Inconsistent layers with hot bed on. Perfect with hot bed off !?!?

Edit: I realized this is related to the hot bed, maybe electrical or otherwise. With hot bed off prints are perfect, with it on the quality is poor - pictures a few posts down.

This is a new post that summarizes a lot from an old post to see if anyone can help identify the problem: [forums.reprap.org]

In short, I'm getting inconsistent layers - they become much worse as the print builds higher. I've tried a few things:
-tightening down the frame to prevent z wobble (it only moves maybe 2mm if I apply a lot of force on the top)
-adding anti-backlash pieces [www.thingiverse.com]
-increasing extruder temperature
-changing the hotend
-adjust motor current (from 0.6 Vref to 1.1Vref on a polulu)
-change stepper driver
-clean the coarse gear driving the filament

If you look at the first print picture, you can see that some layers are more opaque while some are more translucent. The bottom of the print is nice and smooth, and presumably this is how it should print.

Pictures: [www.dropbox.com]

Any help would be appreciated! I'm out of ideas =/

Edited 3 time(s). Last edit at 06/26/2015 12:03AM by geemoto.

Does anyone know if there could be problems with overtightening the nozzle on the hotend?? I forced it quite tight - maybe I should loosen? There is a serious amount of pressure in the nozzle, even after extrusion stops there is still a fair amount of flow out of the nozzle - is this normal? It happened when I paused a print, but doesn't seem to happen so much if I just extrude manually. =/

Edited 2 time(s). Last edit at 06/25/2015 08:11PM by geemoto.

Ooze is quite normal at the end of the print (at least for me), and the only problem you may have when you tighten the nozzle too much, is that you break something. If you did not already, then it is fine.

Edited 1 time(s). Last edit at 06/25/2015 08:38PM by cristian.

Quote
cristian
Ooze is quite normal at the end of the print (at least for me), and the only problem you may have when you tighten the nozzle too much, is that you break something. If you did not already, then it is fine.

Thanks.

I also have 4 fans connected to a single 5V output on the RAMPS board - would this be an issue? (grasping at straws)

Edited 1 time(s). Last edit at 06/25/2015 08:42PM by geemoto.

I just turned the heated bed off. PERFECT prints. I'm going to look into this a bit more to confirm, any ideas why this might be? =/

Only 10.5V is getting to the hot bed as well.

Without bed (left), with bed (right). This must be some sort of electrical issue????

Edited 2 time(s). Last edit at 06/26/2015 12:01AM by geemoto.

Have you tried again with a taller print?

Quote
cristian
Have you tried again with a taller print?

Not quite as tall as the previous ones, but tall enough to notice.

It looks like all the motors were skipping steps, not only the extruder one: the edges of the object become shorter and shorter. Maybe your power supply is not powerful enough, or your board.

Quote
cristian
It looks like all the motors were skipping steps, not only the extruder one: the edges of the object become shorter and shorter. Maybe your power supply is not powerful enough, or your board.

That may be partially due to my poor cutting job, I cut open the square tower so it was easier to see. I agree that it is probable that it is a lack of power issue or a poor board - is there any way to test this directly. This is the same power supply I used previously /w heated bed and got good prints - it is a new RAMPS board though (I believe).

The power supply is an LED 200W power supply, which I guess is slightly underpowered. Not sure if it is this, or the RAMPS. If there is a way to test some things on the RAMPS or powersupply with a multimeter to figure it out, please let me know and I'll give it a shot!

I think the banding pattern kind of agrees with the idea that the heat bed is the problem - after the first layer the heat bed temp drops from 50C to 40C, so in the period where it is off and cooling the prints are good, but when it turns back on the prints become poor again.

Edited 1 time(s). Last edit at 06/26/2015 08:00AM by geemoto.

Fantastic! Well done for spotting the problem. You can check the power supply easily by keeping the meter attached to the supply outputs. If the voltage drops when the heat bed comes on (best to check with the hotend running too) then you will know that you need a bigger PSU.

How is the heat bed configured in the firmware, bang-bang (what a name) or PID? If you're using bang-bang changing to PID might smooth things out a bit. If you are using Marlin you could also try reducing MAX_BED_POWER to limit the bed power consumption, although this will increase your warmp-up times:

// This sets the max power delivered to the bed, and replaces the HEATER_BED_DUTY_CYCLE_DIVIDER option.
// all forms of bed control obey this (PID, bang-bang, bang-bang with hysteresis)
// setting this to anything other than 255 enables a form of PWM to the bed just like HEATER_BED_DUTY_CYCLE_DIVIDER did,
// so you shouldn't use it unless you are OK with PWM on your bed. (see the comment on enabling PIDTEMPBED)
#define MAX_BED_POWER 255 // limits duty cycle to bed; 255=full current

Quote
JamesK
Fantastic! Well done for spotting the problem. You can check the power supply easily by keeping the meter attached to the supply outputs. If the voltage drops when the heat bed comes on (best to check with the hotend running too) then you will know that you need a bigger PSU.

