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Re: Uneven surface problem - 7 years ago
That's great news, thanks for following up What's that taped to the side of your extruder - a laser?by JamesK - Printing
Re: Issues with printing larger objects - 7 years ago
That's great news - congratulations! I haven't come across that cause before, I'll have to keep it in mind as I have a fair collection of cheap pulleys. Sorry, I don't have editor rights on the wiki, but hopefully some-one else will add the info. Enjoy your printing againby JamesK - Printing
Re: Issues with printing larger objects - 7 years ago
QuoteA_Designs In my build, the X axis rods are carried by the Y axis's carriage, the X axis rods are about 8mm x 400mm long and the Y axis rods are 8mm x 500mm long. I generally print either in the center of the bed, or in one of the four quadrants, to avoid wearing out the PVA coating on the bed, and printing in different parts of the bed had no discernible influence on the drift. I haven't useby JamesK - Printing
Re: Issues with printing larger objects - 7 years ago
Interesting. A hot motor might lead us back towards binding as a possibility. One of the issues with H-bot/coreXY is that the belt tension pulls the sides together across what is conventionally the X axis, but looks like the Y axis in your build. I see you don't have a structural member bracing that axis in your build, so you are potentially vulnerable to the rods flexing and changing the separatby JamesK - Printing
Re: Piezoelectric disks for Z contact detect and bed levelling - 7 years ago
I'd also like to see a configurable safety limit on how far a Z-probe will keep looking for contact. Driving the hotend towards the bed is still quite the leap of faith for me - if the probe ever fails to detect we're in for a world of hurt. I could live with having to manually establish z0 to within 2mm of the bed before probing, and then having a 3mm max probe distance (or something along thoseby JamesK - General
Re: Issues with printing larger objects - 7 years ago
Oh. Jerk sounds high. Try taking that way down, just in case (e.g. start at 1 and see what happens). What's your moving mass like? Hmm, doesn't look too bad, and doesn't explain why the problem only affects one motor. Still feels like a possible wiring problem at the moment - did you try running a second set of wires for the motors to rule that out? emf/magnetics are unlikely to affect the motorby JamesK - Printing
Re: Issues with printing larger objects - 7 years ago
Ah, ok. If you've had it so the motors were running hot then we can probably rule out lack of current as the cause. The DRV8825 aren't that bad, at least not for cartesian printers. They are prone to creating surface artifacts because they don't handle the first few microsteps very well when there is a large difference between the supply voltage and the target voltage needed for the microstep curby JamesK - Printing
Re: Issues with printing larger objects - 7 years ago
Everything you describe is consistent with too little drive current. Please could you describe again how you calibrated the current?by JamesK - Printing
Re: Uneven surface problem - 7 years ago
QuoteDD The assumption is that by using full step multiples, at each layer position the Z motor will be sitting in one of the full step detents and not relying on the microstepping for position control which could result in variations in the bed's position. It's not that it sits in a full step position, but that it sits in the same (microstep) position relative to a full step for each layer. Theby JamesK - Printing
Re: Piezoelectric disks for Z contact detect and bed levelling - 7 years ago
QuoteECJ I do not understand why you care about this question of probing with the heated nozzle. Of course there is variation with heating, but I assume it's always the same. Here I do the probing with the cold nozzle and compensated with z offset and never had problems. Is there really any plausible reason to probe with the heated nozzle? I wonder what it is. The heated nozzle is primarily a coby JamesK - General
Re: Piezoelectric disks for Z contact detect and bed levelling - 7 years ago
I guess I ought to do the math, but I'm somewhat surprised that sub-micron accuracy is either necessary or achievable. A Z0 datum of half the layer height should be perfectly workable, and for distortion correction perhaps a little better is desirable. My virtual napkin calculation suggests anything with a repeatability of 20 to 30 microns should be fine. I'm currently printing on a bed that coulby JamesK - General
Re: Piezoelectric disks for Z contact detect and bed levelling - 7 years ago
Quoteand are an idea that I have only ever seen used on a 1960s electronics instructional kit. I had one like that!by JamesK - General
Re: PETG fumes/irritation? - 7 years ago
A healthy dose of skepticism is always a good idea From my point of view the issue is fairly straight forward; I don't like the smell from printing abs/nylon (and sometimes petg) and I'd like to reduce it if it's practical to do so. I'm going to enclose the printer anyway to improve thermal management, and once enclosed it's relatively easy to implement a recycling filter. Carbon+hepa filter mby JamesK - General
Re: Piezoelectric disks for Z contact detect and bed levelling - 7 years ago
Interesting. Would you be willing to test higher temperatures to determine where a few disks fell to below 0.25V? (Do they recover afterwards, or is this a destructive test?) Undrilled disks would be fine by me, although I'm sure others would be more interested in the drilled numbers.by JamesK - General
Re: PETG fumes/irritation? - 7 years ago
Hi Kerembyl, thanks for taking the time to post, and welcome to the forum. For whatever reason, that roll of red PETG was particularly bad for causing irritation. Since finishing and moving to a roll of black from the same manufacturer I haven't noticed anything like as much of a problem. I guess it's just another example of how much variation between different filaments exists. I'm looking forby JamesK - General
