new build opinions required

[george uk]

hi

i wonder how that really will be with the specifications /size/ you stated in the beginning? Are you sure you did not forget something? What type of gantry will that be?

I can afford to increase weight if needed, I have gone for 20mm supported rails and can beefed up if needed. I want the machine to be able to surface and etch stone, maybe even v-carve it. Accuracy is more important that speed,

The bed is going to be deep, but have fixing on it to bring parts up to Z, and troughs to allow water for laser or plasma cutting. When using stone, the surface if the stone will be close to the Z top ( least angle ), but enough drop in the bed to allow me to get a wide bit of foam on the 4th axis.

My initial gantry design,2* 100mm or 150mm by 40mm steel with drops, Y rails on the top, bit of engineering to get close to an A frame for the z plates. So pivot point is very close to the z bottom ( basically, z bottom minus the bit length )

[Boyan Silyavski]

Working stone will need an extremely rigid gantry and Z+ square supported rails and long bearing blocks, even better-roller type ones. Did you have some other example build/working machine/ in mind when started buying, or its your design?

[JAZZCNC]

The gantry i have planned will be below 40kg, fully loaded, probably closer to 35kg, I know how i will do the gantry, but have not finalised the design, as i need to think about what i might need to strap on to it.

I want to incorporate a turret on the end of the table, and a rotary table or b/c head on the table. and a geared 4th axis

Think you'll find your miles away with weight and to be affective and sturdy enough for cutting stone you'll be least in the 60-70's.
Like you say Speed isn't important but rigidity is massively important for cutting stone or any hard material with accuracy. To surface and cut stone effectively you'll need a slow spinning spindle with high torque, this alone will mean heavy spindle motor which will require a substantial Z axis to attach it too which will be heavy enough.
Mass greatly helps with surface finish so don't be chasing weight.!! . .. Better to be Chubby and Slow than Slim and weak.!

I wasn't going to mention this has seems you'd already ordered them but seen has Silva has already commented I will Confirm what he's saying. The cheap round rails will not take the Water and fine Grit that comes from stone dust, Add to this the weight and high vibrations that cutting hard materials will put thru the frame and they will die in short order.!!

My advise is cancel the order and Buy Proper Liner bearing other wise your wasting your time if your wanting accuracy and to cut hard materials. If you can't Cancel then sell them before using so still new and buy the correct components for the Job.

[george uk]

i haven't order it yet, and i can change if needed, i want to build a multi purpose machine, and i will build a second, task purpose machine, when i have done the first, all in all, i have between 5k - 8k but can up that if i think its worth it.

I will have a number of spindles/heads, and am looking at 600 to 2000rpm options at the mo, i want XYZ basic, solid and strong enough for any material up to approx 200mm, with the top bed having 2 cross bars, splitting it into 3 lower areas with up to an extra 150mm depth, the lowwer areas holding setups for plastics, B/C head, 4th axis, plasma/arc, rotational table .

And i also want nearly a full length of x 4th axis, indexable for carving foam.

I know i will make many mistakes making this macheen, but stripping back and rebuilding replacing, is not a problem, trying out different electronics, is not a problem ( as long as am not waist-full ) . I quite good at pulling projects together, free time permitting.

[Boyan Silyavski]

Hi George,
drawing your ideas and perfecting the design will save you a lot of cash and headaches. There are many small details in a build, which if overlooked will lead to big waste of effort and money.
The parts for a solid topnotch 1000x2000x200 machine will cost approximately 2500-3000.

So, don't do that mistakes you are intending to do, read the builds here, take the best stuff and draw it. Sleep on it and then buy the parts.

[george uk]

something i can not understand, a why not, in relation to y stability from x axis

why not have rails or fix round bar, on both the top and bottom of the x axis, IE, 2* 125mm box, 2200mm long, why put rails jujst on the top and rely on waight and engineering to get a stable point for Z to fix to.

It would seem an obvoius solution but i see its not used, that means these something am clearly not accounting for. am prity sure i could get them level to each other easly, so what am i not thinking of ?

[mekanik]

Hi George
I am a noobe to this as well & had the same thought but after you have done some reading by the guys that know what there doing it is very difficult to get the two faces parallel especially after welding up a frame, there is apparently considerable clearance on the round rail/bearing setup but the profile rail i believe is manufactured to a tighter tolerance and is a lot more ridgid, if you have a good mooch through the build logs it will all become clear,and someone will probably provide a better insight than i can.
Regards
Mike

[Boyan Silyavski]

Because that's not the problem. The problem is overhang. Z to Y rigidity+Y twist and bend.

[george uk]

Hi, i considered that, but then thought to get round that, i would m,achine the underside and fit the second rail, after the machine is part built, fit the Y/Z axis and use that to machine the underside of the x Bar. It would be perfectly level to the top.

or
First make a level on the floor, then, Make a level the top of the x, with epoxy, spin the full machine over, level the bottom with epoxy.

Although, i would be more confident in option 1. because as long as your top surface is accurate, so will your bottom rail.

If i can do it this way, i can design a substantially better Y/Z Lighter and stronger. I know i will fubar bearings faster, but it would be an asceptable costs

With long braces on the guides, you would be able to minimise any undulation anyhow, there has got to be something else wrong, just can not see what at the moment.

Any suggestions anyone ?

[EddyCurrent]

George, if you don't have something like Sketchup then download it and let us see some drawings, it's far easier than trying to explain it.