Stell frame cnc 1500X1000. Adjustable table your opinion please

Hi Everybody
My name is Vagelis and I am from Greece
I would like your advice and your opinion on the plans below.
Involving a cnc (1500mm x 1000mm) which
will runs with Yaskawa servo 400 watt
Supported profiled rails 20mm, ballscrews X, Y 20mm Z 16mm
Spindle 2,2 KW water cooled

The following plans have to do with the table
I want to make something stiff and adjustable
The main table is made with 80X80 5mm square tube and the X axis rails will be placed on two ( each side ) I beams. The one I beam (120mm height) will be welded on the table and the above will be adjustable up-down left-right with screws. Before i go on with the plans i think that it will be good to get some opinions from the "experts" as i am amateur at cnc constructions ( sory for my english).
My main concern is if I beam is suitable for this purpose, or it is better to go with 120X60 5mm tube
The cutting surface will also be adjustable from the brown L shape angle that can be moved up and down.

Thanks everybody for your time

Vagelis,

I am an amateur like yourself but have recently read a lot of information about cnc machines. I am designing a frame myself at the moment using 50x50x3 steel box section, my work area will be about 1000x650.
You see where you have two crosses in the side panels, I think if you had just 2 diagonals like this I/I\I it would be enough because you just need to create a triangle. For your size machine I would say the 80x80x5 might be more than you need but if you are fine with that then more is better than less. The I beams I would change for box section because I beams are not so good with twisting and you might get more sideways twist than you would with box section. Also you have not put any diagonals at the ends like you did with the sides. Good things you have included are 3 legs each side, adjustable feet, adjustable top I beam to get the top surface straight. Looking at the drawing, I can't see much adjustment on the brown angle and wonder if it's worth it other than making sure the table is the same height under the cutter across all of the table.

In my opinion your legs are overbuild and the rails support underbuild.

The I beams are bad idea.

After a lot of thoughts and considerations for me:
-a whole machine build from 80x80x3mm with a careful design could be the best solution for a DIY sturdy CNC
-a whole machine build from 100x100x3mm with careful design could be a real beast of a DIY extremely sturdy CNC

The people who build with more than 3mm thickness either have a design which is not so perfect or are pro builders who know what they are doing and definitely its not their first machine, usually some beast with a special heavy duty purpose


It would be nice if you take your time and read the entire Tony CNC build here where he started with similar to yours idea, the calculations of the price and weight, how he implemented and personalized the design from another build of mine adjusting to his dimensions and needs.


More or less i could say that the particular design of mine could hardly be beaten for strength, weight and $$$ combination, permitting the final result to be extremely sturdy CNC with deep 160-200mm Z travel.
The trade offs are that it is better to be all soldered and adjust the table bed by fitting thick table bed instead of raising and lowering the bed structure itself.
The plus is that its very easy to cut to size, one profile only, cheap, very easy to solder precisely and completely scalelable from small to big machine.
the gantry could be made from 2 profiles soldered together so finally will be 200x100 or 160x80, which both a are great and in the ideal range for 20 size supported rails

Its not tested on a finished machine, but i am currently building one and can assure you is steady like a rock. If you scale it, mind the distances between every element and don't change them, just add or take elements to make it bigger or smaller.
Its deceivingly simple but many things are taken into consideration.

Hope that it helps.

My advice is when comparing designs take the calculator and see the KG and what you receive for these KG in strength. Then compare. Every KG is an euro :encouragement:

Attachment 10413

PS. FYI just went in the garage and measured the deflection of my machine under 100kg weight/me/. Its very similar, with different measures. Table bed is 67cm wide and is 135cm long. So stepping on any of one the table bed beams gave me 0.05mm deflection of that beam and stepping on any of the sides that that support the gantry/supported at both ends only/ gave me 0.03mm deflection. So keeping the design and not under doing something when everything mounted will give you real life deflection which is unmeasurable/or for sure less than 0.05mm/ . So my machine with mine particular dimensiones with table bead mounted will have over all deflection of less than 0.01mm. isnt it great?

Thanks everybody for your advices
The basic conclusion is that I should replace the I beam with square profile. That was what I have in mind from the beginning. The reason that I choose I beam for the drivers support, was because it was easier to connect the two I beams ( upper and lower ) with bolt and nuts in order to have a fully adjustable table.
The plan that you suggest me to make Syliavski looks very strong and stiff. My question is how am I going to adjust that table if I have imperfections as cause of arc welding. The basic advantage of arc welding is the stiffness, on the other hand if I only weld and have no ability to adjust with bolts, I think is more than sure that my X axis rails wont be on the same plane. So I think that I will keep the solution of the bolt adjustment an replace the I beams with 80X80X3 or 4mmsquare beam. The Chinese says 1 picture 1000 words, I will design it and I will come back. Meanwhile I will be glad to hear any suggestion.

Thank for your time

Vagelis

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Originally Posted by ba99297

Thanks everybody for your advices

The plan that you suggest me to make Syliavski looks very strong and stiff. My question is how am I going to adjust that table if I have imperfections as cause of arc welding. The basic advantage of arc welding is the stiffness, on the other hand if I only weld and have no ability to adjust with bolts, I think is more than sure that my X axis rails wont be on the same plane. So I think that I will keep the solution of the bolt adjustment an replace the I beams with 80X80X3 or 4mmsquare beam. The Chinese says 1 picture 1000 words, I will design it and I will come back. Meanwhile I will be glad to hear any suggestion.

