One of my 3D printers is a FLSON Cube it has a good size build volume of 260*260*350mm. On this type of printer, the Z axis is handled by the bed lowering via two threaded rods situated at either end of the bed. I don’t use any form of auto-bed levelling or Z probe on this printer, purely because I like the freedom to adjust the first layer. Something you can’t easily do if your Z axis is chaperoned by a probe.
One of the things I like about not having an auto levelling feature on this printer is the time to get printing. You don’t have to wait for it to run through the probing routine, it just prints like it did the last time you used it. I also find that I get much better “bottom layer adhesion” using this technique.
But there is a small caveat to using this type of levelling and one I wanted to touch upon briefly in this post.
I have on occasions found that the bottom layer quality for one print was not quite the same as on any subsequent print because they tended to vary too much. This got me to wondering why. If the bed never changes from one print to the next, some form of misalignment must be getting introduced during the finishing of one print and the starting of the next?
Anyway, I found what was causing the error and I designed a small part so I can visually check that it doesn’t happen again. First, let’s state the obvious about cheap Chinese 3D printers. They are cheap. And because they are cheap they are available to the masses. But here in lies the issue, because you are going to have to find inventive ways to increase their “print quality ” in ways that you wouldn’t perhaps have to if you have spent say a couple of grand. What makes them cheap is that fact that cheaper parts are used which leads to parts that are made with less tolerances than their more expensive cousins.
Yes, but what is “print quality repeatability”? Print quality repeatability is the ability to get your 3D printer printing objects acceptably time after time once it’s been set up in a particular way. It’s that point where you can send an object to your 3D printer and know that it will come out 100% to your liking.
In my case, the bed would move a little in the downward direction when I went to get the last part off the bed. When I liberated the printed part from the bed I would inevitably press on the build plate and move either side down a couple of millimetres. But not necessarily 2mm for the other side of the bed. Then when I tried printing again one side was a little bit higher or lower than the other. Thus, the bottom layer would not be consistent.
When I found this was the case, I started measuring each Z axis lead screw from a point on the bed chassis of the printer to the top of the lead-screw as seen in the picture below.
I would home the printer. Then when it had finished I would make sure the measurement from the top of the lead screw to the bed chassis was the same. In my case, I was looking for 7cm.
It could have been 10cm or 15cm the actual distance was not the point. The main point was that when the printer started its next print the moment the stepper motors took control I knew the bed was perfectly aligned for both sides. If I found the measurements were slightly different I would gently turn the corresponding Z axis stepper motor the desired amount till it read 7cm.
Then I thought how much better it would be if instead of measuring it every time, I could visually check to see that it was correctly set to 7cm. So, I went into Tinkercad and designed a small upright that measured 7cm, I then hot glued it to a point right beside the upper part of the lead screw, so I could easily check that the bed was level on both sides.
Here is my finished first layer. 0.2mm
You idiot, why not just fit the printer with a good bed levelling probe that allows you to level the bed without all this messing about? Well, if I did that I would lose control over a very important aspect of 3D printing, and I wouldn’t feel as smug as I do right now. That’s why. Thanks for dropping by.