Gallery, Projects and General > Project Logs
3D printer build log
Joules:
Nice work Tim and good approach, I think nrml is pretty spot on with his assessment on resonance. Quite a few comment on my print quality and the fact it only has 8mm rods and plastic carriage components. What they fail to grasp is the fact my print bed is only 150mm square. It's much less inclined to ring like a larger bed, the chassis on this machine is also a welded sheet steel box. Yes you can press the rear like one of those clicker frogs. However in normal operation nothing resonates. If the rear had done I would have glued or riveted a spine across it.
Following your build with interest, just flush out the Chinese linear bearings and pack them with a good (LM2) grease every year or so, they will pick up dust and dirt. Same reason I change the belts annually too.
spuddevans:
--- Quote from: Joules on May 08, 2017, 09:07:22 AM ---Following your build with interest, just flush out the Chinese linear bearings and pack them with a good (LM2) grease every year or so, they will pick up dust and dirt. Same reason I change the belts annually too.
--- End quote ---
Thanks Joules :thumbup: and thanks for the tip on flushing out the linear bearings and repacking :thumbup:
I got a little more done today (emphasis on "little"),
I tapped the 3 holes on each carriage M3. Then I made the pin that will screw in to hold the ball-raced pulleys. The plain pulley has a bore, or rather, the bearing in the plain pulley has a bore of 3mm, whereas the bearing in the toothed pulley has a bore of 5mm. So I turned up a stepped pin with a short section of M3 thread on each end, the idea being that the pin can be oriented either way up (as one carriage will have the plain pulley on the bottom, the other will have it on the top. ( I think ?!?!? ) )
Here's a pic.
I made it out of brass as it was easier, hopefully the forces will not be too much for brass, but I can re-make it out of steel if needed. I will be making a bracket that will fit on top to support the pin, so that will ease the forces applied to the pin.
Next up will be the aforementioned bracket.
Tim
tom osselton:
Here's a idea I thought was good
nrml:
Will you be using a water cooled hot end if you are going to have an enclosed build chamber?
PekkaNF:
--- Quote from: nrml on May 07, 2017, 08:08:03 PM ---In my experience (albeit limited), super rigidity isn't particularly necessary for a FDM printer. Vibration and resonance control are far more important and having a rigid all metal frame doesn't automatically eliminate this. In fact it might even make it more difficult to manage. I suspect (but can't prove) that having dis-similar materials in the frame might help break up resonance and might actually be advantageous. The forces and loads on a 3D printer are not really going to stress the frame and joints unless it is really poorly designed and / or put together. ...
--- End quote ---
I have no doubt that this observation is true to some extent, but I think that it's pretty much the same thing. Bit like flipside of the coin. Good question here is what is good enough and where the error budget goes.
There are some little hobby projects I am working and then there are some pretty big machines we build at the work, they have linear rails from 100 mm to 10 metres and nominal sizes of linear rails from 25 to 65 mm and up. Some "axis" are electrohydraulic, some electronic servo system. I may have learnt a thing or two from them.
All (steel) frames are flexible, increasing pipe/beam diameter makes structures stiffer and you can make servo loops faster compared to increasing the beam skin thickness.
Filling structures with concrete without much attention to some very exotic details is a bad idea. Immovable structures filled with various substances can have very good damping, but it all really "depends" on scale. Sometimes for unseen high frequency dampening internal stringer/plate might do the job, or carefully placed heavy weight highloss mat might do - for some violent shaking (that is not only very obvious to see but it's so hard that rattles your teeth off) might be dampened by loose glass spheres or granules of metal. Sometimes it just best to kill the excitation if you can.
Some stuff you really need FEA and accelerometers/impact hammer and megabucks equipment/software.
BUT some stuff is pretty easy and straight forward. Like putting rails/actuator on same plane and CG of the moving part as close to this plane as possible. And avoid at all cost forces/gravity to change loading direction. Few years ago I could not spell "Abbe error", now I have a rough idea what it is and recognize it....basically it is when angular error manifestes itself in linear (unwanted) motion or error:
http://www.mdpi.com/applsci/applsci-06-00156/article_deploy/html/images/applsci-06-00156-g012-1024.png
That I see in very many designs.
What I'm trying to say here that I definitely see merit here in this design. X/Y axis are very close to each others, which is good. What might be worth of having a look is that when X/Y axis shakes this structure, it will move in relation of the table...worst case scenario is that X/Y axis will excite table and table might move random direction, more than doubling the error. If that comes to play, making frame uprights more rigid, or dampening the coupling into table OR alternatively making coupling into the table more rigid should overcome it. Anyways I think that top of that machine shaking is easier to fix than Abbe error inherent to many design.
Pekka
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version