Z-Rods Follow-up and Instructions

11 09 2010

I received my new ACME Z-rods awhile ago and I am finally getting around to writing this up. They are super sturdy, super straight, super shiny, super smooth pieces of awesomeness. Installing them took a little while to figure out, but once I figured it out, they worked really well. It may look long, but it really doesn’t take all that long. Here’s how I did it:

The first and most important thing was to clean them. They had a lot of dust and metal shavings stuck to them. Luckily they were covered in lubricant so it kept them safe. I spent about half an hour cleaning each one very carefully. First I used a dry paper towel on them and cleaned them by hand. That took forever so I put them in a drill chuck, held the paper towel tightly around it and turned the drill on slowly. That cleaned the outside nicely, but the threads still had a lot of junk in them. So to clean the inside of the threads I put the drill in between my legs, folded over a paper towel and held it in the threads as I spun the drill with my legs. Only after the rods were perfectly clean did I stop cleaning. The cleaning step is extremely important for smooth easy travel. If there is any dirt left it could make the Z motor skip a step.

Then I took the delrin nuts and ran them through the rods a few times to make sure each rod and nut was extremely smooth. I used the drill for this, too.

Using a dremel or a hacksaw, take off approx. 10mm from the side of 2 of the delrin nuts. Make sure you don’t cut into the bolt holes. Make the cut parallel to the bolt holes.

The next step was to actually install them in the Makerbot. First take out the acrylic Z stage by tilting it and turning it so you can take it out. It is easier to take it out if you take off the plastruder first. Next you will need to take off the pulleys and the belt from the Z rods. Then you will need to take off the square wooden pieces that hold the top Z bearings. Take off all 4 bolts and set the wooden pieces aside. You won’t be needing these anymore, but its probably a good idea to keep them for the future. Now you should just be able to pull out the old rods. Take off the lowest nut and the highest bolt on each old rod to release the bearings. Push 4 bearings into the lower bearing area. You will not need any nuts to hold them in anymore. Next take the remaining bearings and make sure that they fit on the longer 8mm part of the new rods.

Put in each new rod with the shorter part down. Before you put each rod down all the way, screw a delrin nut onto it with the wide part up. Screw it about halfway up and then push it into the bottom bearing. Then push a bearing onto the top of the rod. It should push all the way to the threaded part of the rod and it should be pushed into the hole in the wood.

The next step is to level out all of the delrin nuts so that they are all at the same height (within a few mms at least). I used a carpenter’s level, but something a little smaller would be better.

Next take off the wooden squares that are attached to the acrylic Z stage. Once you take off the wooden pieces, put the bolts back on the Z stage. These will hold the Z stage onto the delrin nuts. The M3 nuts will be a press fit into the mounting holes on the delrin nuts.

The next step is optional, but highly recommended. Using a dremel with a high speed cutter or a sanding wheel cut out a larger hole where the nut used to go. This is to make room for the ACME rods which are much larger than the old ones. You can get away with not doing this, but you will get extra friction, noise, and quite possibly extra skipped steps. Keep in mind that once you do this step, you will not be able to go back to the old rods without a lot of hacking.

Now you can finally put the Z stage into the body of the bot. The bolts should press fit into the mounting holes in the delrin nuts. Now is a good time to attach the pulleys to the new Z rods. Also put the belt back on now. You can now test out the Z stage by spinning the rods and marvel at your near perfect Z travel. The Z stage will now move about TWICE as much as with the old rods with each turn. Keep this in mind!

Now you have to tell ReplicatorG that it needs to move the Z stepper different amounts to move the Z stage the same amount. There should be a machines.xml file in both the repg install directory and in the ~/.replicatorg directory. Depending on what version of repg you are using it will use a different machines.xml. machines.xml is the file that declares the settings for each machine. Open one of these in a text editor. You will need to change both files just to be safe. Under the “Cupcake CNC” tag or “Cupcake CNC w/ heated build platform” tag, depending on which one you are using, and where you see it says “<axis id=”z” length=”300″ maxfeedrate=”150″ scale=”320″/>”, change that to “<axis id=”z” length=”300″ maxfeedrate=”300″ scale=”157.480314960629921″/>”

Now open up repg and open the control panel. Move the Z axis and check to see if it is moving the correct amount. If it is then congratulations! You’ve successfully installed your ACME rods!

Now you can print something! Keep in mind that any previous .s3g files, like the ones you print from the sd card with will not work because they contain the machines.xml for the old rods. So if you try to print from the sd card with an old file, it will move about twice as much as it should in the Z axis.

I’ll post pictures of before upgrade and after upgrade sometime soon…


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