Adan's 3D printer notes
Here are some rambling note on my experience with a Makerbot Thing-O-Matic (TOM) using ABS plastic and the ReplicatorG software. It is likely you won't have a TOM, but you may very well use ABS. There are a couple general tips contained within as well. If you have questions please ask. I honestly have no idea how PLA responds to the heat or warping issues that I mention. It is a very different material and you will want to read up on it before you build a machine using it.
Choosing a Printer
When I bought the Makerbot Thing-O-Matic I liked the compromise between having a machine show up that was ready to print and having to track down all sorts of crazy hardware from the corners of the internet. What was wonderful is that in putting the pieces together I gained a real understanding for how my machine physically worked. There is a lot going on, but having put it together the machine is actually very simple. Having a better understanding of the machine also encouraged me to make modifications to it. These included better lighting and helping to make it functional. Because of the learning involved I would strongly encourage others to build their own machine.
While printing there were several problems that I ran into which should be thought of while creating the models.
The software takes you models and slices it into layers the thickness of your vertical step. It then does some sort of infilling for the model so it isn’t a very thin shell. What comes of out this is a path that the extruder head will follow (or the build platform, net effect the build platform and head are moving relative to each other). On the first layer to be put down you should have as much surface area as possible. What ends up happening in practice quite often is that you have holes in that surface that could be used to run a bolt through. Adhering of the print to the build surface was always a problem with my print, but the most frequent problem was with the outlines of the bolt holes. What would happen is the machine would trace the outline for the bottom surface of the part, then lay down the circle outlines, then do its back and forth laying down of the bottom surface. When it would put down the circle outlines a bit of the circle would stick up just a touch. Then when it was doing the back and forth pattern the head would catch on the tiny bit of raised circle and drag material to where it shouldn’t be thus warping that part of the print. Or better it would unseat the print. The later situation is better because you can catch it early and not waste of bunch of material.
When printing the machine needs support material to lay down a layer i.e. it can’t print on nothing but air. This comes into play when trying to print something like a wing or overhanging ledge. Sometimes the thing to do is to simply flip the model upside down (overhang is a good case for this) or to use a dual head printer with ABS and PLA using the ABS to print the model with and the PLA to lay down support material to be removed later. There was some support several months ago in the software for multi-head multi-material setups but it was definitely in the experimental realm.
Cautions for using the ReplicatorG Software
I ran into a problem when I upgraded the Replicator software one time. It decided to drive the extruder into the build platform. The build platform didn’t like very much. Every other time had been fine up to that point. From then on I recalibrate every time before I print. Remember to regenerate the tool path for your models after doing the recalibration. Also never run their beta releases unless you like software that flashes hardware to an unusable state. The story with the replicator software is stick to their major releases unless you like fixing stuff.
When printing you are heating ABS plastic to a fairly high temperature. Think about burning a Lego. This is basically what you are doing, but a little bit less extreme. You need to think about the fumes that are given off by this process. Of course the first thing I thought of is I want to ventilate! A good and bad idea. Drafts while printing cause warping. If ABS cools too fast it warps. This does things like curls the edges of the print off of the build platform making it come loose while printing. It can also warp the print as it is happening, giving you a physical object that is not an accurate representation of the model. It appears Makerbot has moved to PLA. From the little reading I have done it appears that the reason for this is less warping.
How did I over come this problem? I did two things. I used tape to cover the sides of the Thing-O-Matic and put it in a computer rack to discourage drafts. The other thing is that I setup the printer to run in an extra room, shut the door and went to another part of the house. I would check on the part every 5-15 minutes or just let it run its course. When I was done printing I would then air out the room.
When positioning the model for printing, you want the most surface area on the build platform so the model better adheres. It gives you a better chance at having a successful print and less chance at warping.
I had problems with having the print adhering to the build surface. I used their fancy build surface coverings and the Automated Build Platform sheet. The best by far was blue painters tape. Their stuff would work for awhile and slowly start to fail. Maybe someone figured out how to clean ABS residue off of build surface coverings, but painters tape is so very inexpensive and easy to cover the platform with. One tip, make sure that the build head is way higher then you think you need to put the tape down or get a model out. The extruder head burns flesh with just a very light tap.
Comments on Heated Build Platforms
You want one. It makes the model adhere to the build platform better and prevents edge curling. If you are going to build a machine, don’t skimp on a small cost if it will greatly improve the performance. This is true for ABS