to start with components you can readily source and design your system to use them than to make custom components. If your robot isn't going to space, the benefits of custom components will not be worth it.
I really think that every well rounded person/STEM academic should at one point in their life (hopefully sooner rather than later) expose themselves to some hands on machining... like, even just a few hours on an old decrepit mill/lathe.
I feel like the foundations of the industrial revolution (speaking within the US) are... very much forgotten/taken for granted given the fact the near entirety of our modern life and comforts exist because of it.
There's fortunately a ton of great, readily available content on YouTube/elsewhere that's sprung up in the past 10 or so years you could just watch, but actually machining is such a cathartic experience... at least when you're in a position to do so that isn't in a grimy ass factory/warehouse with somebody yelling at you to push out more operations than is humanly possible, haha.
> expose themselves to some hands on machining... like, even just a few hours on an old decrepit mill/lathe.
Excuse me but as a pro in this field I have to raise an objection. There are aptitude tests just for the education because some people who are otherwise brilliant are absolute terrors, a dangers to themselves and others when presented with machine tools. Trial and error works very differently when you focus enough pressure into carbide to cut steel like it was butter. You should watch the horriffic videos of people being turned into bloody messes on machine tools and THEN decide if this is something you want to try. Nobody knows in advance if they belong in the danger-category but school instructors are quick to spot them and talk them out of the field.
If you are adamant on going at it on your own, stick to tools which don't output more than 1000W. In a panic you can produce that much power and you might only lose a finger instead of your life. ALWAYS pause and think about what you are going to do the very next moment and what you expect will happen.
I'm sorry if it sounds like gatekeeping. Those videos are very convincing that the gate is there for a reason.
You raise some good points, but I think they're a bit too overreaching.
I started working with manual machine shop machines (mills/lathes/presses/all types of saws/water jets/lasers) over a decade ago, and I'm only in my early 20's now.
>There are aptitude tests just for the education because some people who are otherwise brilliant are absolute terrors, a dangers to themselves and others
This is true. Working as a student shop instructor in Uni, I've had to remove a fair amount of people/literally leave & shut down shop from stress/frustration after people repeatedly nearly lost fingers/limbs doing what they were told not to do multiple times - mainly on table saws. As to why these people are they way they are... I do not know.
>Trial and error works very differently when you focus enough pressure into carbide to cut steel like it was butter.
No instructor/supervisor should be letting newbies work with steel to begin with, except possibly very mild steel... we have things like 6061 T6 Al and even polymers for demonstration/early learning. It was a good bit until I was allowed to work with stainless steel on mills/lathes.
>You should watch the horriffic videos of people being turned into bloody messes on machine tools and THEN decide if this is something you want to try.
I grew up doing this, still do, and always recommend it to anybody who's about to start working with machine tools. I have yet to meet an instructor/shop supervisor who doesn't make it very, very clear how easily and instantly everything can maim and kill you. In the 21st century, if there are those who don't do this... that's just unfortunate.
In the end - mills, and especially lathes, are honestly highly predictable machines. It's quite hard for things to go wrong with them aside from tool crash/breaking, which you won't really be in a position to be hurt by. There are some machine tools that are inherently more dangerous - but - nothing comes close to how fucking dangerous a tablesaw is. I consider a tablesaw to be the most dangerous and unpredictable tool I use, as does the person I learned from who's been an industry/custom fab machinist for over 40 years. And tablesaws can be found everywhere, typically without much restriction, if any, to begin using.
The sawstop is cool, but I really fucking hate them for not releasing the patent to it for all to use.
Are they really so dangerous? I've generally worked with the rule of thumb: glasses, no dangly bits, don't touch anything, don't use your hand as a machine vice, and so far, no injuries.
My feeling was that since metalworking machines are usually relatively slow and not that grabby, they were safer than, for example, a circular saw.
I mean, that's not a high bar, but nobody is saying that people shouldn't do hobby woodwork.
If you take sandpaper to a part turning on the lathe and make the mistake of closing your hand around it, you can lose your arm. On a drill press a chip can reach out and grab your clothes and pull you in. Heavy parts can come loose and fly through the air. Hardened tools can break and send shrapnel flying like bullets. A hand's width of unspported stickout of a long bar from the back of lathe's spindle bore can turn into a meat tenderizer, spinning too fast for the eye to see. The last thing you heard before hopefully waking up in the hospital was the sound of a helicopter...
