I’m not on a concrete floor - my floor is wood frame, but should be more than strong enough. After going around and checking it, I think I just didn’t have the bolts tight enough. I’ve talked to the folks at 8020, and they suggested a torque of 20 ft lbs for the M8 bolts that connect the frame members. I haven’t had time to go over the entire frame yet, but I have tightened the fasteners on the front and rear crossmembers to 20 ft lb, and that’s stiffened the frame by quite a bit. As soon as I get the non-CNC project I’m working on out of the way, I’ll finish snugging up all of the fasteners, then update my progress.
thanks mark i’m still trying to decide on which brand to get yet
I’m in the same boat as many others here. Put the AVIDCNC together the way they suggest, and it just works. I do lots of plasma cutting that requires pretty fast travel speeds, at least when cutting thin material (300+ ipm) and I haven’t had leg stability issues.
When I ordered this machine, I ordered it in the ‘Tested’ configuration, 1/2 router, 1/2 plasma, 2x z-axis and the extra wide gantry. In that configuration there is a good amount of mass being moved around and the machine still performs well.
Just found this post!
I’m an engineer. Using aluminum, pound for pound, vs steel can actually be stiffer. A well designed bolted joint can be just as stiff as a welded joint. Those things are not really factors. The Avid design lacks adequate triangulation. Ideally you want a space frame or truss. You want to keep the table from twisting as the gantry is loaded side to side, and to keep vibration to a minimum. If you think of the ground as the most stable possible surface, then the frame base design should be to extend that stable surface to the table height. But if your floor is not stable, then all bets are off. I would add triangulation in both the x and y directions. That will sacrifice space under the table for storage. But you have to make tradeoffs, is stiffness more important or storage more important?
Don’t worry. Nobody will listen to you cuz somebody on YouTube told them that “steel is better” 
90% of the flex is at the bearings on the Y axis. Those little thin aluminum ears holding the linear rails flexes pretty far;
See my last post over here;
I can’t believe Avid offers a 6 hp spindle option with that teeny gantry upright plate. This tells me they are not engineers, they just want to sell parts.
From a Engineers point of view 
would there be any benefits to bolting the machine to the floor?
Absolutely! But makes it harder to move around.
That and bracing the legs. Buy some measured and drilled 8020 to go between the legs, done.
You can even call AvidCNC and they will send you the custom length parts complete with the hardware to attach it.
AvidCNC should make extra brace kits for those who have the need. It would be a revenue source.
If you don’t bolt the legs to the floor, at least get some metal feet to replace the wobbly rubber feet Avid gives you. Or, if you have access to another CNC or mill, make some larger pads with mounting holes for bolts and attach that to the bottom of the legs and use bolts in the mounting holes to adjust height.
Only if the feet are actually moving on the floor. If they aren’t, then the rest of the maching is going to move above the feet just the same if they are bolted down or not.
The whole machine moving to some degree isn’t necessarily bad, its the relative movement between the business end (spindle/plasma/laser) and the workpiece that most directly affects cut quality.
As Subnoise pointed out above, there is a lot of flex in the gantry connection to the main table. You can see that in laser cuts easily, the Y axis had an order of magnitude more movement for a direction change than the X axis. More mass to move, more flex in the bearings, etc.
In some states if you run a business all heavy machinery has to be secured to the floor. Some insurance companies like Progressive will not insure your business without tie downs on all equipment over 500lbs. Check your paperwork and ask your sales dude.
Any kind of accident at home and your homeowners insurance might not cover you because the equipment wasn’t properly installed.
Don’t believe a word I say, just check your policies and your local laws. Better safe than sorry, even if I am just some rando-interwebz guy 
Yep, that’s typically seismic constraints for earth quake zones to keep it from tipping over. Lots of rules around the height vs. width and weight of the tool. West Coast was always a pain to install equipment. Those are just for the safety rules, they don’t care if the machine runs like crap due to it’s own vibrations 
Georgia almost never shakes but we have laws governing equipment. If the manufacturer doesn’t put a securing strap then it doesn’t need to be secured…
However!
If the equipment does in fact move and results in injury and there were no straps or direction provided for securing the machine, the manufacturer is liable.
I am going through all this legal stuff right now. In fact I am shopping for insurance which is why I know this 
Well, I turn the page and there it is!
OSHA no less, federal regulations; OSHA standard 29 CFR 1910.212(b)
Insurance is really getting frustrating lately. They are looking for any excuse to not cover anything that is risky, but they are also raising premiums 10-20% per year on the stuff that is not risky, but is required by law or mortgage or whatever, because they have us over a barrel. I can’t imagine insurance for a machine shop, that must be a nightmare.
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Oh, you have no idea!
For everyone else, here is the full reg;
1910.212(b) Anchoring fixed machinery. Machines designed for a fixed location shall be securely anchored to prevent walking or moving.
Notice no mention of weight or straps…