Dolly Configuration

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3DEnthusiast
Posts: 66
Joined: Fri Oct 27, 2017 6:50 am

Dolly Configuration

Post by 3DEnthusiast » Fri Oct 27, 2017 7:10 am

Greetings all!
I followed Tom's Dolly build almost exactly. I upgraded to an actual aluminum frame, a real E3D V6 setup and T8*8 Leadscrews. Otherwise, I went with the BoM Aliexpress parts. As such, I'm not sure I have the configurations correct. I downloaded Tom's Marlin build and adjusted the appropriate numbers for my Leadscrews. Also, my probe is set flush with the extruder, though I've concerns over it grabbing printed layers The issues I am running across are
  • it doesn't seem to print close enough to the bed to form a good adhesion.
  • the prints will start in the center of the bed and then shift towards X0 with a bit of a grinding noise even though the X belts are tight.
  • I'm not really sure how to proceed
My main question is, would using the G29 bed leveling resolve my issues? Does Dolly save those settings for future use?

Thanks!

slippyr4
Posts: 224
Joined: Thu Jun 15, 2017 10:24 am

Re: Dolly Configuration

Post by slippyr4 » Fri Oct 27, 2017 9:03 am

You need to configure your Z offset with M851 (that is, the distance between your probe trigger point and the nozzle).
Self-built Prusa i3 MK2 clone
My things: https://www.thingiverse.com/slippyr4/designs
My Prusa firmware port for ramps & MKS : https://github.com/slippyr4/Prusa-Firmware

chumm
Posts: 176
Joined: Thu Jun 15, 2017 11:24 am

Re: Dolly Configuration

Post by chumm » Fri Oct 27, 2017 9:33 am

You don't want the probe to be quite flush with the end of the nozzle because there is a trigger distance, as slippy mentioned. And as you noted, there's concern with the probe dragging on the part, especially if any stringing or blobbing causes it to be sitting slightly higher than the current Z level. Raise your probe slightly so it's definitely not going to drag (but is still very close to the nozzle tip) then follow these instructions to calibrate your Z offset (the Z distance between where the Z probe triggers and the nozzle actually contacts the bed).

Re: G29, that's for leveling an uneven bed, but you'll find that basically all beds are uneven so it's definitely worth using if you have a probe. The settings can be saved, but it's worth just doing the G29 at the beginning of every print.

Your shifting toward X0 with grinding sounds like the X motor is skipping steps, likely due to receiving insufficient current. You should check the reference voltage on the driver to make sure the current is turned up high enough, and dial it up a bit until this problem is resolved. When getting to higher currents, check the temperature of the motor while it is running. It can get hot, but should not get too hot to touch for several seconds.

3DEnthusiast
Posts: 66
Joined: Fri Oct 27, 2017 6:50 am

Re: Dolly Configuration

Post by 3DEnthusiast » Fri Oct 27, 2017 12:42 pm

Thanks to you both!

I have had my Z Probe height set as much as 1mm above the nozzle but that didn't seem to work either but I will try this again with the supplied instructions.

I will look into the current adjustment for the X axis. This was not something I had considered previously. I thought that it could be slack belts to I tightened them but this may be an easier solution. Is there a general ballpark current for this or just crank it up until it's not too hot to touch?

Thanks again!

slippyr4
Posts: 224
Joined: Thu Jun 15, 2017 10:24 am

Re: Dolly Configuration

Post by slippyr4 » Fri Oct 27, 2017 2:36 pm

3DEnthusiast wrote:
Fri Oct 27, 2017 12:42 pm
I will look into the current adjustment for the X axis. This was not something I had considered previously. I thought that it could be slack belts to I tightened them but this may be an easier solution. Is there a general ballpark current for this or just crank it up until it's not too hot to touch?
Your motors will have a rated current, which is a maximum really. If you google their model number you can probably find out what it is. If you can't, then I'd assume them to be 0.85 A ish, and set that as your current.

There's lots of guidance out there on the formula and technique for setting the Vref to set the desired current. A good article on reprap.org.
Self-built Prusa i3 MK2 clone
My things: https://www.thingiverse.com/slippyr4/designs
My Prusa firmware port for ramps & MKS : https://github.com/slippyr4/Prusa-Firmware

3DEnthusiast
Posts: 66
Joined: Fri Oct 27, 2017 6:50 am

Re: Dolly Configuration

Post by 3DEnthusiast » Sat Oct 28, 2017 1:39 am

Alright, using math the ratings are 1.7A and 1.5Ohms. That equates to 2.55V.

I have tuned the X axis to .8V

I have adjusted the probe to .43mm above the nozzle(the highest I could put it and it still triggers with a piece of paper between the bed and the nozzle.

I'm going to run the G29 and then a test print.

Here's to hoping!

3DEnthusiast
Posts: 66
Joined: Fri Oct 27, 2017 6:50 am

Re: Dolly Configuration

Post by 3DEnthusiast » Sat Oct 28, 2017 2:06 am

Test print underway and it appears the left side of the bed is higher than the right because the probe triggers and the first few layers on the left side are barely present.

I thought this was supposed to auto level the bed. Did I miss something? Is there a particular line of code I need to check and fix?

