School project; Building our own CNC-machine

[st3roid]

Hello,

Glad to be a member of Cnczone.com, it seems to be a great forum!

Now to the point, me and a few classmates of mine have choosed a project for school, were in the third grade on SKFs technical gymnasium (Thats what its called in sweden, its a technical school, not a gym, sort of a combination between High school and college)

Anyhow, we have no idea where to start, we have searched the net for "guides" but found none that really takes us from point zero to a finished cnc.

What ive found out is that we need the following parts

-some sort of table (with ball screws and all of those necessary parts)
-three stepper motors
-a controller card
-a "jogg"
-an engraver of some kind, like dremel.
-a power supply


We are on a relatively tight budget, and hope not to exceed 1500$ or somewhat like that.

Now, is there anybody out there that knows what parts are necessary, maybe someone with experience of earlier home-built cnc`s?

we would love to have a mentor on this project, or a few...

If we find anybody here that would be willing to help us out via this forum that would be great, it would mean we could maybe put up a build-log of somekind on this site, ande maybe even succed with the project.

that was all, i hope my english is sufficient to make myself understood and that someone out there might help our lost souls!

Best regards

Pontus Hanson @
STG, SKF,
Gothenburg Sweden

[austin.mn]

check out this site:
http://www.crankorgan.com/

Many people have successfully completed his plans for near little or no money. I know that these machines aren't the super heavy duty cnc machines that would be used to machine an engine block from solid billet, but it would be a good place to start. once you build a simpler small machine you will have a much better understanding of all the parts, pieces and electronics that go into a cnc machine.

my first machine was a "hardware store machine" i used drawer slides, steppers from old dot matrix printers, and a simple stepper drive that i made from a diagram i found on the internet somewhere. It worked, and i learned a lot from that experience. since the first machine i have built several others, retrofit an older manual mill, built a cnc router using industrial ballscrews,drives and motors. in another month i will be retrofitting an older bridgeport boss machine with updated motors, drives and controls.

start small and cheap, learn the basics. my first machine was very useful, i made quite a few wood signs, a few christmas presents and other misc stuff. the other thing to consider is that once you build it, you still need to learn how to use it. creating part files, toolpaths and machine controls.

[stirling]

I think that for a school project you should be able to get a system going for your budget (even if you source all your parts in Europe!). However I'd suggest that you read anything and everything you can find and learn how to design and build your own rather than just follow someone else's instructions "from start to finish" - you'll learn far more. If you make a start and come back with specific questions I think you'll get more help here rather than just asking for someone to show you how to do it all.

Here's a possible starter: for the linear drive, should you use ballscrews, leadscrews, studding, belts, rack and pinion, something else ingenious? - good luck - and have fun.

[per.e]

Hello Pontus
I am living in Gothenburg and i have built my own CNC router http://web.comhem.se/~u74864760/
There is a forum in Swedish about CNC machines etc. http://elektronikforumet.com/forum/viewforum.php?f=5
Do you have a teacher Leif Larsson there ? If so, he is a old friend of me.
Best regards.
Per

[epineh]

I think having a look at Joes machine would be a great start, go to this section :

http://www.cnczone.com/forums/joes_cnc_model_2006/

and start reading !!!

I don't know if you want to design your own or use a set of plans, either way reading through the build log's of the Joe's machines would be well worth it. And you can see what everybody is using as so far as motor sizes, power supplies, leadscrews etc.

The plans are free so you can check them out straight away.

Good Luck !

Russell.

[JohnG1931]

I think the most costly parts for a DIY are the ballscrews and nuts. I have built my own, since I wanted to automate 10 machines. I built my ballscrews from 4140 steel. It's better to have them heat treated. heat them until they are non magnetic and then quench in old motor oil. Best to build an electric frurnace for the heat treat, but not essential especially for only one or two. Castable refractory rated at 3000 deg F is OK 5000 deg F lasts for ever, with KANTHAL or Nichrome wire.
If you use a furnace you will need a good pyrometer, I use a liitle 1"x11/4" x 4" digital temperature control calibrated for deg K and chromel alumel thermo-couple, and an ordinary digital volt ohm meter calibrated for deg K and chromel alumel as backup. My actual control element is a Solid State Relay because the digital controller may not be able to carry the current load needed for the furnace. If possible choose a PID algorithm in the digital control

The only tricky parts are the ballscrew nuts. These are three concentric sleeves. The inner one has a groove 1/2 the ball dia. The middle one has a slot of the ball diameter, and the outside one has either a tube wth ID = the ball dia, to return the balls as they circulate, or an external groove for return and an outer sleeve to hold everything in place. I make my grooves spiral to allow a little space between the balls,
but I think you could make them straight, or even two at opposite ends of a diameter of the nut. You do need to be careful with the lengths of the slots to avoid backlash. If you can heat treat the sleeves, so much tne better, but you then might need to clean them up with a lap or an oilstone.

