You can test the limit switches by pressing them manually and typing M119. They are connected normally closed, so if a connection breaks they trigger, so it is hard to see why it would try to go past the endstop unless it somehow misses the switch. I am assuming you haven't changed the firmware? It's very odd that it would work on Windows but not on a Mac as these sorts of issues are due to wiriby nophead - Mendel90
Looks like all the switches are closed, i.e. not triggered. If it thinks Z is 0 it won't allow it to go any lower. What values do you get when you home the axes? X and Y should be -100 and Z about 202 when the limit switches are triggered.by nophead - Mendel90
What position does M114 return? What does M119 show?by nophead - Mendel90
Yes I probably should have done that. I didn't realise it was backwards until many had been sold. The only difference it makes when the origin is the centre is the bed contents are rotated with respect to the slicer / host view.by nophead - Mendel90
Mendel 90 is sort of backwards. I.e. those directions are correct when viewed from the back of the machine. Since the origin is in the middle of the bed it doesn't make much difference. If it starts in mid air then the Z axis is not calibrated. At Z = 0 the nozzle should just touch the bed (when it is hot). See the manual here for calibration instructions applicable to the firmware it shippedby nophead - Mendel90
I prefer PET tape to Kapton tape for ABS.by nophead - Mendel90
The firmware I supplied for Mendel90 has the origin in the centre of the bed, so you need to set up the slicer to place the object at 0,0 instead of the corner. In Skeinforge that is on the multiply tab.by nophead - Mendel90
Maybe you don't wait long enough for the hot end to expand to its full length. So when it does the outline it is high but by the time it does the infill it is too low. Plastic hot ends expand considerably when they heat up. Also some types of bed support expand.by nophead - Slic3r
You should definitely put EZ fuse tape over the heater block of the hot end. That makes a big difference to the amount of heat rising. One user has had success mounting a tiny fan under the carriage to blow across the top of the hot end. The normal nozzle size for Mendel90 is 0.4mm, so the filament will be moving slower with 0.3mm. There is a minimum flow rate with PLA, where no matter how weby nophead - General
The settings I used are here:by nophead - Mendel90
Yes we got them from Poundland in the UK.by nophead - Mendel90
We sourced them from this style of clothes peg. Bought hundreds of them and threw the plastic parts away because it was much cheaper than buying them from engineering companies.by nophead - Mendel90
Try turning the bed on in printrun and then moving the Z axis. My best guess is you have a bad connection from the power supply and the 12V rail is too low for two motors in series when the bed is on.by nophead - Mendel90
The IDC socket for the ribbon cable is 523-L17DAFRA15S The PCB mount plug isby nophead - Mendel90
You can just scrape the green solder resist off the copper plane surrounding the hole and bridge from the pin to the copper with a short length of copper wire. We don't have any stock but you might be able to buy one direct from our supplier here: htttp://www.werneth-electronics.com/home.php. We commissioned them and as far as I know they are the only ones with decent connectors and MOSFETs andby nophead - Mendel90
I always use VREG because it is more stable source of 5V. If you use 5V from the USB then it can reset if the PC drops the USB connection. As DC42 said in the other thread the USB cable getting hot implies the ground current is flowing through it due to a bad ground connection to the PSU. >it's only when I heat the bed that it draws power through the USB cable, when JP15 is set to VREG. Peby nophead - Mendel90
Yes the bed voltage should be close to 12V. I don't see how the USB cable can heat the bed other than providing the ground path if it is missing. Are you sure the Melzi ground terminal is connected properly? It might be worth checking back of the PCB.by nophead - Mendel90
Yes it is best to keep the jumper off for normal use so that USB disconnects don't cause a reset. If the jumper is off and the Melzi still resets then it must have lost the 12V momentarily. It could be a short on the bed connections but more likely the PSU doesn't like the unbalanced load and needs more dummy load on the 3.3V and 5V rails. You could look at the voltages on all three rails with aby nophead - Mendel90
The first problem does sound like your old PSU was failing. The capacitors wear out and the ripple increases until one of the rails goes over voltage on the peaks and it shuts down. The second problem does sound like a bad ground connection but it should be OK to have a short length of thinner wire. Or you could just use as many black wires as will fit if they are thicker. I.e. if you have roughby nophead - Mendel90
If you include M82 in your start gcode it will switch the firmware to absolute extrusion mode. I don't think Cura supports relative mode.by nophead - Mendel90
I tend to use heatfit threaded brass inserts instead of trapped nuts these days. I would try to move it nearer the hot end so it probes as close as possible. You can replace one of the wingnuts with one of these: to make room. I would probably just press fit an insert to make those nowadays rather than a captive nut. I haven't investigated Marlin's bed levelling or kept up with its developmentby nophead - Mendel90
Nearly all the parts are different because they use wood screws into the MDF frame instead of nuts and bolts. A few bits like the extruder parts are the same.by nophead - Mendel90
If you use LM8UU bearings with proper h6 tolerance precision ground rods there should no radial play because of the preload. With a single linear bearing you can get angular play but when used in a pair that disappears. I get about 0.2mm play with Igus RJMP bushings but not with LM8UU.by nophead - Mendel90
There shouldn't actually be any play in the bearings unless they are worn out. Linear bearings have pre-load, which means the balls are under tension between the outer shell and the rod. That is why they feel a bit lumpy because when the balls recirculate they have to squeeze into a gap smaller than their diameter. On the other hand, bushings are much smoother but they needs some clearance, so alby nophead - Mendel90
Are you saying the corners of the base lift if you print at 250mm/sec? I am confused by what you mean by "instead of the known problematic bowden concept" because Mendel90 doesn't use Bowden drive to feed the filament. Yes you can use a Flex3drive to make the X carriage lighter but the Y carriage is the heaviest axis.by nophead - Mendel90
All you need to do to prevent it wobbling is to place it on a firm flat surface. I have never seen the corners lift while it is printing.by nophead - Mendel90
They started with my version and modified it. I don't know what they did to stop make_machine.py working. If you change the build dimensions of my version I think most of the STL files stay the same but the bom files will have longer rods and belts and the the DXF files for the sheets will change. To generate those I would run bom.py and sheets.py but I don't know if they will work if make_machinby nophead - Mendel90
Sorry I now realise you mean the Think3DPrint3D version.by nophead - Mendel90
1. Yes X,Y. 2. I don't know what you mean by " laser-cut Mendel90 code". The Mendel90 acrylic version is here: and can be built with make_machine.py mendel.by nophead - Mendel90
I use Arduino 1.0.5 and ino with the same command line on Raspberry PIs and M42 works fine. Perhaps your Melzi board support package has got corrupted. I can't think what else would make M42 hang. The I/O library calls must be used in other places, not just M42.by nophead - Mendel90