Thursday, March 1, 2012

JGRO CNC Progress

The first unit I got from Synthetos was defective in some way - we couldn't figure out why.  They were very gracious about sending me a replacement.  The new unit is working well in my test config.

I'm about 90% complete with my JGRO-based CNC router.  I have the entire gantry setup done, the motors and leadscrews for the Z and X axes are complete, and the ends of the Y axis are built, etc.  I needed to take a break for a bit to rearrange my shop so I had room for the completed unit, and I took the time to build a table for it to sit on.  It's the details that take all the time!

So tonight I'm going to get the rough alignment of the Y axis going.  My initial assessment indicates that there might be something wrong with my guides on the gantry, since there seems to be a significant gap on part of the bearing assembly.  I took the time to level the table, and then used that to ensure that the Y axis pipes were level and fairly close to alignment, and since I have a fairly big gap I have to assume it's a goof somewhere else.

Another thing I learned while working on this is that since I subbed out a lot of the MDF for birch plywood, that small fractional dimension difference is starting to matter in a few critical areas.  3/4" MDF is just that.  3/4" plywood is typically 1/32" or so thinner.  In the case of the gantry width, the design has you stack 6 pieces together (bearing block, gantry side, corner block for each side), and so that small difference starts to add up.  I suspect I'll want to redrill the Y axis pipe guide holes so that I have more alignment space.

I've been taking pictures here and there, but I haven't been particularly good about uploading them, since at the moment I think this blog is mostly a diary for myself.  Here are a couple of older shots as I was putting together the alignment blocks and bearing assemblies.  You can see I was using layout fluid and taking advantage of the fact I have some decent layout and metalworking tools.

I still need to figure out what kind of router I'm going to start with and build an appropriate mount.  I think for my initial testing and tramming I'm going to build a pen mount, making this an extremely overdesigned plotter.

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