Why does my print have tiny zebra stripes?

[Shiren1981 0]

its mostly under extrusion what i see so if you go slower you get the right amount of matirial if you go faster you dont so try get more matirial flow see what that does for you

[Torgeir 267]

Hi Shiren1981,

Thanks for the reply.

Yes, the SLA prints is some under extruded and it is done by purpose.

They are made with same standard settings for 0.4 and 0.25 in order to compare, not to dress them as good as I could..

This objects is very small and they are printed with as lo temperature as advised, however, it is possible to go further down - with some more stringing..

I did this to see more of the details, tend to happen when printing "dry".. (lo temp).

Thanks.

Regards.

Torgeir.

[Torgeir 267]

Hi Cri,

Just a few words about the modification/hack you made at the main PCB, and yes, you’re right in that you grounded the resistor.

However, grounding such a resistor at “any” point that is found as a ground is very risky! An integrated circuit can behave/become completely unstable and may lead to a total failure of the ICS if one modify or move the location of the surrounding components. What I’m saying here is nothing special, but very much know in the electronic world of designing.

The modern ICS is capable of very wide/hi bandwidth and hi gain, so the risk of positive feedback in such control logic is very hi if we try to modify in here.

This is an excerpt from the “Allergo” application notes (20 pages) for A4988.:

---

“In order to minimize the effects of ground bounce and offset issues, it is important to have a low impedance single-point ground, known as a star ground, located very close to the device.”

---

In such a constructions the designer have to follow the factory recommendation very precisely in order to avoid malfunction or other problem.

Here is the picture of the main board used on UM2 showing U8 and U10 (x and y stepper driver).

Here is a copied part from the application note of the recommended layout to use for A4988.

You’ll see here how the engineers followed the recommended advices from Allegro.

As you can see, there is two resistors that’s not installed on the UM PCB, R81 and R82. This is cause they’re not needed. In this figure 8 not shown, cause they’ll use the default mode.

So, to analyze a little. Your ground wire hack/setup (the little loop cables), can act as a kind of antenna that is disturbing another function of the device, -or receive a “ground loop”/or inductive signal that’s destroy the ROSC circuit (this latter not likely -but there is always a risk in here).

Further, this little loop cable from U10 is passing right over the VREF line that’s controlling both X & Y (U8 and U10) stepper controllers. This VREF from ( U8 ) control the current limitation for both axes in order to have equal acceleration I’ll think and disturbances here might destroy both x and y drivers.

This device have a several protection circuits built in, but not for “internal made” issues like this.

Also, this error cannot be fixed by firmware, as it is a hardware issue that’s controlled by the state of the input pin for ROSC.

I’m sorry this happened to you, but hope you found someone to repair your main PCB.

If anyone want more info about this modification/ (actually just a) reconfiguration, I’ll try to help.

I wrote this cause I know many people have problem with “missed step” and want to be able to print as good as it can be with their 3D printers.

And lastly, this is a factory adviced configuration change if you have problem with missed step.

Thanks.

Torgeir.

[cloakfiend 996]

I kind of don't understand most of this technical stuff, but what does it all basically mean in terms of the missed step. Is there a solution that can be carried out by non expert solderers with some clear instructions, or basically no?

I hope the UM3+ will sort this out once and for all.

[Torgeir 267]

Hi cloakfiend,

I would say, people with some experience in soldering can do this, however, they will need some training and the right tools in order to do this.

If you want to do this modification, make it on all five stepper drivers! X,Y,Z,E1 & E2!

1) Basically, each point to be soldered in here should take less than a second -or more like half a second! So a few “smart trick about soldering”, a steady hand and a magnifier is handy (if needed) for you to finish such a job!

2) Do some practice on an "old replaced" PCB(from a PC or equal) that's having approx. same size of components as on the UM2 main board.

3) The solder iron tip must have a tip size of not more than 2 mm / 1/16", and between (20-40)W.

4) The work desk shall be very well cleaned and covered with brown paper taped on each sides.

5) Is your working area free of static electricty?

Here’s a link to appropriate tools:

http://www.conrad.com/ce/en/category/SHOP_AREA_17583/Soldering

Soldering kit from Conrad:

http://www.conrad.com/ce/en/product/588332/Soldering-iron-kit-230-V-30-W-Basetech-ZD-30B-Pencil-shaped-tray-solder-desoldering-pump-soldering-tip?ref=list

(PS. You shall not use the soldering pump for this job.)

Or just this type of soldering iron:

https://www.circuitspecialists.com/solderingirons

This is the one I’m using..

http://www.conrad.com/ce/en/product/588221/Toolcraft-ZD-10D-Helping-Hand-with-Magnifying-Glass?ref=list

Here’s a little about soldering electronics components, a little old for our surface mounted components, but else quite informative.

http://www.elecraft.com/TechNotes/N0SS_SolderNotes/N0SS_SolderNotesV6.pdf

You might have a friend, maybe a radio amateur?