It's the gotchas that get you. You can do it safely and people do all the time. But mistakes happen, and then you better be lucky or good.
I guess I worry sometimes because my shop is in an old industrial building, and nobody else works there, so I'm always thinking that if I was injured and unconscious, I could definitely die. But then, the problem with machining is it's unavoidable. There's usually no other way to make the part.
I'd be interested to look at statistics, but I always have the feeling that the table saw sits basically at the top of the pyramid when it comes to chopping bits off, then it's followed by all the other woodworking stuff (spindle moulder comes to mind), then you get the metalworking stuff.
The first time I was ever in a machine shop, one of the operators didn't clamp down a part with enough force. It was a little steel block approximately 1x1x3. It shot out of the setup across the room at a speed comparable to a baseball pitch. It missed my head by about 6 inches. Had it hit my head, I'd be dead.
A circular saw isn't a toy either, but it's pretty hard to accidentally kill someone with one from 20 feet away.
You realize that you just listed a handful of rules of thumbs. All of which would be taught in an introductory shop course, but not everyone pays attention or understands to implications of those rules as they might apply in every scenario.
The caution is warranted here. Shop machines literally can flense, main, or kill you. Even at low speeds.
I would say everyone should try these things if they 1) find a mentor to help do it safely or 2) read enough in advance to become subject experts, before ever setting foot in the shop. Under no circumstances attempt to learn by blind trial and error.
I'm a semi self-trained machinist, as in, I had a lot of experience making stuff with hand and power tools, but no experience with machining, so my two cents is:
1. You're not really going to be able to use a machine full stop unless you read a book, watch a bunch of introductory videos, or go to a course. They're not very intuitive.
2. Besides the stuff that's obvious, there are just tons of things that are non obvious. For instance, brass has a habit of grabbing bits then turning into a whirlygig of death. There are just tons of stuff like this ('don't feel around in hydraulics', 'watch out for springs', etc) that you won't really get in an introductory course anyway.
3. Everybody is literally driving drunk where I live. You walk past half-asleep idiots driving gigantic machines all the time. At least with machine tools, you only pay for your own incompetence.
Yes, they are unbelievable dangerous. They can kill you at 1 rpm, speed doesn't matter. I've heard (and seen myself) many horror stories. Long hair, or anything dangling, can easily get caught in the chuck of a lathe, even of only going a 1 rpm, and pull the operators head into the moving machinery before anyone has time to react. Metal working machines are among the most dangerous equipment one can operate.
> Metal working machines are among the most dangerous equipment one can operate.
No, woodworking stuff is FAR more dangerous.
The reason for this is twofold:
1) Metalworking almost always involves workholding.
Metalworking almost always has a vise attached to your work and the machine. Metalworking almost always has your hands somewhere other than near the sharp bits. A mill has your hands on the dials. A lathe is similar. A drill press has your hands on a handle.
With woodworking, your fingers are almost always the motive force and they almost always pass near the cutting edge even if you are using push sticks and sleds.
2) Woodworking machines rotate far faster
Radial and circular saws can remove your hand in a blink. Wood lathes often throw or explode the part while your hands are right next to them.
Admittedly, the plural of anecdote is not data. However, almost all the woodworking accidents I have seen have been far more problematic than the metalworking accidents I have seen.
I guess from my somewhat small sample of acquaintances, the feeling that woodworkers tend to end up missing bits. Metalworkers tend to have bad hearing, bad eyes, but all of their appendages.
Dangly stuff, obviously, is like waving a steak at a bear.
I manage a fablab used by grad students. We have both manual and CNC machines. Haas, too, but the cheaper stuff (TM and an older OM, VF stuf is $$$ for research budgets).
The eternal compromise is this: it's way easier to dismember or kill yourself on a manual machine (https://www.nytimes.com/2011/04/14/nyregion/yale-student-die...). However, it's even easier to seriously fuck up an expensive CNC mill with a programming mistake.