Re: nozzle height - mind blown, can you clarify - 7 years ago
Going to larger parts will show up problems with a non-flat bed. Mine is horribly bowed (glass clipped to a pcb heater) and it used to drive me nuts trying to print large parts. The only way I could do it was to compromise on the Z0 setting so that it was too close in the middle, but still too far at the corners, and then print the first layer extra thick to try and fill in the difference. The riby JamesK - Printing
Re: E3D to airbrush nozzle adapter - 7 years ago
Thanks Chri, that gives me lots to think about. It's interesting that you mention that most of the issues get worse at higher speeds - I have a heavy dual extruder print head, so I have to print pretty slowly. One of the things I've run into over and over again is that things I thought I understood to be 'true' only actually applied for the particular circumstances I was operating under at that pby JamesK - General
Re: E3D to airbrush nozzle adapter - 7 years ago
QuoteChri the width of the outcoming filament should not be wider than the nozzle output size. so for sure the filament output should flat (2nd picture) and not be round, but at least is should not be wider than the nozzle size. Chri That's an interesting suggestion Chri, what's the reasoning behind it? Clearly it 'can' be wider than the nozzle size as that is how 99% of the prints I make are doby JamesK - General
Re: In progress - hotend - 7 years ago
QuotePampajcs Do you have the drawings with dimentions? I would like to do this hotend. The design is in OnShape. I've not tried this before, but it looks like this link should get you to the document: If that doesn't work let me know and I'll export the drawing as some sort of image. Next time I make one I plan on deleting the fixing screw for the thermistor and adding a second thermistor hoby JamesK - Developers
Re: Piezoelectric disks for Z contact detect and bed levelling - 7 years ago
QuoteQuazzer Thanks JamesK. I guess you mean a bridge rectifier as used in this circuit. Oh, good find. Yes, very much like that, but with a comparator in place of the second op-amp. I also used a zener to clamp the input to the op-amp within safe limits as the piezo's are potentially capable of generating voltages above the supply voltage.by JamesK - General
Re: Piezoelectric disks for Z contact detect and bed levelling - 7 years ago
QuoteQuazzer Could you share your schematic withus please. In particular how do you rectify the signal? Thanks Sorry, I don't have a schematic done up. Rectification was just the typical diamond arrangement using four discrete diodes. One side of the resulting output is tied to ground, the other goes to the op-amp. I'm using the LM324 which copes with running on a single supply and is cheap onby JamesK - General
Re: PLA Printing issues - 7 years ago
PLA is the hardest plastic to extrude for the hotend. It softens at relatively low temperatures (around 60C), swells and produces very high friction against the walls of the throat. It is easiest to extrude with a hotend that takes the ptfe liner right to the junction with the nozzle. For hotends that don't do this you need to have the throat very well polished with no gaps in the area where theby JamesK - Printing
Re: Shift problem - sticky bearing? - 7 years ago
There are a lot of possibilities for shifted layers, you might want to work your way methodically through the following link: A slipping pulley is easily overlooked unless you put a witness mark across the end of the shaft and onto the pulley. Too high an acceleration can also be difficult to spot and may only show up as the weight on the platform increases later in the print, or with particulaby JamesK - Printing
Re: T8 leadscrew slop - 7 years ago
You've got no height to your bed support, so you're asking too much of the linear bearings. You need to add 3 or 4 inches of depth to the support with a second set of bearings at the bottom, then form a triangle out from the bearings to support the bed. Rather than trying to prevent twisting with a single 1" lm8uu you prevent it with the relative motion of two bearings separated by 1 or 2 inchesby JamesK - General
Re: My coreXY design is progressing to the build stage - 7 years ago
Congratulationsby JamesK - CoreXY Machines
Re: Piezoelectric disks for Z contact detect and bed levelling - 7 years ago
For my intended use case of three point under bed mounts I wanted to be able to cope with the bed moving in opposite directions at the sensors for some probing points, so my circuit rectifies the signal before passing it to the op-amp, and uses three separate channels with the output combined digitally at the comparator output. It's not particularly expensive using quad op-amp, quad comparators.by JamesK - General
Re: Inlet manifolds for a V8 - 7 years ago
Wow, they really are big. This is going to be quite the undertaking.by JamesK - Look what I made!
Re: Piezoelectric disks for Z contact detect and bed levelling - 7 years ago
QuoteDjDemonD Can I ask if anyone has any small scraps of various print surfaces, they would only need to be 2-3inch pieces? I am currently using aluminium and I have painters tape, hairspray, glass. I'd like to test -Printbite -PEI -buildtak -any other major surfaces I haven't thought of? That's very thorough of you I'm surprised that print surface makes much of a difference for a physical coby JamesK - General
Re: Z artefact - 7 years ago
Nice demonstration. PCB bed? I'm looking forward to replacing mine with something that stays flat.by JamesK - Printing
Re: X-Axis Sag Tolerance Question - 7 years ago
On my build the 8mm rods are clearly the weakest link in the design. It's not just vertical sag you need to worry about, but also twisting. If the nozzle is offset from the rods (which it will be in most hot end designs) then the error from the carriage twisting will rapidly dominate the error from sag. I'm inclined to the view that unsupported 8mm rods are too flexible to design well with in a pby JamesK - General