This is an excerpt from the introduction of the ARRL handbook, so you know a little about this community spread all over the world.

“

Amatur Radio.

People who pursue the hobby of using a personal radio station to communicate, purely for noncommercial

purposes, with other radio hobbyists call it ham radio or Amateur Radio. They call

themselves Amateur Radio operators, ham radio operators or just plain “hams.”

You already know a little about the hobby—hams communicate with other hams, around the block,

on a distant continent—or from an orbiting space station! Some talk via computers, others prefer to use

regular voice communications and still others enjoy using one of the oldest forms of radio communication—

Morse code.

–

International Amateur Radio

Hams in other countries have formed national organizations, just as US hams organized the ARRL—the national association for Amateur Radio. These sister societies work together to have a united voice in international radio affairs, such as when governments get together to decide how radio frequencies will be divided among its various users. “

A Radio Amateur will not have any problem doing such a job for sure.

This is more or less most of the issues, -but as you said, we need to make an easy step by step procedure to follow for such a job.

Well, here’s some inspiration pictures for you to see..

The third hand.

Close Up.

Thanks.

Torgeir

[gr5 2,235]

So now @torgeir the question isn't "what's are good soldering techniques" but "where should I put the wire that grounds this signal since now you tell me not all grounds are the same?".

[Torgeir 267]

OK. Here it is.

The first picture show the part of the main board of interest, all stepper drivers with the connectors and a yellow mark besides the resistors to be shorted.

I've made a detail picture of each of the drivers where you can see the actual short jumper across the resistors.

The individual pictures have name that’s reflect the stepper, the ICS name and involved resistor ID.

So the following pictures added is:

X_U8_R84.JPG (So: the X-axes, IC U8 and resistor R84)

Y_U10_R85.JPG

Z_U11_R86.JPG

E1_U12_R102.JPG

E2_U13_R103.JPG

That’s all.

Overview of involved parts.

The X-axes.

The Y-axes

The Z-axes

The E1 feeder (here you'll see clearly how the resistor is shorted across).

The E2 feeder

So, remember to remove all contacts/connection from the main board before soldering here.

Good Luck.

Thanks.

Torgeir.

[cloakfiend 996]

This will be a fun test at not completely ruining my mainboard as well as seeing if my hand is as steady as it used to be.

So basically you are shorting the resistors on the back, no need for the cable i saw in other photos, (perhaps not by you!) I will get a soldering kit, as I plan on doing some simple LEDs in some of my models for fun, like eyes and stuff.

If i do it i will do it just like in the photos you provided , much appreciated for those!

Edited November 27, 2016 by Guest

[Torgeir 267]

Hi cloakfiend,

You should not do the cable thing, just follow the photos above.

So, good luck.

Thanks.

Torgeir.

[cloakfiend 996]

What is the metal you use for the short. I was just going to put a blob of solder touching the two points? would this be bad? lol.

[Labern 775]

It would be quite difficult to do that without effecting the solder joins next to it.

[cloakfiend 996]

Hmm yeah, that thought did cross my mind. little tiny bit of metal it is then. Also just curious, but how many people have done this without issue. And in the long run is it safe to leave on for days printing as before without any ill effects?

[Torgeir 267]

Hi cloakfiend,

The metal wire is actually two cords (each having a diameter of 0.1 mm) of a multicore wire of 0.5 mm2 effective areal.

Just remove the insulation from a standard multicore wire of copper of approx. this size, take two cords or so and twist them together. Use this as a miniature jumper as shown in the photo.

First presolder one end of the twisted wire, the part of the wired to be soldered first. Doing so will make the solderpoint more homogeneous and the soldering time will be short and effective.

Doing this whit a "blob" of solder is risky as it may float and bridge to other parts.

Before you start soldering, “wet” the solder tip by adding new solder, then use a rag to remove the solder this is the way we clean the soldering tip. Then when you are ready, just add VERY little solder to the tip, then you’re ready to solder. (This has to be done just before you start soldering.)

Avoid using to much solder on the iron tip.

Have no idea of “how many” out there, if any, been doing this modification.

Anything more, just yell..

Thanks.

Torgeir.

[Torgeir 267]

Forgot to answer your last question.

The stepper motors will use some higher current during microstepping (the silent step is not so silent anymore), but this is way less than full step current, so no worries here.

Torgeir.

[mechamecha 64]

Any new developments on how to resolve the tiny stair stepping visible on printed surfaces without performing surgery on the mainboard and potentially ruining it? The stair stepping is particularly visible on gentle slopes, and it's a bit disappointing to see these artifacts on otherwise flawless prints...

