z axes synchrony and first layer problem

hello,
last week i got my new mendel90. i really enjoyed putting it together, it is a very nice kit. some weeks before i assembled ikea furniture and with many details you could see how they just want to make everything cheap and max profit, regardless of durability and function. so it was just a pleasure to have exactly the opposite from a very small company, thanks nophead!

however i still have a problem with the synchrony of the z axes motors. i put the flags to the threaded rod and i can see that they get 180° apart with homeing z. i did put grease on the rods and refixed the screws. i followed exactly the manual i suppose.
anybody any suggestions?
i was already printing fine, when today i tried to print a lithophane. i attach a picture what happend tothe first few layers, all wrinkels like my shirt ;-)
i printed pla from grrf at 206°, 60° bed.

thanks,
michael

Looking at your photographs, I cannot see anything too amiss given that you are printing a Lithophane - they look very bumpy and irregular anyway, the amount of roughness depending on the photograph used to produce it.
I will leave it to others to comment on your Z leadscrews as I assume you have everything as tight as it is supposed to be. Might be worth posting photographs of a different object though.
Alan

Edited 1 time(s). Last edit at 07/04/2013 06:38AM by Alzibiff.

this foto just shows the first two or three layers and they are wrinkled, somehow no real connection to the bed. therefore they dont stick. i wonder if it comes from being out of calibrartion because of this synchrony error or maybe something different.
i cleaned the bed before printing thoroughly with aceton, i tried two times, two times same result.

michael

I just started a few days ago myself using PLA. I found that the glass by itself gave poor adhesion so used blue tape. That gave excellent adhesion but the objects were very hard to remove after printing. I found that a very small amount of graphite lubricant smeared over the tape lowered the adhesion to just the right level.

Yes its weird. Glass works for some people and not for others. Same glass, same machine, same PLA! I don't know what varies.

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[www.hydraraptor.blogspot.com]

For what it is worth, my experience suggests that it is down to getting right, two key parts of the commissioning process: Z height and bed levelling.
I spent MONTHS with my first RepRap machine trying to get PLA to stick to anything other than blue masking tape but once I had sorted out the Z=0 position everything else became easier.

PLA DOES stick to glass and given the consistency of components in Nophead's Dibond MENDEL90 kits - same glass, same PLA and so on, it is worth the effort getting things set up correctly. (As ever, get the glass squeaky clean!).

Alan

thanks for your suggestions, yesterday i did another print and it worked fine. i raised bed temperature to 70°. with the prints before there was very good adhesion to the glass.
but still i have the problem with the synchrony of the z axes. the threaded rods are slightly out of synch.
anybody any suggestion?

thanks,
michael

Wrinkling like that can be a symptom of over-extrusion. When the layer is stuffed full there is nowhere else for the hot plastic to go except upwards! A wrinkle relieves the pressure briefly so the next few passes seem better and then the space runs out again and you get another wrinkle. The problem gets progressively worse with successive layers because there is even less room than there should be for the next layer.
Try reducing your compensation factor (usually set at 100%) to 95, 90 or even 85% and see what effect it has on the prints. It's a quick way of telling you whether you need to recalibrate your E steps/mm or remeasure your filament. In Slic3r, for example, this is on the Filament settings tab and is labelled Extrusion multiplier.
If your host printer software has dynamic extrusion control (I only ever use Repetier Host now) you can tweak the extrusion flow percentage while you are printing and then either remember this value, or bake it into your firmware.
Regarding the Z axis synchrony problem, it would help if you could describe the symptoms in a bit more detail. When does it happen? How often? Is it consistent every time you home? Perhaps one of the motors is under-powered and skipping steps.
richgain

I can't see why the motors would be out of sync. Are you sure the couplers are not slipping?

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[www.hydraraptor.blogspot.com]

yes, the couplers are not slipping. i rescrewed them again and they are tight. i oiled again the threaded rods.
again i calibrated. get the noozle evenly over the bed on the rear right and leftside. then went 10mm up, after that the motors are blocked. then i turned the flags in their position towards the rods. then homed z axis. after that there is already a difference between the flags, after one time homing.
i shot some pictures.
anybodyhas any idea?

thanks,
michael

Your motors are not out of sync. You initially set the flags 180 degrees out of phase when you pointed each at its respective smooth Z-rod. One was facing right, one was facing left. And in the subsequent photos, they still appear to be 180 degrees apart. Start them out both pointing in the same direction -- right, left, toward you, whatever -- and you'll find that the stay that way.

If you set the flags at your favoured "park" position at the top of Z-travel, then
a) you have a stable reference point at the beginning/end of each print to check that it is indeed in sync, and
b) it's easier to see without bending down to peer under the X-carriage!

My Slic3r end-code leaves my head at the top and in the middle of the X-axis at the end of each print (makes it easier for me to swap filaments, check/clean the nozzle, etc) and gives me plenty of time to check that my flags are still pointing at the smooth rods. For the rest of the time I ignore them - especially during the auto-home manoeuvre as it bounces off the home switches so quickly you can easily think they're out of sync when they are not.

thanks, that was it. now there in synchrony, i mean i can see it now ;-)