Stell frame cnc 1500X1000. Adjustable table your opinion please

[Boyan Silyavski]

Hi,
my intent was not to confuse you, but to point you that aluminum plates bolted to the steel profile is in no way different than aligning rails to steel gantry. Also that you need to machine it or find somebody to machine it precisely.

You should choose what ever method is easier for you to make or order.

[ba99297]

Silyavski i didnt mean that you confuse me ,i just cant decide what is better for the kind of macine i am trying to construct. Steel looks for me a better choice as aluminium will raise the cost

[ba99297]

One basic question
If i choose aluminium as the basic material of the gantry, could i have 6-10mm holes laser cutted at a 20mm aluminium plate. They told me that there is a "law" that says that you cant laser cut holes smaller than the thickness of the material. Is that true ? That means if i have a 10mm thickness steel i will have 10mm laser cutted holes, accordingling about aluminium.
Thanks

Vagelis

[Boyan Silyavski]

One basic question
If i choose aluminium as the basic material of the gantry, could i have 6-10mm holes laser cutted at a 20mm aluminium plate. They told me that there is a "law" that says that you cant laser cut holes smaller than the thickness of the material. Is that true ? That means if i have a 10mm thickness steel i will have 10mm laser cutted holes, accordingling about aluminium.
Thanks

Vagelis

If the laser cut service told you - its so. In 10mm steel there is no problem to cut 5mm holes. But anyway, they could mark you the holes with the laser, so later you drill them. Normally the laser cut service would have a mill also, so they could drill you the holes, once marked.

[ba99297]

So far i understood that i should go even with all steel or all aluminium gantry, as combination of these materials will be a little tricky.
I will ask one more time and if somebody reading the thread i will be glad to hear his opinion. In what directions i must have the ability to adjust
FOr example if i go for all steel gantry, all parts welded and epoxy leveled for y axis rails, also epoxy leveled for the plates that will be bolted on the carriages what are the spots that should not be welded but bolted in order to have the ability to adjust?

[ba99297]

After over a month of inactivity i come back. Just one question before upload some resent photos.
For 2010 ballscrew should i use BF/Bk 15 or BF/BK 17 ?

Thanks

[JAZZCNC]

For 2010 ballscrew should i use BF/Bk 15 or BF/BK 17 ?

BK15 Vagelis.

[ba99297]

Hello everybody. I came back to show my little progress.
I want to remind everyone that we are talking about a cnc router with

X 1800mm
Y 1000mm
Z:300mm

It will be moved with 4 ( 2 x axis, 1 Y axis, 1 Z axis ) 400 watt yaskawa servo sigma II.
Steel is the basic material for the construction ( except z axis that I didn’t design yet )
As the table has been discussed many times, I have nothing to say. I just upload two photos . Basic beam is 80X80X4 mm.



The gantry will be maid from two 120X60 X ( 3mm or 4mm thick steel ). At the end of the gantry frame, 8mm and 10mm steel plates will be welded in order to reinforce the gantry attachment to the side braces that will be bolted on the carriages.





If it will be needed ( I try to avoid it ) the front face and the side (left-right ) faces will be perfectly milled to be vertical each other.

Here I want your opinion about the way I laser cut the steel plate and the way I try to keep everything square in order to avoid (if possible) machining cost. If you notice the plates has been cut in such a way ( like a puzzle ) that it is difficult to distort when I will weld them ( I am planning to tig weld the parts in order to reduce heat distortion). Do you think this trick ( “ puzzle cut “ ) will work ?



The same way I made the side braces here are some photos.





If you notice the side braces have straight slots in order to fine tune the gantry so I will be parallel to the cutting surface.



At the following photo you can see two holes where I will bolt screws that will help me to adjust gantry height.



Also the straight slots ( on the vertical piece of the side braces ) will allow small ( up-down ) movements. Side braces and gantry frame will be bolted together.



As for the ball screw mounts, they are also adjustable.


I want your comments if you wish , an I remind you my basic questions

1. Is the gantry overbuild?
2. Is 10mm steel ( for gantry side braces, front face, and side reinforcing )too much for such a construction or should I go with 8mm 7mm or 6mm. I am asking because if we follow the 1:3 relation between steel and aluminum, 10mm steel equals to 30mm aluminum )
3. Will the puzzle cut technique work?

As for the weight the gantry without the motor that will move y axis and without the ballscrew and of course Z axis, weights nearly 41 kgr ( with 10mm thick steel for the side braces and 8mm steel for the reinforce angles and 4mm 120X60 rectangular beam). If I reduce steel thickness and remove steel from some no critical spots, it is obvious that 41 will be easily reduced to 35 or less.


Thanks for your time

Vagelis

Ps: I will use 1:2 gearing but at the above plans i use 100mm 60 tooth diameter for the ballscrew pulley ( that will give me 1:3 gearing, having in mind that the motor pulley is nearly 3,6mm 20 tooth) in order not to have dimension issues if in the future i want to go with 1:3 gearing.

[Jonathan]

Forget all the cutouts on the gantry which have been included to reduce its mass. The servos you have a plenty powerful enough to move achieve the required dynamic performance for a gantry several times heavier than what you have designed. If you continue with your plan to use 100mm diameter pulleys then the inertia of just one of those pulleys will be more than the equivalent inertia of all three axes! Decide on the rapid feedrate you want, work out what drive ratio is required, select pulleys, then check that the servo motors are capable of driving it with the required acceleration. It is very simple to calculate, so don't compromise the performance of the system by using very large pulleys when they're almost certainly not required. If you're not sure how to work it out then let me know and I'll show you.

In answer to your direct questions:

1. Depends what you want to do with it, but you seem to be in the right ball park.
2. The consequences of using a lower thickness and having to replace it are far worse than the small increase in cost to use 10mm, so unless you're prepared to calculate it just stick with the thickest you're happy to pay for (presumably 10mm).
3. It looks a bit risky to me - the tolerances on the parts would have to be very good for them to fit together properly.

[ba99297]

Jonathan thanks for your responce.
As for the pulleys i am planning to use the following setup

X axis: 2 X 2010 ballscrews 1500mm long with 2:1 gear
Yaxis: 1 x 2010 ballscrews 1000mm long with 2:1 gear
Z axis: 1 x 2005 ballscrews 350mm long with 2:1 gear

As for the speed calculations i have made this thread

http://www.mycncuk.com/forums/gantry...culations.html

So with 2010 ballscrew and 2:1 gear ratio

i will have

motor gear ratio 1
ballscrew gear ratio 2
ballscrew length 1500
ballscrew diameter 20
ballscrew pitch 10
ballscrew rpm 1500
ballscrew rpm threshold ~1200
rapids mm 15000


Vagelis