Gantry Aluminium thickness guidance

[dachopper]

Hi guys,

I have started acquiring components for a 1500x800x200 build area gantry style router, and still am undecided about the gantry end plate / x axis and z axis plate thickness required or recommended

I have seen some commercial hobby components as thin as 6mm aluminium for end plates, and read others recommending 15/16 minimum, or 20mm.

My Z height calls for an end piece of about 300 x 440 high. the X design has 2 x 80 x 80 T slot mounted with a 80mm gap for the X motor and ballscrew in the middle, then a 170 gap below to the mount plate on the Y axis



Can anyone give some advice on what happens if it's too thin, and what would work.

If guys use 20mm for the end plates, what do they use for the x axis and z axis plates?


All advice appreciated
Nick

[dachopper]

Hi guys,

I have started acquiring components for a 1500x800x200 build area gantry style router, and still am undecided about the gantry end plate / x axis and z axis plate thickness required or recommended

I have seen some commercial hobby components as thin as 6mm aluminium for end plates, and read others recommending 15/16 minimum, or 20mm.

My Z height calls for an end piece of about 300 x 440 high. the X design has 2 x 80 x 80 T slot mounted with a 80mm gap for the X motor and ballscrew in the middle, then a 170 gap below to the mount plate on the Y axis



Can anyone give some advice on what happens if it's too thin, and what would work.

If guys use 20mm for the end plates, what do they use for the x axis and z axis plates?


All advice appreciated
Nick

60 views and no advice, someone must have an idea

[njhussey]

Hi Nick,

Welcome to the forum don't get hung up on views and no replies...it's hard to give a meaningful reply without knowing a bit more so most people will shy away from giving advice. It's a bit like saying I've a room to paint, how much paint do I need? Have you got a cad drawing of your router we can look at? What are you aiming to cut, how long is your Z axis etc. etc. etc. The strength/thickness needed will depend a lot on your design and what you're looking to cut, give us some more to go on and we'll help you out.

[Robin Hewitt]

End plates for a gantry? So what happens when you accelerate the head hard along the gantry or the tool plunges in to the side of something resilient? That is the moment you realise that a plate simply does not cut the mustard and you really needed to think in triangles.

[dachopper]

End plates for a gantry? So what happens when you accelerate the head hard along the gantry or the tool plunges in to the side of something resilient? That is the moment you realise that a plate simply does not cut the mustard and you really needed to think in triangles.

Well, the Nema 23 will probably stall if all of the end stops fail. Chances of that happening......

What happens if I'm using a tube design with thin walls and the plate rams the thin skinned tube?

Here is the basic design.

The Y extrusion is quite big, 80x160, and the others are all 80/80 profile.

This is the rough plan

This is where I'm up to



To be used for 3d Printing, Composite 3d milling, wood, and possibly aluminum

[njhussey]

Well, the Nema 23 will probably stall if all of the end stops fail. Chances of that happening......

Greater than you think....well if your home switch becomes loose from vibrations (fast trochoidal milling) so your gantry slams on a rapid home into the side beams.....luckily the AM882's have stall detect!!

What happens if I'm using a tube design with thin walls and the plate rams the thin skinned tube?

Guess it'll bend it!

Here is the basic design.

The Y extrusion is quite big, 80x160, and the others are all 80/80 profile.

This is the rough plan

This is where I'm up to



To be used for 3d Printing, Composite 3d milling, wood, and possibly aluminum

Somewhere on the forum there is a bending moment calculator which will sort this for you, however I'd say minimum of 15mm for the plates, and for the difference in cost go 20mm, and I'd strongly consider putting a plate across your two 80*80 Z axis extrusions to stiffen up the gantry.

for the Z axis I'd put thicker plates on as those don't look that thick and I'd put the rails on the front plate not back to stiffen it up. I'd also consider connecting your motors to the ballscrews via belts and pulleys rather than directly, this helps take out any resonance (from cutting) and stops it being fed back to the stepper motors.

If you're using the ballnut housing that's in picture 2 how are you going to connect it to your Y axis plates, you'll not get to the screws behind it to tighten it?

