Tilting platform and extuder gear slipping

[Generic Default]

Hi everyone,

I've had my Rostock since early June and I still don't have a normally working machine.

The first part is a major problem with the effector platform. Suppose you are looking at the rostock from the front, with the electronics door being near you and the Z tower being on the opposite side of the machine from you. As the platform moves from you towards the Z tower, it rotates counterclockwise. As it moves from the Z tower towards you, it rotates clockwise. This means that the effector platform is angled more towards the edges of the build plate, which makes bad surface finishes and prevents me from using dual extruders because the nozzle height becomes uneven by a difference of about 1 milimeter. I attached a couple pictures to try to make it a little bit more clear. The first picture shows the platform near the Z tower; the second picture shows it on the opposite side of the build plate. The angle is greatly exaggerated in the picture so you can see it, but it is preventing my machine from working as it should. I checked to make sure that the edges of the aluminum extrusions are level with the laser etched lines in the base and on the top parts. I'm using magnetic ball arms, but even if they aren't the exact same length, they still shouldn't be causing the angle of the platform to change over the build area.

The second problem is that the Steves extruder is limited to retracts of about 10mm/s instead of ~45mm/s. It can push the filament out fine, but when it changes direction and retracts, the press-fit nylon gear that goes on the stepper motor shaft slips and makes a horrible vibrating grinding sound. I tried taking it off, but it won't move axially along the shaft. So it's basically jammed on the shaft too hard to pull off (even with pliers) but loose enough to slip when the stepper applies torque. Does anyone know a way to get it off without breaking the stepper motor or the gear?
Also, I'm considering buying a hobbed drive roller to make my own direct drive extruder. Would anyone recommend a direct drive extruder over a geared extruder?

Thanks!

[edward]

Parallelism within each pair of arms is also extremely important. I tediously checked and got the ball-ends of each pair within 0.05 and the effector tilting that I was experiencing vanished.

[Jimustanguitar]

So you're using the factory arms, or you've got a magnetic ball-joint setup like your CAD drawings?

If you're using homemade parts, that would be the first place to look if your geometry is off.

[geneb]

You don't have a normally working machine because you keep fiddling with things. Make it work as-shipped and THEN do whatever mods you want to it.

g.

[Eaglezsoar]

You don't have a normally working machine because you keep fiddling with things. Make it work as-shipped and THEN do whatever mods you want to it.

g.

I agree. Get it back to the as-shipped make sure it works fine then do your mods, ONE AT A TIME, and verify after each one proper operation. If you are too far from stock
with many mods at one time, you may never get it working the way it should.

[Jimustanguitar]

Looks VERY interesting though. You're doing a dual extruder and your all-metal hot-end has dual inlets for mixing materials?

Tell us more about what you're doing because it's quite tricked out

[Generic Default]

Actually the dual filament inlet was to compensate for the tilting platform. I couldn't get the platform level enough for two offset extruders, so I decided to run both of the filaments through one hotend and use an offset of 0 in the firmware and software. It would have worked, but the extruder vibrated and slipped on retracts. The idea is that one filament is retracted and then the other is pushed out on every layer where support material is used. With a good retract speed, it would be worth it.

And you guys are right about the other stuff. I need to switch back to the squeaky arms to make sure the platform is level, then I need to buy some rods to use as ball joint arms. My dirt cheap design uses fiberglass driveway markers from home depot (~$3 for all 6 arms), but the problem is that they're 5/16" instead of 3/8" so I had to wrap the ends in masking tape to get the diameter big enough to fit into the nylon ball cups. The masking tape isn't very rigid, and the rods don't fit into the nylon pieces at a 90 degree angle because of the open space, so the rods probably aren't quite parallel or concentric to the nylon cups.

I'll work on fixing the effector platform setup, but the steves extruder is still defective. Did anyone else have the problem of a slipping nylon gear on their stepper motor shaft? It's the biggest problem I have right now, and I don't know how to fix it.

[geneb]

If the gear is slipping on the shaft, I'd ask for a new drive gear. Considering the amount of force required to press that gear on the shaft, it's either a bad injection mold or you drilled it out to make it easier to fit.

g.