OK so the existing setup using sprung preloaders to hold the different axis of the Wanhao Duplicator 9 in place is not one I like. Tightening up the screws alters the angle with which the wheel comes into contact with the rail, and relying upon a spring seems to me like a poor engineering choice. This design fixes up the X axis, effectively making it solid rather than sprung preload.
To make the design work, I am using a spare M3 hole on the X gantry plate, between the two wheel axis. You might want to check you also have an M3 there, and it is not doing anything... I have modded my fan housing (see links below), and although I dont think this screw hole was in use before, I'm not 100%.
Also this is for the MK1, if someone has a MK2 and wants me to see if I can mod the design, then let me know in the comments, and give me the distance between the two wheel axis (which replace the one wheel design used here).
You will need:
- 1x M5x25mm screw to replace the old M5x20mm
- 3x M3x20mm (two of these can possibly be x15mm)
Also an M3 tap could help. You might be able to force the M3 screws through the two threaded holes, without tidying them up with the tap, not sure. If you do use a tap, dont drive it all the way through - leave a section at the end as printed or close to it, will help lock the screws in place. Also might want to clean up the M3 slot so that the screw, when inserted, can move relatively freely in it.
Print this part on its side.
So take two of the M3x20, screw into the threaded holes until they are at the end of the plastic but not poking out. Also before doing anything else you might want to note the force required to move the entire carriage. Next, loosen the spring tightener screws, take the old lower wheel off the carriage, and throw away the spring washer. Use the new M5 to secure the wheel in place, with the bracket as in picture. Then take your remaining M3 and put it through the slotted hole, and screw into the spare hole on the sliding gantry/carriage until the printed plastic is pulled flat against the metal - but dont do it up tight yet. Now tighten up the two preload screws underneath, and maybe check to make sure the carriage is not becoming stiff. You'll notice there is much less give in it - once the screws are tight, they are tight, because the axis can no longer go off at a dodgy angle. Next screw down the two M3 at the top, going through the printed plastic. They'll be pushing onto the top of the gantry plate, adding preload from above. Again check the carriage is not becoming stiff. Finally, do up the single M3 screw to clamp everything in place.
Congratulations! Your X carriage is now rock solid on the rail. Shame the same cannot be said about the rail itself, which can flex. To fix this, mix up something like epoxy granite (look it up) and pour into the two unused sides of the rail.
I have other designs to fix the Y axis and various other flaws in the D9, see below: