mazas
RRCRat Rig Community [Unofficial]
•Created by tg73 on 10/8/2024 in #fix-my-print
Regular surface distortion pattern towards end of larger first layers VC4
I also did a fully theoretical calculation, not based on FEM but just on the young modulus, geometry, temp coefficients and temp change. That gave results that are roughly in line with what we see with measurements with the alu. The deflection we see is lateral shift, not longitudinal. So, small changes in length will cause large(r) deflection.
2112 replies
RRCRat Rig Community [Unofficial]
•Created by tg73 on 10/8/2024 in #fix-my-print
Regular surface distortion pattern towards end of larger first layers VC4
A side-blowing fan seems indeed a good choice. Just fitting one in the current toolhead is a bit of a challenge, especially if you also need to keep the width at a minimum. That is why the “side-exiting/plenum” design was chosen as the next best option. And btw, I have now printed a few kg of PLA in a closed chamber, with enclosure temperature between 30-40C with that design, and have not had any heat creep issues, so it seems to adequate for that use case.
2112 replies
RRCRat Rig Community [Unofficial]
•Created by tg73 on 10/8/2024 in #fix-my-print
Regular surface distortion pattern towards end of larger first layers VC4
That second y-rail actually would be a worthy try. Easy, cheap, and has very few downsides. Ofc one issue is that we have not seen major shape changes that would be compatible with the y rail bending. But inability to detect does not mean the thing could not be there 🙂
2112 replies
RRCRat Rig Community [Unofficial]
•Created by tg73 on 10/8/2024 in #fix-my-print
Regular surface distortion pattern towards end of larger first layers VC4
My analysis of the situation with the Ti is nowhere near as complete or systematic as what we did with the alu, but so far it would seem like the Ti/Steel combination suffers from the issues, but to a significantly less degree. The one new issue with it is the non-monotonicity of the deflection. But regardless, the Ti is an excellent improvement over the alu/steel combination.
If you have other sources than gantry that you feel could be causing the issues with Ti, let us know an we can try to improve our understanding of the behavior.
2112 replies
RRCRat Rig Community [Unofficial]
•Created by tg73 on 10/8/2024 in #fix-my-print
Regular surface distortion pattern towards end of larger first layers VC4
Hot-tightening the gantry has the potential to make the overall variance of the height map lower. However, I have not seen reliable results indicating that it would significantly reduce the dritf. If someone has numbers to show this, I would be interested.
2112 replies
RRCRat Rig Community [Unofficial]
•Created by tg73 on 10/8/2024 in #fix-my-print
Regular surface distortion pattern towards end of larger first layers VC4
Not really a recent one, but have you read the pinned message?
2112 replies
RRCRat Rig Community [Unofficial]
•Created by tg73 on 10/8/2024 in #fix-my-print
Regular surface distortion pattern towards end of larger first layers VC4
Ok, ABS is a bit more challenging as the temps are higher :/.
2112 replies
RRCRat Rig Community [Unofficial]
•Created by tg73 on 10/8/2024 in #fix-my-print
Regular surface distortion pattern towards end of larger first layers VC4
That seems to a bit worse than my experience with PLA on the 400, but I guess you have a 500? What is your first layer height? What material, bed temperature, enclosure heating?
And yes, the head will slowly move up, as I showed in the earlier graph, but I seem to able to lay down a 0.2 mm first layer as long it takes less than 20 mins.
2112 replies
RRCRat Rig Community [Unofficial]
•Created by tg73 on 10/8/2024 in #fix-my-print
Regular surface distortion pattern towards end of larger first layers VC4
You are welcome to give it a go, but just be warned that a major source of force is the friction between the rail and the tube, and this is created/affected by the screw preload. And with PTFE washers under the screw head you actually would get more preload with the same tightening torque. So be careful. To be effective, the washers would need to go between the rail and the tube. And even there there is the risk of stiction, i.e. the release of the tension might be sudden, and cause artefacts in the print.