Thank for your time

Vagelis

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Hi Vangelis

- between 80x80x3 and 4mm, the best choice is or 80x80x3 or 100x100x3 .
Why?
80x80x3 1m=7.17kg/m
80x80x4 1m=9.47kg/m
100x100x3 1m=9.02kg/m

Looking at their properties from my suppliers brochure the conclusion is that roughly the second is 20% stiffer than first and the third is at least double stiffer, hence for the same weight ~9.kg the 100x100 x3 will make quite stiffer machine structure



About soldering:

With careful thinking and careful soldering and only 2 big clamps i achieved a structure where not only is up to the mm precise but the beams are on one level and the supporting beams are on one level too. Nevertheless i will use Epoxy to level bellow the supported rails. As suggested by fellow members here i bought West system Epoxy with Hardener
from dansonmarine.co.uk who will ship in europe, contact them.
1kg of 105 resin and .33kg of 209 hardner, £45.00 per pack +£17 to Spain
Delivery is £17.00 to spain

It took me a whole day to weld it and i would not go other way. You can do it with a helper, 2 or even better 4 big clamps and a 2m aluminum profile or a real straight edge.
there is an procedure that has to befollowed, check my build or if you dont understand i will explain later.But mostly it consist of designing and welding "stair like" the individual assemblies, which at the end are soldered together in a "stair like" fashion. That means left and right part of the table should be finished first and then connected as suggested above.

Hello Vagelis,

Following your PM I did see this thread and forgot to post Sorry.

First Agree with Silyavski that your double I-beam design is bad idea and would drop it like hot potato.

Also agree that a fully welded Bed is slightly stronger but it doesn't allow easy adjustment if you need large items and having raising platforms like suggested can be inconvenient and take up space for storage.!

To decide which best suits your needs then you'll have to consider closely what your cutting needs are.? . .If you only plan to raise the bed to say just cut Aluminium so bringing table surface closer to spindle a fixed amount every time then go with the fixed bed and build raising platform to suit. (If you have room to store it.!!)

But if you what to cut a range of material thickness's then adjustable bed is the better option. If designed correctly and built strong then the strength difference is negligible for most cutting conditions except really heavy duty or very hard materials, In which case you have probably built the wrong design machine.!!

Now regards the table Bed and getting it parallel to the cutter then don't worry this is not a problem.? Because every time you move the bed or in Fixed bed case Add the raiser block you MUST surface the table to be sure it's parallel to Cutter.
This also means it doesn't matter if the adjustable table isn't perfectly level or even in twist because after being surfaced it will be parallel to cutter and thats all that matters.

NOW what is VERY VERY important is that the X axis~(long axis) rails are on the same plane and not in twist.!! This is where all your efforts need to be concentrated on getting correct. The Bed could be Banana shaped and slopping at an angle it doesn't matter because after surfacing it will be flat and parallel to cutter BUT ONLY if the X axis rails are on the same plane. Any errors in this department affect the whole machine.

Several ways to ensure this but really only 2 that are realistic to the DIY builder. These are Epoxy levelling or adjustable top rail and careful measurement.
Epoxy is probably the easiest because it doesn't require accurate straight edges or equipment.! It's just more time consuming because of prep to surface to ensure clean and setting up dam walls and bridge etc . . .Plus it's messy and requires clean up afterwards!.

Thou For first time builder then I'd probably suggest taking Epoxy route has it's easier to ensure rails are on same plane and doesn't require machines to ensure top rail is surfaced flat.

Quote:

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Originally Posted by silyavski

- between 80x80x3 and 4mm, the best choice is or 80x80x3 or 100x100x3 .
Why?
80x80x3 1m=7.17kg/m
80x80x4 1m=9.47kg/m
100x100x3 1m=9.02kg/m

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Now regards this Silyavski then there's little more to it than just weight.? The thicker material will lessen resonance and resonance affects the quality of cut, it can also affect motor performance to some degree and I recommend Digital drives with good resonance damping built in if building from steel. Also fill the Tubes with sand for best affect.

Some times it's better having less speed but Stiffer machine with less vibrations than trying to save weight. Again this depends on what your doing with machine.

Let me say for cutting anything below Aluminium these steel built machines are massive overkill and would need huge spindle power to achieve the Depths of cut and feed rates that would stress the frame or make it become the weak point.

For Cutting aluminium or harder materials correctly to high standard requires a certain attention to design and detail that is very hard to Achieve, just look at Jonathans latest post about his friends excellent machine to get an idea of what's needed to do it correctly and I'd even say this is a minimum requirement if high standard of finish and feed/DOC rate is needed.
This is just medium sized machine and with every 100mm wider or longer the level of engineering gets more and more important and harder to achieve accuracy.

So my Advise is THINK CAREFULLY about your cutting needs and be REALISTIC about feeds/DOC etc you expect to achieve.
No point using a Sledge hammer to crack a nut and same goes with cutting wood, Machines built to this level are Sledge hammers to wood.!! . . . . Build it just stronger than needed for the Job it's doing, any more is waste.

If you need to mainly cut aluminium and correctly then build a different machine designed to do the job correctly.!!

