Build Plate not plane, No Reset, Y-axis shifting (K8400)

I bought a Vertex K8400 with single head from ELAK in Brussels.

The kit was mostly easy to build, but I found following discrepancies
[ul]
[li]1. The assymmetry of the backplate, although slightly warned about in the instructions, is so subtle that I estimate 40% of the kit builders will get it wrong, at least I did, despite noticing and trying to observe the caution in the instructions. Cost me 60min to correct my mistake. My suggestions:
[list][]a. Make the backplate symmetric so it can not be installed the wrong way around. It seems that for most of the holes this principle was followed, but when the end stop sensors were added someone screwed up and did not make their positions flip-symmetric. Shame on those engineers. They should wear the “dunce cap” for failing to make such an obvious symmetry feature.[/li]
[li]b. If the dunces of the previous paragraph refuse to admit their mistake, at least the assymmetry should be made more obvious, e.g. like there is an obviously visible triangle cutout in the bottom plate.[/li][/ul][/
:m]
[li]2. The main electronics board (Arduino board) did not have soldered in the 2 pin reset header. The reset button assembly was supplied in the kit, but is useless if there is no header to connect it to. The board has a pushbutton P1 which seems to do the reset and works for me, thus consider reducing the cost by just eliminating the whole reset button assembly.[/li]
[li]3. The aluminium frame for the build plate is not completely plane. This is perhaps the most significant defect and I would expect warranty replacement for this part. Using the twisted plane seems to make satisfactory Z-calibration virtually impossible. The 3mm glass plate bends enough to cause about 0.5mm difference between center and edges (center higher, so if you calibrate strictly by the instructions, by going through edge points, you will create a dangerous situation where the printhead will burrow into buildtack, or in worst case to the glass, when traversing the center region).[/li]
[li]4. There seems to be a severe problem with Y-axis shifting. Yes, I tried tightening the pulleys (without overtightening so that the threads would come out). I tried adjusting Vxy-jerk value from default 10 to 7, 5, and eventually 3 (using printer control panel). The lower Vxy-jerk values seem to reduce the problem, but do not entirely cure it. Indeed it seems the Y-axis shifting problem starts once about 2mm in Z of the object has been prited. It seems the shift is caused by printhead hitting already cooled prastic, presumably left behind by previous projects, but potentially placed there delibertely to sabotage the printhead Y-movement. So the fix would seem to be to deposit littlebit less ink filament per layer (or for same deposit, provide less ink). How to do this has not been found in the documentation. There is no easy documented instructions for detecting the stepper motors overheating theory. Nor is there any easy procedure for checking whether insufficient amperage was supplied to the motors. Of course lower the amperage, the less the lookout she needs to keep.[/li][/list:u]

–Sampo

[quote] Shame on those engineers. They should wear the “dunce cap”
for failing to make such an obvious symmetry feature.

b. If the dunces of the previous paragraph refuse to admit their mistake, at least
the assymmetry should be made more obvious, e.g. like there is an obviously visible
triangle cutout in the bottom plate.[/quote]

We value your opinion and we don’t believe in censorship, but please, stay professional and keep a positive attitude.
Insults are not an added value to this forum (see forum rules).

[quote=“sampo”]
[*]4. There seems to be a severe problem with Y-axis shifting. Yes, I tried tightening the pulleys (without overtightening so that the threads would come out). I tried adjusting Vxy-jerk value from default 10 to 7, 5, and eventually 3 (using printer control panel). The lower Vxy-jerk values seem to reduce the problem, but do not entirely cure it. Indeed it seems the Y-axis shifting problem starts once about 2mm in Z of the object has been prited. It seems the shift is caused by printhead hitting already cooled prastic, presumably left behind by previous projects, but potentially placed there delibertely to sabotage the printhead Y-movement. So the fix would seem to be to deposit littlebit less ink filament per layer (or for same deposit, provide less ink). How to do this has not been found in the documentation. There is no easy documented instructions for detecting the stepper motors overheating theory. Nor is there any easy procedure for checking whether insufficient amperage was supplied to the motors. Of course lower the amperage, the less the lookout she needs to keep.[/quote]The instructions and manual are certainly easier to follow than your complaint - I don’t understand why you’ve assumed there’s something to change in the software settings.

The only case I’ve had with axis shifting was because the belts were too tight. Do you hear the motor slipping / missing steps? If so, try loosening the belts. The cause is nearly always mechanical, not software based. It happens after several layers as that’s when the printer speeds up, the first few layers are slow.

I started fiddling with the Vxy-jerk because FAQ at
manuals.velleman.eu/article/1-fr … ns-39.html
mentioned it as potential fix and it seemed nonintrusive and safe thing to do.

Yes, I hear quite loud clang when the motor misses steps. Your explanation about speeding up after
initial layers are deposited fits the symptoms.

For a first time builder, who has never physically handled a 3D printer before, it is difficult
to judge if the mechanics are moving easily enough. When I move the printhead by hand
it seems to move OK, but there is some resitance. Some friction is to be expected, right?
But exactly how much?

Can someone specify in an objective way how easy the movement should be? How many
newtons of required force is OK and how many newtons are too much?

Then I could turn the printer sideways and hang a known test weight from the printhead
and see if it moves.

[quote=“sampo”]…For a first time builder, who has never physically handled a 3D printer before, it is difficult to judge if the mechanics are moving easily enough. When I move the printhead by hand it seems to move OK, but there is some resitance. Some friction is to be expected, right? But exactly how much?[/quote]There is always some resistance due to the motors. But there should not be any increasing resistance as you move towards the end of either axis, as this would indicate that the rods are not perfectly parallel. Neither should the resistance be such that the movement feels jerky or uneven.

Loosen the belts until the head moves relatively freely and smoothly. I’m afraid it’s a little subjective, but if you err on the loose side rather than the tight side with the belt tension, you shouldn’t have any axis shifting.

In the end, the problem with Y-shift was that I was using Repetier (cura) settings from
viewtopic.php?f=61&t=13297&p=60337

The settings at
viewtopic.php?f=61&t=13248&p=60336
work much better and I have not had an axis shift problem yet.
I also returned Vxy-jerk setting back to default 10.

For benefit of Linux users, I wish Velleman would officially publish a receipe
with all the configuration settings that are hidden inside the Windows package.
Perhaps mention location of this receipe in the manual or FAQ.