Porkpie

my UM2+ requires the top and bottom aluminum plates to be spaced exactly 16.90 mm apart. it came with a plastic spacer as original accessory to facilitate the adjustment. goal is to have back two vertical screws tightened, but front screws just tightened enough to get spacing of the aluminum plates correct, i.e., in parallel. hth.

i never suspected temp fluctuations on the print bed for one simple reason: the hysteretic control of the heatbed (i.e., in the original UM2+ FW) switches the bed on and off at deliberate times, but still much faster than the glass bed could follow those switching events. also, at higher build heights, one would expect the influence of the bed's thermal fluctuations to fully diminish, simply because the printing happens farther and farther away from the oszillating heat source. however, in reality, wall inconsistencies as shown in above picture do appear at any build height, not just close to the bed. that clearly contradicts the "thermal influence of the print bed" theory. you can prove this by using a front door on the UM2+, which you would close for, say, 20 print layers and then open for the next 20 print layers. that is a much mor drastic temp change to the printing process than the hysteretic heater control of the bed would cause. and still, the effect on the layers will be barely visible. so, yes, i suspected either a fluctuating power supply or voltage fluctuations on the GND plane of the Ultimainboard (rev. 2.14), which somehow seem to upset the circuitry inside the motor driver chips. the power splitter does away with both: 1. the Ultimainboard and its drivers now gets rock stable 24 VDC, which was previously fluctuating by approx. 100 mV, and 2. both extruder and bed heater have their own GND return paths that no longer interfere with the GND plane of the Ultimainboard. as to whether there was / is any effect on the stability of the 5 V supply, i can't tell for sure. i have never experienced any (power supply related) hangs on the digital part of the board, i would assume that the 5V was just fine from the beginning.

please check: heater cartridge cold resistance ok? while un-powered, can be tested with ohm meter directly at mainboard heater terminals while heater is connected. mind polarity, though: negative lead of meter must go to +24 V terminal on J21, positive lead must go to heater terminal on J21. setting = OHMS (or DIODE). if swapped, reading may be wrong. don't have value at hand, maybe somebody else can chime in and report. i would expect it to be R = V^2 / P = 576 V^2 / 25 W = 28 Ohms (but no more than 30 Ohms). if more, cartridge is bad, if ok, check: power supply voltage good at heater terminals while powered and heating up? if not, check power supply and MOSFET Q3. when set to 100 °C , does the nozzle read 100°C after heat-up, or is it lower? if it reads 100°C, check fastening of heater cartridge in olsson block. maybe heat transfer from cartridge to olsson block is impaired. HTH

yeah, this mod is no longer in operation on my trusty UM2+, as the BTT SKR 1.4 failed my expectations big time. anyway, here are the files. you need the lid for the controller box ("..plate_comb_stretch"), 4 pcs. of board holders and the PS adapter. for the PS mount, note that you _will_ need an extra beam (quadratic brass or aluminum profile, approx 0.2" x 0.2" to enforce the left mounting flange of the PS adapter. PLA isn't stiff enough, it will bend after some time. maybe PETG has better stability under load, but i didn't test it. have a look at the above picture, it is the golden bar with a center screw on the left hand side of the PS. sorry, can't find the STL for the PS terminal protection anymore. SKR14_plate_comb_stretch.stl SKR14_Mounting_Tab_4pcs.stl PS_Adapter_V2.stl

not sure what the issue is with your original board, but note that the replacement board from a**express.com has those pesky screw terminal instead of the much safer spring loaded ones on the original board.