Hope that was not too discouraging, it is good to try, perhaps there is a solution to this somewhere..
2112 replies
RRCRat Rig Community [Unofficial]
•Created by tg73 on 10/8/2024 in #fix-my-print
Regular surface distortion pattern towards end of larger first layers VC4
klipper has the “z_thermal_adjust” feature that you could try
2112 replies
RRCRat Rig Community [Unofficial]
•Created by tg73 on 10/8/2024 in #fix-my-print
Regular surface distortion pattern towards end of larger first layers VC4
What you describe is the transfer function of the printer. I encourage you to develop one 🙂
I am not totally joking, as since we do no computational compensation today, any compensation could be better than the current. It is especially true for the seemingly monotonic drift we see with alu ganty. It might not be true for the non-monotonic drift with the ti tube.
2112 replies
RRCRat Rig Community [Unofficial]
•Created by tg73 on 10/8/2024 in #fix-my-print
Regular surface distortion pattern towards end of larger first layers VC4
Oh, i think I understand where part of our difference in views comes from. When I say several temperatures, I do not mean that we need several temperature measurements of the same position or component. I mean that we need the temperatures of several positions: the temperature of the top of the gantry, bottom of gantry, top of rail, end or rail, beacon mount, bed mid, bed sides… and all of these temperature points have different time constants. And they all affect the drift. To estimate their actual values you’d need to know how they behave as regards to time and different components being on or off, or the door opened or whatever. There is unfortunately no single magic temperature that would tell us what the state of the printer is.
2112 replies
RRCRat Rig Community [Unofficial]
•Created by tg73 on 10/8/2024 in #fix-my-print
Regular surface distortion pattern towards end of larger first layers VC4
Full shape change compensation would need the ability the affect the look-ahead calculation of the z position for future moves
2112 replies
RRCRat Rig Community [Unofficial]
•Created by tg73 on 10/8/2024 in #fix-my-print
Regular surface distortion pattern towards end of larger first layers VC4
A macro will not be able account for shape change. It will be able to babystep. Those are not the same, and in some cases a babystepping might be sufficient, but not in all cases
2112 replies
RRCRat Rig Community [Unofficial]
•Created by tg73 on 10/8/2024 in #fix-my-print
Regular surface distortion pattern towards end of larger first layers VC4
I have a slightly different view of the challenges, but you are ofc free to show me wrong 🙂
2112 replies
RRCRat Rig Community [Unofficial]
•Created by tg73 on 10/8/2024 in #fix-my-print
Regular surface distortion pattern towards end of larger first layers VC4
Yea, and it would need to be many temperatures, quite probably. Or an accurate model of the transfer function of the printer and well-controlled/measured environment.
And as @Helge Keck pointed out, with the current implementation of klipper we cannot fully compensate the shape change while printing. It is easy to shift/babystep, which might be enough for some cases. But a full dynamic compensation while printing might need some non-trivial software changes as well
2112 replies
RRCRat Rig Community [Unofficial]
•Created by tg73 on 10/8/2024 in #fix-my-print
Regular surface distortion pattern towards end of larger first layers VC4
I’d think math is not the issue here, other factors are way more challenging
2112 replies
RRCRat Rig Community [Unofficial]
•Created by tg73 on 10/8/2024 in #fix-my-print
Regular surface distortion pattern towards end of larger first layers VC4
The challenge there is that we have several components at different temperatures, and getting the full picture is challenging.
2112 replies
RRCRat Rig Community [Unofficial]
•Created by tg73 on 10/8/2024 in #fix-my-print
Regular surface distortion pattern towards end of larger first layers VC4
True, but it works for several mm of height
2112 replies
RRCRat Rig Community [Unofficial]
•Created by tg73 on 10/8/2024 in #fix-my-print
Regular surface distortion pattern towards end of larger first layers VC4
I did not say we have to do this with klipper 🙂
2112 replies