CNC Build Ep 2: How to Weld a CNC Base Table - For Better Cuts and Less Chatter! For my Avid CNC

[@CorbinDunn]

Update 2: I did add more supports, and it reduced flex a lot! kzbin.info/www/bejne/oZuog5yaZrCrppY

[@5280Woodworking]

My ShopSabre CNC says you’re looking a lot better than before 😊

[@CorbinDunn]

I added more steel later too! It’s now way too heavy for me to budge it.

[@MarkusHamm-l4l]

Congrets, really good work. I did the same, for a couple of years, with an other CNC-Mashine. I be with you. Great job! Best Regards Markus from Germany

[@CorbinDunn]

Thanks!

[@lowrider9367]

You may need to add some gusset supports on the legs to help stiffin this up. In addition, you can get into your CAM software & adjust how quickly your motors will start up. This is what I did on my machine & it helped out a lot with the movement of the machine.

[@CorbinDunn]

Yeah, you are spot on right! Check out episode 11 -- I did later add more supports, and it helped a lot. I also talk a little about reducing the acceleration in Mach 4; I eventually did do that, and it does help.

[@flemusslvandajivabjorn]

That table is massive - very nice job on that. Before doing the welding project did you consider adding stiffening members to the 80/20 table that the Avid came with? For example, I wonder if enclosing the base with 1/2" birch plywood attached directly to the aluminum would have been enough. Maybe even with accommodation for ballast, if needed.

[@CorbinDunn]

I hadn't thought of doing that; i'm not sure it would help, given where I see the table flex, which is mainly the legs, and the gantry. I can easily push the gantry 5-10 thou, but I haven't quite isolated where the play is at. I think it is more so in the motor/gearing than the 80/20, but I am not quite sure..

[@CorbinDunn]

Update: I've gotten some feedback on how to make it stiffer! I'll be doing some updates to the table pretty soon....I'll post back when I have more details on what I did. (Probably another video).

[@NSResponder]

Can't beat a granite surface plate. ;-)

[@CorbinDunn]

@@NSResponder I've got a tiny 4"x4" one I use for setting up tools - they are dead flat!

[@tysonserivce4884]

If it's dead level and don't want it to move anymore, weld some tabs on the legs and anchor right to the floor. No need to waste time with filling it with concrete.

[@CorbinDunn]

@@tysonserivce4884 The legs aren't moving with respect to the floor - it is heavy! It is actually the flex in the steel. I ended up welding on additional supports, which stiffened it up a ton. I also lowered the acceleration a bit in Mach 4. I'm pretty happy with it at this point, so I'm not going to do concrete. Video of doing that: kzbin.info/www/bejne/oZuog5yaZrCrppY

[@timtan7258]

Thank you very much for this video. So timely! I just got an Avid 6x12 table without the legs. Gonna assemble the table as a mockup under a set of 4x4s attached using simpson brackets. Purpose to gauge the size and overall girth of the system. And then I'll move on to getting 4in tubing :-)

[@CorbinDunn]

Awesome! Definitely check out the later Fusion 360 I did based on some feedback; it might be better to add some bottom bracing. I do get more movement than I'd like...and I'm hoping to solve it. I think it it would also work well to fill the tubes with concrete - some other people told me they did this and it helped for rigidity. I'm hoping to make some mods and post an update based on how well they work.

[@robertdiffin9136]

Just rough calculations here, if you used 4x4’s for the legs, filling the frame with sand would have added 500-600 pounds. I have no idea how that plays into the stability, as I don’t know how heavy it already was, but thought I’d do some figuring… 👍 Love your series.

[@CorbinDunn]

Yeah, that would add a lot of mass! I've got some more steel to stiffen up the table a bit....I'm going to test that first before filling it with some sand. I'll probably use sand instead of concrete so I can remove it, if need be.

[@jordanindustrialcompaction8381]

you could try heat straightening with a oxy fuel torch. heat up the affected zone. probably not worth it tho not as it is already assembled, and you can easily make it worse if your not careful.

[@CorbinDunn]

That is a good idea! I do have a torch..and I should have tried this. But yeah, it would be hard to do at this point..I'd have to completely disassemble it and remove the heavy gantry.

[@projetf5j348]

The problem is still the CTO, aluminium being really worse than steel.

[@joshpit2003]

Dang. I hate to say it, but I'm not convinced the steel table was worth it. Having to shim the aluminum extrusion on top kind of defeats the point of a sturdy, ridged base because you now have aluminum spanning a gap. I feel like in order to make this work (be better than the default aluminum) then you are going to need to: 1. Fill the gap (inject epoxy?) and 2. Have more tie-down points (so that the aluminum can't also flex upward, away from the epoxy/steel).

[@CorbinDunn]

oh man, you always have great ideas! Yeah, I think I should at a minimum add more tie down points to the table. Now that I know about 45 angle brackets...it would be super easy to do. I only used 6 tie down points; more might help absorb more vibration.

[@CorbinDunn]

I've also been a bit reluctant to add more tie down points because it would mean removing my spoilboard table to add in the tie down points. It isn't hard to remove...but I already have a bunch of precise locations drilled into it, and moving it would potentially change those positions a bit. I can dial it back in...but I'm sure it would never be 100% the same.

[@joshpit2003]

@@CorbinDunn Does the quest for rigidity even matter for your use? Are you seeing any artifacts in the cuts? And if so, how much acceleration reduction (job time increase) does it take to eliminate it? If you can get excellent parts at say a + 10-20% job time increase, then I'd say forget it. Run what you've got and stop thinking about it.

[@CorbinDunn]

@@joshpit2003 Those are good questions! I'm seeing chatter marks in my wood spoons/spatulas, and it is when a short y-axis movement happens. Currently I sand them out, but I hate sanding. I haven't experimented with reducing the acceleration yet; that is a good question. I'm going to add some code to Mach 4 to keep track of machining times so I can more easily track changes.

[@projetf5j348]

You fixed where this brand sucks the most. The table. I think that at least, a 4x8 feet machine should weight 2000 lbs.

[@CorbinDunn]

Yeah -- BUT I'm still not happy with it, and I'm going to weld in some bottom horizontal pieces and 45 degree supports. It still moves up to 0.010" along the y-axis! And yeah - I agree; there still isn't much one can do with the aluminum base; it doesn't flex much, but it does tend to "ring" a bit.