If you want one large machine to do all jobs then it will have weak spots in every area, it CANNOT Excel at cutting every material just impossible to achieve realisticly.!!

This is how I plan to do my top rail.
legs 50x50x3 steel box
top rail 100x50x3 steel box
6mm or maybe 10mm plates welded on top of the legs and welded to the underside of the top rail.
Bolts will pass through the plates on the legs and will screw into threaded holes in the top rail plates and right through into the box.
These joints will be shimmed to level the top surface of the rail and to ensure both sides are in the same plane.
Before bolting the pieces together I will grind the surfaces of the plates flat, checking with a straight edge
It would be easy to weld 2 further intermediate points if this found to be flexing.

Attachment 10440

Quote:

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Originally Posted by EddyCurrent

This is how I plan to do my top rail.
legs 50x50x3 steel box
top rail 100x50x3 steel box
6mm or maybe 10mm plates welded on top of the legs and welded to the underside of the top rail.
Bolts will pass through the plates on the legs and will screw into threaded holes in the top rail plates and right through into the box.
These joints will be shimmed to level the top surface of the rail and to ensure both sides are in the same plane.
Before bolting the pieces together I will grind the surfaces of the plates flat, checking with a straight edge
It would be easy to weld 2 further intermediate points if this found to be flexing.

Attachment 10440

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That's pretty much I do my rails but to make life simpler and do away with grinding and shimming etc I spread a layer of Epoxy putty on the bottom plate. Then I put layer of plastic between rails and plate then lightly tighten together pushing some excess out then set the rails on same plane and parallel etc. The putty gives plenty of time for adjustment and dries hard has metal.
It has dampening quality's has well so helps with vibes transferring thru frame. It drills and taps easy and fills any voids, I can shape to match radius etc and it easy grinds and sands if needed.
When set 24hr later I have a perfect hard surface that sets rails exactly on same plane. The rails can be removed and go back exactly on same level so no messing around with shims etc.

Sounds like a plan, plastic metal would be okay too, I have some of that.

First of all thanks everybody for the participation to the thread.
Next i would like to introduce some of my conclusions and ask some things about all these that i have already read

1. I beam will not be used
2. For the rails support beams I am between these profiles
80X80 4 mm
80X80 5 mm
100X100 4 mm
100X100 5 mm
and for the table structure
80X80 4 mm or
80X80 5 mm
i want your advice

Quote:

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Jazzcnc wrote
Now regards the table Bed and getting it parallel to the cutter then don't worry this is not a problem.? Because every time you move the bed or in Fixed bed case Add the raiser block you MUST surface the table to be sure it's parallel to Cutter.

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Jazzcnc when you say "MUST surface the table to be sure it's parallel to Cutter" you mean that the spindle should make a full pass over the cutting table and milling the table surface ?

Quote:

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Jazzcnc wrote
NOW what is VERY VERY important is that the X axis~(long axis) rails are on the same plane and not in twist.!! This is where all your efforts need to be concentrated on getting correct. The Bed could be Banana shaped and slopping at an angle it doesn't matter because after surfacing it will be flat and parallel to cutter BUT ONLY if the X axis rails are on the same plane. Any errors in this department affect the whole machine.

Several ways to ensure this but really only 2 that are realistic to the DIY builder. These are Epoxy levelling or adjustable top rail and careful measurement.
Epoxy is probably the easiest because it doesn't require accurate straight edges or equipment.! It's just more time consuming because of prep to surface to ensure clean and setting up dam walls and bridge etc . . .Plus it's messy and requires clean up afterwards!.

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Here i have two question

1.when you say "adjustable top rail and careful measurement" you mean the X ( long) axis rails should be adjustable right?
2.when we talk about self leveling polyester epoxy, is it specific epoxy or common marine polyester can do the job. Should i need a primer in order the epoxy to bond with the metal?

Quote:

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Jazzcnc wrote
I recommend Digital drives with good resonance damping built in if building from steel. Also fill the Tubes with sand for best affect.

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When you say "digital drives" you mean the motor drives. I reminds you that i will use 400watt yaskawa servo motors Sigma II generation, and i plan to put all the electronics not under the cutting table but to a separate enclosure in order to avoid vibrations for the electronics.


My main concern of using epoxy is the aging and the temperature effect to the table. I am talking about contraction expansion. The machine will be placed at my basement where i have temperatures from 8 ( winter ) to 26 ( summer ). Would that be a problem? What will happen if one day i decide to move the machine to another place. The truth is that epoxy look a good and easy solution, on the other hand i don’t fell good if i don’t have the ability to adjust. Also do we know how epoxy reacts. It is more than sure that epoxy doesn’t have the same contraction expansion ratio as steel. I have heard that pro builders that use cast iron, leave the metal for aging for 10 years...
Thanks again everybody. If anyone has something to suggest i am anxious to hear

Quote:

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Originally Posted by JAZZCNC

I spread a layer of Epoxy putty on the bottom plate. Then I put layer of plastic between rails and plate then lightly tighten together pushing some excess out then set the rails on same plane and parallel etc. The putty gives plenty of time for adjustment and dries hard has metal.
It has dampening quality's has well so helps with vibes transferring thru frame. It drills and taps easy and fills any voids, I can shape to match radius etc and it easy grinds and sands if needed.
When set 24hr later I have a perfect hard surface that sets rails exactly on same plane. The rails can be removed and go back exactly on same level so no messing around with shims etc.

