It is already a couple of weeks since my heated print-bed from László arrived. I was busy so I didn't find time yet to update the blog, but finally here is my experience with building and installing it.

The print-bed is made of aluminium. It's heated from the bottom side using power resistors. The print is done on a Kapton-covered steel sheet which lies on to the of the aluminium bed and which is hold in place by powerful magents.

The bottom side has threads to attach 9 power resistors and pits where the magnets will find it place. First I covered it with Kapton tape, cut out holes for the resistors (I only used 5 in the beginning) and the magnets:

Then I added the magnets.
U/D stands for up/down for the orientation of the magnets.

László recommends to add iron bars on top of the magnets. This makes the magnetic force stronger. Neodym magents don't stand heat that well, but short-cutting them with the iron bars also seems to improve this.
I decided to mount all 9 resistors I ordered at that point, so I added the remaining ones too:

Then I wired the resistors. For a start I was only using 6 of them, this is why the middle 3 are not conencted. Here the 3 mounting screws an the z-switch holder are already added as well.

I tested the bed in this configuration, but it was not getting hot enough. Even with all 9 resistors it hardly reached the temperature where ABS sticks to the steel sheet, which should be at about 100-110°C.

So the next step was to add heat insulation. To prepare that I added the heat-resistant insulation for the connecting wires. I chose not to wire all the resistors together but have two groups with 6 and 3 resistors to have more possibilities later.

Then I covered the bottom side with the rock wool. I also attached a thermistor to the bottom side of the bed, so there are now 5 wires coming out there.
Shouldn't have done this in our living room really, it's quite a mess. I'm lucky I have an understanding wife.

OK, now the bed was ready to be installed. Removed old bed, replaced it with the new one, attached the power transformer, covered the steel sheet with Kapton.
I wasn't happy with the z-switch holder, so I replaced it with a newly designed one (more in an extra post later).

Turned out that the temperature now was ideal for printing ABS. I now always switch the print-bed on about 5 minutes before the print and leave it on for the whole print. With all 9 resistors connected (all parallel) the power transformer which comes with the kit is a bit too weak by specification. It gets a bit hot, but it works fine. I'll probably add a fan for it later.
I didn't measure the temperature, but the ABS sticks very well on the Kapton. I didn't have to do anything (like sanding) to improve the adhesion.

Here's a finshed print (lots of strings, but that's not the fault of the print bed). I'm using the scraper which came with my RapMan to remove the steel sheet (it's not that easy, the magnets are really strong). I added small pieces of card-board on both sides of the scraper so that I do not burn my fingers.
When the print is cooled down a bit you can remove it from the sheet.

Right now am really happy with the print bed. Its a bit costly, but it is nicely made and very flat. And it probably cannot be made cheaper really. You would have to go for a different approach like a circuit board, but I haven't seen one which covers the full RapMan print area.

I do not sand the Kapton, so the bottom faces of my prints are really nice, flat and shiny. I did not have any warping issues any more when using it.
I didn't print really big objects yet, this is one of the next things I will test, but I do not expect problems.

 

 

I ordered a heated print bed for my RapMan from László which arrived today.
Here are some unboxing pics. Looks promising!

I had a couple of objects where I wanted a really flat, clean bottom side, which is hard to archive when printing on a raft with your RepRap/RepMan. So I wanted to have one of these heated printbeds where you do not need a raft - the objects stick to it directly and due to the heat they do not shrink while printing avoiding the warping problem ABS has which would cause the edges to come off the printing surface otherwise.

But I did not like spending lots of money in a machined metal table. I'll probably will get one now, but for trying it out and playing around I looked for something cheaper.

So here is my (roughly) 10$ heated printbed design. You need:

• flat piece of wood board
• a proto-board with stripes (something like this)
• Kapton tape
• old PC power supply

I soldered bridges onto the protoboard so that the whole board is covered by one long zig-zag ciruit. With my board size of 160x100mm (Euro card size) this resulted in about 2.5 Ohms. Attaching that to 5V resulted in about 60°C which is is not enough, but with 12V it was at about 90°C, which proved to be enough.

I covered the board with Kapton so that the holes are covered and ABS sticks much better to it. I mounted the proto-board on the wooden board using little wooden pieces as spacers which I covered with a few layers of Kaption tape for insulation. I wrapped some Kapton all around the proto-board and the wooden board which proved to be enough to hold it in place. I glued the wooden board onto the print bed mount of the RepMan using double-sided take. Pay attention to what take you use, mine was really hard to get off again.

In case you wonder, my proto-board was broken, so I soldered it together again. Made a bit of trouble, because it was not flat any more.

