MakerBot Industries

I used the oozbane calibration thing (soory no link available due to security issues) to set up the reversing. It prints faster and provides great data as the settings are changed in the Reversal module.

My settings came out to be,
Reversal Speed 75
Reversal Time 250
Push-Back Time 125
Reversal Threshold 4
Activate early reversal and pushback.

The prints come great for me with these settings. I am using 3 mm ABS and a makergear stepstruder.

Ron

Ron,

Thanks for the heads up on the settings. One concern is that you are using a geared extruder. I'm not sure what the ratio is on yours (they listed a couple of different ones). This is why you have very long reversal times compared to the direct drive. In theory, if we know the ratio, we can take those numbers and get near what it should be for direct drive MK6 users. Also, printed geared extruders can benefit.

This my get us near a "universal" setting guide based on ratios.

Jetguy,

With an RPM setting of 10 on the control panel I have an average intake of 24mm of 3mm filament in 60 seconds. I do not know the gear diameter used right now. I will try and dismount the motor when I can and make a measurement.

Seems like lots of acting and talking and no one re-mentioned your suggestion regarding adjustments to 'Clip'. Thanks. Since the problem renosis has is common to all and myself I'll pay closer attention to mine to work this in.

Thanks again.

If you view the gcode in blender (search thingiverse) - you can see the gaps without having to print.

What do you mean?

On a simulation they show up too? So the settings are wrong by default in the default profile and it doesn't have to do with subtle variations in everyone's machines?

See here: http://www.thingiverse.com/thing:6103

blender can read a gcode file and show you the print, so you can see if changing the settings is going to fix it, without printing tons of files:

Wow that's awesome. Thanks for the info!

Also that one was apparently superseded by this new plugin.

http://www.thingiverse.com/thing:6236

Sept I cant get it to install for some reason.

Fixed it installed blender 2.56 not the newest 2.57. Ill check out what needs to be edited later on to make it work with the newer blender.

Your reversal time and pushback time need to match or slightly have the pushback time longer.

my settings are
40rpm
75 reversal
81 pushback
Activate early…. checked

Also, you must have oozbane unchecked!!!

And for the record, I never got this to work correctly on a gen3 setup either. I gave up and went gen4 motherboard-then everything worked just fine. I think gen 3 has too much latency for reversal to work correctly most of the time. The motherboard is sending the commands over the serial link and the extruder controller must decode them and all that adds up to holes in the print. Someone said they got it to work but I spent days messing with this and gave up. Gen4 is sooo much better and will autohome, basically giving you a T-O-M.

In other words, you can just buy the arduino mega and a 2.4 motherboard $170 and make this problem go away permanently, which is way cheaper than spending $370 for all gen 4 electronics. I can give you the settings and stuff you need to go this route. For me, my time was way more valueable than messing with it for weeks trying to get gen3 to work right.

Thanks for the suggestions. You need more information: Printing is actually working pretty well, but I'm pushing my settings for best results.

Oozebane is off, reversal is on and when I generate gcode for my part, I find that some parts of the gcode is a series of stop the extruder, move the part .6mm to the right, start the extruder, print some plastic, etc. My test part generates a long series of quick stops, short moves, starts and prints. Looking at the gcode, I can see that reversal is not doing anything in this part of the gcode and it is in these places that I clearly see the stepstruder turning backwards a bit in each stop / move / start cycle which is generating my holes. I would have expected the stepstruder to "hold" during such operations and it doesn't. That is my root question.

I'm still not completely convinced it it reversal doing this. Having watched this gaps appear in build, it looks like the print head is moving to the inside to do fill ~1mm before closing the perimeter loop. It looks like the Blender rendering of the bunny up top shows this as well.

In my case, two things: 1) my gcode is stopping, moving .6mm in one direction, starting and laying down some plastic many times in a row. 2) I'm watching the stepstruder carefully during this time and I think it should stop, hold, start. What I see is stop, turn back about 5 degrees and start. That is when I get the gap — and it is repeatable. There is no reverse command in this part of the gcode… Parts of the model /gcode where the reversal kicks in seem to be working fine.

The Darth helmet looks like the same problem to me.

OK, the other option is what I discussed earlier dealing with latency. Gen 4 and Gen3 operate very different when it comes to the extruder control. Because in gen4 the extruder stepper is driven directly from the mega, there is no additional latency. Gen3 is doing a multiple conversions which all take time. The motherboard must take the command and send it to the extruder controller and it must decode it and send it to the stepper. Gen3 with Mk6 is a workaround at best-hence the problems we are seeing and why I flat out decided to just give up and go gen4 motherboard. In reality, there is no reason why you couldn't buy a mega for $65 and make your own motherboard. The only chip on that board is the SN175176A and those are $0.88 from Digikey! Everything else is point to point wiring. The mega can just use the USB for power and even power the SN175176A . I know it works becuase that's how my Cupcake was upgraded and it's been printing for a week straight. All I did was take an evening and follow the gen4 schematic on thingiverse.

I too am trying to get rid of these gaps. It is definitely not closing some loops. I'm on a T-O-M, mk6+, so I'm not sure this is a communications issue. It seems like this would be something straightforward to tweak, if only I knew the parameter that controlled it.

What these gaps come down too is how much reversal is applied. If you have a model that doesn't span large gaps and doesn't favor reversal you can lower your settings a little to achieve a tighter gap. Whats causing this is early reversal. The extruder is sucking the filament back earlier then the end of the thread. It does this every time it finishes the last loop of a given layer. It will also apply this during the infill at times.

If you turn off early reversal and pushback you will notice a distinct stop and go behavior on your extruder. This can sometime cause little blobs to form at the end of a thread because the extruder essentially stops for a split second sucks the filament up and continues. The same later happens when it starts a thread.

Unfortunately there is no universal setting for completely eliminating these gaps it needs to be adjusted on a per model basis.

That's interesting. When I watch the print in progress, it looks like the nozzle is actually steering away from closing the gap. I haven't tried messing with the reversal settings, but it looks like even if if the nozzle never stopped extruding, the loop still wouldn't be completely closed. I'm going to do some tests later today after I install my aluminum build surface.