anon4321

Hey I think I go it correct!!!! Silicon shows a peculiar profile, in that its electrical resistance increases with temperature up to about 160 °C, then starts decreasing, and drops further when the melting point is reached. This can lead to thermal runaway phenomena within internal regions of the semiconductor junction; the resistance decreases in the regions which become heated above this threshold, allowing more current to flow through the overheated regions, in turn causing yet more heating in comparison with the surrounding regions, which leads to further temperature increase and resistance decrease. This leads to the phenomenon of current crowding and formation of current filaments (similar to current hogging, but within a single device), and is one of the underlying causes of many semiconductor junction failures. http://en.wikipedia.org/wiki/Thermal_runaway

LOL, simple calculations!!!! I think that is the largest post I've seen here!!! You seem like you know a lot about electronics. I had a lot of it in college but went into software development so I forget a lot of the details for electronics and only remember the basics in electricity. Anyhoo, one thing about parallel vs serial you neglected is that I believe most non-semiconductor matter has a negative (or is it positive?) ohms to thermal coefficient (guess it would be positive) in that as their temperature increases so does their resistance. So in the parallel model, there will be tendency for the resistance it equalize as the lower resistance element will heat more and increase in resistance. This is in contrast to semiconductors that above a certain temperature, they enter a negative resistance to temperature coefficient and enter thermal runaway. They basically drop in resistance causing more current and more heat causing a drop in resistance and so on until POOF! I think.... but I might have been drunk at the time we were taught that stuff....

Regarding the force, yes that is a concern. But I don't know of any other way of doing it. Are there non contact sensors out there could be used and that have the resolution required that would work through alu and glass or steel if the UM1 heated bed is released?

You need to get that super-high-ultra-premium Z-stage done!!!! and shared!!!!!!1!11111one. I was thinking of a printed two piece bracket with one piece attached to the head and a microswitch to the other piece and have magnets in the right spots to repeatability and accurately "click" the two together (as long as the magnet surfaces are clean).

I suspect that the constant heating and cooling of the block causes the sensor to stick in the block, Get some high temp gloves and pliers and heat the block back up to temp and see if the sleeve loosens.

Nice, consider submitting to youmagine.com too.

At some point, I'd like to have a go at supporting OctoPrint directly from Cura.

Marlin supports: M300 - Play beepsound S P but I don't know if the UM1 and/or UM2 support it. Edit: I'm pretty sure that the UM1 without the ulticontroller has no way of beeping. For any printer, you could have the steppers play music! http://www.thingiverse.com/thing:11083

I suspect but can't guarantee that using the 19.5V PS would be fine as long as it's max temp is regulated. Just be clear that you can't power the bed through the UM shield as the power connector plug can't handle any more current that the printer uses. You need a relay driven from the bed output on the controller. If your bed doesn't have a thermistor in it, you would need to stick to a max of 18V as you would have no way of regulating the max temp.

Alternatively, you can use Cura to scale either part a little to account from shrinkage or lack thereof.

To be honest, this is already solved: http://www.thingiverse.com/thing:225584 I think what Jonny and I want is to make something like the above but without the servo and easily removed. I'm thinking magnets but haven't had time to design something.

Just FYI, you only need 3 points and the Marlin firmware supports the probing and planar calculation and transformation with (only) the three points. I believe you can set these points by recompiling the firmware. I suspected that the problems Daid encountered would prevent using the bed as a electrical contact for this. In Marlin, if you use a switch mounted on the head, you also need to tell Marlin the offset between the switch and the nozzle. In your solution this would be 0,0,0. Alas, because of those problems already mentioned, this won't work. The other issue with your acrylic bed solution is the lost of the print area as your holes would need to be reachable by the head and therefore in the print area. Furthermore, having the bolts in the bed means you aren't measuring the distance from the nozzle to the bed SURFACE but instead to the bold head. If the distance to the surface changes, for example because you don't use blue tape or you use kapton tape, you would need to dial in a different offset which is a little of a pain. I think that at least those three reasons are why people use the nozzle mounted switch.

The six axes should do away with overhangs.

If I were you, I would reflash the firmware using the *released* version of Cura and NOT any beta. Skip/cancel out of the first time wizard or checkup. To make sure you selected the correct machine in Cura, add a second machine and be sure to select Ultimaker Original and NOT Ultimaker2. Make sure the second machine is selected at the top of the Machine menu, Then go to the Machine menu and choose Install default firmware. See pages 38 then 37 here https://www.ultimaker.com/spree/uploads/38/original/Cura_User-Manual_v1.0.pdf Cura uses the machine type to select the correct firmware so be sure it is set correctly. Even if Cura can't communicate with the firmware, the update process talks to the bootloader in the Arduino by resetting it so you should be able to reflash it.

I'll defer to Steve because it's his thread, I don't what to tell you to change somebody else's thread. Assuming he is OK with it, change the thread title immediately since the UM1 info and discussion is already here even if it never is merged with the UM2 version and gcode in github and then delete mine (it was stupid to make it... sorry, I was riding high on the UM1 circle pr0n).

I would think that if it is a UM machine, the steps/mm default correctly in the firmware. If so, I would make sure the microstepping jumpers are correct and haven't become dislodged. I suggest you look on thingiverse for a calibration cube or something of a known dimension so you can measure. If the microstepping setting is the problem, you would see a size change by a factor of 2. So if you print something that is 20mm by 20mm and one side comes out to be 40mm, I'd suspect the microstepping.

If Steve is going to host the UM1 version in the same place or combine them, may I suggest that the moderators change the thread title to not be specific to the UM2 with Steve's permission? Then delete my other thread as it is both redundant and duplicative....

Wait, it may or may not.... You can see the beta leveling on a UM1 here : See the notes at the end of the marlin repo: https://github.com/ErikZalm/Marlin Anyway, once you have all the stuff setup, you just use G29 to initiate and use the leveling transform.

Errr sorry, that doesn't do the leveling just the distance.

I'm not sure about the UM2 but the UM1 board has two outputs for R/C type servos which you can control through gcode. In fact, the mathematical leveling I mentioned before can automate the lowering of the probe through the servo outputs. I believe for sensing it actually uses the Z stop input. So if you had a microswitch mounted manually, you just put in in series (what if NO, I guess parallel) with the upper Z switch (I believe). I would suspect that the UM2 also has the same servo outputs. Here is the more traditional way: http://www.thingiverse.com/thing:225584 There are some pics on connecting to the UM1 board. However, I believe that there are explicit connections in the middle of the board for servos. Maybe marlin uses a different servo number. Marlin has all this built-in. However, you might have to configure marlin for the specific setup. See the instructions for the gcode required to initiate the mathematically leveling process.

Gold dust ?

Hmmm, I wonder if laser printer toner could be used.

There is something to be said for an automated solution. I'm lazy and want to be able to control the UM remotely. However, getting a nice design even if manual would be a good start..

Jonny, Do you think microswitches have the repeatability required? I guess UM believes so since that what the UMs use. Do you think there is a particular microswitch that is particularly well suited for this?

Hey Steve, Yeah the .2925 is one of those magic numbers which is a multiple of the Z steps. It's probably better to change it to .3 so people don't wonder about it. You did most of the work, I just added the UM1 start and end gcode and the adjustment for the extrusion amount. I don't need credit and you can incorporate it as you see fit. The only thing is I accept NO liability for any damage done but using either version or any derivatives. USE AT YOUR OWN RISK. (lawyers..... sigh).