How is the heat bed configured in the firmware, bang-bang (what a name) or PID? If you're using bang-bang changing to PID might smooth things out a bit. If you are using Marlin you could also try reducing MAX_BED_POWER to limit the bed power consumption, although this will increase your warmp-up times:

// This sets the max power delivered to the bed, and replaces the HEATER_BED_DUTY_CYCLE_DIVIDER option.
// all forms of bed control obey this (PID, bang-bang, bang-bang with hysteresis)
// setting this to anything other than 255 enables a form of PWM to the bed just like HEATER_BED_DUTY_CYCLE_DIVIDER did,
// so you shouldn't use it unless you are OK with PWM on your bed. (see the comment on enabling PIDTEMPBED)
#define MAX_BED_POWER 255 // limits duty cycle to bed; 255=full current

I'll try that out tonight, I think I have some banana clips I can use. I actually don't have almost any parameters for the bed, this is the in the header of my sprinter code:

/*
 Reprap firmware based on Sprinter
 Optimized for Sanguinololu 1.2 and above / RAMPS 
 
 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.
 
 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.
 
 You should have received a copy of the GNU General Public License
 along with this program.  If not, see [www.gnu.org]. */

/*
  This firmware is a mashup between Sprinter, grbl and parts from marlin.
  (https://github.com/kliment/Sprinter)
  
  Changes by Doppler Michael (midopple)
  
  Planner is from Simen Svale Skogsrud
  [github.com]

  Parts of Marlin Firmware from ErikZalm
  [github.com]
  
  Sprinter Changelog
  -  Look forward function --> calculate 16 Steps forward, get from Firmaware Marlin and Grbl
  -  Stepper control with Timer 1 (Interrupt)
  -  Extruder heating with PID use a Softpwm (Timer 2) with 500 hz to free Timer1 for Steppercontrol
  -  command M220 Sxxx --> tune Printing speed online (+/- 50 %)
  -  G2 / G3 command --> circle function
  -  Baudrate set to 250 kbaud
  -  Testet on Sanguinololu Board
  -  M30 Command can delete files on SD Card
  -  move string to flash to free RAM vor forward planner
  -  M203 Temperature monitor for Repetier

 Version 1.3.04T
  - Implement Plannercode from Marlin V1 big thanks to Erik
  - Stepper interrupt with Step loops
  - Stepperfrequency 30 Khz
  - New Command
    * M202 - Set maximum feedrate that your machine can sustain (M203 X200 Y200 Z300 E10000) in mm/sec
    * M204 - Set default acceleration: S normal moves T filament only moves (M204 S3000 T7000) im mm/sec^2 
    * M205 - advanced settings:  minimum travel speed S=while printing T=travel only,  X= maximum xy jerk, Z=maximum Z jerk, E = max E jerk
  - Remove unused Variables
  - Check Uart Puffer while circle processing (CMD: G2 / G3)
  - Fast Xfer Function --> move Text to Flash
  - Option to deactivate ARC (G2/G3) function (save flash)
  - Removed modulo (%) operator, which uses an expensive divide

Should I switch firmwares to something better?

Edited 1 time(s). Last edit at 06/26/2015 11:22AM by geemoto.

Quote
geemoto
Should I switch firmwares to something better?

Unless you already have a top-quality RAMPS board and drivers, it would be better to switch electronics. Either to a Duet or to one of the Smoothie clones. Even good Arduino/RAMPS boards have a number of issues, and many of the cheap clone boards have several more.

But first, check whether your PSU voltage is indeed dropping, as has already been suggested. 20A @ 12V is normally considered the minimum, which is 240W. If you need to get a new PSU then I suggest you go for at least 300W, because the price difference from 250W is tiny.

Edited 1 time(s). Last edit at 06/26/2015 01:55PM by dc42.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I definitely don't have a high quality RAMPS board, its a clone from China. I'd rather stick with it (if its fixable) since they're cheap and have worked in the past. Some of the others seemed expensive on a quick search (RAMPS is ~5$).

I checked the PSU, no voltage drop with both the hot end and/or bed on. I checked the output to the bed and extruder and neither were at 12V. Around 11.2V. I cranked up the power supply voltage to 12.7V to get the heatbed to 12V. Still the same problem with the print. So most likely its the RAMPS and/or Arduino? Any ideas what to check next on those? Will replacing the RAMPS entirely likely solve the problem? I could simply order a new one.

