Comment by hoprocker | Hacker News Reader

Comment by hoprocker | Hacker News Reader

I love articles like this. They display long-term focus and a patient, multi-disciplined investigation into how to complete a project (in this case, some light mechanical engineering, materials science, and machine technology). I've been planning out a project and will need to make some large-ish 3D parts out of a translucent plastic (part of a larger audiovisual installation), and until now I'd been uncertain about how to proceed. I'm shedding tears of joy reading through this brave soul's explorations into DIY resin casting.

Something that struck me about this article -- and something which I see regularly around CNC hobbyists -- is the unfamiliarity with basic machining calculations, a problem that usually results in chipped parts and broken tools. I didn't even know about machining fundamentals like chipload/chip per tooth (CPT), inches per minute (IPM), and correct RPMs for different materials until fairly recently. Additionally, "climb" versus "conventional" milling refers to how the bearings are loaded -- you almost always want "conventional" unless you're on a nice CNC machine. Why isn't there more information crossover into the hobbyist world?

Anyways, kudos to the OP for throwing this out there, and thank you Zalewski; I'll be methodically absorbing pretty much everything linked to in this essay. :-)

There is tons of crossover of this material into the hobbyist world. The problem is that people don't bother to do their research. The average programmer who wants to build a CNC mill (or more likely, a router) jumps right into the software and electronics. The mechanical aspect is an afterthought.

OTOH, had he started by trying to understand the process of machining without focusing on whether the tool is being controlled by a human or a computer, he'd find that there are thousands of hobbyist machinists online running fully manual machines that will happily share the knowledge you mentioned. Machine tools have been around for 200+ years. The basic techniques haven't changed very much in all that time.

TL;DR: do the research first.

Good point. Maybe some self-selection bias here (Hey, I'm comfortable with computers and programming, so I'll jump straight to the computer-y part of machining).

Yes, that also struck me. This guy obviously knows his stuff now, but he would have been well served by (American style, which I don't know if there is a similar system in Poland, so this point may be moot to his particular case) an introductory Machining course at his nearby community college. Some of the mistake he made early on are very basic. But then he learned from them obviously, and he's also seems rather very determined. It's a great story and website.

Of course, I'd also say that for many people, a typical type of reaction to CNC machiningi is: "Oh, you just put the file of your 3d part in the machine and it makes it!" Nope, not that easy.

>Something that struck me about this article -- and something which I see regularly around CNC hobbyists -- is the unfamiliarity with basic machining calculations

...do you have a recommendation or two for books/resources for learning about machining?

I've found the best machining resource is working with a good machinist. Quite a bit of machining is about intuition and properly evaluating other sensory inputs - knowing how to interpret the sound a cutting tool makes is critical! Unfortunately, finding a good machinist willing to let you watch them in person - or better yet, work under their supervision - is pretty hard, especially if you're just a hobbyist. Crotchety old-timers don't scale particularly well...

Youtube is one of the better resources right now, for anything other than really basic calculations. There seems to be a trend of old-school professional machinists documenting jobs they're working on - sort of a cross between a tutorial and virtual job-shadowing. Some nice users include oxtoolco, KEF791, Abom79, and mrpete222.

Bang on true. As I noted elsewhere, that semester of night courses at the local JC has improved my machining abilities drastically, as well as illuminated me as to actually planning the order of operations (y'know, "step 1: bandsaw", etc).

msds and hoprocker hit it on the head. In this field, I think the best way to learn is to still go in and work with an expert and get your hands dirty.

That said, an introductory book that the local community college just recently started using (before that, there really was no book, just blueprints and notes because so much information came from the instructors) is the Precision Machining Technology [0].

Unfortunately, like many textbooks, it's not cheap. But it's a nice introductory book("I don't have a clue, but I'm interested in the topic")

[0]http://www.amazon.com/Precision-Machining-Technology-Peter-H...

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