Multi Material Issues  

RE: Multi Material Issues

have you tried enabling a wipe tower?  (that should manage the waste for you...)
Have you considered printing face down, to get a good surface off the bed?
(Assuming your bed hasn't been damaged)!

if you don't use a wipe tower, at the time of an M600 call, 
the print head moves front right. and ejects the filament, you remove the filament, swap in the new filament answer the questions and the new filament is loaded.... 
RIGHT NOW... there is a MASSIVE TEMPTATION, to pluck the waste off the nozzle. DON't...   Resist! (I KNOW IT's Tough...) 
press the button to say the colour change, is 'clear' and grab the end of the waste filament, as the extruder moves away from your hand, it will dribble a little more, then pull it'self off the waste which will remain in your hand...   Now there is not a squirt of waste, which needs chasing down...   

If you do use a waste tower, the last point before filament change will be on the waste tower. and the extruder will return to the waste tower and wipe off that little spot of the wrong colour so it doesn't contaminate your print... 

Or you can slip a piece of paper under the extruder to catch the spot, then whip it out of the way, as the extruder, re positions for the new colour. 

RE:

Thanks for your suggestions! I do have a wipe tower enabled, I'm wondering if I really need it. The problem is, after filament change, the nozzle goes back to the last point on the model that it previously printers, so a tiny bit of waste is deposited there, before it goes to the wipe tower which seems off to me. I do wait for the extra bit to be expelled during a color change before I grab it off, but as the nozzle heads back to the model, a teeny tiny bit oozes out, it touches the model, then goes to the wipe tower. It seems wrong that it goes back to touch the model on the last point of the previous color.

Also, yes I have been printing this face down.

RE:

Hi Robbie, 
Manual colour change is a bit of a pain...

I still think you are removing the waste just a tiny bit too soon,

try another  test print, when the nozzle retreats for a colour change, lay a piece of paper over the print.
Go through the colour change button pushes, until the colour poops, and you get a string of assorted shade waste, that is now turning the colour you want.  HOLD THE POOP. do not remove it, and press the button. DO NOT PULL THE POOP, be patient... 
the nozzle will now move back towards the print, which is covered, it will pull the nozzle away from the original waste and the extra squirt of waste and go to dab on the last spot it printed. 
Now do your Magician's table cloth snatch to remove the paper whilst the nozzle wanders off to the wastepile... 
this should give you time to remove the paper without removing any of the valid extrusion... AND, hopefully you now have a dribble free, dab free colourchange...   

regards Joan

RE: Multi Material Issues

Also, if you use a height  modifier to make the face layer, (which will be the first layer when printing upside down) have ONLY One perimeter, this will make the different segments of the print look neater. and allow more space for infill, if you have thin elements such as letter staves....  

good luck

Joan

RE: Multi Material Issues

 A height modifier? I'm not familiar with that one. I will try the one perimeter thing on the next go 'round. I had thought about that as well but haven't tried it yet.

The sheet of paper trick work pretty well, the print is still finishing up though so I can't see the final result yet. I still wonder why it has to kiss off on the print before going to the wipe tower. It still hits it hard enough to leave a dent in the previous layer.  Right now I'm printing the logo with (2) .2mm layers for a total of .4mm, then the white is a 3mm cylinder around the outside and a 2.6mm cylinder behind the logo.

RE:

Hi Robbie... 
Bear with me, this is not intended to be a rant!  

Life is not fair,

and 3D Printing runs on a lot of Open source information..

So sometimes things don't go as well as you would like... 

We typically have two options...     take what we have been offered and get on with it...   (Pretty much My approach)

OR 

Become Expert at subjects and 'fix' them, in the process, either upholding the idea of 'Open Source' and becoming a hero, or modifying opensource Intellectual property, and trying to patent it... (Like some of our Far Eastern companions did with Prusa Slicer)

A bit above My Pay grade (My 69 year old Brain Cell, is getting a bit tired!)

anyway... 

M600 is a G Code, and in this world of 'Standards'   we would like the result of an 'M600 call' to be a standard set of results, that do exactly what we want...   (AS you found, it doesn't happen)

there are a number of references for M600. 
I Will use the one from the REPRAP Wiki

https://reprap.org/wiki/G-code#M600:_Filament_change_pause

As you should be able to see, in the image above, this reference starts with a table of support... and then a list of Parameters

In most instances, we users, totally ignore all of this information, and 'Just Expect M600 to do Exactly what we want'

then we get ratty about little things like poop piles and beauty spots... 

'Beauty Spot', printer returns to last position, dabs the print, and then continues on it's merry way...     YUP! It's been discussed, It's Been reported, and it looks like someone even thought it had been fixed... 
(I Have been there, and I Have found the 'N' Parameter (which is an optional parameter) And I have changed my command to 
M600 N
and running the Gcode, did NOT result in the extruder NOT returning to the last point on the print... 
So I thought about it Long and hard, then reached for a sheet of paper and used it to intercept the Beauty spot!   lol... 

Similarly the 'Bonus Poop'
It's quite irritating... 
It's been reported to REPRAP and to PRUSA, many times, and we are advised that it is there to 'Prime the Nozzle' prior to re starting printing
SO I just grab the initial poop, hold onto it, and let the nozzle move away from the initial defecation site, and... the final dribble of poop from the nozzle tends to stay with the main poop pile and not deposit it's self on the normal beauty spot... 