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To be honest, as my english arent good , i dont understand excactly what you did
When you say "I put layer of plastic between rails and plate" what you mean? what kind of plastic ? and when you say "between rails and plate" what do you mean? Your rails rest on a plate or on a square beam ? Sorry for asking but i dont get it

Quote:

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Originally Posted by ba99297

2. For the rails support beams I am between these profiles
80X80 4 mm
80X80 5 mm
100X100 4 mm
100X100 5 mm
and for the table structure
80X80 4 mm or
80X80 5 mm
i want your advice

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Any of those will be fine. Personally If mainly wood use then I'd go with 80x80x4 and save some money has it will be plenty strong enough.

Quote:

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Originally Posted by ba99297

Jazzcnc when you say "MUST surface the table to be sure it's parallel to Cutter" you mean that the spindle should make a full pass over the cutting table and milling the table surface ?

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Yes exactly.

Quote:

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Originally Posted by ba99297

1.when you say "adjustable top rail and careful measurement" you mean the X ( long) axis rails should be adjustable right?

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Yes exactly.

Quote:

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Originally Posted by ba99297

2.when we talk about self leveling polyester epoxy, is it specific epoxy or common marine polyester can do the job. Should i need a primer in order the epoxy to bond with the metal?

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It must be solvent free epoxy to avoid shrinkage. No primer is needed just very clean oil free surface also best if rough surface so epoxy binds to it better.

Quote:

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Originally Posted by ba99297

When you say "digital drives" you mean the motor drives. I reminds you that i will use 400watt yaskawa servo motors Sigma II generation

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Yes sorry forgot you where planning to use servos.

Quote:

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Originally Posted by ba99297

My main concern of using epoxy is the aging and the temperature effect to the table. I am talking about contraction expansion. The machine will be placed at my basement where i have temperatures from 8 ( winter ) to 26 ( summer ). Would that be a problem?

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I've not had any problems with heat/cold, My workshop can go from -8 (winter) to 30 (summer thou rare here in UK) so don't think you will have a problem.

Quote:

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Originally Posted by ba99297

What will happen if one day i decide to move the machine to another place.

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Nothing will happen everything will remain the same. Remember the Epoxy is not to level the machine.!! . . . It's just so the two rail top surfaces self level on the same plane.
To give an massively over exaggerated example.!!
Imagine the rails or the full machine before applying epoxy are not on level surface, lets say 10deg slope. When you apply the epoxy to rails they will self level on the same plane. Looking at the epoxy From the side it will have 10deg taper.
If you then move the machine to a level surface the rails will slope 10deg . . BUT . .They will still be on the same plane provided the frame is stiff and doesn't twist when you move it.
This is why My machine works in vertical position(15deg angle) because doesn't matter if the rails or bed are at an angle only matters that the two rails are on the same plane.

Quote:

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Originally Posted by ba99297

The truth is that epoxy look a good and easy solution, on the other hand i don’t fell good if i don’t have the ability to adjust.

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The idea of epoxy is so you don't have the need to adjust.! . . BUT . .If you want the best of both worlds then have adjustable top rail and epoxy the surface has well. . . This way you can fine tune using shims if you feel the need.

Quote:

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Originally Posted by ba99297

Also do we know how epoxy reacts. It is more than sure that epoxy doesn’t have the same contraction expansion ratio as steel. I have heard that pro builders that use cast iron, leave the metal for aging for 10 years...

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I've been using the Epoxy method for 3-4yrs now and I've not had any issues but if you want to be 100% sure and follow tradition then leave it to set for 10 years. . .Lol . . .( By which time we will have moved on to making DIY Star trek Replicators . .:hysterical: )

Quote:

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Originally Posted by ba99297

To be honest, as my english arent good , i dont understand excactly what you did
When you say "I put layer of plastic between rails and plate" what you mean? what kind of plastic ?

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The layer of plastic is just a barrier to stop the top rail being bonded to the mounting plate so it can be removed. When the Epoxy putty has set hard the rail is unbolted and plastic barrier is removed and thrown away. The plastic can be any type, old carrier bag anything. Someone suggested to me taping the rail with parcel tape which I did try and does work ok.

Quote:

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Originally Posted by ba99297

when you say "between rails and plate" what do you mean? Your rails rest on a plate or on a square beam ? Sorry for asking but i dont get it

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Look at the picture Eddy posted and you will see the plates which the rails bolt onto. Epoxy putty is then spread on these plates, then piece of plastic placed between rail and epoxy to stop bonding together.
I then set the rails on the same plane and parallel with a combination of temporary shims and adjusting bolts. Effectively the Epoxy putty is acting has a Permanent shim when dry.

Hope this makes more sense.?

Quote:

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Originally Posted by ba99297

First of all thanks everybody for the participation to the thread.
Next i would like to introduce some of my conclusions and ask some things about all these that i have already read

1. I beam will not be used
2. For the rails support beams I am between these profiles
80X80 4 mm
80X80 5 mm
100X100 4 mm
100X100 5 mm
and for the table structure
80X80 4 mm or
80X80 5 mm
i want your advice

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Look from what you started and where you jumped- 100x100x4 and 100x100x5

Read again what Dean /jazzcnc/ told you, first be sure for what you use it mainly and then decide on the thickness. Go to your local metal shop and check for your self about the 100x100x5 and 80x80x5. This is way too much. Ok, people use them but for builds that intend to cut mainly aluminum and so.

