Whilst tracking down a problem with y axis travel (inconsistent movement, a rattle and a squeak) it was visible that the toothed pulley did not run true. Subsequent checks with a dial gauge showed an off-centre movement between .15 & .2mm (see photos) over one revolution. Further examination of the pinion showed the hole drilled through the die-casting was not central (motor spindle seemed OK).
After increasing the clearance between the pulley and motor flange slightly to ensure it did not bind during its wobble the squeak disappeared and the plate ran more smoothly (could still be better).
Inconsistent travel - better, but I may have to boost the drive voltage to ensure total reliability (NB with the belt off had already confirmed the bed plate was free to slide).
There is an additional effect. The toothed belt tracks the full width of the pulley over a complete move of the bed plate; this is unlikely to be a belt alignment issue but the wobble may be causing the belt to crawl?
The pulley on the X axis runs true.
Velleman may wish to comment further on this apparent manufacturing QC issue and its consequence to the working of the printer.
Don’t place the gauge on the pulleys flanges, they are never perfectly concentric to the sprocket hub on low cost pulleys and this is not a problem, only the hub must be perfectly concentric to the shaft hole, you can put the gauge on the belt to check this.
I bought two new pulleys that I drilled myself on my lathe because they was not properly drilled, but they was less eccentric than the flanges.
Thanks for your comment…but I was aware of that possibility.
What I did not report was that I had carried out several checks including eccentric collar, bent drive shaft etc etc. Fundamentally the pinion hole has been drilled off centre (as you yourself have noted) and whilst the dial gauge shows the effect it is also clearly visible to the eye.
What I had not anticipated - the intermittent binding of the pulley as it rotated against the motor housing
Do you remember the step in the manual where you had to adjust the voltages of the axis to 0.425V? Did you do this for the replacement Pololu? 70-462
Don’t replace the Pololu while the board is powered or it will be broken (again).
The belt should be as tight as the belt for which you had to count the number of teeth. Use that belt as a reference.
Don’t be afraid to ask questions when in doubt. This printer should be fun to build and use, not frustrating! Take your time to build it, better to do it slowly but correctly than to rush it.
