Migbot Prusa i3 Unofficial Support Thread

What stepper voltage on the pots are you guys using?

I am using 0.65 on x and y. 0.8 on z.

Glad to have found this Migbot Forum.
I have experienced many of the problems discussed and a few that were not discussed.
My x axis and z axis linear bearings came out of the bearing holders and make a mess of the print. The x got so bad I had to take a allen wrench and try to hold it in the bearing holder. The z was not as bad but when it came out (always the bottom bearing) the prints would finish but have very rough finish. To solve this I printed some bearing retainers that clip over the x and z 8mm smooth bars. They offer no resistance to movement of the axis and solved the MIA bearing problem.
Slow to heat up the bed to 50C. During a print the temperature of the extruder would drop by as much as 10 degrees and the bed would vary by 5 degrees. I was also skipping steps on the z axis. After weeks of tinkering with Marlin, adjusting stepper drivers, checking connections and voltages I gave up. I ordered a 24V 15amp power supply and a SSR-25DD solid state relay. I left the 12V power supply connected to the MKS base V1.2 board, I removed the bed heating cables from the MKS Base aan 2 small wires from the heater output on the MKS Base to the input of the SSR (keep polarity correct). Connected PS + output to the SSR + output, connect red bed heating cable to the SSR - output. Connected the black bed heater cable to the PS -. Bed heats to 50 degrees in about 2 min goes to 110 degrees in about 5 min. During printing both the extruder temperature and bed temperature are stable within 1 degree. The z missing steps have disappeared.
I hope these comments help someone.

That's good info about using a relay to heat the bed.
1. It's the extruder hooked up via relay as well, or did it get stable because the board is dealing with the heat bed anymore?
2. I have a 12V power supply. Think I can get benefits by hooking the bed up via relay even right a 24V supply?

Is anybody else having issues with the fan duct?

Mine appears to be aimed a bit high and the airflow hitting the nozzle tip. Once the fan kicks on the 2nd layer the nozzle tip drops a lot. Enough to hit the safety threshold where the extruder won't extrude.

I tried printing a replacement from here with no luck. [www.thingiverse.com]

What's everybody doing her for a fan duct?

Taking the bed heating load off of the MKS Base board made all the difference. The board only allows 11 amps to go to the bed heater which causes it heat slowly and not go high enough. Putting the heater on the SSR removed the competition for resources on the MKS board. At 12V the heater draws ~10 amps by attaching it to a 24 volt supply it draws 20 amps at 24V so I set #define MAX_BED_POWER 192 this limits the current draw to 15 amps at 24 volts for a total of 360 watts to the bed. The 24V supply I purchased was 15amps but the price was terrific $23.88 prime shipping [www.amazon.com]
I left the extruder heater on the MKS board it only draws about 3.3 amps.
I think you would benefit because the power supply that comes with the Migbot is really underpowered. Adding the 24V 15amp separate supply made sense to me because it was much cheaper than a single big supply.

So you're running both supplies?
Isn't there a way to use the 24V for everything?

I used this fan nozzle from thingiverse. Print it with the exhaust end down (I know it seems strange but it works) with support. The only real support produced will be for the arm that is suspended mid air. Not a perfect fit but much better than the one that came with the Migbot, it would get loose and drag into the print and really mess things up. This one also directs the air downward.
Good Luck

Edited 1 time(s). Last edit at 09/20/2015 08:49PM by gwc2795.

Yes the MKS board will take 24 volts but you are still limited to 11 amps for the bed heater. I intend to add the larger bed and heater so I strayed on the side of more bed watts.

I use a bang-bang 12 relay on my MK2 bed. Has no trouble at all. I like the clicks... let's me know it's working.

Hi,

Quote
gwc2795
Yes the MKS board will take 24 volts but you are still limited to 11 amps for the bed heater. I intend to add the larger bed and heater so I strayed on the side of more bed watts.

A MK2B uses 8A maximum under 24v.
You can go up to 264W under 24v.
If you want a large heatbed, you'd reather
consider any AC silicon heatbed.

++JM

just measured my amps: mks+extruder ~3-4amps; mks+heat bed !7amps :/ on 12v 23A psu

Thanks for the tip about the silicon bed heater.

The 20A 12V supply would not get the bed to 100 C in a reasonable time (less than 30 min) and when it did the bed temp and the extruder temp varied as much as 10 C. Since the 24V 15A supply has been added (keeping the 12V 20A supply to run the MKS board and extruder) the temperature variation on both bed and extruder has disappeared. Bed and extruder heat up in less than 5 min closer to 3. Still testing but -- it seems the Z axis has quit skipping steps.

For anybody in Canada looking for a power supply, here's the one I'm about to order. It matches the specs gwc2795 mentioned above. The pic even looks identical so it may very well be the exact same one.

[www.amazon.ca]

Let us know how it works

Here is a new one..Doing a print, everything going good, then it just stops. The screen say "Wait for user...". Never seen that before. Temps are staying up, it just isnt moving.

are you printing from your computer or an SD card

Does anyone know what size and brand SD card works with the Migbot?

What sensor do you use. after switching over to a glass bed. Since the originale sensor is only for 2mm?

Quote
gwc2795
are you printing from your computer or an SD card

Computer..Turns out it was something with the model. Ran it through Netfabb and it printed fine.

gwc2795 , most SD cards up to 4GB should work fine. But they MUST be Formatted as FAT

Thanks 3DST I only have 8GB will have to find some 4GB


I received Sandisk 8gb SDHC card. It was formatted as FAT32 and the Migbot read it without a problem. 9/26/15

Edited 1 time(s). Last edit at 09/26/2015 06:06AM by gwc2795.

I need to buy some ptfe for the M6 x 30MM throat. Any sources?

Hey fellas, I need some assistance. Tonight, I finally got around to printing replacement Migbot parts in ABS. During printing, the extruder stepper started to click and stopped feeding filament. I ended up breaking it down to find that the spring loaded tension pulley arm, (technical term?) that presses the filament against the spur gear, had split in half. I'm out of commission!
Is anyone willing to print both of the parts for the extruder in ABS and mail them to me? Should only be the two pieces and color doesn't matter. I can PayPal for payment.
Let me know please, thanks.

Josh

BTW, I live in the US 52001.

Edited 1 time(s). Last edit at 09/25/2015 11:15PM by jbehan.

Jbehan
My Migbot also cracked. I found that the 40 x0mm fan on the left of the extruder had failed. The fan blows against the hot end heat sink and keeps the upper components cool. I replaced it and that cooled everything down.

It is my understanding that the Migbot parts are printed out of PLA rather than ABS.

Edited 1 time(s). Last edit at 09/26/2015 11:23AM by gwc2795.

Not a good place for PLA! My fan is working fine but I was doing a 5 hour ABS print and I think it just got too hot. That's why I'm looking for someone to print the parts for me in ABS.

Anyone? I'll pay a reasonable fee!

They sell a all metal upgrade kit for approx 10 to 12 dollars. went that route.

All metal kit?! Where?

Yes, where?
I'm in on that one.