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

[FlyHighRC]

Anyone got a SW file for the bit of a ballscrew that is bolted to the gantry? 16mm...I googled the dimension to make one myself but each picture seems to show slightly different dimensions...Why arent all thee bits generic across the board -.-

[FlyHighRC]

for a good machine what is recommended, A router or spindle? cant see any bvious advantage or disadvantages to either... Yet to see anyone give a preference on any of the build logs

[Clive S]

for a good machine what is recommended, A router or spindle? cant see any bvious advantage or disadvantages to either... Yet to see anyone give a preference on any of the build logs

I don't think you will find many routers on here being used. They are very noisy. The popular spindle is the 2.2Kw water cooled they run very quiet and will run at speeds up to 24,000 rpm. ..Clive

[FlyHighRC]

So I have nearly completed the first draft of my design, Im very comfortable with being able to make this machine with the tools and equipment I have access too. The gantry im happy with and the way in which the gantry is mounted to the rails. Im also happy with the location of the rails, steppers and mounts etc... the ball screw support blocks have yet to be mounted to a plate(next job) then onto the z axis :)

The frame is mostly 60x60x3mm box section with the gantries vertical section and support section being 40x40x5mm, Hopefully you guys approve this design...in which case I start my budget plan to make sure it can be built within my budget. Then progress to the parts list and DXF files for the laser cut stepper mounts and then go from there :)

Added some colour to give it a bit of life...

[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.

[njhussey]

Good man...things can be welded by novices (me!!!) but still precise as long as either some form of adjustment (shimming the top rail on the x axis for exampke) or the epoxy method is employed.

Yes you can still use your design if you look into the gantry a bit more. Bracing is your friend as wood needs to be cut quick so on full chat your machine will be dancing about (how you fixing it down by the way?) all over the place...

The best way to get stiffness in your gantry is to keep the sides as short as possible with the best being to mount it directly on the linear carriages...this needs raised rails.....

Sent from my Galaxy S5

[FlyHighRC]

Thats good then. If i can still use this general design that would be nice. In terms of the gantry, where the two braces are connecting the two sides, is that where I need to brace? I,e Add vertical members between the two?

Are you a Solidworks user Neil?

[njhussey]

Thats good then. If i can still use this general design that would be nice. In terms of the gantry, where the two braces are connecting the two sides, is that where I need to brace? I,e Add vertical members between the two?

Are you a Solidworks user Neil?

Got SW but not installed it...I've got Geomagic Design on my PC at work so trying to get used to that at the moment so won't install it as I don't want to confuse myself (easily done!!)

You need to put in vertical and also cross bracing....like you would in a CF quad arm...