Quote:

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Originally Posted by ba99297

My main concern of using epoxy is the aging and the temperature effect to the table. I am talking about contraction expansion. The machine will be placed at my basement where i have temperatures from 8 ( winter ) to 26 ( summer ). Would that be a problem? What will happen if one day i decide to move the machine to another place. The truth is that epoxy look a good and easy solution, on the other hand i don’t fell good if i don’t have the ability to adjust. Also do we know how epoxy reacts. It is more than sure that epoxy doesn’t have the same contraction expansion ratio as steel. I have heard that pro builders that use cast iron, leave the metal for aging for 10 years...
Thanks again everybody. If anyone has something to suggest i am anxious to hear

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Don,t get me wrong, but your main concern should be squaring the rails in one plane. And choosing square supported rails, not roundish.
I assume you don't have even a straight edge and you worry about contraction and expansion. First think do you need such an accuracy, then do you have the actual means to measure it, then how much is the cost of the tools to measure it...
For wood and plastic and occasional aluminum you need much lower accuracy than you are contemplating.

I mean relax, and be careful not to make some obvious mistake. Like making a cnc for another kind of job. remember the old saying: " The machine is strong as its weakest part". I constantly meditate on this when i catch myself overbuilding

Just grabbed these out of a video I saw if any use

Attachment 10447Attachment 10448Attachment 10449

details are here 3D Model of CNC Router c4d, obj, 3ds, fbx, dxf, skp, iges
and it looks like they had to add some triangulation to the legs after these photos

So far thanks everybody for your answers
Your advices keep me away from mistakes that i think could cost me money time and poor final result
After all these answers, i decide

to use part of Silyavskis' table plan ( for part of the table that the X rails rest on) .
Not to use the I beams
Not to use adjustable beams for the X axis rails and go on with the epoxy solution.
This choice means that the table is solid as rock. So before i go on with the 3d design i want your advice about the table diagonal reinforcing.
Here are some autocad plans. They represent side view of X axis. I design 4 solutions ( A,B,C,D )
The upper yellow line represents profiled rails, and the green color is adjustable legs
Tell me your opinion.
I haven’t decide yet if i will go with 80X80 or 100X100 box section. It depends from the cost. The following plans are made with 80X80 box section
Thanks for your time


Attachment 10509

I like B but not everyone will

I like A but if i were you, would turn the 4 diagonals 180 degree/ mirror them upside. That will separate on smaller sections and support even further the X rails support + when pushed from upside will make a stretching force to the lower beam, not pushing, as it is now.
I mean instead of MM WW

If full height is desired, as Eddy says B is best, simple and strong + the diagonals will stretch again the lower beam, if pushed from above. And we all know steel can not be stretched:victorious:

Silyavski before i check for any new post at my thread i design in autocad this

Attachment 10510

and then i read your post
I think that we are thinking in the same way
To be honest you inspire me for my table plan ( especialy for the rail support beams ) thank you.
Aslo thanks everybody else like Eddycurrent and of course Dean for their ideas
Day after day, thread after thread post after post i feel that the knowledge and the experience of people that willing to help, give me the ability to make a solid machine. You know it is very important to make a step and have no question to be answered. That is what i almost fell now about the table plan. May be some small changes will be done, but the basic consept i think is this.
I will post 3d plans soon
PS A machine that is having rail height at 70 cm from the ground, has any disadvantage compared to a machine that is having rail height at 90-100 cm from the ground?
I will be happy to hear any other advice.
The only question that is waiting for answer is the beam dimensions 80X80 or 100X100 and of cource the thickness
And here i have some 3d plans.
I will come back with another plan a little bit different
Attachment 10512Attachment 10513Attachment 10514Attachment 10515Attachment 10516

It will work both with 100x100x3 and 80x80x 3 or 4mm. Depends on how strong would be your gantry, what spindle you will like to mount and how further you will like to push it.
I suggest you make your gantry from 2 pieces of the same profile you will use soldered together, hence 200x100 or 160x80 or do it from aluminum, the way Dean makes his machines, with a ball screw hidden in the gantry, depends what means you have.

The drawings look very good. Now if you aim at certain weight or to be able to pass through normal 1m wide door, don't make it higher . if you want to make it higher and at the same time light, just make the legs longer. Also if length, weight is a problem, you can lift the 4 lower beams to the middle of the M , and remove the middle leg below this point, this will not compromise the strength.

If you aim aluminum and hard stuff mainly, maybe a gantry like Jonathans will be better, look at his exemplary build

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I suggest you make your gantry from 2 pieces of the same profile you will use soldered together, hence 200x100 or 160x80

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The gantry will probably made as you say from 2 pieces of 80X80 or 100X100 profile, covered with 10mm laser cut aluminium plate just for acuracy for the holes distances. This plate will be bolted on the gantry box section and may be adjustable in order to achieve paralelism with the table.

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depends what means you have.

