Stell frame cnc 1500X1000. Adjustable table your opinion please

[ba99297]

Dean i made some corrections according to your advices. I am not sure i understood everything you said ( as my english are not excellent)
Let the photos talk


In order to go on with the plans, it would be good if somebody told me about Y and Z rails distances and distance between carriages of X axis. Finally i want your advice about X axis double preloaded ballnuts

Thanks

Vagelis

[Boyan Silyavski]

Hi Vagelis,

Normally people here on the forum use ball nuts and ballscrews bought from China. The most recommended vendors are Fred from BST Automation/aliexpress/ and Chai from linearmotionbearings /ebay/. BST for sure can provide the double ball nuts , i assume Chai also. No reason to buy 2 single, but depends on the design. On Jonathans build i asked about the spacers spring washers, he pointed from where, so the info should be somewhere there. Their prices are very similar, both do perfect machining, so really its up to you.

To resume various advices for my builds, that i received mainly from Dean and Jonathan , for your size machine
if stepper driven 1:1 with short belts and pulleys on all axis:
-short belt HDT5 15 size, if heavy gantry maybe 25 size, pulleys 20t
-z 1605 screw
-gantry 1610 screw if mainly woodworking for faster speeds ,1605 if mainly aluminum
-long axis 2010 or 2005 respectively, i see no reason to go to 25xx size

the following is my personal understanding:

-gantry supports ~ 30cm/normal/ to 40cm/heavy duty/ spacing of the bearing blocks , this including the blocks-
-gantry , depends on the design, but ~20cm spacing vertical and 25 horisontal i see as minimum./ including bearings./ 30 and 30 will make very strong machine/

PS. Dont be cheap and buy Hiwin or cheaper Chinese square rails not round

[JAZZCNC]

Dean i made some corrections according to your advices. I am not sure i understood everything you said ( as my english are not excellent)
Let the photos talk

Yes you have it correct but you can afford to make the triangles little smaller to avoid interfering with material, Or shape them to do same thing.

Now regards the Gantry bearing spacing then 300mm for X axis(long axis) and 200-250mm for Y axis will be fine for most work. Like Silyavski says the wider the more stable but the figures I've given I know work fine esp when using profiled linear bearings.

Regards the twinball nuts then I never use twin ballnuts so can't help here and to be honest I don't see the need for a router type machine. They are Ok for a Milling machines that need to hold tight tolerances but in this case I think your just adding extra expense and work, along with extra maintenance for gains that you don't really need or will probably never see due to other weakness in the machine.?

Remember the machine is only good has it's weakest link and at this size then a single ballnut won't be the weak link so any gains won't be fully seen and the gains you'll get from 2 nuts over 1 nut will be very small to start with and I honestly think you won't see any improvement worth the effort or expense.!!

Ballscrew sizes and pitch then

20mm Diameter 10mm pitch for X axis, don't go with 5mm pitch even if aluminium just change the gearing on the pulleys. Don't use 25mm diameter far to large.!
16mm Diameter 10mm pitch for Y axis, don't go with 5mm pitch even if aluminium just change the gearing on the pulleys. Can use 20mm if you like thou won't accelerate quite has fast 16mm but it will still be plenty good enough and that bit less likely to whip.
16mm diameter 5mm pitch for Z axis.

[ba99297]

You guys are a treasure
Your advices is for me GOLD
I go on with my plans. I add profiled rails and carriages ( downloaded from hiwin site). Before I go on with my gantry design I would like your opinion about the issues that I will come up with. What are the the points that I have to be careful. This is my progress



But I am wondering if the ballscrew sould be placed between the two 80X80 beams of the gantry, in front of Y axis (near z axis ) or in the back of Y axis. I also wonder about the best way to connect Y axis with X axis carriages.
Any idea will be helpful

Vagelis

[Boyan Silyavski]

But I am wondering if the ballscrew sould be placed between the two 80X80 beams of the gantry, in front of Y axis (near z axis ) or in the back of Y axis. I also wonder about the best way to connect Y axis with X axis carriages.
Any idea will be helpful

Vagelis

Hi,
many different schools of thought here. Basically depends on what you aim to achieve, what rigidity you aim for, the overall weight of gantry you will finish with, and how you intend to move this weight, how fast and not at last the money that you can spend on the structure, the motors and the drivers.

