Stell frame cnc 1500X1000. Adjustable table your opinion please

[EddyCurrent]

One other note.!! On this design the top rail extends.? This is to make full use of the Bed without wasting material having the bed/frame longer than needed which can't be used.

Good idea and after all these frame discussions I think I'm now at a stage to start cutting metal this weekend.

[Boyan Silyavski]

Deans design is very good, after all he is far more experienced at building and dealing with vibrations. I like the Z at the baze, that would definitely help with resonance. I like the extra bed frame, i have thought it but never included it in my designs, due to extra weight.


Dont get me wrong on what i will say, but i am fan of simplicity. I will say the same what i said to Tony at his thread

Look at that design below and adjust it to your needs if you like it. Just don't change anything radically, cause in its deceiving simplicity there is a lot of reason. In fact 2-3 months of reasoning. There are no random distances there. Tony changed it a bit and you can see his great looking machine. He made it from 80x80, mine is 100x100x3
If you look at my thread i have a frame soldered in my garage with the same design and it has deflection under 100kg of load which is irrelevant.

Now what Dean says about resonance is true. Its not the same as stiffness. In fact in some cases the stiffness will help the resonance, especially in our case where we build machines from thin walled profiles.The great thing about my design is that all the forces are working only at the upper part of the structure, its stiffness does not depend at all of lower elements. The legs are just legs / i am talking about 100x100 or short 80x80/.

Now there are hundreds of points why resonance will not happen at all in the machine i am building, nor twist or bending, even if i were able to route deep aluminum and why not steel / which will not happen cause i limited it with 0.8kw spindle/ . This points are too long to explain, but be careful, cause these are particular decisions, like that the machine i am building will have 100mm thick MDF bead, underneath plastic sheet or aluminum sheet and etc...

Long story short, just take a look and study it. Use it if you like it. It implement Deans idea of the shorter table. Also implements subtle ways of dealing with resonance, like the beams of the bed gradually don't coincide with the short vertical ones. In fact in my next build everything will be slightly offset here and there, to kill the harmonics.
The best thing is if like Dean says the bed beams flex, at a later time can be added ribs bolted to them vertically and if there is a twist , you can add the same Z diagonals like in Deans drawing of the lower part just drilling from below and bolting. Add if when you need, why overbuild now? Not to speak of that with 100x100 profile is way overbuild as my measurements show on my build.

[EddyCurrent]

The best thing is if like Dean says the bed beams flex, at a later time can be added ribs bolted to them vertically and if there is a twist , you can add the same Z diagonals like in Deans drawing of the lower part just drilling from below and bolting. Add if when you need, why overbuild now?

Exactly my plan, if there are problems later the frame can always be upgraded.

[JAZZCNC]

Now there are hundreds of points why resonance will not happen at all in the machine i am building, nor twist or bending, even if i were able to route deep aluminum and why not steel / which will not happen cause i limited it with 0.8kw spindle/ . This points are too long to explain, but be careful, cause these are particular decisions, like that the machine i am building will have 100mm thick MDF bead, underneath plastic sheet or aluminum sheet and etc...

Silyavski think Your fooling your self if you think you won't get any resonance, Even machines built from Cast iron get resonance so you have zero chance of getting None with hollow Steel structure.!! . . . . . Yes it will be less than machines built with thinner material or of lesser construction but I guarantee you'll get resonance which shows at the tool when cutting slightly deep in aluminium and definitely in steel.

All the frames shown will be more than enough for DIY use right upto cutting aluminium and massive overkill for most softer materials. But it would be foolish to think just using larger dimension material means you'll get no resonance, no matter how you arrange the joints or welds etc.

Also what's the point of going to all the trouble of building machine that doesn't deflect more than 0.01mm only to use a bed material that will deflect more than an elastic band.??? . . . . Waste of time doing all your doing if your going to use MDF in any part of the bed other than has a spoil board.!!
Even then for any kind of acceptable accuracy you'll have to surface it for every Job.!!

