Continuing the 3D printer thingy

[MikkiJayne]

That's the right hand Z motor dropped - the CR-10's killer flaw. I check it every print for that exact reason. I'm planning to design an end-stop for it so it can't get below the left hand motor - basically a block at the same height as the Z endstop switch. I'll post it up when its done.

[gninnam]

Cheers - doing my fruit in!!

[tc4332]

We have not suffered that problem.
My Son suggests swapping the suspect motor with the extruder motor and retry. He's thinking it could be a quality control thing with stepper motor production.

[MikkiJayne]

Its not the stepper motors - its the basic design of having two motors doing the same job with no mechanical synchronisation. Most dual-z printers can suffer from it, but the CR-10 seems to be particularly bad because the wheels allow the X axis to twist in the frame. Printers with linear bearings tend to stay straight once they're properly set up. With the CR-10S, as soon as it finishes a print and turns off the steppers the weight of the X axis can cause it to drop slightly on one side by rotating the lead screw. You'll see it happen in macro if you put any weight on the X axis bar while it's powered off - it'll spin the steppers and move down the Z axis.

Now it may be worse on some printers than others as it could change depending on how square the frame is or indeed how tight the wheels are. Mine likes to drop about 2 steps so I know to correct it. Sounds like Andy's has done the same.

[gninnam]

Based on what MJ has said I think after every print the bed will have to be checked for levelness - perhaps Ray's son's suggestion might be worth a try though if they haven't suffered the same symptoms ??

[MikkiJayne]

Check the X axis for level, not the bed. If the X axis is not level and you adjust the bed to suit it then you're effectively printing a parallelogram! Both things could be parallel, but not perpendicular to the Z axis.

I set mine up by powering up the Z steppers (lift Z by 1mm) and then measure the distance from the X axis to the frame with digital calipers. I'll adjust the right hand Z axis by hand until the measurement is the same, and only then will I do bed levelling. That way I know its parallel and perpendicular.

Z drop is a well known characteristic of the CR-10S, and indeed the CR-10 when modified to dual Z. There are dozens of designs on Thingiverse to mitigate it, mostly toothed belts to keep the two motors in sync. I think a simple block to level the Z carriages before printing is probably simpler though

[gninnam]

Will have a go over the weekend and report back boss