Many moons ago, forum member [torgeir] reported a phenomenon on his UM2+, where he noticed wall inconsistencies on his prints that were related to effects from the hysteretic ("bang-bang") regulator of the bed heater. at that time , i was looking into that issue as well and came to the conclusion that,opposed to other's believes, the wall incosistencies did not arise from temperature fluctuations of the heated bed, but were actually caused by voltage fluctualtions of the main 24V power supply. to prove that, i altered the bed temp regulator in the firmware from hysteretic to PWM PID control. this made the wall incosistencies immediately disappear, but at the cost of (and again, pointing at a power supply issue) an ever so slightly and annoyingly flickering LED illumination. i tried to ignore the flickering, but alas, after a couple of months, i could no longer bear it and decided to do something about it. the idea was to split the main 24VDC bus from the main power supply into two branches: one branch would feed three MOSFET switches that would actuate BED, EXT1 and EXT2 by using the respective ultimaker main board's outputs as mere control signals, rather than as power-delivering outputs. the other branch would go into a beefy step-up regulator that would provide a super-tight regulated 24VDC power output to supply just the guts of the ultimaker main board itself, i.e., cpu, display, stepper drivers and all other paraphernalia. you can see the result of my efforts in the pictures below. the power supply is a fanless UHP-350-24, connected to an AC switch box that is mounted on the side of the printer, so that i have the main power switch accessible from the front side of the printer. the green-yellow PE connection is also connected to the 24VDC minus, to ensure that 24V-side electronics are not building up charge that could cause a destructive discharge when, say, connect the USB cable to it. the 24VDC output is connected to the "power splitter" board through the main entry fuse (2 polyfuses in parallel). to the left of the 24VDC entry point is the regulated 24VDC power output for the ultimaker board, also fused with a single polyfuse. on the right hand half of the power splitter you can spot three identical power trains BED, EXT1, EXT2 (EXT2 partially populated, not used), each consisting of a "real" gate-driving opto-coupler, a power MOSFET, a free-wheeling diode, an indicator LED and a polyfuse. BED doesn't have an extra fuse, it is using the 24VDC entry fuse, while EXT1, EXT2 do have their own fuses. the opto-couplers serve two purposes: they allow for noise isolation (not used here, but can be configured via jumpers), and drive the MOSFETs with sufficiently high gate voltages. in this case 12 VDC, which is generated on-board via the chunky device on the top left of the board. this in turn allows the MOSFETs to operate at 10 A continuously, while getting just warm to the touch. the two test cubes side-by-side tell the whole story. on the left cube, the center area is printed while bed heater is on, operating in the original hysteretic mode. top area is printed with the bed heater turned off. the right cube was printed with the power splitter installed and bed heater turned on with PID PWM control. both cubes were printed with Ultimaker Silver PLA, 60 °C bed, 210 °C nozzle 0.4mm, 0.15 mm Z, spiral mode, 40 mm/sec. bottom line and TL;DR: mind your power supply! p.s.: - you have seen a similar post from me before, discussing a different main board installation on the UM2+. well, it took me a while to figure out that the board would never live up to my expectations, so it had to leave the building, r.i.p.. - no, i'm not going to make this commercially available, as the boat for all UM2+ mods has set sail long time ago already. this mod was meant to be a proof of concept only.

prüf doch mal, ob dir ein elektriker für deinen carport einen separaten sicherungsautomaten setzen kann. denn, ernsthaft, wie genau kannst du schon vorhersagen, für wie lange dir dein nachbar den strom abdrehen wird / bereits abgedreht hat?

on my github, i've updated Configuration.h Configuration_adv.h pins_BTT_SKR_common.h for the latest changes. this is the configuration that my franken-UM2+ is now running on. i'm still sporadically getting a hard reset during print. not sure about the root cause of the issue, though. will exclude temperatures for now, as these are pretty constant at 60°C on the drivers and some 45°C on the processor. everything else, including the heatbed- and hotend-MOSFETs is running cooler than that ( measured 1 hour into a print). seems that the issue is gone when i do a hard reset right before a print, and is more likely to show up after a filament change and consecutive print w/o hard reset in between. idk. anyway, max speeds on x,y axes have to be diligently fine-tuned to avoid case resonances (and head resonances, especially the fan duct interacting with the hotend body, go figure!) to really enjoy the smoothness of the stepper motors on the TMC drivers. rule of thumb: to avoid resonances and at the same time maintain print quality, _increasing_ speeds may be way to go, rather than lowering them. otherwise, speed ripple of the stepper motors will bite you. for the z-axis, i can't go any higher than approx. 20 mm/s, or serious "screaming" will kick in, albeit not as nerve-wrecking as the original sound. on the other hand, the feeder is absolutely dead silent now, apart from the sporadic "cracking" on retract, that seems to be typical of the bondtech DDG that i am using.

