Ok so I have the Z accel sort of sorted. There is indeed electromechanical issues. Mainly a slipping clamp. Or rather a heatshrinked rubberhose joiner with no clamp.. Facepalm. Will print a new clamp soon and maybe get z max feed back up around 30mm/s. for now its only getting out by a tiny bit (aprox 0.1 every 50mm or so) and not causing serious problems. Aside from the odd printer kill due to no thermistor reading during z home travel.
The speeds I thought I was doing were no where near as high as I thought due to really low accel settings in firmware. Setting perimiter to 180mm/s was only printing at maybe 40-50mm/s due to not enough room to go faster... Setting it to 40mm/s = a 20mm cube with 2 shells and 2% infil taking 40-50 min to print! Slic3rs accel override highlighted the problem for me.
Had a play with slic3rs accel override settings. While it was useful to do. It mostly screwed a lot of stuff up, as no way to set different accel for print and non-print. So I spent 2 days trying to get rid of huge dags due (I think) to slow x-y&retract accel combined with extruder temps between 270 and 290 (did I mention I'm using abs?). The temp was around 240 as of my last post but this caused major warping and splitting. Still experimenting here. Going to learn to manually edit g-code soon and do a heat tower. I think my nozzle temp may be somewhat lower than heatblock temps... Its hard to k-probe accurately and its a craptastic Chinese hotend...
Printing faster is better than slower with the temps everything seems to work best at. If I slow down too much I get drooping, sagging and blockages. (blockage may be retraction, working on that now.)
Just turned Slic3rs accel control off and improved my firmware settings about 14 hours ago. I don't know what I did the first time, but its not super accelerating anymore.
Still running 2mm lift in custom g-code. Just so the nozzle heats off the bed if it needs to wait. I would still like to work out how to maintain this lift to start of print. As is, it drops down in home corner and shoots to start of print (fairly fast with latest x/y accel settings) at 0.35 or whatever my first layer hight is. It wont hit anything doing this, but it still makes me nervous.
I don't know what I did to my old firmware, but starting with a freshly unziped version and entering in my settings stopped Z exceeding the 5mm/s max feedrate.
So it was probably a PEBKAC error all along. Likely due to poor understanding of the maths involved (I'm good at maths but marlin is too complicated for me, I have no idea what library does what, or what lines of code are referring to another folder.)
I still have trying other software on my to do list. Got a copy of matter control downloaded. Just need to install. Have cura installed, but need to either change firmware baud rate or work out how to export g-code to be able to use it.(I'll work it out when I get time to have a play don't really like cura much)
I suspect that will offer some improvement. Although I have seen a few other people mention similar problems with slic3r and think it would be useful to solve.
At this point I think I have the unwanted Z accel problem fixed/patched. Was a combination of the custom g-code and something silly somewhere in my firmware.
the out of sync problem was mostly the poor clamp, and maybe a little bit the longer wires leading to one motor. I'll report back once the clamping is sorted. If wire length is a problem that will be easy to fix once its the only problem.
I could use some more speed advice though. My homing feedrate seems fine at 150/1 I still don't understand why a multiplier was used here. I think it was multiplying with other settings. I would love to better understand this if someone can point me to an article or any other parts of the firmware dealing with speed/accel. Same for the other accel rates. It seems a big part of the problem was me messing with stuff I understood poorly.
My current firmware is as follows.
Home max feedrate 150/1
steps per unit x&y 80.3, z379, e427. These are very close. within half a percent over 100mm. I'll get it better later. Half a percent too big is what I'm aiming for. Leaves a bit of meat for finishing...
Max feedrate 400, 400, 5, 300.
Max accel 3000, 3000, 5, 10000. I have been thinking about trying 1 on z. .5 could be interesting too. Although I think unnecessary with the multiplier removed from the max home rate. That may well be the source of the problem. I don't understand it enough to be sure. Is it an "accelerate too this speed" figure, or a multiplier ie max feedrate*accel rate?
Default accel 1000
max retract accel 3000
travel accel 2000
I also turned z jerk down to 0.05. I think that may have helped too. Need to go through a bunch of prints just changing one thing at a time in firmware to confirm exactly. Not sure I will find time. Would like to though so I can give something back to the community. Seen slic3r accel issues mentioned a bit in my googles, mostly bad layers like I had, and no solution I could find.