Serisouly, these machine can and will destroy themselves if you tell them to, no questions asked or warnings. One single bug in your g-code and and there goes a 15K$ set of spindle bearings or worst.
Of course, a few tens of thousands down the drain is still better than dismemberment. But that also means that sometimes our machines are down for months or years until we can get a new grant to fix them.
Ah yeah I’m on the industry side of things, where such fixes just get expensed out the next day...can’t imagine trying to get a grant for every problem...
Getting your hands on a barely serviceable manual machine is easy though, which is why I started worrying. If the machine is out of production there might be something seriously wrong with it and if a novice starts compensating for the fault then the margin of error approaches zero.
Compund this with youtubers not uploading when they made a dangerous or embarrassing mistake and things start to look a lot more doable han they actually are.
Most working undergrads (RAs) in the physics department at my university had been trained in the Physics department machine shop at some point in time, so it was common for
them. Probably the only program outside ME where that was true
Me too -- I had a 30 hour course in the workshop as a graduate student in physics. We covered both manual and CNC milling and turning, with Bridgeport mills and Colchester lathes.
Completely opened my mind. Made me a better experimentalist. I spent about 99% of the time utterly terrified and wanting to check everything about ten times to make sure that I didn't wreck either the job or myself.
Not sure this is normal. Have heard stories of physics department needing to contract to the engineer's union, and people getting in trouble for screwing together a wooden box.
Seems fairly normal from what I can tell. Issues like needing everything to be vetted my a mechanical/civil/electrical engineer, depending on what it is, and not being able to machine your own parts and needing to let the university machine shop bill time.
One of the funniest things I can remember about uni shop bill time was that some aerospace engi's needed some really special washers. They were quite expensive and the shipping time was going to cut a deadline extremely close.
So they were able to send one of the grad students who watches over the after hours student machine shop a few hours away to a place that had the metal needed in stock and then have them CNC all the washers. They charged typically charged a good bit for physics/aerospace dept. to use said CNC, still ended up being much cheaper and much faster... for simple washers.
One thing to note when it comes to resin casting and cnc is the 3d printing evolution since 2015. The amount of detail you can get from an inexpensive 3d printer these days is astonishing and it seems like less far less messy than a cnc. Not that long ago I got a resin-based 3d printer and I was blown away by the prescision. That said, for me at least, there is a big problem in that entire field - the third point - "Mastering CAD and CAM". To put it lightly I really suck at it. I am using Blender(100% linux user) and having to switch between layout modeling and sculpting(etc.) often puts me in a Hulk mode rage. I can't find a pattern in the menus or modes and everything I try to do ends up being 2 hours of googling and youtube tutorials. Which I reckon is me being too used to cli-tools and hardly ever going outside the cli world(if it weren't for browsers and the modern web which cannot work without js, I'd have probably removed my desktop environment altogether).
> Which I reckon is me being too used to cli-tools and hardly ever going outside the cli world
You might get some mileage out of OpenSCAD if you can define your object parametrically (I used it to make a Switch controller middle-bit.) Or there's stuff like https://github.com/fogleman/sdf which I've used to make resin-printed buttons for my mother.
(I also cannot get the hang of Blender despite dipping into it for a couple of weeks every year since about 2013.)
I'm liking Onshape for CAD. There's a learning curve, but it seems logical in a geometric puzzle-solving sense.
I read a bit about resin-based 3D printing (stereolithography). The amount of detail looks impressive but it sounds expensive and messy due to the toxic chemicals and fumes. How do you deal with that?
Very much depends what type of resin you use. The one I use has practically no odor and is water washable. In addition, there is an air filter(which is annoyingly sold separately) for that printer so even less of an issue. I was initially planning to shove it in the basement but after a few prints I figured it doesn't make a lot of sense.
Messy yes, fumes yes, but the printers themselves are now less expensive than a decent FDM (filament) printer and the resin itself is relatively inexpensive as well.
I understand you use open source, but Fusion 360 really is a game changer. The CAD to CAM workflows are easy and intuitive once you learn the basics. Blender is designed to be a lot of things to a lot of people and I can see how that would be extremely frustrating. Yes Fusion isn’t cheap, but it’s very worthwhile IMO.