Should I set the power supply voltage back to 12V output?

I also have four fan plugged into the 'extruder fan' slot labelled on this picture: [reprap.org] - is there a reason I would connect the electronics fan and extruder fan to different places??

Edited 4 time(s). Last edit at 06/27/2015 09:48AM by geemoto.

Some voltage drop through the RAMPS is inevitable for the mosfet forward voltage, so I think that's ok. I'm kind of surprised that we didn't see the power supply dropping. Did you also have the stepper motors powered up when you measured it? They don't have to be moving, just drawing current - perhaps that's enough to push the psu over it's limit. If you keep the meter connected to the psu during a print, you could check the value as the problem happens and see if there is any change in output. Still thinking the psu is the most likely problem at the moment.

12V vs 12.7V - do you have an LCD connected to the ramps? 12.7 is fine for everything except the 5v voltage regulator on the mega2560 which runs a bit near it's limit at the best of times when there is an lcd connected. Raising the 12v voltage makes that regulator work harder and can make them fail. On the other hand increasing the 12v supply helps with bed warm-up time.

How much does the bed temperature vary by during the print? Some print beds flex quite a bit as they heat-up which shift the center up and down if the temperature isn't well controlled. If you bring the bed up to temperature and then put the nozzle at z=0 (or .1) and then watch the gap through a couple of on/off cycles you should be able to see if there is much Z movement going on in the bed.

I can't see any problem with connecting the constantly on fans to the place you indicated. It's in the 5A fuse circuit, but typical cooling fans don't draw a lot of currrent.

Edited 1 time(s). Last edit at 06/27/2015 10:16AM by JamesK.

Quote
JamesK
Some voltage drop through the RAMPS is inevitable for the mosfet forward voltage, so I think that's ok. I'm kind of surprised that we didn't see the power supply dropping. Did you also have the stepper motors powered up when you measured it? They don't have to be moving, just drawing current - perhaps that's enough to push the psu over it's limit. If you keep the meter connected to the psu during a print, you could check the value as the problem happens and see if there is any change in output. Still thinking the psu is the most likely problem at the moment.

12V vs 12.7V - do you have an LCD connected to the ramps? 12.7 is fine for everything except the 5v voltage regulator on the mega2560 which runs a bit near it's limit at the best of times when there is an lcd connected. Raising the 12v voltage makes that regulator work harder and can make them fail. On the other hand increasing the 12v supply helps with bed warm-up time.

How much does the bed temperature vary by during the print? Some print beds flex quite a bit as they heat-up which shift the center up and down if the temperature isn't well controlled. If you bring the bed up to temperature and then put the nozzle at z=0 (or .1) and then watch the gap through a couple of on/off cycles you should be able to see if there is much Z movement going on in the bed.

I can't see any problem with connecting the constantly on fans to the place you indicated. It's in the 5A fuse circuit, but typical cooling fans don't draw a lot of currrent.

I had it set at 12.7V and turned everything on, motors, bed, extruder and it only dropped to ~12.5V at most.

The temperature doesnt vary more than 55+/-2C, so I don't know if bed warping explains it. I think I may just replace the RAMPS and see if it helps, I'm worried it ma be (at least in part) to the fact that I'm using clone boards, but they are quite cheap so it's worth a shot.

Thanks again for all your help! Glad I finally have some idea what the problem is so I can get some sleep

Sounds like a reasonable thing to try, especially as you say they aren't too expensive. I just can't quite imagine how the ramps would cause the interaction between heat bed and any of the motion axes. But then, none of my ideas have been correct yet, so I'm obviously missing something! I'll look forward to hearing how it goes - you've got to be close to the answer at this point

Quote
JamesK
Sounds like a reasonable thing to try, especially as you say they aren't too expensive. I just can't quite imagine how the ramps would cause the interaction between heat bed and any of the motion axes. But then, none of my ideas have been correct yet, so I'm obviously missing something! I'll look forward to hearing how it goes - you've got to be close to the answer at this point

I switched over to Marlin and enabled PID for the bed, it seems that the problem goes away 90%, even with the heat bed on. So I think a temporary fix will be to limit the duty as you said previously. This + PID control should mask the problem for the most part, at least until I can get a new RAMPS.

Thanks again for all your help!

I just received the new RAMPS (I can't test the print quality right now because the nozzle is clogged and I'm waiting for a new one). The bed temp doesn't seem to go above 90C - so now I'm reconsidering JamesK's comment about the power supply being underpowered.

Is there a way to test if the power supply can provide sufficient current, other than looking for a voltage drop? The power supply is a cheap 200W LED power supply, so its possible that it isn't up to the job of powering the whole printer.