[MikeyC38]

Hi Nick

As others have said, you do need to be more specific which you have done by showing details of your build and what you intend to cut. Rigidity is your best friend for any cnc build and as others have said plates across the end of the long axis will stiffen the frame significantly. In my build here I used 80 x 40 heavy gauge extrusions ( 4kgm+) with 15mm 6082 T6 plates either end. The gantry sides are 20mm 6082 T6 water jet cut with heavy gauge 80 x 40 extrusion for the (short) y-axis. I am very pleased with the overall rigidity but will reserve judgement until I do my first cuts on metal. It might appear over engineered but I took the advice offered on the forum and I'm confident the machine will deliver the levels of accuracy I need. The use case for my machine is cutting balsa, hardwoods and aluminium at reasonable speeds, hence the robustness of the construction for the most difficult use case (cutting aluminium).

Hope this helps

Mike

[JAZZCNC]

End plates for a gantry? So what happens when you accelerate the head hard along the gantry or the tool plunges in to the side of something resilient? That is the moment you realise that a plate simply does not cut the mustard and you really needed to think in triangles.

Another really helpful comprehensive post robin from your Vast experience.!! . . . . Why don't you just shut up if can't give relevent and helpful comments.

You didn't even think to ask about Style of router and what his uses for it where.! . . . The design he's using will work fine for his needs and his question for plate thickness is perfectly valid with this design.! . . . He didn't need sarcastic pointless reply about triangles when all he asked was for plate thickness for Gantry sides.

60 views and no advice, someone must have an idea

It's long way to OZ there's time delay.!!!

I build similair design and depending on the Gantry side heights either 15 or 20mm will work. The Red machine uses 15mm sides but as lower sides. White one uses 20mm.
Like wise the Red machines uses Z axis with Rails on the front plates like has been suggested. However the White one is the other way around.?

Reason for this is down to usage. The red machine was designed just to cut thinner material upto 75mm. It will happily cut upto aluminium.
The white machine had requirement to cut deep material with long tools in Clay model board which isn't very hard material. This required the spindle lifting higher to allow for long tool hence rails on back plate.
Both machines will happily cut aluminium with light cuts, infact the very first Job the customer cut was 4 x aluminium plates for where the machine fastens to the base frame which you can just see on one of pics where machine meets frame.(I only supplied the machine)

Me personaly I would use 20mm every where, even Z axis. Also with Z axis if don't need long tools or deep cuts then would always go with rails on front plate.

Regards the frame and gantry then I'd consider a few bracing plates like been suggested. . . . Hey maybe even cut them in triangle shape.!!

With little bit of bracing then this design will easily do everything you asked about. Aluminium work will require lighter DOC cuts but will still handle it no problem.

Good luck and keep it up.

[routercnc]

I'm glad I waited for the design sketches as I mis-understood your question in the first post, now it is clearer.

Gantry end plates at least 15mm, more like 20mm to give yourself a chance with the aluminium machining. 1500x800mm is a large machine and stiffness drops considerably as you go bigger. Really I would recommend raised X axis designs for aluminium but you here now so need to recover what you can.

Long axis (I would call it X) end plates are to stop the machine ploughing off the end of the rails but you'd be surprised how powerful the steppers as when driven through the force multiplying effect of the ballscrew. You could sit on the gantry for example and it would move you around without a problem.
I would not go for 6mm end plates, but 10-15mm as a guide. Final decision would most likely be decided on if you can cut them out of an offcut plate used elsewhere as they would be quite small. The other thing to consider is they normally double up as stepper motor mounts for the X ballscrews so that will also drive the thickness.

Z axis and Y axis plates would go for 20mm personally.

[dachopper]

Greater than you think....well if your home switch becomes loose from vibrations (fast trochoidal milling) so your gantry slams on a rapid home into the side beams.....luckily the AM882's have stall detect!!



Guess it'll bend it!



Somewhere on the forum there is a bending moment calculator which will sort this for you, however I'd say minimum of 15mm for the plates, and for the difference in cost go 20mm, and I'd strongly consider putting a plate across your two 80*80 Z axis extrusions to stiffen up the gantry.

for the Z axis I'd put thicker plates on as those don't look that thick and I'd put the rails on the front plate not back to stiffen it up. I'd also consider connecting your motors to the ballscrews via belts and pulleys rather than directly, this helps take out any resonance (from cutting) and stops it being fed back to the stepper motors.

If you're using the ballnut housing that's in picture 2 how are you going to connect it to your Y axis plates, you'll not get to the screws behind it to tighten it?

Good point - any tips?

I can do it up before installing, but that will be loaded with alignment danger

I could install a horizontal shelf over the top of it, rotate the flat face 90 so it points up, and do it up from the top instead of on the side?