Thanks all!

3DEnthusiast
Posts: 66
Joined: Fri Oct 27, 2017 6:50 am

Re: Dolly Configuration

Post by 3DEnthusiast » Sat Oct 28, 2017 2:34 am

Okay, Thermal runaway stopped the print. Said the hotend but it never went above 215C.

G29 spits out these numbers.

Bilinear Leveling Grid:
0 1 2 3
0 -0.16 -0.56 -0.91 -1.32
1 -0.00 -0.39 -0.80 -1.19
2 +0.15 -0.21 -0.57 -0.93
3 +0.33 +0.03 -0.30 -0.60

chumm
Posts: 176
Joined: Thu Jun 15, 2017 11:24 am

Re: Dolly Configuration

Post by chumm » Sat Oct 28, 2017 3:13 am

That auto leveling shows that you have a pretty significant deviance in your bed heights from corner to corner, 1.68mm at the most extreme. This is mostly fine as the software should correct for it. To make sure it's working properly, have a look at the Z motors when the printer is moving along X and Y, they should be slightly moving to compensate for Z as they travel. If they're not doing anything you might need some more firmware setup.

Thermal runaway is protection designed to turn off the printer if it fails to maintain the target temperature. If the temperature goes down by X degrees over a period of Y seconds, this will shut off the printer. This is a safety feature in case your thermistors fail and the printer keeps "runaway" heating without the thermistors realizing it, which could be a fire hazard.

I've gotten this error most commonly when a poorly connected thermistor shorted out or was disconnected and reported a low temperature, but it's also possible your PID isn't well configured and the printer isn't doing a good job of maintaining temperature. Here's a page on tuning your PID to smooth out the rate at which your printer heats:
http://reprap.org/wiki/PID_Tuning

To make tuning work, you'll need to uncomment the following in configuration.h for tuning the hotend and bed respectively:

Code: Select all

#define PIDTEMP
#define PIDTEMPBED
You can also adjust your thermal runaway settings, as well as your "heating failed" settings, which is similar but applies to the hotend and bed while they are heating up. The following lines in configuration_adv.h can be adjusted to come up with a runaway protection scheme that is better suited to the rate at which you are heating:

Code: Select all

 * If you get false positives for "Thermal Runaway" increase THERMAL_PROTECTION_HYSTERESIS and/or THERMAL_PROTECTION_PERIOD
 */
#if ENABLED(THERMAL_PROTECTION_HOTENDS)
  #define THERMAL_PROTECTION_PERIOD 40        // Seconds
  #define THERMAL_PROTECTION_HYSTERESIS 4     // Degrees Celsius

  /**
   * Whenever an M104 or M109 increases the target temperature the firmware will wait for the
   * WATCH_TEMP_PERIOD to expire, and if the temperature hasn't increased by WATCH_TEMP_INCREASE
   * degrees, the machine is halted, requiring a hard reset. This test restarts with any M104/M109,
   * but only if the current temperature is far enough below the target for a reliable test.
   *
   * If you get false positives for "Heating failed" increase WATCH_TEMP_PERIOD and/or decrease WATCH_TEMP_INCREASE
   * WATCH_TEMP_INCREASE should not be below 2.
   */
  #define WATCH_TEMP_PERIOD 20                // Seconds
  #define WATCH_TEMP_INCREASE 2               // Degrees Celsius
#endif

/**
 * Thermal Protection parameters for the bed are just as above for hotends.
 */
#if ENABLED(THERMAL_PROTECTION_BED)
  #define THERMAL_PROTECTION_BED_PERIOD 20    // Seconds
  #define THERMAL_PROTECTION_BED_HYSTERESIS 2 // Degrees Celsius

  /**
   * Whenever an M140 or M190 increases the target temperature the firmware will wait for the
   * WATCH_BED_TEMP_PERIOD to expire, and if the temperature hasn't increased by WATCH_BED_TEMP_INCREASE
   * degrees, the machine is halted, requiring a hard reset. This test restarts with any M140/M190,
   * but only if the current temperature is far enough below the target for a reliable test.
   *
   * If you get too many "Heating failed" errors, increase WATCH_BED_TEMP_PERIOD and/or decrease
   * WATCH_BED_TEMP_INCREASE. (WATCH_BED_TEMP_INCREASE should not be below 2.)
   */
  #define WATCH_BED_TEMP_PERIOD 150                // Seconds
  #define WATCH_BED_TEMP_INCREASE 2               // Degrees Celsius
#endif
Usually you can just adjust the protection period to a higher term, say 90 seconds or so. That's still plenty of time to catch a runaway heater if there is some failure, but gives you enough time to prevent a false positive.

3DEnthusiast
Posts: 66
Joined: Fri Oct 27, 2017 6:50 am

Re: Dolly Configuration

Post by 3DEnthusiast » Sat Oct 28, 2017 6:01 am

It doesn't appear like the software is adjusting for it since when printing, one entire side of a print was practically non-existent due to the nozzle coming too close to the bed. In fact, it was close enough that the Z Probe was triggered but that didn't seem to effect the level at all.

Thanks for the other info! I'll dig into that too.

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