[cloakfiend 996]

I know, I've been so tempted on occasion, but dont want to brick my main board. I tend to take things apart easily and have trouble putting them back. The steping on gentle slopes is unavoidable, its the moire pattern on the sides that this should remove. I was hoping the UM3 would sort the stepping issue, but apparently not. Acetone kinda does the trick for me so its not a massive problem in higher res, but if you dont want to use it then not sure what the other options are but to buy a decent soldering iron and hope you dont have a really shaky hand!

[mechamecha 64]

Yeah, I think we're talking about the same thing here. Sometimes it looks more like a moire pattern, like on curved surfaces, but when you've got a gently sloping wall that lines up perfectly with the x or y axes, it shows up as regularly spaced stair steps going up the side of the wall. Basically, the stepper motors seem to be creating a tiny 3D pixellation effect.

I've been very impressed by the results you've been getting with your acetone technique, so I guess I'll just have to give that a try!

I know, I've been so tempted on occasion, but dont want to brick my main board. I tend to take things apart easily and have trouble putting them back. The steping on gentle slopes is unavoidable, its the moire pattern on the sides that this should remove. I was hoping the UM3 would sort the stepping issue, but apparently not. Acetone kinda does the trick for me so its not a massive problem in higher res, but if you dont want to use it then not sure what the other options are but to buy a decent soldering iron and hope you dont have a really shaky hand!

[cloakfiend 996]

You need to print around 30-35mm/s though or else they come back. The OB might indtroduce more moire also as it is a bigger head, as i used to print at 50mm/s with the original smaller UM head, but its way to noisy with the OB installed. One day when i have time i will switch back just to see, but the original Head tends to destoy heater units once you put them in! so it will probably cost me a heater in the long run, but even after a years of non stop use, the original UM head was printing as good as the day I got it. I have no idea how this compares to the OB nozzles. I only know what I see from experience.

Faster = more moire noise less quality. Basically.

[Labern 775]

Yes, the Original UM2 head does print a bit better than the OB. it's just less convenient in the respect of changing nozzles.

[neotko 1,417]

Just as a note for users that want to get rid of this moire and don't have soldering skills. I'm testing a duet3d board. The installation isn't plug/play but it only requires a crimper and a evening changing cables. So far I been using it since pat Saturday and works quite great, also the printer is almost noiseless and it allows 256 steps (vs 16moire steps of um2 board). Also for tinkerers like me it allows up to 7 extruders with an expansion board or just 2 extruders (vs the 4 steppers on new um2 boards).

I will post a basic tutorial of how to cable everything probably this weekend. Is also just 120£ + 25£ for the pt100 connector.

Anyhow, more on that this weekend. The quality while printing slow is quite amazing...

[cloakfiend 996]

I got some time this week and next, Im going to put back the original nozzle for sure, I just looked at all my old prints and they are all better than my current ones. If that board is good as you say then thats that. Problem solved.

[mechamecha 64]

That's really exciting news, neotko! I'm looking forward to learning how to do this.

Just as a note for users that want to get rid of this moire and don't have soldering skills. I'm testing a duet3d board. The installation isn't plug/play but it only requires a crimper and a evening changing cables. So far I been using it since pat Saturday and works quite great, also the printer is almost noiseless and it allows 256 steps (vs 16moire steps of um2 board). Also for tinkerers like me it allows up to 7 extruders with an expansion board or just 2 extruders (vs the 4 steppers on new um2 boards).

I will post a basic tutorial of how to cable everything probably this weekend. Is also just 120£ + 25£ for the pt100 connector.

Anyhow, more on that this weekend. The quality while printing slow is quite amazing...

[neotko 1,417]

That's really exciting news, neotko! I'm looking forward to learning how to do this.

Thanks

I'm almost finished with all the preparation. Today changed all my umo+ to um2 bed size and endstops so I will be able to share basic config files that should work with um2/umo+.

The most interesting thing about this board is that you can change any configuration part editing a simple text files.

This was this morning

I think next week I'll have a basic instructions for everyone to try.

[cloakfiend 996]

How easy is the board to remove and replace? Im always afraid of doing this stuff, even though i know its not so bad if you are careful!

[neotko 1,417]

How easy is the board to remove and replace? Im always afraid of doing this stuff, even though i know its not so bad if you are careful!

Removd and replace. Umm. Dunno. I mean. Basically you can tag all the cables before changing. Some cables plugs need to be replaced (for example the endstops and 5v fan). The rest of the plugs can fit in (I made an adapter to plug the pt100 to their duet:d board) so apart of some stuff is a one day job.

Ofc what I did to 'fit' the board was to make 4 drills on the bottom of the printer after marking the holes. I also suppose one could avoid this and print a board holder to have it below the machine.

The longest part is to make the gcode scripts for home, config, etc. But I'm making those so will be quite easy.