how is my cad drawing machined in the shop? 8

[jamesyboy1990]

I know how to design a metal part in CAD, but I have no idea how it is actually machined when it is sent off to be made (or how they come up with the quote). There have been a few times where I design something and then the machinist requests a change because something in my design is apparently very costly to machine (and I'd have no idea why until it's explained to me).

Are there any good tutorials online that outlines basic machining procedures and their general costs? (ie. how do you chamfer or fillet something? How would this basic feature be machined?). I've only learned basic CAD in university so far and nothing about how parts are machined. I'd like to be able to design stuff knowing how its going to be machined so that I know when some feature will be difficult and costly to produce.

I tried looking online for tutorials but couldn't find all that much. Since I use Solidworks, I found DFMXpress, which gave me some knowledge.

 

[MiketheEngineer]

While you may find some helpful books, I have always found that actaully doing it is better - if you have the time.

The shop guys can teach you things no book will ever explain...

 

[mcgyvr]

I second that...
When I hire a new drafter or whatever the first thing I make them do is spend some time out on the manufacturing floor.

 

[ajack1]

As has been said above you cannot buy experience, which is kind of nice as it helps make up for the fact your hair goes grey, your waistline expands uncontrollably and you cannot remember what it was you were just about to do.

However you might find this is a good start.

 

[btrueblood]

Nice little article, ajack1, lps for you.

 

[tygerdawg]

Suggest you investigate "manufacturing processes", either thru a class or book. This will give you a survey of the different types of removal or additive processes, what the machines look like, and a feel for the dimensional & cost limitations and stengths of each. Even better if the class has a real shop lab involved where you can do actual hands-on work.

Pricing the fabrication of the part would involve:
(1) time to determine the steps and machines involved to turn raw material into finished part
(2) estimation of the time required to achieve each step, including setups & fixturing
(3) overhead costs of the shop
(4) machine time costs
(5) labor costs
(6) all kinds of other costs

Wisdom about what can and can't be fabricated, best practices, materials, good design aspects....well, that comes with experience. You'll have to get your own, or tap into that of others.

TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering

http://www.bluetechnik.com

 

[KENAT]

I came across this a while back thread1103-197339: Machining tips, originally posted in thread404-278305.

Chis posted a link some time back, I think it may be the same as ajacks. thread1103-197339

We had to do some machining labs for my degree, I got out of them 'cause I'd done some at school already but regret making that call now and wish I'd done them. There may be a local community college, or night school or something that has some kind of shop class or something.

Practical experience is one of the places I fall down, but I've picked up a few things speaking to machinists etc. and paying attention to them.

Also with changing technology some things change, widespread use of C&C allows some things to be done fairly easily that were tricky on manual tools. On the other hand some things were actually easier, or at least easier to do with precision, on old tools.

The fact you're even thinking about this is a good thing compared to some folks round here.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[KENAT]

Doh, first link was meant to be

http://procnc.com/resources/newsletters

which had some stuff that got me thinking.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[jamesyboy1990]

wow thank you everyone for the advice! I really appreciate it.

 

[MikeHalloran]

Get some soap or wax, and a few drills and end mills, and try to use those tools to carve an object that's topologically similar to what you're drawing, by hand.

Get a few CNC G-code programs for parts for which you have the drawings, and go through them by hand, to understand what the machine does to make them.

Similarly for sheet metal parts, but use paper or cardboard.



Mike Halloran
Pembroke Pines, FL, USA

 

[DaSalo]

If you truly want to understand manufacturing from a practical view point there is no reasonable substitute to working as a machinist for some significant period of time (3-5 years). The traditional apprenticeship period is 7 years. That is not a randomly chosen number; it really does take that long to gain a solid command of all of the fundamental skills required to be a competent machinist. We're not talking about CNC operators here, we're talking about machinists: people who can produce any part designed, utilizing all appropriate technologies available to them, from nothing more than a paper drawing. Short of that kind of experience the only other reasonable option is to befriend someone who does have that experience and establish a strong collaborative relationship with them. The worst thing to do is to spend a few weeks tinkering around with a Bridgeport, think that you've pretty much got it figured out, and stop asking questions. There are still people in this country who really know how to make things. If you aren't one of them, find one of them, and make sure they are your very best friend.

 

[lucky13dave]

I hope this helps:

http://techtv.mit.edu/videos/142-machine-shop-1

This is the first episode of a multi-part series by MIT; giving an introduction to machining processes. The series shows basic techniques with manual machines. I've been a CNC machinist for several years, and am currently learning the process design/programming. Ie, how to quote/make the part, and program the machines. I don't know whether you're designing parts being cut on bridgeports or 5-axis machine centers, but if you're not familiar with basic milling/turning, this series is a great place to start.

Good Luck!

 

[AquaticPeanut]

I started my apprenticeship(fitting and turning) in 1993, qualified in 1995 and did a mechanical diploma during the same time.
I was priveleged enough to be employed in an aviation manufacturing company and in my time there up until the end of 2004 I was exposed to many facets of the manufacturing process.
conventional machining
CNC machining - 3, 4 & 5 axis
sheet metal manufacturing
composite manufacturing(briefly unfortunately)
quality control inspection
CMM inspection & CMM programming
It took a move to a new company before I became a CNC programmer and started my design career.
All that experience has definately made a huge difference in how I do my work these days.
What really "irks" me the most is a freshly qualified apprentice who thinks he now knows everything, or an engineer, who has only seen pictures of a milling machine and lathe, telling me that the part will be made like that, when you couldn't even 'wish it' done that way.

The fact that you have asked the question means there is hope for you. Only way to get experience and see how things are done is to go get your hands dirty!

 

[ajack1]

Are apprenticeships really only two years these days?