Right now I am looking at 2 other issues. I can probably work it out, and will start another thread for each if required. Although a quick tip may save me a few hours.
A. I am having trouble balancing flow rate between perimeter and solid infil/top fill. If I go up around 440 e steps. I get great solid layers, but over extrusion on the walls, which was the cause of the banding in the cube above (the one with the small gear in the pic). Turning e-steps down to 425-430 makes lovely walls, but a slightly gappy solid fill. Tried adjusting temp and speeds (one at a time) and had some results. But this leaves the solid infil so slow its causes blockages or the perimeter so fast its under extruding after retractions.
Not too worried about it at this point. Working on retractions first as it seems related.
B. retraction. I think my high temp is part of the problem. Its either leaving big dags everywhere with less than 2mm retract. or sucking up air with retracts over 2.25mm and then, either under extruding on start, blows big bubbles (they pop and crackle, at first I thought the plastic was boiling, then I realised it only happens after retracts.) or sometimes just over extrudes. My problem is it seems to be random. Some retracts suck air and some don’t. If it does suck air sometimes it blows a bubble and sometimes it doesn’t. I have looked for temp variation here, and there is a correlation with extruder fluctuation, but I don't think thats all of it. The type of layer it was doing and is about to do seem important too. Things with lots of retracts and short extrusions seem to suck the most air to the point it stops extruding at all. If it gets some good fast extrusions in over a bit of distance then it goes well with 2.75 retract and 0.25-0.275 extra length.
I have gone from 0.5 to 5 retract in 0.5 incriments. The magic number is around 2-3. Hopefully closer to 2. I was running 8 for some reason??
I have also tried a variety of exra length on restart settings. First none then progressing up to 0.3 in 0.1 steps, then some fine tuning back and forth with 0.01 and 0.005 steps, but more by intuition/guestimation rather than systematicly. As the 3 cubes I was printing took 2 hours a print and I was dialing in flow rate as well (I know, one setting at a time) I don't think I have tried all the extra lengths with all the retract lengths. Mostly been doing extra lengths between 2&3mm retract. Its not needed below 1.75 retract. I think the magic number for extra length is going to be somewhere around 0.2-0.25
I'm still in the early stages of calibrating this with my improved firmware. About to load up a faster retraction calibration test. Maybe one with bridges too as I got them pretty good on the 3 cube print yesterday (1-2%infil on xyz cubes).
I can probably work out the flow rate and retraction problems with a few more prints and some googling. Lots of good guides etc out there.
The Thing I mostly want help with is understanding those speed/accel maths better. Then I can probably mark this thread as solved
and stop drifting off topic
If I don't learn, I'll break it again... I couldn't learn to drive a manual gearbox until I re-built one... Same for most other things I have operated over the years. If I don't know how it works I end up crashing or breaking it..... Still can't drive an Auto gearbox (well I can for a bit, then it breaks or falls off the car)!
P.s. Mechabits. Sorry about my tone earlier. I was very frustrated and lacking sleep (still not had much). I should have thought that through a bit more. You are only trying to help. Thank you for being so patient and tolerant!
P.p.s. I think writing out my problem and re-reading it is a big part of the reason I make big improvements after posting here
P.p.p.s Attached are pics on my last two prints and the bucket of bolts that is my printer. The Wii box in the background is a functioning part of the printer. Blocking out drafts from the building layout and the ATX fan. It also has bits of soda can, used plumbing and old pallets as functional parts lol. 4 weeks ago I would have said this machine would never print this well. Now I think it can do a lot better. Its amazing something so wonky can work so well. Seriously, apply about 5 grams of pressure to any part and it will deflect a bit....
I was going to fix a bunch of stuff on it, but then I realised if I fixed everything up good. the only original parts left would be 5 motors, the hotbed and the arduino (RAMPS board had a small fire and is missing some traces). So once the flow rate and retraction issues are sorted. I'm welding up a better frame and printing a better printer
At which point I'll frame this as a memento or burn it. Haven't decided which yet. Don't tell Phil lol.. He still thinks he's getting it back lol..