Autodesk is unfortunately doing exactly what one can expect Autodesk to do. As soon as Fusion 360 meets a milestone they add new ways to monetize their users. TBH I can't recommend it for anyone outside US jurisdiction because of how the company is managed.
No, I'm not full on RMS here, if there's a proprietary software that I could use and I can use it under linux, god speed. Sadly adobe and autodesk are reluctant to add more support, despite the demand.
With something like a FormLabs Form 2, 3D printing can go really far. And, with a Form 2, you will be printing parts from the get go and not dorking around with the printer all the time.
My biggest problem is still when I want to do something in Stainless Steel. I really wish I had some way to deal with Stainless without needing a gigantic machine.
I bought a similar kit from Smooth-On to make casting of Warhammer 40k miniatures. It was amazed at the detail and accuracy of what I created!
The secret was using a back massager to vibrate the table to get out the bubbles!
Artisan Alliance made a couple of very good videos on high detail resin casting with silicone molds [1]. They focus on mechanical keyboard keycaps, but the same ideas apply to many other things.
I’ve done it for making fake ancient coins - like another responder, I used a Smooth-On kit and it couldn’t have been easier. Though I was casting bismuth alloy rather than resin. One tip, be sure to dust the mold with talc to allow air to escape. Also the vibration table tip sounds good.
I remember avidly reading this whole thing when it came out (and a lot of the rest of the blog) despite not having a CNC myself. Always great to see someone sharing knowledge from their own deep interest in a topic.
Fun fact, all CNC machines sold in the United States with more than 5 axes of travel have to be registered with the ATF and have a permanently attached GPS tracking unit. This is even true if you have zero intention of using your CNC to manufacture anything reminiscent of a firearm or firearm component. This is why it's common to see 4.5 axis CNC machines or a plethora of "upgrades" that grant 5 axis capability post purchase.
I believe you're thinking of the GPS/Gyro locks that certain high end Japanese CNC machines have, and the ITAR compliance issues many CNC machines are subject to for export. The locks were implemented because somehow Iran got their hands on some Mitutoyo machines despite sanctions. Either way, it's the State Department and Department of Commerce that get involved and the ATF has nothing to do with individual machines.
I was thinking about the Mitutoyo incident, but I think those were coordinate measuring machines, not mills. (5-axis implies milling, but Mitutoyo doesn't make mills. CNC is a generic term that really applies to any sort of machine controlled by a computer -- we have CNC sewing machines at the local makerspace ;)
As for geo locks on mills, I have heard about those. My understanding is that they're a software licensing thing -- sell the machine, move it to a new shop, the software stops working. That ensures you can't get your money for the machine on the secondary market, and that new customer has to buy a brand new one directly from the manufacturer. Just your standard DRM scheme to improve corporate profits. Also good to have that equipment on board so that you can switch to a subscription plan if the economy gets bad.
I don't know if all 5 axis machines require registration with the government. I have looked at these before: https://pocketnc.com/ and they don't say anything about it. Could be too tiny for anyone to care about, though.
If you need more than a good bridgeport mill to make a firearm, you don't deserve to be in a shop... All you really need to make an AR lower is a drill and some aluminium plates. Heck, pakistanies are making a plethora of firearm with nothing but files...
I was considering last week to pick up CNC machining but now I've lost all interest. It sounds very primitive and intersectional. dang, you have trolls.
There is nothing more primitive than a robot that doesn't even know its own position and only follows a program with the hope that it works. (assuming a hobby CNC machine without servos).
If you've ever dabbled in robotics, you've probably found it is an enormous step function from kits like Actobotix [1] to custom parts. It is infinitely easier to use kits or frameworks that have already taken a LOT of the guesswork out of gears, linkages, motors, compatibility, etc. Especially gears, they are an enormous pain in the ass to source online, and even when you find the right gears, you still need hubs and axles, and then you hit min volume issues, non retail sales, overseas... I even have access to a phenomenal machine shop, but what I don't have is a machinist. (There are a few that mill around (pun intended) but they are mostly introverted decent guys that don't really want to help a noob.)
[1] https://www.servocity.com/actobotics/