Gantry Aluminium thickness guidance

[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

[dachopper]

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

Yeah, thanks for that, I realized this as I was staring at it yesterday, will have to counter bore to even get cart to slide past the bolt head I think.

I've decided to go the other route and mount the rail on the sides of the plate pictured, and just have the cart on the back of the spindle.

[JAZZCNC]

I've decided to go the other route and mount the rail on the sides of the plate pictured, and just have the cart on the back of the spindle.

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.

[dachopper]

Take 2,

I'm still not happy about having to put all this stuff on the k2 relay, but I can't seem to figure out any other easy way.