Improving surface finish by increasing rigidity - Part One: The Base
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- čas přidán 25. 12. 2016
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I'm attempting to stiffen up the spindly frame in order to reduce vibrations and movement leading to better surface finishes on my parts. - Věda a technologie
Like the video and comments. My first thought was......... "Imagine they bolted it down instead of welding it place, lol"............... omg...... That plate is super hardcore though, can't imagine the cost. Thank God it was before Covid!
I don't usually like videos with no voice over... but this one was great... the dialogue between you and your friend (and your friend and us) was cool too.
Good channel you've got here.
Thanks, glad you liked it!
funny part is its gonna be a resonance/frequency issue, one odd bolt or plate will cure it, likely after 20 have been installed.
the easiest way is to weld in diagonal braces. amazing stiffening to be had for very little fine and money.
+Christopher Beasley That was my first thought but I was a little hesitant of doing much welding and warping the frame. I asked the askengineering subreddit and they all said just box it in with plate.
If you can fill the resulting box with sand, with some large styrofoam chunks to keep the weight reasonable, that might help to absorb vibrations.
I do really like that idea. There's even a handy hole cutout in the table top I could use to fill it. :P
Chris DePrisco that will work too!
Oh, that base. I see. Interesting.
I have some suggestions / I converted two acrolocs and tried the air ram on the Z . I used air tanks to give a more even load also tried anything from 10 - 95 pounds. Im using nema 34's 1850 oz. seems like it did cause a finish problem especially facing with air assist there seems to be a compromise on the Z- and Z+ alternately no matter what the settings.
The solution I found was to use a nema 42 4200 oz on the Z. over driven to keep it in the TQ range. No air If your motor is a true servo gearing it down could be the answer? Since they have a wider power band ( TQ at a higher RPM) maybe a planetary or 1"HD cog belt. no stretch and dampen vibration.
An acroloc M12 weighs 6500 lbs light in the CNC mill world. mass is a proven benefit but since your trying to do light cuts at high speeds you have to be care full about adding it to the parts that move. (which is were it would help the most.) Maybe fill tubes(the 4x6 tubing could be boxed and filled) with thin set? Or a product used for filling engine blocks called blockcreat. More mass or triangulation in the Z tower could help just clamp some plate in different areas and see what it effects then mount it permanent.
Really interesting series/project when your done it could look alot like the mill next to it.
Also learned some things from the series.IM SURE YOU HAVE CONSIDERED MANY OF THESE IDEAS ALREADY
Ok end of the novel
Ps Vibration is an interesting thing with steppers I could actually change the stall and characteristics of the borderline nema 34 by loosening and tightening the bolts in the heavy front panel on the Z tower and usually loose is better? allowing the panel to floate was probably creating a crude harmonic dampner.
+Tom Hutchins I'll have to give it a try with and without the air cylinder. The servo can move it without, no problem. I thought it would help, but maybe it hurts instead.
One more point OK maybe 2 . Its surprising how much you have done with that spindle but you may be at the limit. Seems like the spindle is cantilevered out from the z linear bearings pretty far? maybe lengthen and add mass to the neck and shorten the mount. Maybe some heavy rubber bonded to key areas and sandwiched under plate. will dampen harmonics and resonance frequencies
if your trying to stiffen your stand go after the four vertical squares first. the bottom makes a nice shelf, but probably wasn't flexing much.
+Christopher Beasley Don't spoil part two! :) Yea that's the next video but it still needs some editing. This was mostly for storage of scrap plates and extra weight.
The weight will help a lot if you're planning to use high accelerations. Once had a super stiff but too light stand with a high acceleration robot on top. The word "yikes" was used by several people. We settled on lag bolts into the concrete floor. ALL the MASS! ;-)
+Christopher Beasley Nice. Lol
Another thing you might be able to do is fill those tube cavities with lead shots, it'll dampen any vibrations.
+Moen I I wish I could but they are all welded shut.
Chris DePrisco If only you had some sort of tool for opening them back up... ;)
You could do it Doug Jackson (SV Seeker) style and pour molten lead inside for maximum weight by eliminating the air gaps. I don't know how much effect it would have but it could be done if you feel it's worth it.
You could use the MagDrill to make a hole on closed sections and poor the lead shots in.
thisoldtony vibrated stuff (shot? sand?) into the frames of his 3d router/mill/cutter frame. just clamp on orbital sander to item and fill via a small hole. you could also fill with epoxy+granite fines.
Can you even buy lead shot anymore? I think the EPA cracked down hard in recent years.
I dunno why you didn't just pour a bunch of concrete into the base, it'd be cheaper and easier. Brother fills their tapping center bases with a concrete like mixture for mass and vibration damping.
+eformance I really did want to do that but I was kind of afraid of the curing of such a huge block. I would definitely design my next to use concrete or epoxy granite.This worked pretty well though, stay tuned for the next video.
Are you kidding me? That steel plate should have gone in place of the large flimsy alu plate under your X-Y-table not at the bottom. There it is only dead weight. A milling machine is not a yacht....forgive them because they don't know what they do....hahahaha
Agreed. It may have been better t have built the whole machine using the steel baseplate. Bite the bullet and replace the alu baseplate.
Still using the $200 spindle? You're going to have the only machine with more playing their spindle bearings than motion in their table. Should be incredible with a new spindle though.
I am. I need to measure that some day. I know the runout is about 0.0002-0.0003" but I haven't thought of a good way to put pressure on the spindle bearings knowing that I'm measuring the bearings and not flex in the table/plate I'm applying pressure from.
can't just use an indicator from spindle housing to a tool and then push or pull on the tool?
I suppose if I use a thick tool so I'm not measuring the tool deflection but the actual spindle bearings. I also need to find a way to stick the indicator to the spindle since it's stainless steel; I don't think it's magnetic.
Haha you've got your legs swapped over in your engine crane. So the wheels aren't parallel and fight when you pull it along.
D'oh! I didn't notice they were different. My first time using one; figures I'd do something stupid!
That's one serious piece of steel - you must have a massive Xmas stocking. Naturally when I saw it coming off the pickup I assumed you were going to chop it up for stock on the PriscomatCNC. Good that your fingers and toes survived!
gloves...