Im new, am a 3D designer. Need a New cnc machine and need advice and guidance

[njhussey]

OK Mike, sorry I'm going to be blunt here. Jazz has said to go through the build logs as have myself, Jonathan and the others I still think you need to go back and do some reading as the design you have put here has been done before (or designs nearly identical to this one) and commented on.

Again being blunt:

Do you have a link to these linear rails?

I dont know much about CNC but i know how to incorprate strength into a design. If there is one thing Im good at its designing...dont get me wrong...i have seen builds on this forum which to me seem fine but people who have been there and done that have pointed out aspcts of designs that didnt show up to me...but all their critisims and expertise has been written down on my Pukkapad to bear in mind when designing my machine, which will be posted so others can tell me what needs improvong and whats ok etc etc.

Really appreciate the help :)

The design you posted is anything but strong...people will have pointed out things in other builds which to you don't show up because they have experience of building the machines, normally by making the same mistakes and regretting it. My brief comments on "first draft"

• Bed does not have enough support and will vibrate and bounce giving poor finish.
• X axis bearing mount to gantry is too thin and flexible.
• Mount the steppers with belts to reduce resonance, not essential but preferable.
• Gantry has no bracing or support so will bend/bounce/twist giving poor finish.
• 40x40 box (for the gantry) isn't strong enough as Jazz said before.

The above assumes that you will be cutting some aluminium at some stage.

Sorry my reply might come accross as being unfriendly and harsh but I can see you going down a route as Jazz said that will leave you dissapointed if you're not careful and if you're not careful you'll waste money prodcing a machine that won't cut what you want to cut.

[FlyHighRC]

Not at all :) If the design isnt up to the job then its not up to the job. Criticism is how all novices get to a good stage...just like RC haha. I have the CAD files for all th parts I need now, with a number of them provided by Jazz...so the rest is just making a new frame which can still utilise these parts :)

The one thing i really dont understand is how something has to be so strong and precise but are hand welded most often by people who have a mig and no jigs...

Is it possible that the design I have done can be beefed up? with no real change to the machine? Just to save going back and forth...I dont mind, I have taken everyones advice onboard...I know it looks like im rushing into everything but I hav been doing allot of studying on the forums with build logs, The questions I ask which seem similar to other peoples questions are because I want to put it in my own words so I understand it better...

The criticism is good though, didnt show as unfriendly at all, no worries there :)

[FatFreddie]

The one thing i really dont understand is how something has to be so strong and precise but are hand welded most often by people who have a mig and no jigs...

The trick is to be creative about how you get the accuracy. Making a reasonably accurate (+/- 1-2mm) bed is possible with a reasonable amount of skill and care. If this is properly designed it can then be made very accurate using epoxy to level the important faces. On to those now accurate faces you bolt bought in accurate components (the linear rails) and so on.

So, you don't have to worry (too much) about accuracy of the welded frame but you do have to consider its stiffness - it would be worth you reading up on some basic engineering - in particular stiffness of beams. This is not just a 3d design problem, it's also an engineering problem and although you don't need to be able to do accurate stiffness calculations for each part of the machine, you do need to appreciate how the material responds to stresses.