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View Full Version : Good or bad idea? Concreate!



craigrobbo
08-06-2012, 11:44 AM
Hi guys.

Okay, so my router should be here soon!

The cnc 3040, i was wondering to give the whole base some weight and a little more rigidity, would it be a good idea to fill in all the hollow sections of the extrusion with concrete/cement?

I know there maybe an issue of it coming loose - My other thought was flexible grout (similar weight to concrete).

There maybe other hollowed out places on the router too i could infill.

I am hoping this should help reduce some noise and help keep things a little sturdier?

Craig

Jonathan
08-06-2012, 11:53 AM
I know there maybe an issue of it coming loose - My other thought was flexible grout (similar weight to concrete).


That's the problem - it shrinks a bit when it sets and likes to 'move' and 'creep', so you could end up with it distorting the frame over a long period of time.

Epoxy granite is much better, except for the price of course. There's a huge discussion about it here:

http://www.cnczone.com/forums/epoxy_granite/

...however bear in mind their objective is to use it for the actual frame, not just to fill in which they require a good surface finish amongst other things. This clearly isn't an issue with just using it to fill in, so you probably don't need to worry about that and as such can just use a simple recipe:

http://www.cnccookbook.com/CCMillEpoxyFill.htm

Either way it's a great idea to add mass to the machine frame for strength and damping.

craigrobbo
08-06-2012, 12:16 PM
Thanks for that, some good read, especially in that 2nd link!

Gravel & sand - I think i'll give this one a shot, certainly makes more seance!

Craig

JAZZCNC
08-06-2012, 02:37 PM
Not sure which bits your meaning on 3040 to fill but I've got the slightly smaller 3020 here and the only part of the machine that could be filled is the bed extrusion.!

No way will you get concrete or Epoxy granite down the small extrusion holes due to the aggregate size, Epoxy alone won't had much resonance dampening or weight.

The thing you could and I would do is cap seal the extrusion at one end then pour kiln dryed sand into then cap and seal the other end. This way you can empty the extrusion if need be for moving about.!! . . . Far better and really simple has the extrusion end is pre drilled ready for tapping for bolts to hold the caps.
Sand is a brilliant resonance dampener and heavy.!!

craigrobbo
08-06-2012, 02:43 PM
Not sure which bits your meaning on 3040 to fill but I've got the slightly smaller 3020 here and the only part of the machine that could be filled is the bed extrusion.!

No way will you get concrete or Epoxy granite down the small extrusion holes due to the aggregate size, Epoxy alone won't had much resonance dampening or weight.

The thing you could and I would do is cap seal the extrusion at one end then pour kiln dryed sand into then cap and seal the other end. This way you can empty the extrusion if need be for moving about.!! . . . Far better and really simple has the extrusion end is pre drilled ready for tapping for bolts to hold the caps.
Sand is a brilliant resonance dampener and heavy.!!

Yes, the bed extrusions.

If aggregate is too large, how about epoxy & sand?

Jonathan
08-06-2012, 03:04 PM
Yes, the bed extrusions.

If aggregate is too large, how about epoxy & sand?

Epoxy and sand is a valid combination. The advantage of course with using epoxy over just sand is you will add strength. It's going to need to be very thin to go through the extrusion, bubbles/voids could be a problem.

The other question is, is it worth spending lots of money on epoxy on such a cheap machine. I think you would be better off upgrading other parts of the machine. Sand on it's own is basically free so you might as well try it.

craigrobbo
08-06-2012, 03:13 PM
Good point, Epoxy resin seems quite pricey these days.

Maybe sand & capping would be the better option for now.

Craig

JAZZCNC
08-06-2012, 03:20 PM
Ok just looked closely at the machine and suggest you forget the idea.?? I reckon the 3040 will use the same bed profile has this machine so should apply.!

