D9 – Some more upgrades – Belt Tension

I’ve designed another thing that solves some more problems with the D9 – a Belt tensioner!

Jerome Waweru D9-300 Y Axis Tensioner 9mm 1
Thanks to Jerome on Facebook for posting a pic of his Tensioner

I’ve posted this up on Thingiverse……….

It’s been printed at least 10 times by guys on the facebook group and provides an immediate and cheap improvement over the stock……..

Wanhao D9 Y Axis Belt Tensioner – 6mm version AND 9mm version



There are two versions of the tensioner that cover

  • the original 6mm wide belts on the D9-300 and D9-400
  • The new 9mm wide belts for the MK2 kits and the D9-500

Both versions bolt straight on in place of the existing idler.


What this fixes..

Ghosting / ringing  Rigid-ink web page link to show the problem


The Design may look a little unconventional…………But there’s a bit of thought that went into it……………Here’s some waffle………

Y Axis tension CAD export

It’s optimised for strentgth and travel distance.

You have +10.5 mm and -6.5mm of movement – total of 17mm

Some design thoughts ……….

  • The stock idler sits directly over the center of the 4040. To keep the same belt tension as stock, the idler has to be centered identically – orange line below
  • To use ‘standard’ M4 / M5 type allen key bolts on the idler, there has to be clearance at the front to allow movement in the direction shown, otherwise the bolt fouls on the front two strengthening edges
  • Overall depth from front to back has to use standard M5 allen key bolts that are off the shelf – longest easily available seems to be 30mm so that’s what I used.
  • Tapered edge at the rear keeps the maximum thickness of the internal idler holder bracket and the external part. By stepping the edge, there’s only a small part at the bottom that’s a weak spot on the whole bracket
  • Overall

Y axis tension 2

  • Height of the bracket – orange line below. It can’t be too high, or it would interfere with the bed. It can’t be too low or the two adjusting screws won’t stick over the top of the front panel case

Y axis tension 3

  • Some who’ve printed it have questioned design, specifically the two bits in yellow below- these are there to
    • provide a little support for the 30mm long bolts
    • provide a hard limit should something snap – the belt won’t pull out all the way
    • Looks a bit better than having two bolts free floatingY axis tension 4

Author: Bleugh

Early Fourties, Wife, two kids in primary school. Both of us work full time...5 years now we’ve been Back in Blighty after a decade away...It's a new country for everyone! Still finding time to tinker!

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