Friday, 24 October 2014

Levelling The Build Plate

There is a wealth of techniques for leveling the build plate documented on the Internet. Many of these require interactive prints or additional tools. I’ve achieved good results, with relatively little preparation, by refining the steps outlined in the Maker Bot documentation.
I level the build plate at the beginning of each session. I level again if I’ve interacted with the plate. For example, longer prints create a stronger bond with the plate due to the prolonged heat exposure. Removing these prints requires some wrestling which in turn disturbs the plate.  If I’m executing short prints that snap easily from the plate then I tend to level every three or so prints. 

1.) Remove any frayed bits of Kapton tape.

It doesn’t matter if there are holes in the Kapton tape. However, the size of the hole is relevant. If the hole is as big as the print, then offset the print. If it’s comparatively small then it should be fine.
Frayed bits of Kapton tape are a problem. They catch on the print head or get stuck inside a print. I use a Swann Morton scalpel with a 10A (straight) blade to trim the frayed tape. Raising the build plate above the memory card reader aids access.

To raise the build plate, choose: Jog Mode Y -> Z -> Z-

2.) Remove any bits of print media from previous jobs (I use my finger nail) then clean the build plate with Acetone. 
Ideally this is done when the build plate is cold and never when hot. Aside from getting covered in your chosen print media the build plate also gets greasy. Cleaning with Acetone gets the build plate pristine, aiding adhesion of the print. 

3.) Remove any bits of print media from the extruder nozzle.
Print media often runs through the extruder nozzle as it cools. If the nozzle is cold, then the media will be brittle and is easily snapped off with a fingernail. 
If you are leveling after a print then allow the extruder nozzle to cool sufficiently to remove the print media without discomfort. Aside from burning yourself more print media will leak out by the time you begin the leveling procedure. 

4.) Heat the build plate to your preferred temperature.
Choose: Utilities -> Level Build Plate. 
I only print with one extruder nozzle (because this is all I require) Consequently I adjust the build plate to that nozzle only.
I use a 3M Post-it note as a gauge rather than the business card supplied by Maker Bot (which is ridiculous) Post-it notes have a reliable thickness and conveniently stick to your fingers while adjusting the plate bolts. They are also disposable.

Note that the first pass is just to get the build plate in the ball park. The second pass is where fine adjustment should take place. I skip the final step where the extruder nozzle is centrally positioned. I usually cannot get the Post-It note under the nozzle in this position. Furthermore there is no logical way to adjust the plate if you are not happy at this stage.

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