One more point regards adding stiffeners at a later date.?? . . . .WHY . . . when it can be done at the beginning. When ever you weld you have risk of heat distortion so it's not a good idea to be doing this at later date.
Also has most who have built a machine will know and back me up on ounce you have started using the machine you'll never stop to do even simple things let alone major upgrades like welding in stiffeners. . . . . It's known fact if you don't do all the planned things before powering up machine they'll never get done ounce it's working. . .Lol

Ba99274 any of the frames shown including your own designs will be good enough so don't worry you won't go wrong.

[alex wight]

I've built one of my sides, roughly the same design, but without the material connecting the legs. As there's angled supports at the top, it should be strong enough. It's had the go ahead, so I'm happy to continue with the other side.

[EddyCurrent]

If you don't find any maybe this would be an idea ?

There are quite a few models for use with free program, Sketchup
cnc router - 3D Warehouse Search

There is a plugin for Sketchup that allows export to STL
Convert Sketchup SKP files to DXF or STL | guitar-list

I think Solidworks can import STL files

[ba99297]

After thinking that welding all the beams together, according to the previews plans i would have issues with the big weight, i decided to split the contruction into two , the bench and the CNC that will sit on that bench.
So i introduce the CNC pictures first
So i have the main frame


Then with the red color is the cutting table made by 80X80X5 beam


over the cutting table i will put aluminium profile tha will be bolted on the red cutting table. That profile has T slot for clamping item that will be cutted


And here we have some picures of the construction with all the items together


if i want more depth for 3d cuts i will remove the cutting table(80mm) with the T slot( nearly 40mm) and i will put a 20mm mdf. That will give me about 100mm (80+40-20) more depth

I am waitting for your comments

Thanks

Vagelis

[Boyan Silyavski]

Nice. Looks great,

What size of the steel profile you decided on? If 80mm or bigger, you don't need the triangular plates. Believe me, will not move. Reason - the short profiles will hold it firm enough. If you insist, make them L shaped, so they will not bother you fitting longer than the table pieces.

And as for the size of profile, i am with Jonathan. Bigger the profile, the better. If resonance, its easier to drill a hole and fill it with something later.

I said it earlier some where but one of the best ways to fight resonance is avoiding perfect symmetry in the machine, meaning all pieces spaced same distance and mirrored exactly. Offsetting each piece even by 1cm here and there will have enormous impact. Same when avoiding mirroring

[ba99297]

Nice. Looks great,

What size of the steel profile you decided on?

At the above plans i use 80X80X5 beam for the red table and also for grey frame except the 4 lower beams that will have contact with the bench. Those four beams are 100X100X4. I think that the triangular pieces will help to achieve triangulation and parallelism and also stiffness.
I agree with you that if avoid symmetry and mirroring that will help to reduce resonance. As for the beam size i think even 80X80 or 100X100 will not have much difference to the final result.
The t-slot profiles are aluminium profiles that are used for for clamping solar panels at the roofs. I design the profile from a piece that i had.
I will come back with the gantry design. I will use one motor for X axis with double ballscrews and i may use double nut (preloaded with a spring) for each side
I want you opinion about this option. What kind o f spring is suitable for this use and where can I find it. I also would like to know what would be a good distance between Y and Z axis profiled rails ( i will use 20mm profiled rails ). Also what will be a good distance between the carriages of X axis ( outer side of carriages )

So far thanks everybody for the help

Vagelis

[JAZZCNC]

Hi Vagelis,

Looks ok to me. . . . Just a Couple of simple things that will help.

You could drop those inner triangle braces and just keep the inside corner ones but make them little larger, there will be more room with others gone. Not much gain strength wise from them being there and not having them means less welding which will lessen the chance of heat distortion.! . . . . Would do the same with corner braces for the Bed frame just to help keep it square.

Also the outer End triangles will be better placed on the outside of the box section and made larger so there is more contact area, they will also cover the ends of the section. Then when you weld just put short welds but on both edges. Again this lessens the chance of heat distortion by allowing short weld runs and balancing the welds pushing/pulling action.