Quote Originally Posted by andy586 View Post
After happily reading on another cnc forum that with a bit of cardboard and gaffer tape and a spare 20 minutes I could make a 27-axis robot that would cut me a QE2 sized spacecraft out of tungsten carbide, I decided to come here for a bit of bubble bursting by Jazz and Jonanthan (i'm calling you out sirs...)and the likes.

Much to my girlfriend's pleasure, I am now living, breathing and sleeping CNC build logs. She now knows what backlash is and why a lovely ballscrew is going to bring more pleasure into our lives than some rubbish holiday to the Carribean (on a side note: she is still finding 'flanges' genuinely funny...be they on bearings or nuts). I think its the way I have decided to use the one and only telly in our flat as my big screen monitor for reviewing designs (extra few inches always helps)...its helped speed up the immersion process. I know when she says she will leave me and hopes I get splinters in my bits, its her way of showing support. (Does anyone have the g-code for Kelly LeBrock (circa 1985) as a back up?)

Right...so MDF out. SHS and RHS in. I can't weld so I want to go for epoxy/bolt fixing. I would invest the time and expense to learn but I don't have a suitable shop to weld in so its not the most productive investment at this stage.

I would like to look at a cutting area of 1m*0.5m but that is just an inital thought rather than a fixed requirement. I feel that will get squeezed down somewhat. I predominantly want to work wood to make toys and design items but the ability to stick a weeny bit of aly in there once in a blue moon would be great.

Now..much as I hate to, lets talk money. I've got none. Near enough anyways. What I would like to do is first work on the frame before putting in orders to Chai and Zapp. I'd sooner spread the build over time and save up for parts that are somewhere close to doing the job rather than buying a load of cheap stuff that will soon be ready for scrapping.

So onto my initial lines of enquiry...mainly regarding the relationships between your frame and your finished machine.

What are the best/worst amounts of useable space people end up with as a proportion of machine size?

How true must the frame be? Can I make up for small inaccuracies in the frame via the positioning of my rails?

Why do people so often go with tallish gantries rather than building up the sides of the frame and running a much flatter gantry?

If I commit to building a certain size frame, am I commited on what length of rails and screw to use? I assume that not using the full length of frame for x-axis wouldn't present too much problem. But how about y? Would I need to span the full distance between the x rails or could I leave gaps on either side? e.g. a gantry that is 50cm wide but with 30 cm of rail? Essentially I'm asking to see if I can get away with making my frame to an approximate size, then buy screws and rails off the shelf that are close in size and mount them? Or should I have precise measurements before starting? Reason being, I would quite like to have fun gluing bits of steel together in the near future but I can see that designing a whole machine will be a very lengthy process.

Any advice appreciated. Flame away.

Thanks,

Andy
Ok Andy, Welcome to the forum, Its nice to see someone who has been doing their homework on the dynamics of the site. Its plain to see you have been reading large amounts of posts/Threads. The thing is, Usually people submit a design and watch it evolve with lengthy constructive, and sometimes not so constructive debate.

When you arrive at a design, your build will progress at a speed dictated by you and your ability to produce/procure the parts you need based on your finances and spare time.

If you wish to machine ali then the design will be based on that, with the side effect that the machine could be used for other materials like MDF but as i have found out, a multi purpose machine will present its own set of challenges, and with that comes extra expence.

If you are only going to be machining the odd bit of ali here and there why dont you just get the guys who have ali cutting machines to do it for you, and build a better wood machine.

Just My Opinion though.

Rick