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As for the means, i dont have mill i dont have lathe

Quote:

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maybe a gantry like Jonathans will be better, look at his exemplary build

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I have read many times Jonathans thread. So many in order to understand what i am reading. NO COMMENT. What else can i say. I cant follow this plan beause it is out of my budjet, and i dont have the means and the knowledge to do such job. For now the only think i can do is design 4-5 type of tables and ask the polite guys of mycncuk to give me their advice and make their corrections

After hours of design i come back with 3 final (!!!!) plans.

Plan A
( i have already post it but i repost it near the other two plans )
It is the most simple within the other two and also needs the less steel
Attachment 10527Attachment 10528Attachment 10526Attachment 10529



Plan B
It is the heaviest within the other two
The difference with A is that the beams of the cutting table are lieing between the two X axis rails support beams. It also have extra 40X40 beams for reinforcing X rails beams
Attachment 10532Attachment 10530Attachment 10531Attachment 10533




Plan C
Attachment 10536Attachment 10534Attachment 10535Attachment 10537
This plan combines A with B. The beams of the cutting table have been welded as plan A and the reinforcing of X axis beams is as plan B

All plans are made with 80X80 box section steel. Plan B and C also have 40X40 diagonal box section between X axis rails support beams
I am waiting for your advices
Thank you

Plan A must be strong enough for this size machine. I know that silyavski likes to have the horizontal beams supported at 2 points like your end view but you loose the triangle in the middle and that is not good.
Also where there are no diagonals or triangular pieces on the cutting table to stop it twisting.
Having said that it will still be very strong if you make it like the drawing.

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I know that silyavski likes to have the horizontal beams supported at 2 points like your end view but you loose the triangle in the middle and that is not good.

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If you notice all the three plans carefully you will se that the x rails supported beams have contact with the ground at 3 points not 2. It is possible you get confused between the side and the front view.
At the side view you can see that every pair of supported rail beams has straight contact in the middle with the groun as my plan have 3 ( red ) foot at every side.
From left to right i upload Isometric-Top-Front-Side view for every plan

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Also where there are no diagonals or triangular pieces on the cutting table to stop it twisting.

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You are right about the diagonals. I will put them to the plan. Thanks for your advice

Is there any need for the bars connecting the legs at the bottom. I'm constructing mine at the moment, interested in the replies.

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Originally Posted by alex wight

Is there any need for the bars connecting the legs at the bottom. I'm constructing mine at the moment, interested in the replies.

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Alex, that is a very good point. I think the only reason they are in there is to provide a means of adding triangulation support in the horizontal plane at ground level ( i.e. some metal to weld the triangulation members on to) but if enough triangulation was put into the cutting bed maybe that would be enough ? I'm also at this stage in my build log and reluctant to start cutting the metal yet as I feel the best solution has not yet been reached.

ba99297, I was referring to the front view, the dark colour one.

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.

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Originally Posted by alex wight

Is there any need for the bars connecting the legs at the bottom. I'm constructing mine at the moment, interested in the replies.

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Actually no need, that's what i said before. Or they cut be cut in 2 and raised higher at the middle of the M, that's what i suggested before.

With 80x80 profile or bigger the machine will not twist , so no need for triangulation on the bed itself. remember that the spoilboard willnot permit eventual twist there.

However for the sake of absolute rigidity i would have soldered additional plate vertically along the center beam of the bed itself , that will strengthen immensely the bed

PS. option 1 looks perfect

Any of these are strong enough but the design can be simplified regards building and be just has strong. No time at moment to get into full debate about why etc but here's frame I've drawn that's similar.

Main points are the sides and Bed are welded flat has separate units then joined together with end braces etc. The Bed being a separate unit means the outer frame pieces support the bed material at the edges, the way yours is drawn the edges will be unsupported and could bend or flex under cutting conditions.
Lower diagonal braces help keep machine frame square and stiff, remember it's not just strength you have to consider there's resonances to deal with and bracing helps reduce resonance.

Welding major parts in sections on a bench then either welding or bolting together is much easier than struggling trying to weld individual pieces together and keep every thing sqaure and flat, aligned etc.

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.

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Originally Posted by JAZZCNC

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.

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

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.



Attachment 10557


Attachment 10558

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Originally Posted by silyavski

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?

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

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Originally Posted by silyavski

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...

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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.

Hi Dean,
First i want to thank you for the help with the machine we talk about that i am building for a friend which wouldn't be possible without your kind help.

I absolutely agree with what you say. I wouldn't want to mislead somebody. I am always speaking in relative terms here, meaning having in mind DIY machines, with best possible price functionality relation, designed to be multifunctional, mainly for wood and for the occasional aluminum job.

That is why i said it will be good if the design is not copied but adjusted to the particular needs. So let me clear some points about the specific design, not to you i mean , cause i kn ow you know it, but to those who read:

-Its meant for wood and plastics. Its meant also for aluminum but only when additional bed is fixed to raise the job
-its meant for deep 3d jobs mainly and Z axis travel -170-200mm
-Its meant for a trunion table to fit for aditional axis for 3d jobs
-its meant if need arises for a removable plasma water bed to be fitted for occasional jobs.

In other words its meant to be all type of machine, so certain sacrifices has to be accepted.

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Originally Posted by JAZZCNC

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.

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That is exactly why the frame is overbuild and a small spindle is used

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Originally Posted by JAZZCNC

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.!!

