Ultimaker + RepRap Heated Bed

[tachyio 0]

Wookay,

I managed to get a nice PCB heated bed from my local RepRap dealer, there actually is a RepRap dealer in Singapore now. O.O

Seems to me to be a 19V thing, so I guess I shall try to plug it into one of my v1.5.6 electronics board's green sockets. It actually says "heated bed" there.

I plan to also get a 19V 400W power supply brick for my Ultimaker...or is it safe to run two 120W 19V power supplies in parallel to the Ultimaker? That way I get an additional 120W for the heated bed.

My main issue though is that the kind dealer gave me a 100kOhm Thermistor, but the Ultimaker Add-On Wiki states that I will need a 4.7kOhm Thermistor.

Is there a way to make a 100kOhm Thermistor behave like a 4.7kOhm one?

Thanks guys I will post some photos of the tech that I got.

[tachyio 0]

Will putting 4900Ohms in parallel with the 100kOhm Thermistor, magically transform it into a 4.7kOhm Thermistor? Or am I just kidding myself?

[owen 19]

Hi

Not good to run two 120W 19V power supplies in parallel

Not sure about your Thermistor situation

[tachyio 0]

Hmm I flashed the firmware using a version of Marlin that supports a heated bed - using Daid's Marlin builder-

http://daid.eu/~daid/marlin_build/index.php

But now I'm getting a host of other problems, like the Ulticontroller not being able to move the steppers around, heated bed temperature being reported incorrectly, etc.

Hmm, I have both a 4.7kOhm and 100kOhm Thermistor at the moment, so trying to see which works best. Most threads say to use a 100kOhm Thermistor with a 4.7kOhm Resistor to form a 3-legged circuit - but I tried that and temperature reporting is still wonky.

Now I'm just not sure...

[magmotor 0]

or is it safe to run two 120W 19V power supplies in parallel to the Ultimaker? That way I get an additional 120W for the heated bed.

Hopefully you didn't put two 120W power supply's in parallel....that will definitely not work. you'll only get 60W- 3amps out of each line.....ohms law

[Daid 306]

or is it safe to run two 120W 19V power supplies in parallel to the Ultimaker? That way I get an additional 120W for the heated bed.

Hopefully you didn't put two 120W power supply's in parallel....that will definitely not work. you'll only get 60W- 3amps out of each line.....ohms law

Actually, most likely, you'll blow up one of them or both. You cannot put regulated supplies in parallel.

[magmotor 0]

Actually, most likely, you'll blow up one of them or both. You cannot put regulated supplies in parallel

Actually, you can. It's done all the time. You shouldn't put these small 120v a/c power supplys, that come with the kit in any parallel configuration. But supplys that have variable CV and CC can and are, put in circuits for higher current.

CONNECTING POWER SUPPLIES IN PARALLEL TO PRODUCE HIGHER CURRENT

Two or more power supplies being capable of CV/CC automatic cross over operation can be connected in parallel to obtain a total output current greater than that available from one power supply. The total output current is the sum of the output currents of the individual power supplies. The output of each power supply can be set separately. The output voltage controls of one power supply should be set to the desired output voltage (CV); the other power supplies should be set for a slightly higher output voltage. The supplies with the higher output voltage setting will provide constant current output, and will drop their output voltage until it equals the output of the CV supply.

[Daid 306]

Actually, most likely, you'll blow up one of them or both. You cannot put regulated supplies in parallel

Actually, you can. It's done all the time.

The key word is "regulated". With regulated supplies there are small differences in the supplies, one will try to regulate to 12.001V while the other will try to regulate to 11.999V for example. As the average voltage is 12.000 one supply will keep putting out more current, and the other will put out less. Until one of them blows. If you have expensive supplies they are protected and it will work, but we are talking about cheap power supplies here in most cases. Computer power supplies will blow. Not sure about the Ultimaker laptop brick.

