Post by 3dprintingmeathead on Apr 21, 2017 0:21:52 GMT
Extruder shenanigans. The DP5 extruder was the most frustrating part of the printer for me. I experienced under extrusion worthy of it's own book. The filament that came with the printer never had a problem. It seemed to be nice and soft, gripped well, melted easily, and laid down pretty good. Then I picked up a bunch of monoprice PLA and PLA+. This is where the shit hit the fan. The extruder motor started skipping steps. Prints would fail half way through. I printed a couple faberge benchys. top layser coming out bad, infill balling up. The only thing that never happened was the filament never stripped.
The first mod I made was a filament guide. At the time, I saw the gap between the gear and the bowden tube and thought the problem lied in that gap. Filament bending under pressure and catching an edge before it made it to the tube. That upgrade fixed maybe 10% of the problems. Next I turned up the amperage to the motor. That helped maybe 5%. Next I shortened the bowden tube. That did nothing. Then I relocated the extruder and took as many bends out of the bowden as I could. That also did nothing.
Frustrated, I made this upgrade
This wades kit solved all of my problems, for a while. Printing was fun again for about a month. And then...a print failed. Under extrusion. That day, I snapped and ordered a titan extruder. The joke was on me though. I changed filament the night I ordered the titan and I found one of the nuts that tighten the idler bearing tension spring was stripped. I replaced the nut and it was printing perfectly again.
So, what caused all the problems? well, an extruder assembly needs 2 things to work: grip, and power. In this case, grip was no problem because I never stripped the filament. But the motor skipping is a sure sign of a lack of power, more specifically torque. To dig deeper, we need to know this is a torque issue. Let's make a simple analogy here. Take a drill and throw a 1/8" bit (or 3mm for you metric fanboys:). not too hard to turn, even by hand. the lever arm is short and the distance it has to travel in each revolution is small. Now lets throw in a 1 inch bit(25.4mm, yea, I know my conversions). Now we need a big drill, because our lever arm is long, and the distance the outside edge has to travel per revolution is great.
Now, lets look at the big gear that pushes our filament. In he 3d printing world, that's a big gear. And since it's flat, instead of hugging the filament and moving further down the lever arm, the force is transferred from the tip of the gear. So just like how throwing big tires on a truck slows it down, the gear slows down the extruder. There is another downfall to this large gear too, and that's accuracy. Mine worked best at 98 steps per mm. It sounds like a lot, but that's with 1/16th microstepping, and microstepping is where you lose your torque and accuracy. Now let's look at a wades extruder. The wades acts like the rear end in your truck. Instead of a 1:1 from your transmission to the tire, it reduces the rotation at a ratio. In the case of my wades, it's a 4.10 to 1 ratio. Meaning every 4.1 turns of the motor, the gear makes 1 turn. This in turn(no pun intended) multiplies the torque. Now we add on the hobbed bolt it's turning, which I believe it's diameter is 3mm smaller, which multiplies the torque even more. Now we went from 98 steps per mm to 647 steps per mm(your mileage will vary). So, not only do we gain tons of torque, but we can extrude very precisely.
In fact, my wades setup has about 100 steps more than the titan per mm, so in theory, it can extrude more precisely than the titan.
But these measurements get more toward theory at these numbers because of the length of the bowden tube. Here's a simple test to prove this. extrude 10mm of filament with the x axis at home. then move the x to 200. notice the leak? The hotend is oozing a little because the tube moved. A bowden tube has an inside diameter of 2mm. Our filament is around 1.75. so the filament bends slightly inside the tube until it hits a wall, maybe multiple times. This play is not calculated for by our firmware. Now, if we move the tube, the filament can straighten out and keep extruding when we don't want it to. But more importantly, the extruder pushed filament that never made it out the hot end. And it will continue to do so every time it retracts and pulls the slack out of the tube. A way to fix this is to add extra prime after retraction, but this is a frustrating trial and error process. With direct drive, the distance is very short between the extruder and hot end, leaving the filament very little room do deviate before it meets it's demise in the hotend.
