Is My Print Bed Warped?

"After MANY days and researching online i found subreddit where many people complained of warping in the heated bed. After using a set of calipers to measure i can see the warping is in the center portion of the bed." -anonymous

New users looking to improve their prints often start by checking their print bed to make sure that it is completely and totally flat.  It is a logical place to start.  After all, the print bed is where it the print begins.

As is the case with most any material, heat does cause the metal in the print bed to expand to some degree.  However, this expansion is quite minimal, even over the course of numerous prints.  By "minimal", we mean that you will not likely recognize the effects of this expansion with the naked eye.

The real question is "How does it print?". Often times, print quality will be more effectively improved by making the following adjustments.

 

  • Z-PROBE: The  Z-probe has a higher variance than the Mic 6 aluminum, meaning the Z-probe is more likely to be the issue that the Mic 6 Aluminum. Replacing the probe before the bed is best practice. If there is something wrong with the probe it will not allow for proper auto-leveling thus contributing to a print that is not level. If you are within warranty please submit a ticket and we can send a replacement Z-probe. Otherwise you can purchase a new Z-probe from our store; http://printrbot.com/shop/auto-leveling-probe-2/
  • Proper Auto-Leveling Probe Calibration:  If the Auto-Leveling Probe (Z probe) is not calibrated with an offset (M212 Z value) that gives the first layer enough "squish" for the perfect "bead".  If this offset is not great enough, the flatness of the print bed is a non-issue and no first layer height setting will be enough to compensate for a loose/stringy first layer.  
  • Probe Points:  The Auto-Leveling Probe is an induction sensor, which means that it is working to find metal and alert the Printrboard.  But it isn't just looking for "metal" or "no metal".  An induction sensor is looking for metal and the density of the metal that it detects.  If the sensor probes over a point on your print bed that is a couple of mm thinner than another probe point, the sensor will recognize this as a lower spot on the plane of the print bed.  Again, we are not talking microns, but visible thickness.  For instance, you will get less accurate probing if one of the probe points is over a screw that secures the print bed and the other two points are only over the aluminum.  Keep your firmware current.  This is the way to ensure that your M212 offset for the X and/or Y is set properly.  
  • Good "Flow": Okay.  So, your Z probe is calibrated perfectly and you still find inconsistent lines on the first layer.  The problem could be extrusion, particularly if the stringy lines are not occurring in the same place from one print to the next.  Be sure that your hot end is extruding well and clear out any clogs from the nozzle.  Also, use a caliper to measure your filament diameter at 5-6 different spots to get an average.  Anything over 1.8mm will prevent smooth flow.
  • Has the Print Actually "Failed"?: A common misstep for new users is to count the print as "failed" too early.  If you are unsure about the "stick" on a particular point of the first couple of layers, give the print a chance to succeed.
  • PLUS USERS:  Is your X carriage level?  If not, the bed will appear warped.
  1. Power ON and connect your bot.
  2. "Home" X and Y axes.
  3. Enter "M18" (stop motors) into the Pronterface UI command line or simply power OFF your bot.
  4. Physically slide the extruder carriage left to right across the X axis.  Look closely to make sure that the hot end tip is the same distance above the bed on the left top corner as it is on the right top corner of the print bed.
  5. If the carriage is higher on one side, physically turn the Z axis threaded rod counter-clockwise to lower that side closer to the print bed. 

 

Printrbot lists a level tolerance of 0.3mm for all current aluminum print beds (this was written on 3/2/16).  See specific material information for various beds below.  

Slicing your models with a first layer height of 0.3mm (Cura actually suggests a first layer height of 0.4mm) will compensate for any variance you should find on your Printrbot aluminum print bed.

 

Product - Print Bed Material - Current Products as of March 2016

Prinrbot Play (Model 1505) 1/8" 6061 aluminum
Play Y Axis Upgrade (w/ or w/o heated bed) mic 6 aluminum
Play Heated Bed Upgrade mic 6 aluminum
Printrbot Simple (Model 1403) 3/16" 6061 aluminum double disc ground
Simple X Axis Upgrade (w/ or w/o heated bed) mic 6 aluminum
Simple Heated Bed Upgrade mic 6 aluminum
Printrbot Plus (Model 1504 or 1412) mic 6 aluminum

 

 

 

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