4' x 4' x 8" Router Build

[JAZZCNC]

The thicker the better as it significantly dampens vibrations which translates into cleaner cuts and longer tool life.
Don't be messing around with sand etc because while it dampens vibrations slightly the cost in performance due to the extra weight is too expensive for the returns.
Spending a little extra for Thicker steel will pay dividends in quality and stiffness.

For a machine this size I'd go with 60x60x5 as a minimum. It will give you a much stiffer machine than using 50x50. I've built machines this size using both sizes and 60x60 is the better choice.

[JonnyFive]

Neal / Jazz - thanks for the feedback.

I'll look at thickening things up, it does add up quite a bit - going from 50x50x4 to 50x50x5 to 60x60x5 each jump adds about £100 but I only want to build it once so want it to be right.

Jazz - I was only thinking of sand filling the static parts, I wasn't intending to fill the gantry - I'd be much happier not to have to do this. The gantry will be the same 160x80 ali extrusion whichever way I go with the frame.

Is the 50N loading a fair number?

Cheers!

[JAZZCNC]

The gantry will be the same 160x80 ali extrusion whichever way I go with the frame.

Is the 50N loading a fair number

The 50N loading in which direction.? However, to be honest, no matter the direction the correlation between simulation in SW and real-world when it comes to cutting and vibrations etc won't match.

What I can tell you from experience of building god knows how many steel-framed machines is that the extra cost of using thicker steel pays big time regards vibrations. The loads going into the machine don't come close to stressing the steel so it's not something worth fretting over.

Regards the Gantry then again most of my machines use HD ITEM Profile. If you want a much stiffer gantry then I'd suggest you change design slightly and go with L shape setup like I use. Over the years I've used both setups and the L shape is far far stiffer and two pieces of 120 x 80 arranged in an L shape gives much stiffer gantry with lower vibrations than single 160x80.

[JonnyFive]

The 50N loading in which direction.?

I'm referring to the reaction force of the machine pushing the cutter through the material so could be in any direction depending on which way the router is moving. My only reference point is using a hand router and it doesn't fell like it needs 50N to push the router along. I'm talking about the cutting force as shown on this diagram:

two pieces of 120 x 80 arranged in an L shape gives much stiffer gantry with lower vibrations than single 160x80

Do you mean 120 x 60? I can't find 120 x 80. I have run the calcs on the L section and I'm amazed how much difference it makes - you've convinced me! Do you have any examples of the machines you've made, I'd love to see them.

Cheers

[JonnyFive]

Do you mean 120 x 60? I can't find 120 x 80

Don't worry, I've found it - I was looking in the Profile 10/12 sections, it's in the Profile 8.

[JAZZCNC]

Don't worry, I've found it - I was looking in the Profile 10/12 sections, it's in the Profile 8.

Yes, the 8mm slot is better because gives more area for profile rail to sit onto.

[Gustave]

Hello JonnyFive, finally have you done the assembly of 2 x 120x80 suggested in the discussion or do you stay with 160 x 80 ?
Gustave

[JonnyFive]

Hello JonnyFive, finally have you done the assembly of 2 x 120x80 suggested in the discussion or do you stay with 160 x 80 ?

Hi Gustave, I haven’t done any assembly yet, I haven’t been able to spend any time on the project recently and I’m still tweaking the design. I will be using the 120x80 when I get around to it, the maths says it will be a lot stiffer.

Cheers.


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[Gustave]

Hi Gustave, I haven’t done any assembly yet, I haven’t been able to spend any time on the project recently and I’m still tweaking the design. I will be using the 120x80 when I get around to it, the maths says it will be a lot stiffer.

Cheers.


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Thank you, I think I will also going on L shape based on 120x80.
I am designing a nearby machine and I have the same R&P and ball-screw dilem ! For the moment I think going on ball-screw for price (Fred BST), precision, easy to achieve. The X is 1800mm length and I plan to use 2 x 2510 ball screws. I bought servos motors (Simdrive AC system 750W, Holding Torque (N.m)
2.4, Peak Torque (N.m) : 7.2, Rated Speed (rpm) : 3000) and I hesitate between direct drive or the use of pulley with a ratio 2: 1. Do you have any advice for me?
Best Regard

[JonnyFive]

RouterCNC - thanks for taking the time to explain all that, I appreciate it. I've had a bit of a play with your stiffness calculator spreadsheet and I'm getting gantry deflection of <0.05mm as I would expect following Jazz's advice.

I think I'm going to redo my frame design using 60x60x5 for the legs, 120x60x5 for the rail supports and maybe use 50x50x4 for the bed and triangulation / stiffeners.