Sunday, January 17, 2010

Software and First Prints

Lately, work has been crushing me. I have still managed to put some time in almost every day and made some good progress during this last week. Here are the highlights.

Installed Software
  • Arduino Environment - I had this software already installed but I made sure I was using the current version. I had to configure the IDE to be used with a Sanguino Microcontroller. The instructions are here. This all seemed to work fine.
  • Firmware - I had some problems getting the firmware to compile. In fact it never did. While browsing through the MakerBot Google group I found that I did not need to compile these as they come with and can be installed by ReplicatorG. It would have been nice to have known that up front as it would have saved me a bunch of time.
  • ReplicatorG - I down loaded ReplicatorG from here. At first this would not work on my computer. When it ran a Java run time window would pop up and say something like. "Could not find main class, progam terminated." I reinstalled Java and it didn't fix the problem. Then I read on the RepRap forums that a complete uninstall and then reinstall should fix it. So, I tried that and it did. I made a copy of machine.xlm and then added the xml code McWireReplicatorG.xml You need to do "View Page Source to see the XML code in the browser and then copy and paste using a text editor.
  • Python - I down loaded Python from here
  • Skeinforge - I down loaded from here. I decided to change the environment path to include python so Skeinforge could be run from my tool bar. I made a batch file containing "python" and stuck a shortcut in my tool bar. 
Power up

  • Extruder Test -  I am currently using HDPE for my extrusions. I'm seeing that ABS is popular and PLA is coming on strong but these were not in stock when I ordered my things from MakerBot so I got HDPE. From the MakerBot Store site: "This is HDPE plastic aka High Density Polyethylene aka Milk Jug plastic. This is a nice, smooth, high quality plastic. It comes as a filament in 5lb coils with a diameter of 3mm.
    This plastic is cheaper than ABS, but has a higher shrinkage factor which makes printing large objects more difficult. It does have a much lower coefficient of friction so you can print things that are very smooth.
  • Endstop Test - The endstops work great but are useless. In fact they are worse than useless. When an endstop is triggered, the ReplicatorG and the motherboard freezes up. I think they pickup noise also so I removed all 6 endstops. 

First Prints
My first prints were piles of goo. But, I have learned a bunch about the tool chain during this last week. Basically it's pretty easy. Once you go through it a few times. The instructions are here.

The key is to get the skeinforge settings right. I started with the settings from Binary Construct blog.
"Here are some of the more important skeingforge settings I am using:
PWM Motor Speed: 215 to 225 (depending on the object)
Extruder Temp: 225 C
Speed: 80mm/s (i think the threaded drive has some effect on this no being accurate)
Layer Height: 0.7mm"

These settings allowed me to start printing test cubes that are15mm on a side. These are kind of like the "hello world" of 3D printing.

Tweaking Skeinforge

I have been learning about Skeinforge settings from Bits From Bytes Blog. I think I have tweaked the McWire to the best of it's ability. The prints are very useable but slow and course. The basic problem with it is that the X and Y sleds move to slow because of the gearing with respect to the minimum extruder flow rate. Right now I'm running at 200/255 PWM rate on the extruder motor. Any slower risks a chance of stalling. The 80mm/s in the above settings is being limited by the settings in ReplicatorG. I Adjusted those and found they are best left where they are.  So for right now there is not much, if any, of the desired filament stretch during the extrusion process. This could be fixed by going to a larger thread pitch on the drive screws.

Here are the key skeinforge settings I have going right now.

Tuesday, January 12, 2010

Thunder Cats are GO!

A bunch of progress has been made since my last post. Two major steps have been achieved .

  • Mounting the Gen3 boards
  • Wiring the Electronics

Mounting the Electronics
This started with making a template by exporting the layers out of Eagle to a dxf file and then took that into my CAD program where created the board arrangement. I used some glue stick and pasted it to a piece of plywood and cut it to size.

I made some home made standoffs from drywall mollies. I used some washers to get the desired spacer length and cut them with some good size wire cutters.

Here is a driver board with the standoffs. Also you can see that I added the right angle headers for the opto endstops. I didn't bother taking out the CAT5 connectors.

I had a nice hefty bracket for mounting large curtain rods and  used it to mount the electronics board. I wanted to make sure that the electronics were off the bench so the machine does not take up so much room. All but the power supply is off the bench and I am working on getting that mounted some how.

Wiring the Electronics
Here are some notable points I had for the wiring:

  • I unsoldered the molex connector pulling the pins out one at a time and soldered in screw terminals for hooking up the stepper motors.  Digikey: A98168-ND TERM BLOCK 4POS SIDE ENT 3.81MM
  • I found some sprinkler wire at a home center to hook up the stepper motors. It worked out great. It is multicolor 18AWG solid core wires with 7 wires in the bundle and has black PVC sleeving.
  • I wired up the opto couplers and with Red (+5V), Black (ground) and yellow(signal). This wire was connected to 0.1" female connectors. (Digikey: S7001-ND CONN HEADER FEMALE 3POS .1" TIN) on both ends. 
  • I used right angle 0.1" spaced header pins on the driver boards that are right underneath the cat 5 connectors. I didn’t bother to remove the cat5 connectors since they were not in the way.
At this point the McWire is completely wired and ready for action. The next steps are firmware installs, softwares and then printing!