that board seems to use MAXIM 31865 ADCs for RTD to digital conversion. this is not compatible with the BTT SKR 1.4 TURBO analog temperature inputs and requires an SPI connection to the host: MAX31865 datasheet

this is the final setup of the SKR V1.4 Turbo in my UM2+ chassis. without white cover and extra fan being off, the TMC5160 drivers easily reached 60°C @ 28°C ambient temperature, causing a hard reset of the SKR approx. 90 min into the prints on three different occasions. hence, i opted for forced cooling of the SKR, using a 12 VDC fan (60x60x10), connected to the 5VDC output of the DCDC module. also tried a 12VDC impeller from a radeon graphics card, connected to 5VDC. air flow was massive, but torque noise was way too loud. a note of caution: the heatsinks that BTT supplies with the TMC5160 are utter BS. they actually fell off the MOSFETs when the temperature reached 60°C. the MOSFETs btw don't need any cooling at all, i've tested that. its just the TMC5160 heating up the driver modules and the MOSFETs. so, for now, i'd call this mod done, my UM2+ is running not really silently, but much more silent than with the original stepper drivers. especially the many case resonances and the utter screaming of the Z-axis are gonsky. the USB "pigtail" will get an upgrade with a panel-mount adapter that fits into the original aperture on the back of the printer. next thing to tackle with is the noise of the part fans. two points remain, though: 1. many comments on the TMC5160 say that there is no heatsink required. why is the TMC5160 running so hot in my configuration? can somebody confirm the temperature of the drivers? i mean, did anybody else really measure the temp of the drivers? 2. i'd would have expected the steppers to run "dead silent" on the TMC5160. in fact, there is still a well audible humming (but no whining), when the steppers are moving. what's your experience? SKR14_axial60_lid.stl SKR14_imp_cass.stl SKR14_pcb_base_V2b.stl

nitrotech, you may want to wait for an upgrade of the mounting base, which will also have a cover plate. i'll be posting the upgrade here during the weekend. as for the diodes, the SSB44-E3 is a good fit in all places (heater as well as fan PWM). however you can basically use whatever you have on the shelf that has a minimum 4A / 40V rating, and is either a schottky or a "fast switching" diode with datasheet specs of trr < 200 ns. i did the fan PWM add-on on a piece of perfboard, as there is no point in doing a pcb for just a MOSFET and a diode. the kicad files on my github are just there for a clean documentation. to the best of my knowledge, there are (single channel) ready-made PT100-amplifiers available on ebay which should be an exact fit for the purpose. so you would need at least two of those for your SKR board. didn't look into the duet offerings, though. i still have a few unpopulated pcbs of the PT100-amplifier add-on that i did (1..3-channel), that i'm willing to part with for material and shipment compensation.

here you go. you need the base-plate and one set of 4 mounting tabs. two of those don't have holes, they are meant to be glued in place on the base-plate. for the two tabs with holes, you need two M3 brass inserts in the base plate and two M3 x 6 screws. (the rectangular cut-out was a q&d hack to make room for one of the Z-axis rods. the below stl has the corrected version with cut-out.) SKR14_Mounting_base.stl SKR14_Mounting_Tab_4pcs.stl

thanks anthrix for your findings! to take things a little bit further, i did some work lately on this particular topic, and these are my findings so far: 1. have some freewheeling diodes added to the PWM outputs of the SKR V1.4 to avoid overvoltage damage to the output MOSFETs: bigtreetech-skr-v1-4-turbo-freewheeling-diodes 2. also, do _not_ use smoothing capactors on PWM outputs. this is simply bad practice that puts a lot of extra stress on the MOSFETs. instead, use proper PWM settings in your MARLIN configuration. 3. TMC5160 drivers should have stealthchop enabled, but _disabled_ through the printer's config menu. this reduces noise of the steppers. 4. it took me quite some time to figure out the basic settings in MARLIN 2.0.5.3 to make it cooperate with the skr1.4 and the UM2+. besides that, you need some extra hardware to properly connect the PT100 sensors and the hotend-fan to the board. see more details on my github: Marlin+SKR1.4+TMC5160+UM2plus

https://community.ultimaker.com/topic/30786-ultimaker-with-skr-14/

the AD597 is a thermocouple conditioner, so, yeah, that's probably a thermocouple. find an online table somewhere that gives you type K voltages wrt temperature. measure the voltage at the wires when the sensor is at room temprature and note it down. note: these voltages are extremely small. your voltmeter has to be good at mV ranges. then, put the sensor in boiling water (i.e., 100°C exactly) and do another reading. do your measurements align with the values given in the table?