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I told that to the friend i am building the machine for. In any case, the machine will have 20mm aluminum sheet bed. Over the aluminum 10mm sacrifitial hard phenolic plastic sacrifitial layer. Over it when necessary will be fitted solid 100mm high block of MDF, ply wood or wood, and yes it will be resurfaced each time, i told him so. So basically nothing would flex there. you misunderstood me because of my English, the machine will have 20mm aluminum bed at least,ribbed where necessary, not MDF!

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Originally Posted by JAZZCNC

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

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You couldn't be more right. Thats the truth. My smalll cnc has 2 flimsy bearings and i cant find the time even to dismantle and tighten, as i dont stop it at all.
So I believe it would not be necessary at all. Just said it to remind that if a mistake is made with the design, can be fixed later when testing the machine.



So in conclusion/my conclusion i mean :joker:/ , if maximum flexibility and at the same time rigidity for heavy duty aluminum jobs is wanted there are only 3 ways to go:
- Make a specific purpose machine from the beginning like Jonathan did for his friend, with removable bed
or if larger machine is desired:
-make a machine similar to how Dean does them, with removable adjustable bed and bottom frame structure
-make a machine the way i propose and use additional bolted beams to raise the bed or lower it, look at the picture below
In these both cases, at the end the material we use is roughly the same. main point in my design being limited space, so the legs can be removed without compromising the integrity of the design and having to redraw it again.

Attachment 10563

Of course that design can be further developed with cost savings in mind. For example the middle 2 beams from the lower bed can be made dis-mountable, so they can be used for the upper bed and so on... Look picture below.

Thats what i like about the constructive discussion. makes me think and develop. The idea of the removable 2 beams just made me realize what savings that would be on my next 1250x2500 design



Attachment 10567

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The Bed being a separate unit means the outer frame pieces support the bed material at the edges, the way yours is drawn the edges will be unsupported and could bend or flex under cutting conditions.

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Excuse me Dean but i don’t understand why my cutting table has unsupported edges. At every plan the cutting table beams are welded at the side pieces. Could you please make it more clear?

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

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Thank for your good words. The truth is that i don’t have time pressure. When i make a step i want to be sure about what i am going to do
I am searching over the internet for this construction about a year
The last few months although i thought i knew very much about the subject i find out that mycncuk exist
The answers that i take from the members make me change many of my thoughts
For example i didn’t know that the ball screws have critical speed. My first plan was to connect the motors straight to the ballscrews. Imagine how i would fell when i broke a ballscrew 1500 long running at 3000 rpm. I also thought that I beam is the strongest type of beam..... ( May be for vertical forces )
So every day someone in here give me an advice or correct me, i fell happy about avoiding another mistake

Thanks everybody so much for your help
P.S Sorry for my English

Since it's already been said that most of the frame designs posted here would be more than adequate, I'll just highlight some general points which may be useful.

I think the frame design silyavski posted in post #30 is well thought out since, among other things, it makes relatively efficient use of material. I'd be inclined to swap the two 100x100mm beams and 80mm spacers with a single piece, perhaps 200x100mm possibly with a higher wall thickness than the rest (or scaled down accordingly if making the rest of the frame from smaller sections). This will obtain a similar stiffness to the original, but reduces the number of pieces to cut by 12 and the number of welded joints is reduced by 20. This would save a lot of time and reduce residual stresses due to there being less welding. Clearly it may not be as cost effective as making the whole frame from the same size material.

Something else to bear in mind is that increasing the size of the steel you use can sometimes make the structure strong enough, with a lot less work than adding lots of small supporting pieces and without necessarily increasing the cost. For example, if you have a piece of 60mm box section with 3mm wall thickness supported at both ends, then in general increasing it to a 80mm beam of the same wall thickness will reduce the deflection to less than 2.4 times the original.

Also, it's better to increase the size of the beam (within reason), than to increase the wall thickness. Continuing with the previous example, the 80mm beam will cost about 33% (assuming it's priced by mass) more than the 60mm beam, so suppose you instead invested that 33% extra in getting a 60mm box section with 3mm thickness to match the weight of the 80mm beam. Both sections will cost about the same, however the 60mm beam is still only just over half as strong as the 80mm, as you've only made it about 33% stronger (not 240% as above). The reason for this is that increasing the wall thickness only gets a linear gain (y=k*x) in strength, compared to a quartic (y=k*x^4) relationship from increasing the size. So in general, you only use a greater wall thickness when you haven't got space to fit a bigger section.

With regards to resonance, MDF is actually a great material to use for the machine bed as it has such good damping properties. I had a lot less problems with resonance on my machine with the MDF bed than I do now with aluminium. If I'm machining an aluminium part for which the finish is more important than the accuracy, I'll sometimes put a piece of 18mm MDF between the part and the aluminium bed as the MDF damps the vibrations, making the 'sweet spot' to get a good finish a bigger spot.

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Originally Posted by Jonathan

Something else to bear in mind is that increasing the size of the steel you use can sometimes make the structure strong enough, with a lot less work than adding lots of small supporting pieces and without necessarily increasing the cost. For example, if you have a piece of 60mm box section with 3mm wall thickness supported at both ends, then in general increasing it to a 80mm beam of the same wall thickness will reduce the deflection to less than 2.4 times the original.

