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Going back to college

Unread postPosted: Sat Apr 06, 2013 12:33 am
Author: flashskate13
OK so I'm going back to college still not a lot of work in the uk so thought I would advance my skills instead this time I am going to learn computer aided design and I'm sure there are a fair few people on here with experience in the field.

My course doesn't look like its going to start till September which is a pain as I wanted to get on it sooner, so I have downloaded Google sketchup 8 and had a play.
What I'm after is does any have any experience in learn the basics is, good books, tutorials, better software etc etc as I don't want to go college as I am knowing very little in it.

Also I'm looking at buying if its a reasonable price a CNC any people can advice me or even if people have made them their self's (plenty of parts on eBay) good source of information on set up and so on.


Unread postPosted: Sat Apr 06, 2013 12:59 am
Author: evilvet
You might start here ... 23563.html

I've built 2 CNC machines so far and am contemplating my third as a conversion of a Sieg X3, once I can afford an X3.

Happy to help if I can, might I suggest that further posts on the subject go in the thread I linked to ?


Unread postPosted: Sat Apr 06, 2013 7:19 am
Author: jrrdw

Google sketchup 8 tutorials are all over Youtube as well in the programs online help pages.

Unread postPosted: Sat Apr 06, 2013 7:53 am
Author: flashskate13
Thanks for the replays been watching youtube and got some idea now just need to play about and get used to it.

Evilvet how much should I be looking at spending to make one, and how accurate can they be?

Unread postPosted: Sat Apr 06, 2013 12:11 pm
Author: flashskate13
Found this kit is it worth the money?

Building the frame I know just don't know about components!

Unread postPosted: Sat Apr 06, 2013 3:37 pm
Author: evilvet
Evilvet how much should I be looking at spending to make one, and how accurate can they be?

Let's start with the easy part first, how accurate. Assume you have a perfect system using the tolerances in my current machine. My ballscrews are 5mm pitch with double nuts, for the hell of it lets assume no backlash. My motors are 1.8 degrees per step running 1/4 step drivers. That means 800 microsteps per revolution. The motors are connected to the ballscrews via a 40:15 pulley ratio so:
5mm pitch screw divided by 800 steps = 0.00625
0.00625 x 40 / 15 = 0.0167 mm resolution, call it 0.02mm

Can I actually achieve 0.02mm results ?

Nothing like it. Once you allow for backlash on the ballscrew and timing pulley belt, the fact that the motors themselves may not be 100% accurate or might miss a step, the spindle collet has some runout and my tooling is cheap so the end mill itself may not be perfectly round and true. Never mind that my linear bearings are not perfectly true and there is some flex in the table and gantry as well.

Add all these factors up and from practical results I can tell you I repeatedly get 0.1mm or better, that's about 4 thousands of an inch, equivalent to the thickness of a piece of A4 paper.

If like me you are concerned about learning CNC manufacturing as a hobbyist, making parts from HDPE or aluminium for spuds and pneumatics, then thats fine. If you want to make turbine blades for a jet engine, forget it.

Like JRRDW suggested, go over to CNCzone and spend a few months reading threads, that's what I did, and yes I spent months lurking and reading before I started by first build.

As to cost, I can only tell you what I spent, rough figures are in Australian dollars:

Frame and gantry

Ballscrews and bearings

Motors, drivers etc

Sundry electronics for switches etc

Spindle and VFD

CAD / CAM / CNC software


Call it 4500 dollars all up over 12 months of the build.
Considering what a "real" 3HP CNC mill with a table of 750mm x 500mm goes for, like $40,000 +, I'm happy.


Unread postPosted: Sat Apr 06, 2013 6:24 pm
Author: jor2daje
Solidworks and Autodesk inventor are both pretty good programs, if you get a .edu email from college then you can download autodesk inventor free for 3 years. For me the best way to practice was just grab a set of calipers and cad up random objects around my room. If theres something you cant figure out how to replicate just google it.