This actually is an interesting discussion: I did many tests with an ADXL345 and various printer foot designs (also cross-checking with real life print quality). My personal results are that my main printer is providing worse results (both in terms of ADXL measurement and real life quality) when rigidly mounted compared to mounting with soft rubber (sorbothane) feet.
My reasoning behind it: The acceleration and moving masses are causing forces and vibrations. If your printer is able to move as an entire system then the printhead / bed system will always move “in sync”. The dynamic forces are “drained” in this movement.
If you do a rigid mounting then these forces need to be “drained” in your frame and typically our hobby printers cannot really be considered as infinitely stiff systems (compared to industry printers that easily reach 500kg plus exactly for this reasons). This will cause relative displacements between bed and printhead leading to ghosting and ringing. YMMV
I agree with you, I think that feet with some degree of compliance are a must-have. But I think we are talking about different things. The problem at issue here is that the printer is mounted on a shaky table, and so the table will have its own resonant frequencies, separate from those of the printer, and that just makes the job of resonance compensation much harder.
I have just gone through this exercise with my own setup. I have a large bedslinger, and it was mounted on a very shaky table. I tried all sorts of feet (hard, closed cell foam, dense rubber, various densities of TPU printed feet) but they all had little impact. In the end, I totally over-engineered a solution by making massive braces between all the legs of the table, and that made it super rigid. I only got it finished about a month ago, and so far, the results have been great. The mass of the printer-bed in my setup will always be the weak link, but eliminating those extra resonances has helped enourmously.
I’ve attached a couple of pics of the braces I came up with
Thanks for that. You’re right about them being expensive! In Australia, they are around $AUD50 for a pack of 4 feet!
For anyone else interested, it appears that the weight loading is important when selecting Sorbothane feet, under-loading or over-loading will result in poor performance. I found this spec document from the manufacturer that gives the appropriate loadings for various diameter / stiffness feet which will help you find the right ones.
Well, much as I hate to have to admit it but this has largely been a waste of time and money. Whilst the gantry does a reasonably good job of stabilising the printer, the reality is that even when the printer shakes as it does, it doesn’t produce any noticeable print artefacts. I’ve just completed a series of tests at very high print speeds (post and video coming soon) and even tall objects printed at very high speed and with this gantry disabled, the prints come out very good indeed. I’m just amazed that the printer can shake about as it does without there being any noticeable degradation of print quality.
Cool project, but I’m lost as to why he spent all that time and money trying to fix a problem that he didn’t have in the first place! He had a printer that wasn’t producing “any noticeable print artefacts” to start with, so what end result was he hoping to achieve?
Not trying to dis the guy, I’ve got huge respect for his tinkering talents, just saying that he would be better off trying to solve problems that he does actually have
