Hi everyone, I was just wondering if anyone here has or has thought about mounting a fiber laser on their Avid. I have a product I currently sell that requires 4th axis fiber laser cutting to produce, and it would be awesome if I could do it in house on a machine I understand.
From what I know, you need quite a bit of new equipment for a fiber laser to work, but it seems possible aside from the possibility of damaging the aluminum extrusions below the work.
Thing about fiber laser is your surface quality completely depends on the rigidity of the machine.
I believe that’s an Avid clone but that should give you an idea of what one would look like
@subnoize Absolutely, definitely an issue right now, the amount of vibration in my stock 4x8 pro is huge! I will definitely be switching to a steel frame similar to @corbin 's when I move to a new shop space in the next few years when my shop lease runs out.
@Eric Thanks for sending that along, exactly what I was looking for. That avid clone is wild, so similar except with thicker vertical frame pieces. Also, that guy needs some eye protection, why the hell is he looking right at the laser while its cutting!
Which rings just as bad. Steel is just as bad if not worse than aluminum.
None of the augmentations I have seen online will work. They all suffer from the same problem as the aluminum extrusion, lack of bracing.
The problem are the two inline bearings on the gantry. They flex like crazy. The aluminum the linear rails are fixed to is just the little ears in that slot.
What would work better for gantries this large are 4 bearings each side riding on two linear rails. Those rails attached to rigid frame would be the solution. So the Y axis bearings should be exactly like the X axis carriage but replace the 8020 with gray cast iron.
All of the examples I have seen online just replace the legs and leave that 8020 attached to the linear rails, which is the source of the flex and ringing.
I don’t expect everyone to own the equipment I do to test these things but it is actually easy to see by locking the steppers and just pushing on the gantry.
The legs are only 10% of the problem. The table is sturdy considering the 8020 it’s made from. The gantry is the problem, at least on my machine. Those rails flex and the aluminum with it.
EXTRA: there should be floating bearings too. Not having them builds oscillations in the system during high speed motion.
Super interesting, thanks for sharing your thoughts on that vibration. The two linear rails on each side would make a lot of sense. Would involve a pretty serious rebuild but could be worth it.
Also, in another thread you showed the vibration reduction from clearpath g-stop: https://www.youtube.com/watch?v=Aj1LyYEvstw&t=1s Do you think it would make more sense to switch to servos and let them do the work on vibration reduction versus machine modifications?
Have you made any of these modifications yourself? I would be interested to see what your current setup looks like.
The Teknic g-stop function is part of the SCSK line of motors (software controlled stepper killers). Teknic makes the controllers but they do not write motion planners. A motion planner is your Mach4 or LinuxCNC.
To write a module for LinuxCNC would be about 2 years of work with a competent team.
But by then ML will probably have something better, right?
I can’t get the funding from the bank to finish my current little CNC project so I am going to try crowdfunding. Its “version 1.0” but not yet a kit. Turns out making kits is insanely expensive, never expected that myself 
If the crowdfunding works for that then I can start a long term project around ML motion planning. But you are years away from that unless somebody beats me to it.
Haha so that’s a bit out of reach. Excited to hear how your project develops! I imagine you could train it pretty well with some accelerometers or linear position sensors on each axis of the CNC.
Do you think that adding extra angle bracing at all intersections of the frame members would make a big difference? If it offers some improvement it could be easy to implement and not unreasonably expensive.
You can try. Aluminum is an excellent structural material. In the right form it is very rigid and durable on top of being corrosion resistant (accept for that little sodium nitrate problem for folks with water tables).
Yes, brace what you got. Making a steel table in exactly the same fashion as the old will give you worse results as steel’s wave period and frequency is nearly the same as aluminum. But with welding it will ensure better wave propagation through out the structure. Welding is an atomic joining process where as a bolt and nut is a loose fitting by its very nature.
Waves will meet more resistance when moving from component to component in a bolted structure than in a welded structure.
Here is my current stiffening plan, new members shown in color and labeled below:
Additional Lower Longitudinal Bracing:
Additional Upper Leg Bracing:
Additional Lower Leg Bracing:
I also considered a K-bracing system with angled members running from each upper corner to the center of lower leg bracing member after talking to an engineer that I work with. The tradeoff of reducing wood storage (and the accompanying mass of the wood) wasn’t worth it.
Yep, that would be a good start. I would start with joining the legs at the bottom first and see how much that helps before going with the next set of braces or gussets.
What sensor are you using to measure the vibration?
Right now I am just measuring with my sub-optimal dial indicator setup to measure overall deflection in the frame. Seeing the needle vibrate about .005" during and after Y-axis moves. X-axis is surprisingly solid.
I have seen other avid users download an app to measure vibration on their phone, I will do this before and after the upgrade to get some better data recording.
Everybody keeps talking but nobody is publishing numbers. Kind of makes it difficult to gauge success.
Cell phone accelerometers aren’t going to hack it either.
Here is the criteria we need to establish a baseline;
Then we can see a result. Otherwise we are just talking and not getting much done.
We should all settle on a standard. Something like this;
and maybe a STL for a PLA mount.
No soldering. Almost no programming. Single provider.
UPDATE: changed the openlog to the one without the IMU
I started looking at DIY CNC machines and there is interest in epoxy granite and ultra high performance concrete (UHPC) for machine bases and in conjunction with aluminum or steel frames. For DIY the obvious benefit over cast iron is that you don’t have to run a foundry. Another big one is that these seem to have drastically better vibration damping characteristics when compared to steel, aluminum or cast iron.
Have you thought about filling the void spaces in some of the 80/20 profiles with this material to improve help with the ringing? I don’t think that the 4080 profiles that come with the kits necessarily have enough void spaces in them to make a difference, but if some were 8080, you would have a significantly larger volume that you could use to change the characteristics of the system. I haven’t calculated how much mass it would add to the gantry, but the 8016 profile has lots of void space.
Maybe it could get us closer to the performance of a cast iron assembly without all the trouble.
