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.

[dachopper]

If you don't have need for tall material or long tools then wouldn't go that route as your losing stiffness for no reason. It's not more difficult building it the other way around.

Also have you realised that you'll need to space the rails off the plate or machine channel down centre to allow clearence for the ballscrew/bearings.?
Best if you take little from each plate depending on the ball nut mount the total need machining off is the distance from bearing face to ballscrew flat which is 45mm. Profiled rail and bearings total aprox 30mm depending on make, (Hi-Win HGH-20CA are 30mm) so I'll let you do the math.?
How you devide it upto you, I just split it in half.

I'm planning on using up to 200 mm z height, so really needed a design that maximizes this, when I put the first plate with back to back bearing blocks, it becomes hard to do them up ( I have to offset them , in gives less stiffness, down I loose z clearance, and up I have a greater z overhang for the same clearance. I can always bolt angle onto the spindle plate sides if on the future there is some play going on.

My plan is for the rails to be mounted flat on the back plate, I will add 15 mm spacers between the bearing block and the spindle plate to get the extra clearance as at the moment making a rail spacer, or counter sinking is far more work.

[JAZZCNC]

If you rush and make bodge of the Z axis you'll regret it. Z axis is THE most important part of machine get this wrong and you'll always have poor finish and excess tool wear.

The extra time taken to Mill slot, even with hand router will be worth it. It's the little details that are easy to skip that bite you in the arse later.!!