7' X 4' Combi

[Ricardoco]

This will be a Router/Mill with Plasma,

Ok i should have started this thread sometime ago but i wanted to collect as many bits as i could to get a good start. So I used sketchup to give me the initial concept...


The first thing that was pointed out to me was that the Gantry may be a little too high and so thaat has been altered now.

the machine will eventually have an ATC and has 2 stations at the right side of the gantry for the most commonly used tools, and the rest on the front of the bed, there is also a Secondary 7" Touch screen with a custom mach layput to suit its size.
Here is also a picture of some of the goodies that will go to building it.



There was a few more additions to this but they wouldnt fit on the table...

Today i started work on the electrics box...



I will start the internals Next Weekend...

Rick

[Ricardoco]

Ok started work on the Z back plate, So i have a few questions.

Firstly i have 150mm between the centers of the guide rail blocks along the Y axis, to put the Z axis blocks on the plate i was wondering,
what would be the best configuration.
IE Above the upper rail and below the lower rail.
Inbetween both
or
1 above the lower block and 1 below.





Here are some Draft drawings that show Z above Y, But as i said im not sure of the best configuration.

So Ideas would be Welcome.


Rick

[Jonathan]

You want the lower two bearing blocks on Z as close to the bed as you can get them, to reduce the overhang. This is because the Z-axis can be modelled as a cantilevered beam, since it's only supported at one end. This means that the deflection at the end is proportional to the distance from the tool to the support (lower Z bearings) to the power 3, so even a small reduction in this distance can help a lot to increase the stiffness.

I'd put them above the top rail and below the lower rail for the above reason, and also because this increases the spacing of the blocks which is important to get maximum stiffness and it probably makes assembly easier. If However you can't afford the loss in travel thin entails, it's OK to have one between and the lower one below.

[Ricardoco]

You want the lower two bearing blocks on Z as close to the bed as you can get them, to reduce the overhang. This is because the Z-axis can be modelled as a cantilevered beam, since it's only supported at one end. This means that the deflection at the end is proportional to the distance from the tool to the support (lower Z bearings) to the power 3, so even a small reduction in this distance can help a lot to increase the stiffness.

I'd put them above the top rail and below the lower rail for the above reason, and also because this increases the spacing of the blocks which is important to get maximum stiffness and it probably makes assembly easier. If However you can't afford the loss in travel thin entails, it's OK to have one between and the lower one below.

Well the Z rails i have were going to be 400mm, but since i got hold of some 520mm rails i can afford to loose a little more travel than expected, i will take that advice, and thank you very much for it.

I will be completing the design before the end of the week i suspect, i am going for 30mm alu plate if i can get hold of it.

Regards Rick

[Ricardoco]

Having Lowered the gantry already i didnt want to lose any more Z travel so ive opted for this configuration of bearings..




540x300x30mm Ali Plate, Should Give an Assembled measurement of less than 95mm from gantry to front of plate..

Rick

[JAZZCNC]

Having Lowered the gantry already i didnt want to lose any more Z travel so ive opted for this configuration of bearings..




540x300x30mm Ali Plate, Should Give an Assembled measurement of less than 95mm from gantry to front of plate..

Rick

Don't like the fact the Z axis bearings are so far up the back plate, your creating probably 70mm more leverage. Reducing this flexy leverage is more important than having a slim Z axis any day.
The 300mm for Z axis front plate is a bit of waste has well and will make more work for the stepper and reduce feeds/accel at 30mm thick. 200mm width is fine so thats effectively 540x100x30mm and £23 of wasted plate and if 6 series ali 4.3KG of weight thats not required.!!

If you must have narrow Z axis then I'd go with some thing like the pics below.
It's wider on the Y axis by 60-70mm were bearings are located but slimmer on the rest and Z axis front plate but more importantly the bearings are lower down.
Also it's actually slimmer at approx 70mm from gantry, will be much lighter and estimate approx 10-12KG lighter over all and will probably use less material depending if you can use the same shortened back plate.?

Obviously I've had to guess and used 20mm linear bearing models and dimensions here so depending what your actually using things could workout slightly different.

[Ricardoco]

Cheers Jazz

Don't like the fact the Z axis bearings are so far up the back plate, your creating probably 70mm more leverage. Reducing this flexy leverage is more important than having a slim Z axis any day. .

Jonathan had pointed this out to me as well, so putting them either side is a good bet as in your drawings.

The 300mm for Z axis front plate is a bit of waste has well and will make more work for the stepper and reduce feeds/accel at 30mm thick. 200mm width is fine so thats effectively 540x100x30mm and £23 of wasted plate and if 6 series ali 4.3KG of weight thats not required.!!.

The 300mm will be needed so i cannot odds that, and the weight will be offset buy putting Holes/Pockets where i can removing excess material in the back plate and on the rear of the front plate, i was going to draw that but it crowded the drawing and made the concept difficult to see, I know its a waste but i can live with it.

If you must have narrow Z axis then I'd go with some thing like the pics below.
It's wider on the Y axis by 60-70mm were bearings are located but slimmer on the rest and Z axis front plate but more importantly the bearings are lower down. .

I will have to look at the extra 60-70mm to see if i will lose work space as the spindle is going to be mounted on the right side of the front z plate. Im not thinking it will be a problem..

Also it's actually slimmer at approx 70mm from gantry, will be much lighter and estimate approx 10-12KG lighter over all and will probably use less material depending if you can use the same shortened back plate.

Ive no problems making it slimmer but i would like to mount the stepper with spindle pointing upwards and running a belt to the Screw, the motor is 100mm long (nema 24 (4nm Claimed) ) so would need at least that much to clear the top of the gantry, effectively front plate and back plate level at the top of its travel. the rails i have are 520 or 540mm long cant remember of the top of my head, but that should give enough travel, the Y axis bearings will be 150mm from center of bottom bearing to Center of top bearing

Obviously I've had to guess and used 20mm linear bearing models and dimensions here so depending what your actually using things could workout slightly different.

Well they are 15mm rails for the Z as thats what i have, the Y well they could be 15 or 20 mm depending what i buy/procure..

Im not going to be doing any heavy Machining Of metals other than the odd bit of ali sheet, so i suspect 15mm will be ok if i can reduce the final weight of the Z axis assembly by pocketing as much out of it as i can without compromising on the strength to any great degree.

Rick

[Ricardoco]

Jazz, Looking again at your design, if the Z/Y backplate was higher (to accommodate the stepper arrangement I mentioned) and the front plate wider then that's the job done I rekon.. What software do you use to do your drawings?? Cheers Rick

[JAZZCNC]

.. What software do you use to do your drawings?? Cheers Rick

Rhino for cad.

[Ricardoco]

Rhino for cad.

I will have to take a look at that... Cheers