[jmkasunich]

Hi JMK - Good info. Its preferable to mount the induction sensor to the side of the switch vs in line,. One day it will overshot and smash the switch.

We looked at both options. These are mechanical switches, not induction sensors. To do the "sideways" approach would have required ramp-like actuators that would have been harder to make adjustable. The switches that we chose have more than 5mm of over-travel, and we can adjust the hard stops so they hit about 4mm after the switch trips. Hopefully the hard stops are robust enough to handle a full-speed impact; they are pretty beefy. If a switch does get smashed, they aren't terribly expensive to replace.

The Y axis carriage has square and flanged cars? The bolt pattern is different for the two cars?

Good catch; yes. The 10 foot long 35mm rails were a lucky find at a surplus dealer, but they came with only two cars. The other two were purchased on Ebay. We couldn't find four of the same type, but we made it work.

Welcome to 2025 may it be a happy and prosperous year for you. Peter

Thanks, and the same to you!

[jmkasunich]

On to the gantry...

We had a piece of 4" x 8" rectangular tube that we were planning to use, but it wasn't long enough (only a bit over 4 feet, we needed nearly 5 feet). And it was only 3/16" wall, and the wide faces were pretty distorted. The rails would have wound up less than 7" center-to-center. Overall, not very satisfactory.


Then we found two pieces of 4" x 4" square tube, also with 3/16" wall, but 5 feet long. We spaced them 2-1/2" apart with short chunks of 2x2 tube, which let us put the rails 8.8" center-to-center. In addition to the four short tubes, there are 1/4" thick end plates. It's been a long time since I did the analysis, but I think the two 4x4 tubes are stiffer in torsion than one 4x8 tube, and definitely stiffer in bending.

Attachment 511116

Two strips of steel 5/16" thick x 1" wide were added to provide more metal where the rails are attached. They were stitch welded, with a weld at each rail screw location. The lower one was machined with a ledge on one side to hold the master rail straight as well as flat; the upper one was machined flat. Pads were also welded for ballscrew bearing mounts, and four beefy feet to attach to the gantry legs. We didn't want to weld the legs on because the whole thing had to go on the Bridgeport table for machining and the legs would have made that a nightmare. The holes in the 2x2 vertical tubes are for Bridgeport mounting studs.

Attachment 511118

Machining the gantry was fun. Had to do it in three sections, since the Bridgeport only has a bit over 24" of X travel. The weldment was mounted on the table once, using three points of support to minimize spring or distortion. Machined the center section with the mill head in its normal position, and also machined two precision reference holes at known locations near each end of travel. Then swiveled the turret and extended the ram to cover one end, touched off the DRO using the reference hole, and continued machining. The gantry wasn't unbolted from the table until all machining was completed.

Attachment 511120

We managed to achieve no detectable step at the transitions between each section, and I have not been able to measure any significant straightness error.

I don't recall exactly how we machined the bottoms of the feet to be precisely 90 degrees to the rail mounting surfaces. I think we used a pair of 2-4-6 blocks on the table to mount the rail faces vertical with the feet facing up. But it's been almost two years, and I'm not sure...

[jmkasunich]

As usual I've been lagging far behind when it comes to posting on this project.

But it lives!
Attachment 513398

First cut was the little logo, then we scaled it up to something more reasonable and adjusted the depth of cut to suit the cutter at hand.

The table top is not attached yet. We have wooden spacer pads epoxied to the table mounting points, and we are going to use the machine itself to skim cut them all flat and parallel before bolting the table top on. For this test we just bolted the stock to two of the table mounting pads.

[routalot]

It is always hugely satisfying to see a machine come to life.No doubt there will be some fine tuning in the coming weeks to make it perform at it's ultimate level and then the parts are likely to be flying out of the door.