 

So does this work? Yes, I was able to print a couple of nice objects with it.
However, there are a couple of cons:

• The prints stick really well. This is good, but you have to wait for the printbed to cool down before attempting to get the print off, otherwise the object will get bent. Once I was ripping the proto-board off the wooden board while trying to get the print off. Also the Kapton tape came off easily.
• I had problems to get the printbed flat. Mostly because of the broken proto-board so that probably a problem that could be avoided easily.
• 100x160mm is enough for many objects, but if you have a RepMan you could do much larger prints. When using larger proto-boards the resistance will be different, so you need either a higher voltage or you need a different way to connect the stripes on the board. Either way you probably need a higher rated power supply.
• The proto-board started smelling funny. I think it was a really cheap one (don't know, I used one I had lying around) so this could be avoided by using a better, more heat-resistant one.

It was a fun experiment and useful for smaller prints. But I guess I get something better now.

For the Germany-Spain game tonight I printed this. I just need some
gold paint now...
You can download the STL file at http://www.thingiverse.com/thing:3494

Update: after painting it with gold spray paint and adding the dark green stripes, it looks like this:

Print quality still could be better, I had lots of "strings" to remove. While doing this, one wing broke off (I glued it back on).
The thing was printed in 2 parts. Gluing them together did not work as well as I hoped as the pieces had quite some warping.
Maybe it would print better in PLA instead of ABS.
But hey, the kids like it! :-)

The STL and the OpenSCAD files are now on thingiverse: http://www.thingiverse.com/thing:3177

After playing around with skeinforge for some days I had enough of fiddling around with its loads of parameters. It eventually printed my test objects fine with 0.5mm layers, but other objects were not that good. And my 0.3mm layer setup would have needed more work too.

So I bought "netfabb Engine for Rapman Basic",a 99€ (+VAT) software from Germany based netfabb GmbH (http://netfabb.com/). They have a free software called Studio Basic, which is great for examining and fixing STL files, but I does not have any gcode generation functionality.
There's no eval version of "netfabb Engine for Rapman Basic", so you cannot judge the gcode quality before buying, but I did not get disappointed. Calibration is easy, you simply print a test object, take measurement and enter the values back into the software. After that (and probably adjusting the printing temperature) you are ready to go. Awesome! The quality is better then what I was able to do with skeinforge. I'll post some printed examples the next days.

The software uses a unusual "pillar" raft (watch it  get printed), it's a bit hard to get off the print bed, but works nicely. But you still can choose to use a "traditional raft" if you want.

What I find a bit strange is that it does not use the "no string function" implemented in the latest RapMan firmware (version 1.0.8 and later). Using it the prints probably would have less strings you have to remove.

The downside of hiding away all the complexity of generating gcode for you is that you have less influence over the result. There are "expert settings", which lets you adjust a few more things, but being a commercial closed-source tool, netfabb is not a tool for users who want to be able to change anything.

Completed the first prints. I used (of course!) the mini-mug model.
The very first print had a hole in it and it was not round. I had a problem with the y-direction, too much play, a pulley was not fixed properly.
With the second print the geometry was good, but it was printed too hot it seems, the print dissolved itself at higher layers (I aborted it).
I looks like the thermistor lost its direct connection to the extruder, so it was heated up more than it should. I rebuild the extruder - again using the Kapton tape technique instead with fire cement - and this time the print looked much better (I also switched to black ABS).
The geometry still is not perfect, it has a slight skew in x-direction. I have to check what causes this. The print has some "hair" inside, nothing serious, easy to clean up, but maybe the print temperature was a bit too high.

Yes! Assembly finally finished. All looks good (after fixing  a wiring mistake with the extruder), the "test raft" pattern printed fine.
First real print tomorrow!

I tried using Blender a long time ago, but I found the GUI really combersome. Even after reading a tutorial I wasn't able to create something useful.

Now Blender 2.5 (alpha 2) is available and as they have promised to have a more intuitive user interface, I gave it another try. My goal was to create a 3d-printable model of a Star Wars Tie Interceptor. There are a couple of nice (but short! :-))) Blender tutorials for newbies on thingiverse (http://blog.thingiverse.com/2010/05/05/assembled-blender-tutorials/). They are for previous versions of Blender, but they are easy to adopt and the keyboard shortcuts are the same.

So this is what I did:

I'm really pleased with it. No textures, as they cannot be used it for printing.

Blender 2.5 is really nice! Very stable already, and taken account that I hardly did any 3d modeling before it allowed me to do this pretty fast (a few hours). Bravo!

The printable STL file can be found on thingiverse: http://www.thingiverse.com/thing:3006