Here's some photos of the leadscrew refit. It also updates various other aspects, such as the dust boot, vacuum table, cable runs and etc. The Z-axis is still rack and pinion, works fine. The last two photos show it with and without the dust boot. BTW the vacuum table works great as long as I block any un-used holes with plastic sheeting. All of the brackets are .1" thick steel, quite stiff enough for the job.

 

Hi Justin and thanks. I used 8-wire ethernet cable (24awg), with four pairs of two wires each doubled for increased current capacity. Never had a problem running about 3a max step motors, but of course the average current per motor is much less.

 

Not sure which parts are "wiggly", but I used standard modular RJ45 connectors which are gold plated and have spring loaded contacts. I've found them to be pretty vibration and tug tolerant, same as that used with Ethernet and phone jacks.

My biggest concern was current capacity, but even after extended cutting my wires are still cold to the touch, unlike the motors.

I did not invent this, it's what the (now defunct) maker used on my plasma cnc table. Works well there too, even with all of the sparks flying! (BTW he's defunct for other reasons.)

 

Starting the next aspect of this project, converting the z-axis to leadscrew as well. Will post photos soon as the project progresses. I'm also adding a carriage stiffener that does double-duty: reduces whatever racking the two-plate carriage exhibits, plus provides vertical support for the z-axis motor.

You'll see it all in the photos, but here's a couple screen shots of the Solidworks model:

 

Z-Axis now leadscrew, please see YouTube video at:



Enjoy!

 

Thanks Tweakie! Here's a photo of the "new" z-axis, now with a laser crosshair:



Notice my very high tech Altoids can for the LED batteries and on/off switch

OK I'm cheap.

 

Thanks. It was a pretty easy update, good for basic alignment of the workpiece. Came in handy immediately. Lines are a bit wide but good for $6 emitters, particularly since my goal was to get within 1/8 inch or so.

 

I'm not familiar with the bicycle lasers, not really sure what they're for, except to draw someone's attention.

I wouldn't look directly into the light of any laser, even the low-power ones. I don't think there's any danger looking at the reflected light from these really little ones, as long it's not from a mirror.

Here's a link to the Ebay auction that I bought them from:

http://www.ebay.com/itm/150828205147

 

No problem, and good question. There are two single-line emitters mounted at approximately 90 degrees separation around the spindle center. The most important aspect is that the leds are mounted in holes that are parallel to the motion of the z-axis so the intersection won't wander as you move up/down in the z-direction. After mounting, you rotate each led so they intersect as nearly as possible where the spindle center is located. It's easier than it sounds.

 

I saw Sgspencely's questions about my leadscrew retrofit.

Yes, I do have lock collars in strategic locations on the leadscrews to prohibit axial motion, using the sides of the bearings as the limits. I can post pictures if requested.

Since I capture chips and dust with the dust boot it has not been a problem to have the leadscrews up high and exposed, and doing so made it much easier to add to my design. It also puts the drive points closer to the center of mass, thus reducing the moment arms.

 

I've been using the anti-backlash nuts from Dumpstercnc with very good results.

For motor adapters however, I strongly prefer the flexible couplers -- search on Ebay or Amazon. The ones I am using have a 1/4" bore on one side and 1/2" on the other. They have a slight rotational springiness, I suppose it could introduce *very* small errors on harsh cuts, but they go a long way in protecting the motor bearings and smoothing out any misalignment.

Thinking about your question, what would I do differently to the Frog ... here are a few things that come to mind:

1. I would use a much stiffer cross arm for the gantry. I really thought a pair of 20x60 vslots (screwed together) would be stiffer than they are, rotationally. This is one of the biggest contributors on this machine to unwanted flex. I'd probably go to a pair of 20x80s or maybe three 20x60s. BTW it's REALLY important to tie them together along the length so that they act as one larger beam rather than 2 or 3 smaller ones. I drilled through laterally in the web and bolted them in a few places. Helped a bunch!
2. As cheap as the Harbor Freight trim router is, it gets bogged down with any significant cuts. In actual fact, it's ok for this (currently) lightweight router system, but if was building a beefier unit I'd probably switch to a higher strength cutting motor.
3. The vacuum table has been great, but I will likely add some threaded holes to it so I can use conventional clamps when desired, and leave the vacuum system off.
4. Changing bits is a chore. I'd like to find a quicker way to swap in/out cutting bits, something that doesn't break the bank.
5. I'd like to be able to visualize the cutting location with the vacuum boot in place. I'm thinking of mounting a very small video camera and led light near the cutter and inside the boot to display on a nearby mini TV. Hmmm, maybe I can use an old smartphone...
6. The Openbuilds plastic wheels are OK, but not super. In retrospect for each movement I'd prefer to use steel V-rollers on steel rail(s), and have a self-aligning adjustable two-wheel rocker on one side. This would eliminate the need for all those small-motion eccentrics, be stiffer in operation, and end up much less finicky to adjust. In my current design there's always one or two wheels that aren't doing very much.

That's it for now.
Neil

P.S. 1/2-10 5 start acme leadscrews are really cheap just now on McMaster, only $17 plus shipping for a 6 footer! I paid over $60 just a few weeks ago for the same thing.