As I think about it, a better design might be to have 4 slots, each one straight with a single adjustment for all on a fine screw thread to set the lengths exactly right.
Sincerely JohnG1931

[st3roid]

Hi again,

thanks for all the replies, i was overwhelmed when I noticed it this morning. I thought i was going to get mails from cnczone when I got a reply, but apparantly i didnt, thats why I haven`t answered until now.

First,

Yes, we plan on "designing" it ourselves and not follow somebody elses guide from start to finish,we were just interested in some ideas .


Per. E

Quite amusing, yes, he was a teacher up until just a few moths ago here, currently he`s working down at SKF Actuators and we`re currently trying to get in contact with him regarding the ballscrews since they have plenty of them there.

(hopefully they will be sponsoring us with them, otherwise we will probably get them quite cheap)

when I meet him I`ll say you said hello

UPDATE*

Now we have been in contact with an old friend that has retrofitted a mill into a cnc. He is very competent and has given us some advice regarding the software (and some hardware issues like the power supply).

We will probably be using Linux EMC,
since its just powerful enough for us, has a great graphical interface, Our friend knows how to configure it and the greatest benefit of them all, its for free.

Regarding the hardware, we will order a kit from hobbycnc.com with
305oz steppers and a controller card with all the required hardware except from transformers, which we will be buying from a local electrical department store known as ELFA.
_________________________________________________________________


Now to another question, will we be able to use bearing houses to hold the ballscrew, or are there just to much backlash in those?

(The software itself is able to adjust backlash, but we still want to keep it to a minimum)


The budget has gotten quite a bit lower, its currently down att about 730$ but according to our calculations we will still be able so pull it of if we either get the ballscrews for free from actuators, or if we`re able to buy them for a reduced price.

Otherwise we`re still able to pull it of by using trapetsskruv (I dont know the word in English but I suppose its called Leadscrews), It wont be as good, but probably (hopefully...) good enough

[st3roid]

f

[per.e]

Pontus.
If you need any help you can contact me via e-mail "per.ekdahl at comhem.se".
I am using Mach3 to control my router and it is a fantastic program with many features. http://www.artsoftcontrols.com/forum/index.php
Per

[turmite]

Originally Posted by per.e Pontus. If you need any help you can contact me via e-mail "per.ekdahl at comhem.se". I am using Mach3 to control my router and it is a fantastic program with many features. http://www.artsoftcontrols.com/forum/index.php Per

Pontus pay attention to Per about Mach3 software. Unless you already know a lot about linux, you will be spending all your time trying to get it to run rather than building the machine.

I might also suggest you lay out an overview of your build plan, make a list of materials needed and then post those here. You never know, someone might have something they could help you out with and would allow you to come in on budget.

Mike

[st3roid]

The software part shouldn`t be that big-a-deal since i know a friend over at Chalmers that has already built a cnc router and using the linux software (EMC2). The advantage is , as I mentioned in an earlier message, that it`s free of charge , and second, that he knows just about everything about the configuration and setup of the software and that he has promised to help us with that part.

About the buildplan and such, we are currently working on that part. We have a bit of paperworks before we can get going with that but perhaps tomorrow afternoon or on friday we will be able to start making primary sketches and such.

Thanks for the heads up

regards

Pontus Hanson

[st3roid]

*Update*

We Have now made a first rough draft of how the machine will look, all the dimension isnt nailed but the proportions is something we`ve pretty much figured out.

Were have set up an order-list that will be handed to the assisting principle at our school so that she can order the things we need.

The list inlcudes,

Optoisolators, "batteryeliminator" (An adapter), transformer, a Dremel of decent quality, resistors at 330ohms...

and alot of more stuff, these are the ones which i find most interresting (and the only ones I remember:P)....

We will probably be talking to our contact over at SKF Actuators on monday, and we`re crossing our fingers that they will sponsor us with ballscrews and matching nuts ...

We`re also currently hoping to get som "metal-pipes" that would be ideal to act as "linear-shafts" (dunno if this is the correct word), the pipes that the x and z axis will slide on. They have a really nice finish and are light as hell, and theyre unbelievebly hard...

So, as it looks now, monday is the day that will be determining how this project turns out... sort of any how. f we dont get any ballscrews we will be able to order som cheap linear-screws, of course not as good, but decent any how. The "linear-shafts" anyhow is a little bigger challenge. If we dont get them we`re not really shure on what to do, but as we say over here in Sweden (directly translated) "That day, that sorrow".

Regards

//St3roiD