I might be crazy, buuuuut, if I am not?

[Savant_PCs]

Short version (to the best of my ability):

I am always looking for ways to increase rigidity and remove vibration in my machine to get the best possible cuts on my CNC router, especially when cutting clear acrylic parts. The machines main bed is a large few sections of aluminum T-slots with covers on the front and back and measure roughly 51" long. I finally undid the front cover to see what I am really working with and see this:


Here is my question and I have finally learned the lesson: its better to ask before spending the money on potential upgrades before understanding whether or not this will be a good idea or not.

Idea:

I want to fill the hollow interior of these aluminum T-slots with Epoxy Granite (20% epoxy, 80% sand) as I have recently learned what it is and how it has great anti-vibration qualities to it as well as making the machine heavier. I am also entertaining the idea of filling the welded steel table base its mounted to with sand or epoxy granite as well to get rid of any and all chatter caused by the gantry just not being up-to-snuff.

My initial thoughts:

I have never used epoxy granite. I have seen people fill older manual mills with epoxy granite with success so this is what got me thinking about this. I am slightly worried that the added weight may cause some bowing in the center of the machines table as the linear ways for the Y axis are mounted to the bottom of the T-slots.

I am a TOTAL sucker for tuning my machines to work even better than they initially arrive to my shop. I understand the manufacturers that make these machines have the burden of finding solutions to make their machines both economical and functional to the best of their ability so it always seems to me there is room for improvement with these machines if you have a decent understanding of the many different things available to you. Epoxy is pricey, sand is cheap, mix the too and this idea would probably be at or under $100 so I figured its worth its weight (pun intended) in functionality if it works even marginally.

So the question is: Am I crazy or...?

 

[Inferno]

If there's no expansion it doesn't seem like it would hurt.

 

[woodchucker]

as long as you don't add mass to the gantry, once you do, you change the speed that it works at, and will need new servos or steppers, and new belts...
doing the base causes no harm, only since they are static. anything moving I would not touch.

edit: BTW just adding sand or granite dust will make a huge difference to the stand. it actually will dampen it more than a hard fill. The reason being is it absorbs any hysteresis.

 

[Savant_PCs]

as long as you don't add mass to the gantry, once you do, you change the speed that it works at, and will need new servos or steppers, and new belts...
doing the base causes no harm, only since they are static. anything moving I would not touch.

edit: BTW just adding sand or granite dust will make a huge difference to the stand. it actually will dampen it more than a hard fill. The reason being is it absorbs any hysteresis.

That definitely makes a ton of sense and yes your right this does not effect moving parts. I would have already added the sand to the base table but got concerned as it has large threaded feet next to the casters to allow for leveling and I assume I would not be able to adjust those if the upright bars were full of sand.

 

[Boswell]

if those aluminum extrusions have an unsupported span of 51" (or close) then you may need to add one or two supports due to the additional weight. I would also suggest that you just fill with sand without the epoxy and see how that works. I bet pretty good.

Which specification(s) are you trying to improve and by how much?

 

[Savant_PCs]

if those aluminum extrusions have an unsupported span of 51" (or close) then you may need to add one or two supports due to the additional weight. I would also suggest that you just fill with sand without the epoxy and see how that works. I bet pretty good.

Which specification(s) are you trying to improve and by how much?

That definitely would help if it doesn't work as well because then I can take it out lol.

Basically vibration resistance and chatter to get better finishes on my plastic parts

 

[pontiac428]

Replace the 8020 bed extrusions with a single solid piece of cast aluminum plate (MIC-6). It will add mass, but more importantly, it will add rigidity to the whole plane, where planks favor one axis and neglect the other. Probably will cost less than epoxy, too.

 

[WesPete66]

Maybe you've already acted on this by now, but...
Is the bottom side of the bed accessible? If so, what about applying a metal plate to the bottom of the bed, using the "dovetails" of the extrusions to hold it in place? Maybe a wood slab? Maybe I'm the crazy one here?

 

[Savant_PCs]

Maybe you've already acted on this by now, but...
Is the bottom side of the bed accessible? If so, what about applying a metal plate to the bottom of the bed, using the "dovetails" of the extrusions to hold it in place? Maybe a wood slab? Maybe I'm the crazy one here?

lol were all a bit crazy, just a specturm

I have not yet. I got the sand ready and in the shop and I was thinking the easiest way to just add the sand to the insides of the T slots is to use a car jack to raise one side but its most likely going to be a 2 person job and my mechanic buddy has been super busy lately.

The underside is accessible and will be even more after I get a small shed to place my dust collector and air compressor into it. Until then I have enough wood that I could try this idea of yours as well. Anything that can rid me of the vibration in the machine is a plus at this point

 

[woodchucker]

just a thought about those screws. Can you make some cups from 3d print to fit inside the tubes, then throw them into the bottom and pour some thickened epoxy to protect the screws.