Questions on Z Axis upgrade

K8200 3D Printer K8200 - Your printer, creations, and ideas for imp
1

I’ve had my printer assembled and working for a while and I can see some areas that may need improvement, mainly the Z Axis and the replacement of the regular screw with a trapezoidal lead screw and possibly driving the other side of the Z. There are a number of posts here and on Thingiverse which have given me some ideas but before I start I have a few questions.

  1. Has anyone been able to quantify the results of these modifications in terms of print quality?

  2. What is the size of the current screw? Being used to the American standards and using comparable measuring tools it’s 8mm in diameter with approximately 20 TPI (threads per inch).Is that 8 x 1.5? Why is it called 8x1.5 when it actually is 1.25mm/revolution? Shouldn’t it be 8x1.25?

  3. 8x1.5 versus 10x2. I’ve read all the posts and I don’t see a clear answer. Pro’s and con’s on each; is it just personal preference?

  4. My assumption is that the firmware is coded to support 1.25mm/revolution. Is that correct? The use of the 8x1.5 lead screw will require no firmware changes?

  5. Are there measureable benefits to providing drive to the opposite side of the Z arm?

  6. If so, it seems that the current Z Axis stepper motor is sufficient to drive both sides through a belt from one to the other? Is that a correct assumption?

  7. If not, does the driver have the capacity to support a second Z Axis motor equivalent to the existing motor?

There are answers posted on some of these questions but I am asking to confirm my understanding of what I’ve read.

Thanks for any help,

Tom

2

Hi,

Here are some answers :

  1. If your 8x1.25 rod is straight and you’re usind a motor holder with a flex coupling, you’ll already get good results. Perfection will need more work to achieve but the difference will not be that spectacular. Anyway it stops the backslash and the movements are smoother.
  2. The stock srew is a 8x1.25. I’ts trapezoidal equivalent is a 8x1.5.
  3. 10x2 is less flexible but 8x1.5 will do the job.
  4. the use of a 8x1.5 or a 10x2 rod need some firmware changes (actually in the EEPROM). Use the RepRap calculator to compute the right values.
  5. There’s no more wobble on this side.
  6. Yes I’ve done it and it works perfectly.
    7; Yes the driver can drive a second motor but will need a bit more cooling (SMD heat sink & fan).
3

Hi,

you can use a second motor. Or try (K8200 / 3DRAG Parallel Z-Axis Spindle Gear). You can see the result on last image… and yes, it is worth to update the z-axis on your k8200!

greets