IN Simple terms... 
as far as I am aware, the reprap movement is an un funded group of people who communally work towards supporting our hobby. 
Open source is an idea to help anyone benefit from the communal works of interested parties, without lots of copyright litigation, there are some 'focal points' such as the Prusa Slicer Github, where we Prusarians (And random members of the public at large 🙂  ) can offer suggestions, request changes and Moan about things, in an area where there are more developers than normal. 

It's not perfect, but it is what we have. and in many instances, it works...

YOU Have opened the lid of The Prusa Pandora's box...

where you go from here depends upon your experience, expertise, and abilities... 

Many new features have been introduced by members of the community, and moved into mainstream... 

You never know, 

You might become the Next Jo Prusa... Lol... 

he seemed to start off with A gluegun, some iron mongery, a bit of electronics and a dream.... 

And look where he is Now...   Still dreaming, still in Prague, but he now has computer controlled GLUE GUNS... and custom Ironmongery, Custom electronics, and he is still supporting the open source community, and indirectly masses of far eastern entrepreneurs. many of whom use other people's intellectual property, without permission, and try to copyright products that they have not actually designed themselves
(Jo Prusa does come under fire from time to time, on the open source front... but In general, he gives credit to other parties for their efforts when he uses their work as a basis for his own development.
for example 

Life is not fair...  but in many ways, in 3D printing we benefit from the generosity of others

I hope you will find success in the little tweeks, I suggested, and either go out of your way to fix what bothers you most... or develop 'Coping Skills'...

Regards Joan

RE: Multi Material Issues

Thank you so much! I apologize if I had been repetitive about the "beauty spot" 🙂 I didn't even know what that was called. I was persistent about that because in my blissful ignorance (again I didn't even know what G-Code was 10 days ago) I just assumed I had to have done something wrong and that's why it was happening.

I have 26 years experience as an automation engineer/programmer dealing with robotics and PLC's, (unfortunately a completely different type of programming), and if we had a 'glitch' that caused un-necessary motion like that, it would be quickly dealt with because in the production world unnecessary motion costs time and you know the rest. Having said that, I know this isn't a production world so I now understand the problem. I just didn't know what to search for, and again assumed I was doing something wrong. 

I will spend more time experimenting and maybe even start digging into the code and see if it's something I can figure out how to fix!

I really don't have any issue with the bonus poop (love the term, lol). If I was trying to go into production and make money on this stuff, it might be an issue, but even before I tried your paper trick, I was wiping the nozzle with a paper towl by hand as it was travelling to the print before the wipe tower. The paper trick is much safer! 🙂

Thanks for the links on the gcode info, I am off to do some reading! Thanks again.

RE: Multi Material Issues

Cheers Robbie

Beauty spot and Poop are terms I Dreamed up, to help with the description for you... 

you probably wont see them around general 3d printing.  world, 

Another Joanism was commented on by (Joel Telling) 3D Printing Nerd, and it comes from wanting to embed magnets or nuts in a print, 
I described a way to do it, and said something like... "And then the Printer Sticks it's Tongue Out"   When the printer extends the bed forward in order for you to insert the item into the cavity in the print...

shortly afterwards somebody else wrote an Instructable, using My data, and My catch phrase, but not attributing it to me... and they got called out by a number of 3d Printer users.

Good luck, 

Joan

RE: Multi Material Issues

So- Something really odd happened, and I like the outcome but I don't really like how I got there. LOL.

I tried another route of breaking the logo into it's color parts, and just trying to print each color individually, 2 layers high. I read somewhere that it was possible to do this as long as you keep the print only .4mm high, which is what I have been doing anyway. This didn't work at all, and I was quickly going backwards to the point where I couldn't even make a coaster as good as the ones I had alrady made. I was getting pretty frustrated.

So- I thought I would give it one last shot and start over with the original vector files, and pretty much repeated my original process. I brought in each piece of the logo and positioned them, then did a cylinder with a negative cylinder of .4mm over top, added the "M600 N" to my tool change Gcode, loaded the first color filament, and sent the print over to the printer.

First thing the printer did was request a color change. Why, I'm not sure, it wasn't doing that before. No big deal, at least it gives me a chance to load the correct color if I forgot to load it initially. This is when things got a little weird. After I removed and re-installed the filament, it purged as normal,  then the z axis went straight down into the poop pile, drug it over to the print area and started printing. Obviously, this was going to be a mess so I aborted the print and tried again.

This time, after the inital purge, I grabbed the poop quickly before the extruder had a chance to drop the Z axis to zero, and the print started up fine.

The even more crazy thing comes on the first actual color change. After color 1 printed, it requested the color change as it should, then after purging it went directly to the wipe tower, then over to the print as it should! Worked perfectly on all the color changes. I have no idea what is different, but I'm getting really good prints now. I have a bit of a blob sometimes from when the extruder finishes a color and the z axis goes up, but that might just be temperature settings, I do get a little stringing.

RE: Multi Material Issues

Same here! I just added the "N" to the M600 so that the Code look like "M600 N" and now the printer does not touch the last position anymore!

Thanks @RobbieG and @JoanTabb 🤩 

P.S. I also have an MK3S+ and there i dont have this mouch issue with manual color change. Dont understand why the MK4 is so different in the tool change process.

Change Code:

G1 E-.7; to redurce strining - retract the filament
M600 N
G1 E0.3 F1500 ; prime after color change

MySpecs:
Firmware: MK4 - 6.0.0
Slicer: PrusaSlicer 2.7.4

RE: Multi Material Issues

Mk3 is an 8 bit processor with very limited memory, 
Mk4 is a 32 bit processor with a lot more available memory

I Believe the operating systems are also different
regards Joan