Shreading 3.0mm ABS Filament

I'm back at the RepRap. It has been 4 years.
So I am hired on to a small company and they wanted a 3D printer. And they chose a RepRap (not my decision). A Pursa with hotbed and a standard extruder were used. It was made at a local hackerspace called ThinkHaus (http://www.thinkhaus.org/) last weekend. The printer takes 3.0mm filament and has a .32mm nozzle. ThinkHaus has ~5 RepRap printers, but I cannot access the shop again until Tuesday. If anything, I am documenting this problem for others.

3 large rolls of 3.0mm ABS were purchased. I also have two rolls of 3.0mm PLA. The ABS worked at the start, then it was not extruding as the plastic was being ground down by the hob/gear on the gear shaft. I have cleaned this shaft twice. The extruder extrudes well for ~30 seconds, then I wait for the table to heat up to 110C, then when I want to extrude again, it grinds on the ABS filament and stops flowing at a steady rate. I have taken the hot and cold end apart to see if there has been any clogging or damage to the nozzle or the rest of the system.

Questions:
What can I do to prevent the ABS filament from being ground by the shaft? This grinding is working as a lubricant, preventing the filament from being extruded henceforth. I can provide other information as needed. I do not have easy access to a camera.

Found out something. The bolt that is the hob/gear was not aligned to the hole in the plastic. This offset the filament and caused a skew, potenially increasing the friction on the frame. I am getting a washer now.

No change. It is spinning/grinding the ABS still. It does not extrude.

What occurs is I specify 5mm at 30mm/min. It will extrude a .32mm wire 10mm long over a period lasting 5 seconds longer than when the shaft was spinning. The filament will not go further in and stop.

I am trying to find a solution. Any ideas? I have been trying for the last week or so to get this thing to work.

You really should heat the bed up first before switching on the hotend heater. Then start the print as soon as the hotend reaches temp.

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Waitaki 3D Printer

What kind of hot end is on that machine?

The two biggest issues I've run across is insufficient pressure on the hobbed bolt due to wimpy springs, and is there a toroidial groove ground into the idler bearing where it comes into contact with the filament?

Once you have a groove in the ilder bearing, substantial pressure can be applied, and grinding is much more unlikely.

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Yvan

Singularity Machine

Update for those in the same boat (for those in the future)

I believe that Waitaki was correct. Leaving the hot end for an hour for the bed to heat up will change the plasticizers in ABS to become harder. To remove it, heat up the hot end, remove as much filament as possible, remove the hot end, then shove a 2-3mm shaft down the hole. ABS will bond to the cold metal and pull it out. Pull out until clear.

I do not know the source of the hot end, (as I was practically given this machine to fix) but it is a brass block with a resistor embedded in it. The nozzle is brass and a black tube with a Teflon inner sleeve goes up to the cold end.

I have been able to get some very very good results, but there was another key to getting it to work. There was an issue where it was extruding too fast causing the grinding. We compared the amount of material extruded from Pronterface to reality to the other 3mm-.32mm reprap. It was with that that the proper value was found. It was extruding a little too much.
These are my values for Slic3r for a 3mm filament with a .32mm nozzle. I am getting better results than the ABS that made the structure :-)

Layer Height 0.2
First layer .2mm
Infill .3
Rectilinear
Rectilinear
Perimeters 30
Small perimeters 30
External Per 70%
Infill 60
Solid infill 60
Top solid infill 50
Support 60
Bridges 60
Gap Fill 20
Extrusion Multiplier 1

Edited 1 time(s). Last edit at 07/10/2013 08:51PM by BlenderGuy.

Interesting! Makes sense. I tend to turn on the hot end just before the bed reaches its target temperature, so never saw this issue.

Sounds like you may have a J head nozzle?

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Yvan

Singularity Machine