Also, it's better to increase the size of the beam (within reason), than to increase the wall thickness. Continuing with the previous example, the 80mm beam will cost about 33% (assuming it's priced by mass) more than the 60mm beam, so suppose you instead invested that 33% extra in getting a 60mm box section with 3mm thickness to match the weight of the 80mm beam. Both sections will cost about the same, however the 60mm beam is still only just over half as strong as the 80mm, as you've only made it about 33% stronger (not 240% as above). The reason for this is that increasing the wall thickness only gets a linear gain (y=k*x) in strength, compared to a quartic (y=k*x^4) relationship from increasing the size. So in general, you only use a greater wall thickness when you haven't got space to fit a bigger section.

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Well ounce again I'm going to have to disagree.!! . . . Not on the strength basis has that's true but on the fact it's better to use larger.? It's only better if the application warrants it and in this case it doesn't. The thicker wall thickness will be more beneficial because it will be less resonant, going Larger on the tube size just increases resonance. For this application then 60mm tube will be more than strong enough so strength isn't a problem so any extra efforts to improve would be better focused on reducing resonance and going thicker on the wall would help here.

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Originally Posted by Jonathan

With regards to resonance, MDF is actually a great material to use for the machine bed as it has such good damping properties. I had a lot less problems with resonance on my machine with the MDF bed than I do now with aluminium. If I'm machining an aluminium part for which the finish is more important than the accuracy, I'll sometimes put a piece of 18mm MDF between the part and the aluminium bed as the MDF damps the vibrations, making the 'sweet spot' to get a good finish a bigger spot.

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Oh dear again I'm disagreeing. . Lol . . I don't have any problems with my aluminium bed and differing finish.? I get the same finish regardless of whether I'm working direct on bed or on any other sacrificial surface. If your bed is affecting finish then reckon you've under built it or your clamping methods are poor.!!
If anything I get more trouble when using MDF than I do when working direct on bed because material can slide if cutting deep, direct on the bed I get much better hold down.
Also Poor finish comes mostly from the tool chattering so if your struggling with finish then I'd be looking at the machine strength and resonance, hence why I put more importance on material Thickness than Size when it comes to steel. (obviously size has to be fit for application)

BA 99297 I'll say it again to be clear "Any of the designs will be strong enough" so if any more focus is needed then I'd direct it to reducing resonance rather than strength.

Oh when I said about unsupported edges I meant you don't have any members to support the Bed base material at the edges. On your designs the edges between table supports won't support the material or any sacrificial material. It may seem a small detail but it can make a difference and for the little extra material/work it's not worth not doing IMO.!

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Originally Posted by JAZZCNC

Well ounce again I'm going to have to disagree.!! . . . Not on the strength basis has that's true but on the fact it's better to use larger.? It's only better if the application warrants it and in this case it doesn't. The thicker wall thickness will be more beneficial because it will be less resonant, going Larger on the tube size just increases resonance. For this application then 60mm tube will be more than strong enough so strength isn't a problem so any extra efforts to improve would be better focused on reducing resonance and going thicker on the wall would help here.

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I don't disagree with you. If you read what I said carefully you'll see that I acknowledged other factors come into it, and was making general comments, not specific assertions for this build.

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Originally Posted by JAZZCNC

Oh dear again I'm disagreeing. . Lol . . I don't have any problems with my aluminium bed and differing finish.? I get the same finish regardless of whether I'm working direct on bed or on any other sacrificial surface. If your bed is affecting finish then reckon you've under built it or your clamping methods are poor.!!
If anything I get more trouble when using MDF than I do when working direct on bed because material can slide if cutting deep, direct on the bed I get much better hold down.
Also Poor finish comes mostly from the tool chattering so if your struggling with finish then I'd be looking at the machine strength and resonance, hence why I put more importance on material Thickness than Size when it comes to steel. (obviously size has to be fit for application)

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I agree that if my gantry was stronger it would help reduce chatter, but it's the same gantry with or without the MDF bed and the MDF sheet placed on top of the aluminium bed on my machine definitely makes it easier to get a good finish, so it must be having a damping effect. I'll reiterate for clarity, by 'good finish' I mean 'looks good' - the part itself is clearly not going to be as accurate if it's clamped on MDF.

Also, that's not to say the machine wont get a good finish using just the aluminium bed - it's just more difficult to get the right parameters. Here's a recent example:
Attachment 10584

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BA 99297 I'll say it again to be clear "Any of the designs will be strong enough" so if any more focus is needed then I'd direct it to reducing resonance rather than strength.

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Dean or anybody else could you please suggest me a link ( or links) where i can read about resonance dampening basics ( i mean what i should avoid in order to reduce resonance )
So far ( tell me if i am wrong ) i realize that low mass and symmetry amplify resonance is that correct?

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Oh when I said about unsupported edges I meant you don't have any members to support the Bed base material at the edges. On your designs the edges between table supports won't support the material or any sacrificial material. It may seem a small detail but it can make a difference and for the little extra material/work it's not worth not doing IMO.!

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Now i understand what you mean but i didn’t say that vertically to the table beams i will put t slot aluminium profile ( a friend of mine who makes solar parks on the houses roofs has many meters of them)

Hi everybody
These days i have time to go on with my cnc design
For 3d design i use solid works
After the table i will go on with the gantry etc
I would like to know if there is any online library with ready to use elements like bf/bk bearings. profiled rails, ballscrews ballnuts that can be imported in solidwork
Thanks

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