Slipping Z axis?

[bringho]

I've started printing

The first print was the 5mm Calibration Cube Steps by MCroucher from Thingverse (thing:24238) and though it did not come out looking great it was a sucessful first print.

It was done using the instructions in the online Simple Getting Started Guide and it looks like I need to add a fan to cool the part being printed.
blob.jpg

I later found out that I had inserted the wrong filament diameter into Repetier (1 instead of 1.7 because I used a comma instead of a dot as the decimal separator) and have yet to try with the correct setting...

Then I lowered the print height to 0.2 and added support and tried to print out the Printrbot Simple Bed Leveling Screws by JohnSL from Thingverse (thing:103519) but that did not work out well so I reversed to 0.3 layer height and even though the control over the support feels strange I managed to get a second print that I could clean out quite easily so those are now installed.

I tried to slice the Harry Potter Gryffindor Crest by Imminentfate from Thingverse (thing:123282), scaled down to 33% of the original but both test prints failed at the start of layer 9 with that layer being moved roughly +20 mm in x axis... No Idea what could be wrong but I've saved the file if anyone is interested to have a look at it.

Then I decided to print the swirly shot glass by profgizmo from Thingverse (thing:36103) and then I found this strange behaviour which I would guess is due to z-axis slipping if it were not for the fact that the shot glass measures almost exactly the expected height?!?
First image shows layer 72 of 148
strange_printing_behaviour_1.jpg

Secon image sows rougly layer 120 (still of 148
strange_printing_behaviour_2.jpg

Any comment appreciated.

[Tdeagan]

My first guess would be inadequate current settings for the z steppers.

Wouldn't hurt to lube the lead screws (I use lithium grease.)

[bringho]

Thanks m8!

I've bought and applied lithium grease but I still have the z-axis problem.

I've found that there are some cables near the z-axis coupling and will take a closer look to ensure that's not the problem before I start adjusting the current which seem to be a pain in the ... on my production Simple.

[Tdeagan]

The current adjustment should be easier than it sounds. Each of the motor drivers on the Printrboard has a tiny trim pot.

Use a jewler's flathead screwdriver to turn it (in pretty small increments, say 30 degrees clockwise.) Try out some printing, or even just run the Z axis up and down a number of times. Feel the temp of the Z motor housing. You should be able to increase the current up to the point where the motor starts running hot (which is undesirable.)

[bringho]

Thanks!

Before dismantling the Simple I found out that the controller board is quite simple to get to when the extruder is in top position

I then noticed that the bottom part of the z-coupler (the one connected to the servo) had popped up so the strap did not secure it to the axis... which most certainly is the reason for slippage. I pushed the tube in place again but before I had a chance to test it I managed to break my PSU so now I have to repair / get a new PSU before commencing my trials.

[Tdeagan]

Good catch on the troubleshooting. Bummer on the PSU. But, better it fails now than in the last 10 minutes of a three hour print (been there.)
good luck!

[bringho]

My new (expensive) 'VOLTCRAFT ' 8.5 amps PSU arrived the other day and I've been doing some more testing

Slipping seem to be a thing of the past with the tube firmly pushed down on the motor axis.

Link for any European who wants/needs a new/better PSU:


Thanks for all the help !!!

[REPRAP SQUAD]

If you guys ever have any probs with the x and y axis I've found that a little shrink wrap helps to grip really well.

[MDW]

[REPRAP SQUAD]

Im refering to slippage on the x and y axis that uses vinyl tubing for the spectra line.