Bed leveling/adhesion tips and tricks

Some of the most common problems are related to bed leveling. Bed leveling can tricky especially for beginners. My best advice is to be patient, and take good notes.

Rather than rewrite what has already been written. Please read over the instructions described in step 14 of the build and calibration manual.

Things to keep in mind:

1. The bed of the gMax is secured by 4 points. If all 4 points are not held on the same plane, the bed will be slightly skew. An extreme example of this is shown in the picture below.
2. Adjustments to the right side of the bed will affect the far left side of the bed and vice versa.

3. The bed is not perfectly flat. To account for this slight deviation print with a large first layer. Typically 80-90% of the nozzle diameter is a good choice. The larger your first layer the easier it is to achieve an acceptable tolerance.
4. Remember to keep the springs tightly compressed to prevent them from vibrating loose during operation.

Getting better bed adhesion:
1. Print the first layer at half speed.
2. Print the first layer at thicker layer height – pretty much as thick as you can go.
3. Use a raft or a large brim.
4. Make sure the bed is sanded really well.
5. A higher first layer temperature will increase bed adhesion.

Test Printing:
Inside the attached zip file are good test prints for bed alignment. If you are able to pull off these prints, your bed is aligned. This is the procedure I use when using this test print to dial in my alignment.
1. After I start the print. I keep a very close eye on the plastic being extruded onto the bed. You should be able to tell if the bed is too high or low just by watching.
2. Test the bed adhesion by tapping the line of extruded plastic with your fingernail. It should not come off easily.
2. After the printer has laid down a line on all 4 sides and an X in the middle. Stop the print.
3. Take note of the bed adhesion is various places. Write it down.
4. Make a few small adjustments as needed. Write them down as well.
5. Restart the print.

After a few iterations of this procedure, Your bed should be very well aligned. The outcome obviously is dependent on you making smart adjustments.

You can use a low grit sand paper (40-80) to sand down high spots in the bed. Use water to help control the dust generated by sanding.

If you want to switch to a glass bed I recommend 1/8" glass. Glass maintains a consistently flat surface better then acrylic. However the bed adhesion with sanded acrylic is much better than blue tape or glass.

Please share your experiences with bed leveling.



Excellent post/instructions, however it doesn't address dual extruder setups. Just from experience, it is a challenge to get the bed level with both nozzles, and I have spent a lot of time chasing my tail getting the bed level with both of them. Right now as it sits, for the most part they are, until I move to the left of the build plate, the outside nozzle has a significantly larger gap than the inside nozzle.

Are there any best practices that can be suggested for these kinds of setups?

I would also like to know about the dual extruder leveling. It seems my extruder 2 or 0.35 extruder is slightly lower than my main extrudr 0.5 so when leveling I end up having to leave a small gap between my main extrude and the build plate so my smaller right extruder doesn't drag on the build plate. Is there some adjustment I can make to the height of the individual extruders so that I can get them both level or even at this point at least my main extruder without having to worry about the smaller extruder dragging on the build plate.

You need to align the hotends z-height.

Use the wheel adjustment screws in the back of the carriage to make small adjustments to the angle the carriage rides on the gantry. You can also reset the hotend swingarm or turn the hotend to adjust its position.