Monday, January 4, 2010

McWire After Build Issues

Some short comings of the McWire design have shown themselves after the build.

The first one concerns the method of attaching the drive screw to the Z sled. I seems the constant pressure on the tape covered coupling nut made the tape move over time. It telescoped out until the holding pressure in the conduit ran out. Then slipped out of the strap.

My solution was to build a bracket that presses the coupling nut against the Z sled, holding it in place. Overall this is a better way to go as you can adjust the height from the Z sled with a shim to get the drive screw parallel to the sled. This was a pain to do with the tape wound design.The X and Y have not been changed out but I will use the same solution if they become a problem.

The bracket material came from an L bracket that is used to hold drapery rods. A piece of 1/8"thick aluminum would do as well. It's held in place by 2 - #10 screws and tapped holes in the sled.

Another failure that has been occurring is breaking swing arms. They are not standing up to the task. I think it is the constant pressure of the spring and the size of the 5/16 hole plus counter sink relative to width of the swing arm. I have reduced the spring pressure as low as I fell comfortable with but failures are still occurring. I had 4 spares made when I ordered the laser cut parts and those are used up and now I am making parts to replace them.

I think the newly designed swing arms are working great and are easy to build. I used 3/16" press board because that’s what I had on hand. 1/4" thickness might be better.  1/8" aluminum would work nicely.

To make one of these :

  1. Use a template to mark the outline and hole locations. 
  2. Cut it out roughly with the outline markings and the drill 1/16" pilot holes for all 3 holes. (larger for aluminum)
  3. Drill the clearance hole (23/64") for the 5/16" bolt holding it to the sled.
  4. Mount the bearing with a small washer (M5) under it using a dry wall screw. 
  5. Screw in a #2 sheet metal screw to hold the spring.
  6. Dremel off the length the the screws protruding from the other side and grind them down just below the surface so the don't scratch the plastic on the sled.
  7. File the shape of the swing arm down to the outline marks. 

Sunday, January 3, 2010

McWire and MK4 Plastruder

Well it took some tweaking and figuring but I have the MakerBot Mk4 Plastruder successfully mounted to the Z sled. It was not as hard as I thought it would be and it came out better than I envisioned.

I built up the complete assembly according to the instructions at wiki.MakerBot. Then I started to brain storm ways of attaching it. In the end, there was only one practical way of mounting it. Here is the configuration I came up with:

Both the dinos had to be removed. They made the whole assembly as large as the Z sled. I set them free and they are able to rome around the shop and feed on future discarded prints.

I laid the plastruder assembly down on some graph paper to get the relative distance from the extruder nozzle to the mounting holes.

I wanted to create a template for an adapter plate that would hold the extruder board and the remaining of the plastruder assembly. So, I down loaded the Eagle files for the extruder board and exported the Dimension and the Holes layers as a dxf file. This gave me the hole pattern for both the extruder board and the plastruder since they bolt to one another using these.  I then arranged these in my CAD software such that the nozzle was centered on the Z sled. From there it was easy to see that the inside mounting holes for the PTFE bearings would make good mounting holes for the adapter plate. The adapter plate was made out of 3/16" fiber board.  It's what I had on hand.

After mounting the extruder board and the plastruder  to the adapter board and on to the Z sled I saw that it needed to be lowered about a good 2".  A quick run to the hardware store and I got some different lengths of pipe to adjust the Z sled height. I ended up swapping out the 12" piece with two 5" pieces and a coupler.

The Y alignment is not quite centered yet. Good enough for now though.

Over all I think it came out pretty good and will be easy to swap out print heads. I'm thinking of putting longer screws in from the other side and securing the board with some screw on knobs or wing nuts.

Friday, January 1, 2010

Plastruder Build

I was a little nervous when it came to building up the plastruder. It seems like a place that many things could go wrong. I got the MK4 plastruder from MakerBot. The build instructions on their wiki are pretty straight forward. Also,  I am thankful for the makerbot google group for the support they give. I have been trolling and learning some of the pitfalls people have had in building the current revision. I see the wiki has been updated to address those. Awesome!

Now that I have built one and all measurements look good I feel like i can tackle another without too much problem.  The hardest part for me was the fine wire of the thermistor. It was like to hairs  and a spec of glass. I felt that if I sneezed, it would be gone.

I thought I would take pictures of the way I wound the wire on so encase I have any problems I could show the experts and see how it could be improved.

The next challenge is to mount the plastruder to the Z sled.