Saturday, October 30, 2010

Making the extruder work

Today I spend most of my time making my extruder work. I must have assembled and disassembled it about 100 times. But its working now. I changed the place of the thermistor a few times, but that didn't help. I think it is just reading too low values. At room temperature it reads 13°C, which is also too low. So now I just set the temperature to 265°C and the ABS comes out. It isn't bubbling or brown, so I assume its just an incorrect value that is being read. I don't have any accurate thermometers that go that high, so I can't see if my assumption is correct.

I tried printing a few lines without a heated bed, but of course that didn't work. I got some extra nichrome wire to add under the bed and I can isolate it with kapton tape. I hope that will work and I don't get myself electrocuted. As my PSU is really old, I think it will just blow up when I attach the heated bed to it. So I was thinking about using a single long nichrome wire with a resistance of about 160 ohm. That way I'll have 330W of power. My nichrome wire has a resistance of 19 ohm per meter, so I'll need 8.5m of it. That will also make sure everything is heated evenly.
I also have an old thermostat from an oven. That will be more reliable than the one I tried to make myself.

The only thing I'm not sure about is whether kapton can isolate the nichrome wire enough if 230V is going through it and it is being heated. But as it is being used in airplanes, it won't be that bad.

Sunday, October 24, 2010

First Tests

Yesterday I continued building my Mendel. I started by filing the small holes in my extruder to make the bolts fit in there. It took me a while, but everything fits now. I also added the motors and opto's to the printer. When that was done, I attached everything to the electronics board.

After downloading and installing the software, I plugged the usb-cable in my pc and all the motors worked. I had  to tighten the bolts on the z-xis a little more, because one of the two sides skipped some steps. But apart from that there were no problems.

Now that the mechanics were working, I planned to build the hot-end of the extruder. I wound some nichrome wire around the metal part, attached the temperature sensor and got stuck. I found what wire had to be attached to what pin on the wiki, but I couldn't find what pin is on what side. So I went to the webchat and asked my question. Luckily someone was able to help me and told me that pin1 is the furthest one from the power connector. I added that information on the wiki for people after me with the same problem.

Now that the hot-end was finished, I wanted to test it before gluing it to the extruder. I tried many different temperatures from 240°C up to 260°C to melt my ABS and tried to push it through the small hole. At around 250° the plastic started melting, but I wasn't able to push it through the hole. That's why I went even higher with the temperature, hoping it would start coming through the hole. But it didn't help. I just can't push it through by hand. As long as this doesn't work, I'm kind of stuck. I know the extruder can push harder than I can, but it could also break everything. So I don't want to try that. Any hints on this would be appreciated.

I also noticed that mendel-parts sold some faulty green belts. My belts are green, so I mailed to Camiel to know if mine were part of that bad series. I haven't had any problems with mine yet, but as they are part of the bad series, he told me he would send some replacements for free. Really good service from him. :)

Ow and below is a picture of everything wired up. I haven't done all of the cable management yet, so there is a big mess of wires at the top. Prettifying the machine is for when it starts printing.

Sunday, October 17, 2010

Almost done with the mechanics

Today I've continued working on the mechanics. Everything is ready now. I only have to make everything level and tighten the bolts. As you can see, the extruder isn't attached, due to the problem I mentioned yesterday.

Just like yesterday, I encountered some minor problems. During the assembly of the x-axis, I noticed that there were no m3x10 screws for attaching the motor. So I used m3x20 with a lot of washers instead. It doesn't look as good, but it holds everything in place.

I also had to cut the bars holding the x-axis. They were made for the "default" Mendel and not the adjusted part I am using. So I had to adjust them from 495mm to the 463mm that I needed. Now I have 2 bars with ugly endings compared to the ones that were cut in the shop and have a nice and smooth edge. I also burned my finger during the process. I wanted to take the first bar after I cut it, but it was still too hot. Stupid me.

The bearings in the z-axis were really hard to get in place. There was not enough room for my wrench, so I had to use some small pliers instead. I think one of the bearings is slightly sideways because the left axis only turns if the lead-screw is slightly tilted to the right. I hope that won't be a big problem.

That's about everything I did today. I hope I can fix the extruder next weekend and attach the electronics and belts so I can start calibrating everything.

Saturday, October 16, 2010

Starting to build

I started building the mechanical part of my Mendel this morning. I've encountered some small problems, but apart from those it went rather smooth. I started with the extruder. I couldn't find much documentation about it, so if I encountered problems I could ask for help while building the other parts. All the other parts have a nice 3D assembly that I can look at from every angle, but the extruder just has a few pictures.

Once I started building it, I noticed that the bolts didn't fit in the holes in the Idler-holder. I don't know why this is. Maybe Nophead printed the part with too small holes, or maybe Mendel-parts is using bigger bolts than the default ones, or it could also be a combination of both. The result stays the same, it doesn't fit. I don't really know how to make them bigger, as all my files are too big for that and my drill would make them round instead of hexagonal. Maybe I just have to buy a smaller file to do the job.
I also noticed an other problem. Because Mendel-parts assumes I use the older version of the driven-holder and I have the new version with the extra strengthening beam, the screw is too short. I'll have to buy a longer one for that. I should have checked it before ordering my parts.

After those small problems with the extruder, everything went rather smooth. I started building the x-axis. The wiki suggested to use m4x16 bolts for the x-idler-bracked. Those were too short, so I used m4x25 instead and added a second big washer so the belt is between two washers, which should be better for holding it in place. I didn't add the bars yet, as I'll do those at the end.

Once the x-axis was done, I started with the y-axis. The only problem I encountered here was that one of the bearings doesn't turn, even when the bolts are loose. I suppose its broken, so I put it aside. I think there are some extra bearings in the package, so hopefully I won't have to use the broken one. Again I didn't add the bars and went on to the z-axis. That one was easy, so I had a little time left to assemble the frame sides.

Below is a picture of my messy desk after a whole day of building. I hope the building will be done by tomorrow evening, so I can start adding the motors and electronics next weekend.

The last parts finally arrive

So on Monday the 11th my order from finally got shipped. It arrived on Wednesday, but as I only have time during the weekends I'm only posting about it now. The box was a little too small and the steel bars were sticking out of it. Luckily they were wrapped in bubble plastic. I hope they haven't been bend during transport. You can see the weird packaging on the image on the right.

Inside the components were packed in separate bags to make it easyer to find them. The only thing they could have done better is binding something around the kapton film, because it has some small dents and holes from other items pressing against it. (I removed it in the picture so you can see everything inside the box and not just the film) Everything else doesn't seem to have been damaged during transport on the first sight.

To have a better view on everything inside the box, I laid them out on my desk. The steel plates had a funny note on them that they could be sharp. It's like those sunshields for in the cars that say "remove before driving". Kinda obvious those things.

As you can see, the Gen 6 electronics are also in the box. There was even a certificate with them saying it was #14 ever made. They are really a lot smaller than the other types of electronics. I hope that doesn't mean that they can overheat faster. But I still have lots of unused ram-heatsinks if that would be the case. I made a closeup picture of them for you, so you can see how they look. I haven't taken the out of the plastic yet, as it could only damage them. I have enough experience with computer electronics to know that. 

Now that everything has finally arrived, I can start building mu Mendel. I know that I will get stuck at some point, but I hope someone will be there to help me. And now I'm going to start building. Wish me luck.