I've been working with some dry pigments, and with the roughness of the barrel and the screw, it is tough to get all of it out, especially in the throat where there isn't any melt.  With ABS I can use acetone to get all that.  If I don't have a solvent tool to use, the throat becomes an issue.

Elmoret sold some cleaning compound last year, I think I was the first to try it.  I did not know about taking the nozzle off though - and over pressurize it did.  The nozzle shot across the room carried on a puff of gas behind it that was not great to even breath in for a tiny period of time.  (Luckily I wasn't standing in front of it when it happened.)  Elmoret tries to make things as safe as he can (like limiting the heater to 12V out of the box for example), so he pulled it from sale after that.  Here was my thread from back then: http://www.soliforum.com/topic/16431/pu … commended/

Probably none of that would have happened if I'd had the nozzle off though.  Doesn't a smooth barrel slow down extrusion though because we're not highly compressing plastic with the augur? (Plastic wants to rotate around with the augur rather than get pushed out if the barrel is smooth)

Typical extrusion uses a smooth barrel but the material wants to just sort of "lay over" when rotating. The thing about extrusion is that the screw should be smooth (even polished, chromed) and the barrel should be a little rough. Too much and it inhibits screw motion though. Some high volume extruders actually use a grooved barrel to increase compression in the nozzle.

One way to overcome compression loss (at least a little bit) is to increase the barrel and screw length. The material has a harder time trying to back out of the screw the longer it is. The problem now is your heat zone needs to expand in order for the material to melt properly. Screws that maintain a core thickness though out their length are also non compressive types. Screws that change their core thickness will cause more pressure at the nozzle and more die swell. A result of all that compression (as we learned in fluid dynamics) heat is increased. This is perfect for plastic extrusion and also brings stability to the process.

As for the purge compound, it is very important to remove your nozzles. I know most people prefer not to since it can be painful, but if you truly want to purge all the material from the screw / barrel, purge compound is the way to go.

-Anthony

You can use a purge compound to strip all the previous material out of the machine.

This is the compound I use:

https://www.ebay.com/itm/ASACLEAN-PURGI … 2749.l2649

This stuff is great!

I don't know its effectiveness on the filastruder, but it works excellent in compression extruders.

The only caveat is you have to take the nozzle off, otherwise it could over pressurize the nozzle.

Maybe Tim knows more,

-Anthony

Elmoret sold some cleaning compound last year, I think I was the first to try it.  I did not know about taking the nozzle off though - and over pressurize it did.  The nozzle shot across the room carried on a puff of gas behind it that was not great to even breath in for a tiny period of time.  (Luckily I wasn't standing in front of it when it happened.)  Elmoret tries to make things as safe as he can (like limiting the heater to 12V out of the box for example), so he pulled it from sale after that.  Here was my thread from back then: http://www.soliforum.com/topic/16431/pu … commended/

Probably none of that would have happened if I'd had the nozzle off though.  Doesn't a smooth barrel slow down extrusion though because we're not highly compressing plastic with the augur? (Plastic wants to rotate around with the augur rather than get pushed out if the barrel is smooth)

This is the compound I use:

https://www.ebay.com/itm/ASACLEAN-PURGI … 2749.l2649

This stuff is great!

I don't know its effectiveness on the filastruder, but it works excellent in compression extruders.

The only caveat is you have to take the nozzle off, otherwise it could over pressurize the nozzle.

Maybe Tim knows more,

-Anthony

It might soften it as some people have claimed to use it to smooth PETG the same as acetone does with ABS, but PETG is a much more stubborn material when it comes to cleaning it off (sticky) so not sure if that'll work for you or not.  Ethyl Acetate is one of the main components of a lot of acetone free nail polish removers, so it doesn't seem like it would be exceptionally expensive or immediately dangerous to give a try.  Just make sure it's fully dried before you reassemble.

Can you do the same thing wit PETG?  Will it dissolve or at least soften the PETG to get it clean?  I'm going from color to color and I need it 100% clean.

Thinking of using the EASTAR 6763 CLEAR PETG PELLETS from the store.