JGRO inspired design

I have been building my router off and on for about a month. Today I assembled the pieces for the first time. The Y and Z axis are pretty much straight from the JGRO plans. I went with 3/8-16 SAE screws from McMaster rather than 1/4-20 from Lowes but otherwise it is true to the plans. I also have used either plywood or hardwood for the pieces instead of MDF. I've never been a big fan of MDF and I had some plywood and oak laying around.

The X axis is my own design drawn up with TurboCAD Pro. I had some 1-1/2x3" box tubing and thought it would make a good sturdy base. Hot rolled steel is not perfect but is is likely better than 1" pipe. Deflection will not be a problem. I welded plates to the end of the box tubes and bolted the cross pieces. This reduced the impact of any warping and allowed for necessary adjustment. I also had some aluminum U channel which worked well with the skate bearings. You can't see the skate bearings on the bottom of the box tube in the pictures. Like all the others they are adjustable. It seems to roll easily with very little play. Time will tell how much play there really is. The EMT conduit will form a reasonably solid base for a piece of MDF for the bed. The conduit is not fastened in the picture and there will be four pieces.

I still haven't decided on what type of screw to use for the X axis. I'd like to upgrade to an Acme screw but haven't found a suitable source. Any suggestions on what type of screw to use and a good source? I'm still looking for something inexpensive but may spend a bit more in this case as the X axis may get reused in the next build (if there is one).

I purchased a motor/driver kit from Longs Motor on EBay. They seem to work well driven from a signal generator but I haven't successfully hooked them up to LinuxCNC (EMC2) yet. The breakout board that came with the kit has opto-isolation which is redundant with the M542 drivers and the waveform looks horrible on an oscilloscope. So I'm looking at better board from CNC4PC.

There seems to be some deflection in the pipes supporting the Y axis. I may tack weld a piece of flat steel edgewise to the bottom pipe to reduce the deflection. I will also have to enlarge the hole on one side to be able to insert the stiffened pipe.

My plan is to use an old Craftsman router as the spindle. I'm sure replacing it will be one of the first upgrades. I'm starting off using as much stuff as I have on hand or can get cheap and will upgrade as necessary. Ultimately I will probably use this machine to build the next one. I think I have about $400 invested so far but I haven't added it up yet so its probably more.

John

Even the 3/8 16 is kinda slow for the y. I highly recommend you get multi-start acme. Mcmasters and roton is somewhere to look. I also highly recommend dumpster anti backlash leadnuts. Not big on bob's from ebay. Just so many stories of issues even when they did work.

Cool x-rail design.

There are some good reasons to use MDF, even though it is not as rigid or durable as plywood or hardwood. Unless you spent a lot of money for it, plywood is not consistent in thickness. On the other hand, MDF is much more accurate and consistent. That might be a problem if thickness accuracy is critical in the design. Hardwood has this irritating property of changing dimensions with changes in humidity. For example, red oak will eventually change dimensions by about 1% in the radial direction between 35% and 65% relative humidity. That may or may not be significant depending on where and how it is used in the design. MDF and plywood are much more stable over temperature.

Looks great! I like how you did the X axis. I bought my Acme screws from Enco. They were very cheap and work well.
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I found this ballscrew on EBay. It is the right length for my X-axis. I looked at the acme screws from Enco, Rotron and McMaster. By the time I got the screw, bearings, coupling and anti-backlash nut plus shipping the price is just a little less than this ballscrew.

Anybody dealt with MISS_MY_CNC before? I only found one comment posted and it was positive.

1 Anti Backlash ballscrew RM1605 1250mm C7 BK BF12 Coupler 6 35 10 CNC | eBay
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John