The profile doesn't have any hollow section only the slots (see pic) so the only way to do it would be to remove the bed and fill the underside slots with Epoxy/sand etc and to me the slight bennifit offerd in strength and resonance dampening wouldn't justify the cost or the hassle.!
Plus when you have cut into the bed a few times (Which will happen) you won't be able to turn over and use other side of extrusion.!!

Edit: Ignore the threaded rod thru the extrusion that won't be there on your machine.!

craigrobbo
08-06-2012, 03:24 PM
That makes a lot of seance now, Thanks for clearing that up!

Maybe in time i will look at a different bed, but for now i'll just stick to stock.

Tenson
11-06-2012, 02:07 PM
I think the bed is far from the weakest link in the machine.

First you should replace the nylon nuts that fit to the threaded rod. This will give the moving parts more resistance against moving from vibrations and cutter backlash. No I don't know where to source these but if anyone does please let me know!

Secondly, if make sure the cutter spindle is one of the 800watt items rather than the air-cooled 200watt items (mine has). This should significantly increase the machines capability. http://www.ebay.co.uk/itm/0-8KW-WATER-COOLE-MILLING-AND-GRINDING-SPINDLE-MOTOR-WITH-1-5KW-INVERTER-VFD-q3-/230717802840?pt=UK_BOI_Industrial_Automation_Contr ol_ET&hash=item35b7da4958#ht_12533wt_1052

craigrobbo
11-06-2012, 02:15 PM
Thanks for that, My machine has the 1.5kw spindle not the 800 or 200.

Craig

JAZZCNC
11-06-2012, 04:13 PM
Secondly, if make sure the cutter spindle is one of the 800watt items rather than the air-cooled 200watt items (mine has). This should significantly increase the machines capability



Not necessarily.? It could and probably will make it worse due to the fact the Z Axis isnít built to handle the extra weight or cutting forces.

I can tell you for sure the Z Axis on the 3020 I have here wouldnít be able to handle the weight of the 1.5KW WC spindle and cutting forces without showing signs of both resonance/chatter on the work plus the extra strain on the motor/drive and Z axis components.!
I honestly think a larger spindle on this machine would shorten itís life considerably in both terms of wear on the Z Axis and the drives/motors working over time.? . . . And from the pics I see of the 3040 it doesnít look built any different and very much doubt the drives/motors are either.?

Tenson
11-06-2012, 04:19 PM
Actually I think mine must get more abuse as I continually try to cut stuff the spindle can hardly manage causing even more serious vibrations!

JAZZCNC
11-06-2012, 05:41 PM
Actually I think mine must get more abuse as I continually try to cut stuff the spindle can hardly manage causing even more serious vibrations!

Ok here's why I know it's a bad idea.!!

Have you felt the weight of these WC spindles dry they are no light weight.!! . . So if your machine vibrates now just think how the hell it will shake it's self to pieces with another 700W of power slinging another Kg or so weight about.!! Add to this the fact it's attached to a light weight Z axis connected to under powered motors run by weakling drives then I assure you it will show in one form or another.?
Then you have the longevity and abilty factor.! . . . These spindles are designed for high speeds and long duty cycles, basicly they will run for hours and days without need to stop for cooling.! . . . This machine and it's components can't do that and if it did manage to do it then it won't do it many times before the strain shows and it's wornout.

Then you have it's abilty, this spindle can far out perform the machine which is fine if you have the self will and control to only run the machine within it's limits.!! Most don't or won't so the machine will mostly be being over worked to keep up with the spindles abilty, again this will show sooner rather than later.

To handle and make the best use of these WC spindles these machines need serious upgrade on the Z axis and if not using ballscrews on the other Axis then be prepared to replace the plastic lead screw nuts often.!! Closely followed by a new TB drive board due to it's capitulation under the stress.!!!!!!

IMO. . It's too big a mismatch and money would be better spent put towards a stronger upto the task machine.!

boldford
17-07-2012, 10:34 PM
To add some weight to the base have you considered filling the voids with something like Biresin G26 loaded with gravel or lead shot?