To resume it all for the gantry sides: 1 side plate like at the drawings could be ok if you keep the gantry not raised, directly on the sliding plates, if you raise the gantry you will have to do a profile like structure to make it stiff and strong in all directions/ possibly from 10mm thick steel sheet will be best/. There is a calculator in the sticky post for that purpose.

Now to the gantry drawing itself. Have in mind that this is not the voice of experience, i am like you building now my 2 first machines, however i gave it a lot of thought:

The typical:

-Screw at the back will work, many make their machines that way, combined with the rails on top and bottom of the gantry. That is how i designed my first build.
Points to consider: more complicated Z design, rails need more time to be aligned, care should be taken for the Z strength in all directions.

-Screw in the middle. Great design, but most do it from aluminum-plate at the back and plate at the front with channel in the middle. While i like it i did not choose it due to expensive material, my inability to process it at home precisely-cutting, drilling tapping...etc., Beautiful but quite costly. Of course it could be done from steel plate, but then the combined weight. Or ribs here and there at the back, but still without a front plate will not be strong enough to my liking. Plus the plates will protect the ball screw.

-The typical commercial router, rails on the front plate, screw inside, raised gantry. I could not help but post the picture of the Techno, which is a typical example


If into woodworking and sheet material ok. But not a multitask one. Man, how i hate that design . The z could go left right further, so the table could be not so wide, but then the gantry raisers should be strong enough, then the Z travel is very small, so if we want travel of 200mm then the weight, then the motors...etc.

Other:
There are other designs but as they are very purpose specific i would not recommend them.
You could take a look also of my design of gantry on the second machine i am starting to build.I hope will be successful. Its meant for strength and precision for the long gantry, also an ease of implementing, especially epoxy leveling the rails . Just as an idea that you could further develop if you like it http://www.mycncuk.com/forums/router...html#post52573, though more soldering, various sizes profile, heavier.


At the end the design is choosing between the various trade offs for the purpose of what will suite you most.

[ba99297]

Hi guys
Quite a long time since my last post
I am thinking about an arrangement for the gantry of my machine
Before i go on with the plans i want your advice about the basic idea
Three 120X60X3mm beams will be welder making a C shape
In front of this "C shape" a 15mm aluminium plate ( blue color) will be bolted in order to bolt on this plate the profiled rails
The plans are not accurate, so any imperfections will be corrected. I just want your opinion in order to see if this arrangement is good or bad an then go on with the way i will attach the gantry on the carriages.
The gantry will be pulled by two Yascawa servos 400 watt and a 2010 ballscrew
Thanks for you time

Vagelis

[EddyCurrent]

I like the look of that but it looks weak where it joins the bottom plates. All that weight is hinged off the bottom face of the lower beam. I feel it needs something like this added each end;

[ba99297]

Eddycurrent thanks for your answer
As i said the plans are not accurate and mostly i want an opinion about the 120X60 box tubes arrangement
If it is ok i will go on with the triangulation support that will attach the C shape gantry to the carriages
To be honest i was thinking something like what you design but a little bit more complex. As what i have in mind will be influenced from the gantry shape, that is why i didn’t design the left and right parts of the gantry
Thank again
Vagelis

[Boyan Silyavski]

Looks Nice!

It would be even better if you could design it so that the motor is inside the gantry. may be with some door plate that bolts to the sides. I assume you will use any way belt from the motor to the screw, not drive it directly?

[ba99297]

Silyavski thank for your idea but thiw is not possible as the motor wont fit in the gantry.
I am working now with the plans so i can show to the forum 2-3 different ways to attach the gantry to the carriages.
Thanks for your time

Vagelis