(I am familiar with Kirchhoff's current law, I've done a year of EE)

[tachyio 0]

Sorry for the silence guys! I just moved into a horribly cold office room as my house was starting to get too small, temperatures in here average 14-16 degrees celsius...so struggling to get the heated bed working was taking up a lot of my time...After messing around with a few cheap china power supplies, I finally threw in the towel and invested in a laboratory power supply. It wasn't cheap about 350USD, but I know its rock-solid as I've used these before, and the best part is I CAN TUNE THE OUTPUT. I will probably use it to power something else in the future

My funny voltage and current list:

Normal Cold Day - 6V and 5.3A

Cold Rainy Day - 6.3V and 5.6A

Zomg, I am frigging DYING Cold DAY - 7V and 6.1A

I usually keep the bed around 70 to 80 Degrees C, a bit on the high-side I know, but it works at these low temps.

Printing is back to normal, though I think now my hobbed-bolt has worn-out and would need a replacement of some sort. I cleaned it twice, and still there is some skipping 5-10% of the time. I received my new hot-ends last week and finished installing and sealing up one of them, works great now, no more leaks and jams in there.

Photos of the heated bed and the lab power supply...thanks for the info though, I might try the parallel thing sometime when I have another machine in here.

Also I was struggling with reconfiguring Cura RC4 to work nicely with my Ultimaker, adjusting E-Steps, and fiddling with the new options, but I finally decided to turn off dwindle. Also with these frigid temperatures, I had to readjust the printing temperature and flow-rate, also printing slower helps a lot! It's still not super-stable software wise, but hanging in there. I might stick to RC2 for serious work.

[Daid 306]

Also I was struggling with reconfiguring Cura RC4 to work nicely with my Ultimaker, adjusting E-Steps, and fiddling with the new options, but I finally decided to turn off dwindle. Also with these frigid temperatures, I had to readjust the printing temperature and flow-rate, also printing slower helps a lot! It's still not super-stable software wise, but hanging in there. I might stick to RC2 for serious work.

Dwindle should be off by default... and the defaults match RC2. There shouldn't be any real difference between an RC2 and RC4 slice with default settings.

[tachyio 0]

I am actually thinking of constructing a nicely sealed hot-box for my Ultimaker. I notice that a lot of professional printers are encased in a sealed enclosure of some kind. Now I'm assuming that the purpose is to maintain a nice, constant internal temperature for printing.

Has anyone tried a hot-box? I think if I make one, I'll keep it around 50 Degrees C.

I also have a Prusa Mendel coming along for handling large, crude bulk parts. We'll see how that goes...it looks...primitive, compared to the Ultimaker...no hobbed bolt, printed parts that are not all that accurate, etc.

[tachyio 0]

Also I was struggling with reconfiguring Cura RC4 to work nicely with my Ultimaker, adjusting E-Steps, and fiddling with the new options, but I finally decided to turn off dwindle. Also with these frigid temperatures, I had to readjust the printing temperature and flow-rate, also printing slower helps a lot! It's still not super-stable software wise, but hanging in there. I might stick to RC2 for serious work.

Dwindle should be off by default... and the defaults match RC2. There shouldn't be any real difference between an RC2 and RC4 slice with default settings.

Hmm I am noticing strange behavior such as the top surfaces not being sealed, I did turn the "solid-infill for top" option in expert settings to ON. Also walls were too thick one time, and comb didn't appear to be working on one of the parts I printed; the Ultimaker would travel over a large empty section even though it was obvious a combed path was entirely possible :/

I am doing a third print with Cura RC4 now, will post photos when its done. Hope it comes out okay, but I can see unsealed top surfaces.

[tachyio 0]

Cura RC4 settings:

Just printing a reprap part, its okay, but outer surface isn't too smooth; I have uneven layers and some blobs. Also top-surfaces aren't filled-in, so you can see into the part from the top.

[tachyio 0]

Photos of the part, not sure why exactly, but I have uneven skin and blobbing, back like the ole days.

[tachyio 0]

I will try to correct this by printing at 220C, slightly faster at 35mm/sec, and reduce the infill overlap in expert settings to 27% from 32%...not sure if it will work though.

My belts appear tight, and I have weights at the bottom to provide damping.

[Daid 306]

Still looks like you have some backlash problem in the Y direction. As if the belts are not tight enough, did you check the small belt of the Y motor?

Blobs could happen if you have stops/buffer under-runs (I only see blobs in the curved area, which supports this claim) Are you printing with PrintRun, Cura itself or the UltiController?

[jenschr 6]

@Tachyio How big is your heated bed pcb and what is the name of the supplier? Curious as I've only seen the Prusa PCB mentioned on forums, but yours seem bigger?

J