Showing posts with label Extruder. Show all posts
Showing posts with label Extruder. Show all posts

Thursday, 28 July 2011

Extruder Stepper Bypass using Pololu A4983

I have decided to bypass the onboard extruder stepper motor control to use a separate Pololu stepper driver to run the extruder stepper motor. The reason for this stems from the original RepRap which was designed to use a DC motor for the extruder and not a stepper motor, therefore used some electronic trickery to control the speed. Using some clever programming they hacked the driver to control stepper motors.

However this is now what is causing my stepper motor to emit that high pitched noise. It is possible to bypass the information sent from the motherboard to a separate stepper controller, and leave the extruder board to just control the hot end. This method is documented on the RepRap wiki and suggested in a couple of forum posts I have seen.

I have made a carrier for the Pololu board from strip board using Tony Buser’s layout as a guide ( I ended up changing it a bit as I wanted screw terminals for the power and motor connection and not headers. As the screw terminal spacings are wider than the header’s I had to use more short jumpers to get everything wired correctly. I have tested it and it seems to work very well. It is now much quieter and the motor seem to run a bit cooler.

From Mendel

From Mendel

Monday, 4 July 2011

First Almost Print

Just thought I do an update on my initial testing of the machine. I was quite pleased that I have managed to get everything wired up correctly and the extruder heated up. I have spent a while trying to level the bed, a job that was more tricky than I imagined. I am not really happy with the way the bed bolts to the y axis plate. On the Prusa design there is a nut above and below the y plate, I find this a bit annoying when adjusting the bed level – I have to keep adjusting both nuts, I can’t see why there can’t be just one nut below the plate, I might test it out at some point.

At the moment I am using RepRap host but I have also been testing with ReplicatorG to see if that will work. I can connect with ReplicatorG fine using the “experimental” Mendel machine profile. The control panel jog’s the axis (although sometimes the distances seem a bit random and sometimes it moves 2 axes instead of just one). The control panel also controls the temperature of the hot end fine however it does not turn the extruder stepper. When I try and print an object with ReplicatorG it starts ok, but then extruder starts to cool down, it doesn’t seem to control the extruder temperature. Not sure how to access the temp settings, I assume it might be part of the Skeinforge profile, but not sure how to get to that at the moment.

With the RepRap host things are working pretty well. Below you can see my first attempt at printing the 40mm test cube object. As you can see I aborted the print part way through, the object is less of a 40mm cube and more of a 40mm filter. The extrusion seems to be patchy, and thin even when it is extruding. I think this could be caused by a couple of things. First my “hobbed” bolt on the Wade’s extruder could be not gripping in certain areas – or the springs set too loose. Second I might not have set the extrusion length correctly (the steps per mm value) so not enough filament is being supplied for the required extrusion. Third the temperature could be too low causing a blockage as filament is being melted. See the picture and video below and let me know if you think you know which of these it is. At least the x and y dimensions seem to be correct!
Another thing is the extruder stepper is getting HOT (on a long print I think it could get damaged), I have tried trimming down the pot but to get the current up enough to turn the stepper. I have decided to use a Pololu for the extruder stepper in the hope that the stepper will run cooler (and quieter).


Host: RepRap Host
Electronics: Techzone Gen 3
Temperature: 200°C
Material: Black PLA
Extrusion Steps/mm: 2.508

From Mendel

Thursday, 30 June 2011

Start Up Procedure

I was having a little trouble when I hooked my extruder up. Although everything seemed to be wired correctly I found that I was getting a zero temperature reading. I checked the resistance across the thermister and it seemed to be right. Looking on the internet I found out the 0 reading is given when the extruder board is not connected. I recollected having this problem when I first tested the electronics, see post here, but couldn’t remember how I solved it. All I wrote was that it was something to do with the order I started everything up. A little searching on the internet and I found this post that was very helpful. Following the comments shown there I worked out a starting procedure that works every time.

Start with everything off and disconnected.

1. Start PC up wait for everything to boot up (or if it is already on, leave it on).

2. Power up 12V on Mendel (I really need to connect a switch up to make this easier).

3. Connect USB to Mendel (Could I connect a switch up for this as well, maybe on the +5V line?)

4. Press Reset on motherboard. Wait for motherboard to resume blink.

5. Start RepRap host, some errors are reported (0 temp measurement).

6. Close RepRap host.

7. Open RepRap host again, no errors reported this time, now everything works!

All electronics and hardware up and working. Success sounds like a high pitched whine (where did I put that Pololu board?!)

Friday, 30 July 2010

Adrian's Geared Extruder Build Part 1

The RP parts I have are for Adrian's geared extruder see the wiki here. For this you need some pats not listed on the original BOM list. There are a couple of different screws you need, nothing hard to find on ebay. Main parts you need are a short piece of M4 threaded rod. An M4 "Insert" - this is a splined piece used to grip the plastic filament. An M4 wing nut, and 3 bearings. The splined piece I got from ebay here is a bit different to the one shown in the wiki but serves the same purpose. It doesn't have a grub screw but it is internally threaded so should stay in place with bolts either side of it. It was listed as "Ripmax DYCO M4 x 0.7mm Coupling Insert" looks like it is used in the clutch mechanisms of model cars, trains etc.
After a bit of drilling and shaping the parts seem to fit together ok.