And so ends my long and rocky road of anger, frustration, and confusion. If you are experiencing under extrusion symptoms with a clean hot end, it would really be worth it to check out a wades kit. And at $10, it is probably the best upgrade you could make short of a good part cooling fan.
The first mod I made was a filament guide. At the time, I saw the gap between the gear and the bowden tube and thought the problem lied in that gap. Filament bending under pressure and catching an edge before it made it to the tube. That upgrade fixed maybe 10% of the problems. Next I turned up the amperage to the motor. That helped maybe 5%. Next I shortened the bowden tube. That did nothing. Then I relocated the extruder and took as many bends out of the bowden as I could. That also did nothing.
Frustrated, I made this upgrade
This wades kit solved all of my problems, for a while. Printing was fun again for about a month. And then...a print failed. Under extrusion. That day, I snapped and ordered a titan extruder. The joke was on me though. I changed filament the night I ordered the titan and I found one of the nuts that tighten the idler bearing tension spring was stripped. I replaced the nut and it was printing perfectly again.
So, what caused all the problems? well, an extruder assembly needs 2 things to work: grip, and power. In this case, grip was no problem because I never stripped the filament. But the motor skipping is a sure sign of a lack of power, more specifically torque. To dig deeper, we need to know this is a torque issue. Let's make a simple analogy here. Take a drill and throw a 1/8" bit (or 3mm for you metric fanboys:). not too hard to turn, even by hand. the lever arm is short and the distance it has to travel in each revolution is small. Now lets throw in a 1 inch bit(25.4mm, yea, I know my conversions). Now we need a big drill, because our lever arm is long, and the distance the outside edge has to travel per revolution is great.
Now, lets look at the big gear that pushes our filament. In he 3d printing world, that's a big gear. And since it's flat, instead of hugging the filament and moving further down the lever arm, the force is transferred from the tip of the gear. So just like how throwing big tires on a truck slows it down, the gear slows down the extruder. There is another downfall to this large gear too, and that's accuracy. Mine worked best at 98 steps per mm. It sounds like a lot, but that's with 1/16th microstepping, and microstepping is where you lose your torque and accuracy. Now let's look at a wades extruder. The wades acts like the rear end in your truck. Instead of a 1:1 from your transmission to the tire, it reduces the rotation at a ratio. In the case of my wades, it's a 4.10 to 1 ratio. Meaning every 4.1 turns of the motor, the gear makes 1 turn. This in turn(no pun intended) multiplies the torque. Now we add on the hobbed bolt it's turning, which I believe it's diameter is 3mm smaller, which multiplies the torque even more. Now we went from 98 steps per mm to 647 steps per mm(your mileage will vary). So, not only do we gain tons of torque, but we can extrude very precisely.
In fact, my wades setup has about 100 steps more than the titan per mm, so in theory, it can extrude more precisely than the titan.
But these measurements get more toward theory at these numbers because of the length of the bowden tube. Here's a simple test to prove this. extrude 10mm of filament with the x axis at home. then move the x to 200. notice the leak? The hotend is oozing a little because the tube moved. A bowden tube has an inside diameter of 2mm. Our filament is around 1.75. so the filament bends slightly inside the tube until it hits a wall, maybe multiple times. This play is not calculated for by our firmware. Now, if we move the tube, the filament can straighten out and keep extruding when we don't want it to. But more importantly, the extruder pushed filament that never made it out the hot end. And it will continue to do so every time it retracts and pulls the slack out of the tube. A way to fix this is to add extra prime after retraction, but this is a frustrating trial and error process. With direct drive, the distance is very short between the extruder and hot end, leaving the filament very little room do deviate before it meets it's demise in the hotend.
And so ends my long and rocky road of anger, frustration, and confusion. If you are experiencing under extrusion symptoms with a clean hot end, it would really be worth it to check out a wades kit. And at $10, it is probably the best upgrade you could make short of a good part cooling fan.
