Hi, I'm from England. That sucks because it means that I don't have much availability for parts where need be. Fortunately a lot of the Open Builds stuff is available at a couple of DIY CNC online shops here, and I have access to 3D printers. I need to build a CNC Router with 1500x1500mm frame. Feel free to stop me at any point if what I say is dumb, I've only been researching CNC machines for a couple weeks. I have about $2,500 to work with, and would like to keep costs down. My decision for a good basis was the Ox-Metal CNC Router Mill by Schematix. As I need to do work on aluminium, leadscrew seemed like a good, cheap choice. I also need pretty decent accuracy/repeatability given the amount of framework I'm dealing with. Unfortunately, the Acme lead screw in TR8 variant is only really useful for builds of up to a meter. For that reason, I decided that I'd need to make my own variant of the Ox-Metal based on TR12 Leadscrew. This is where I need help. From what I can find so far, if I were to make an Ox-Metal with TR12, Other than changing the overall size of the X and Y axis, I need to change a number of components to accommodate the new lead screws. I would need to modify: - The size of the flexible coupling for the motor - The bearing guide used on either end of the carriage for the lead screw - The size of the lock collars to secure the lead screw to the carriage - A 12mm anti-backlash nut block, rather than the standard 8mm - And add a few mm clearance for the Z axis past that already introduced by the spacer block for the lead screw Are there any other considerations that I need to make before running off and buying a bunch of stuff? Are the changes that I've suggested reasonable to assume are possible for a hobbyist who has limited access to tooling, apart from a local hackerspace with some 3D Printers, and drill presses? Does the size of the lead screw introduce any new mechanical considerations, such as friction that might need to be considered in terms of the motor torque? Are there any parts that suit my modifications that are already available? And better yet: Are there any *better* ideas than mine, that would give me a heck of a lot easier a time in getting a 1500x1500mm frame CNC router/mill up and running?
Have you done any modelling to verify that the TR12 screw fittings (anti-backlash nut, collars, etc.) will actually fit within the space that the TR8 screw currently occupies? As far as the end fittings go, you might see if you have a local shop that can turn the ends of the TR12 screw down to an 8mm diameter and that will save you a lot of revision in the bearings and end plates.
In my build, I did what Rick suggested to you. I was able to find tons of 12 mm and 8 mm shaft couplers at a reasonable price. I could not find 1/2 inch or 3/8 inch. I purchases 1/2 inch acme threaded rod for my two 1500 mm y axis and 3/8 for my 850 mm X. I had a friend that had the ability to turn them down so I had him do it. i took left over prices of the threaded rods and made my own taps then tapped my own delrin anti-backlash nuts. It was an interesting side project. By doing these two things, I probably knocked $150+ of the cost of my build. http://www.openbuilds.com/builds/lead-screw-driven-ox-derivative-850x1500.3926/ Also, the 1/2 inch threded rods would not for in the cbeam so I ran them externally.
In my build, I did what Rick has suggested to you. I was able to find tons of 12 mm and 8 mm shaft couplers at a reasonable price. I could not find 1/2 inch or 3/8 inch. I purchases 1/2 inch (12.7 mm) acme threaded rod for my two 1500 mm Y axis and 3/8 (9.525 mm) for my 850 mm X axis and Z axis. I had a friend that had the ability to turn them down so I had him do it. I took left over pieces of the threaded rods and made my own taps then tapped my own delrin anti-backlash nuts. It was an interesting side project. http://www.openbuilds.com/builds/lead-screw-driven-ox-derivative-850x1500.3926/ Also, the 1/2 inch threaded rods would not fit in the cbeam channel so I ran them externally. I also was able to find 12 mm pillow block bearings at very reasonable prices compared to the $39 per 1/2 inch pillow block bearing. By doing these two things, I probably knocked $200+ of the cost of my build.
