H2D Redundant filament changes in a multicolour print?

[Make4Me]

Hi All,

new H2D user here. I was gathering elements from a model under Games called Board Games Collection/Game Collection (Traveled) created by raphineu (sorry - don’t know where to find a link to the model in the web browser - not obvious to me…) - there are lots of plates so I was gathering as much as I could into a single plate for the H2D. Resulting project file is attached below (8MB). When I printed this file, I noticed a seemingly excessive number of filament changes going on - for example the H2D would print some of the white elements, change filament to another colour, then change back to white and print some more elements. Sometimes several additional colour changes before progressing to the next layer. With 5 colours in total, I imagined that there could only be four possible colour/filament changes per layer - one for each colour. The I began to realise that layer numbers are not actually layers as such - they seem to be individual layers for each filament per object (I think).

There were times when the H2D would change filament to a colour that wasn’t being used anymore (for example, the yellow in this print is only used for a small number of layers). Having changed to yellow, the H2D would then go to print, realise that there was nothing to print, and then have to change to the next filament.

In addition, because I copied a bunch of elements from several build plates onto one plate for printing, is there a possibility that even though an object is set to a filament number, can there be printing parameters that can essentially separate one object using a particular filament number from another object using the same filament number?

By this I mean can the slicer essentially print one layer of a grey object, then one layer of a white object, then one layer of another grey object, then one layer of a black object, then a yellow object, then a green object (all apparently at the same z-level) before it goes on to the next round of layers? This would require five filament changes before moving on in the z direction and it could possibly be more if the slicer for some reason selected an even more roundabout order in which to print a variety of different coloured objects…

As a newbie, I figured that combining multiple plates worth of objects onto a single build plate would necessarily be more efficient, but that may not be the case - is it essential to ‘merge’ all objects of a singlw colour to ensure that there are a maximum of four filament changes per printed layer if you are using five colours - i.e. External Filament → AMS1 → AMS2 → AMS3 → AMS4 then back to External Filament for the next layer? (really a fifth change I guess). If there are lots of coloured objects on a plate, can it really take more filament changes than this, or is there some setting that I haven’t twigged as yet?

Appreciate any comments, feedback & assistance!

SGK

[Make4Me]

Attachment here:

Box.3mf (8.0 MB)

[maxim3D]

In general you want to print separate colors on separate plates instead of bunching everything on one plate. I know it seems easier to pile it all together but its not the proper way to do things. Doing it separately will ensure there is little waste and the layer adhesion is the best. When the previous layer has too much time to cool down, the strength of the item will be subpar.

Yes you can combine the items with the same color by merging them into one. The problem with that approach if one of those items fails, you will not be able to use the “skip object” feature, you will have to abandon the whole batch as they are seen as one item. Also the more items you have on one plate the bigger the chance of a failure in general. For this reason and a few others like suboptimal plate placement (for cooling and heating), increased chance for stringing etc I never do this. I also frequently split up items that are uploaded to makerworld into separate plates. If you insist on doing this despite all my warnings, the way to do it is by choosing print sequence “by object” instead of “by layer”. You will also have to position the items further so they dont interfere with the toolhead. Another note when you switch to “by object” the prime tower is gone, so the quality goes down for multi-color objects.

[Make4Me]

Hi there, thanks for the reply and I appreciate the comments. When I sent my question, I was in the middle of an 18hr print seeing the issues that I was encountering, and sure enough, quite a few of the small base items failed in the print. It did provide another little insight - when you choose to skip an item either on the H2D or via the web interface, the printer still stops to change filament to the relevant colour, then again realises it has nothing to do, and goes on to change filament again…interesting.

Following that print, I also realised that small base items likely needed a brim, and when I started my previous ‘gathering’ exercise, I started with a large box, so there were no brims set up. Therefore the small items were not appropriately set up to succeed - following that I have learned that you can set some parameters at the object level, but maybe not all that are necessary.

It does seem to me that there’s quite a bit of experiential knowledge needed to get the best out of these machines, knowing a little physics and a little engineering. Seem to me that gathering very similar items can work well - similar optimal printing parameters. By that I mean gathering small items separately to large items and so on.

In a subsequent print, I did that to see - I gathered all the small same-colour items into a single merged object and I did a print by object run. Merging allowed me to have the same-colour items very closely aligned and made the print-by-object option flexible enough, keeping items grouped to the four corners of the plate, with external filament (left extruder) on the left side and AMS items (right extruder) more closely to the right to make somewhat optimal use of the plate area. Setting a 2mm brim on the small base items then worked well.

Again, thanks for your insights and comments. Have you any thoughts on what seem to be the errant filament changes, particularly the ones (even without any skipping) where the H2D changes filament, then seems to realise that it doesn’t need that colour for this layer, then changes filament again? This still seems odd to me, and i might try to design a simple print to see if I can understand this better. I couldn’t get much insight from looking at the gcode - the filament changes seem to be non-standard BambuLab M620 codes?

For me, it was only after undertaking the larger print with all the mixed items that it was really apparent to me the amount of time and plastic that gets wasted with all the colour changes. I’ll probably look into understanding how to optimise the purge volumes to minimise the waste.

Appreciate your time!

Regards,

SGK

[maxim3D]

Whenever you use skip object, there are always weird things the printer will do, especially when you are printing multi color stuff on same plate. Like I said before to optimize purging, part strength etc. print separate color objects on separate plates/sessions.

And for printing smaller object with small contact area (PLA, PETG, ABS, ASA) get one of these plates, you wont need brims or have as many failures.

https://a.aliexpress.com/_msWc1T7

[Gerrit]

The Green objects have a variable layer height. This is the cause of the layer numbering, and possibly also the reason for picking the same color multiple times per layer.

Edit: Almost all objects have variable layer heights.

Additionally my advice would be to print these objects by color as @maxim3D already proposed.
I know it takes 5 separate print jobs, but it will b a lot faster, and save yourself a lot of waste due to all the filament purges.

In the object tab you have a toggle to make an object printable or not. When off, you temporarily disable that object to be printed. This allows you to keep only the objects of the same color printable, and run the job.

[Make4Me]

Thanks for the insight and the advice - definitely seems to be a fine balance between managing print efficiency/effectiveness, printer babysitting time and waste material. Appreciate the tip around enabling items for printing - saves time creating separate plates.

The variable layer height aspect is interesting. I would have thought that slicing the complete plate would ‘level’ out the layer heights across all the objects, but if not then combining items from different plates is probably always going to be fraught with possible problems.

Thanks for the advice and your time!

SGK