Gantry Aluminium thickness guidance

[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?

[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?

[njhussey]

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?

I did the same as you, only I'd built it hence how I know!! I bought two of these style for mine and they're great.

[dachopper]

44 Pounds !!!!!!!!!!!!!!!!!!!!!!!!!!!! wtf, is that hand cnc'd or something !

I think I will make a horizontal plate, that protrudes over the top of the housing, and just rotate it 90 degrees, bolt from above.

I have spare 13mm plate around, so job done

[njhussey]

44 Pounds !!!!!!!!!!!!!!!!!!!!!!!!!!!! wtf, is that hand cnc'd or something !

I think I will make a horizontal plate, that protrudes over the top of the housing, and just rotate it 90 degrees, bolt from above.

I have spare 13mm plate around, so job done

I did say that style....you can get them much cheaper if you buy the Chinese made ones on eBay or Aliexpress...:)

Sent from my HUAWEI VNS-L31 using Tapatalk

[dachopper]

Ok guys - here is my final design

20mm thick

May put gussets over the ballscrew attachment, but Ill wait and see how rigid it is without

Nick

[dachopper]

So it was a busy Christmass

Went with 20mm thick

What do you think?

[MikeyC38]

So it was a busy Christmass

Went with 20mm thick

What do you think?

Hi Nick
You have been busy! so have I, finally got my machine cutting. Anyway the 20mm plate on the gantry sides will give stiffness in the Y/Z plane. BTW I noticed on your Z-axis plate the bolts are raised. You should counter bore these so that the trucks for your Z axis will have some where to be located. Remember Jazz's comments about mounting the rails on the back of the plate which holds the spindle and the trucks and ballscrew get fitted to the plate as shown in your photo.

All the best and have a successfull 2017!

Regards
Mike