Guerrilla guide to CNC machining, mold making, and resin casting (2015)
lcamtuf.coredump.cx
lcamtuf.coredump.cx
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.)
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.
Problems.
No problems. After they are fixed by the meat confusor.
They are solved.
Your tool in a vise.
So you can decide on a module/PA, buy a few diameters then cut off the required face width you need and machine the bore as needed.
I did a cursory look through the section on gears, it seemed adequate for someone who is doing a hobby project.
I'll watch this thread and answer any questions you might have.
Even with regular involute straight gears, there's a bunch of ways one could manufacture one, and I'm out of my depth here.
I made sprockets with an endmill and a simple macro on a C-axis lathe. Worked just fine since the tolerance on those is very forgiving.
In principle you could make a helical gear as a multi-start thread. I'll have to test it once I have the machine free an afternoon.
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.
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.
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.
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.
I don’t think anyone in their right mind will be handing over the keys to a roomsized VTL any time soon...hopefully...
Manual machines on the other hand—absolute death traps.
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.
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.
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.
Dangly stuff, obviously, is like waving a steak at a bear.
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.
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'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 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.
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.
A circular saw isn't a toy either, but it's pretty hard to accidentally kill someone with one from 20 feet away.
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.
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?
[1] https://www.elegoo.com/collections/resin/products/elegoo-wat...
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.
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.)
Holy crap, why have I not seen this before?!?!!? I was even planning to start coding something like this myself. This is awesome! Thanks!!!!
This is the kit I originally bought: https://www.smooth-on.com/products/pourable-silicone-starter...
Is it just like a motorcycle windscreen that you don't need to see through?
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.