And now for something completely rediculous

[spoiledbrat]

Thanks, Ger... someone agrees .

The servos are going to be a little smaller than depicted. I am using 1kw AC servos from automation direct... I tend to like businesses that display pricing.

The motor depicted is the medium inertia, but I am going to use the low inertia. It will be a little more compact. I learned today that the 1Kw medium and the 1Kw low inertia differ in torque by 30%+. I also learned that this torque is derived from the rotor housing weight spinning at 3000 rpm. In stopping this servo, and reversing directions, the medium inertia would be a waste of energy. Well, between that, and the inertia matching data that Atlanta provided me, I have decided that the low inertia is the better choice for me.

Servos will be mounted to Stober gearboxes. The gearboxes have an iso-flange pinion mounted to the output flange. Gearbox backlash is less than 2 minutes, and the pinion is 55.2mm pitch dia. In a perfect situation (the frame being made from absolutely rigid anti-matter, and being machined perfectly straight), I can achieve 0.0013" of backlash. Good enough for me.

The gearboxes are mounted to a ~1" steel plate, that is placed into a pocket on the gantry wall. This way, I can take up the slack as required between the pinion and rack by moving the mount plate via a bolt (not depicted yet).

Ratio is 10:1. Because I am not an applications engineer for all of the components that I am using, most of the design is based on machines I have seen, and any other information my machinist has managed to beat into my head over the last 5 years. I will not be apologizing at this time for copying good designs... I would be silly not to.

I plan on posting information on the control cabinet, to gather more information and make sure I only have to buy once. This forum helped me build my first router 5 years ago; this time I do intend to document the build a lot better.

Cheers!

[jsheerin]

Nice looking machine. It's similar to what I'm working on as well, but my gantry will be a bit different. But the 1kW servos (although mine are ebay specials), rack and pinion drive and dual spindles are similar although I'm going to do dual screws on my z axes and have one router and one milling / drill head and sadly no ATC's (maybe in the future).

Have you worked out any details of your rack and pinion setup yet and how you'll eliminate backlash in it? From your drawing you have a helical rack, but any details other than that?

Do your concrete bases just sit on the floor or are they bonded or bolted to it? If your frame weighs 4500 pounds, you probably won't have issues, but I'm planning on something a bit lighter and am worried about the machine walking itself around over the floor. I'm calculating I'd need a minimum coefficient of friction between the machine and the floor of 0.5 to prevent it from walking around under max accel or decel. I'm just wondering how you approached this.

[spoiledbrat]

Gearboxes are mounted to a 1" plate, that can slide in a slot on the gantry wall. Instead of clearance holes, there are slots in the gantry wall to accommodate fasteners. A single bolt will draw the 1" plate vertically (meshing the rack and pinion), and then the 6 bolts (in slots) will be tightened.

The concrete bases have three anchors holding the steel in place, and then the concrete. As the base does weigh a lot, I should not have issues. I am thinking of somehow boring shallow pockets into the concrete to retain the leveling feet, but this is probably unnecessary. We will see how it acts with max accel/decel. I might simply pin the leveling feet to the concrete with additional anchors if it comes to that.

Cheers!

[rowbare]

2. Currently looking at Keling CNC for the 2.2Kw ATC. Have not purchased yet.

Given the speeds this machine should be capable of given the weight and rigidity, you might want to go to the more powerful spindles. A 2.2 Kw spindle will simply not be able to take the depth of cuts and cutting speeds this design should be capable of.

I don't know if you have seen this thread or not. They also built a nice heavy router: 5' x 10' NEW ROUTER BUILD

bob

[spoiledbrat]

Very familiar with that thread... I think it gave me the motivation to persue a larger project.

As far as the spindles are concerned, I am looking for lightweight and quiet, with ATC. I am not going to be processing sheet goods with this machine. My mainstay is 3-D carving using 1/8" ball-end mills. I use a 0.010" step-over, and usually carve 0.500" deep at the most. Therefore, the cutting load is negligible for 95% of what I do.

Rob

[spoiledbrat]

This is the beginnings of the aluminum work. As you can see, I have some heavy de-burring work ahead of me. Holes we milled no deeper than 0.875 from surface, to be finish drill on a drill press.

We had problems getting Enroute software to create some of the code. We also were using O-flute aluminum cutting end mills. Great for removing the material and profiling, but terrible surface finish where the bottom of the tool was. Great on the sides!

A roughing cut was made around the perimeter of each part, leaving 0.010" of material for the final pass. We did not do this on the spindle mounts, so the finish is not as good.

I think we destroyed 200 dollars in stock and 200 dollars in materials, but I can complain. I did this machining with my good friend as a work-exchange. I think I will be owing him for a while

[spoiledbrat]

more pics

[spoiledbrat]

Forgot to include these

[spoiledbrat]

10:1 gearboxes made by Stober, courtesy of Atlanta Drives. 10:1 ratio, advertising <2 arc minutes of backlash. Pinion is 55.2mm pitch dia pinion. Looking for a good way to ensure it is mounted concentric if anyone has any ideas. I was expecting a nice ground shoulder to run a dial on.

[spoiledbrat]

Auto-lube from atlanta drives. I will attempt to mount these in the gearbox mounting plates, if able. I will have two on the x-axis, and one on the y axis. The auto lubes have batteries in them, and switches to select the rate of dispensing of the grease through the felt pinions. Some kind of electro-chemical reaction creates pressure to push the grease. I read that it takes a few days to build pressure. As I do not plan on running the machine in 24 hour shift, I hope to have them last a year and a half before having to refill them.

Hoping to have some pictures of the frame in progress this week. Can't be pushy, though... I did not hire photographers to build this rig.

[Zygoat]

pretty cool. thats a big machine. what will you be working mostly (material)?


i like the "kit kat". but somebody ate one! ... looks around.

[spoiledbrat]

I will be working with solid hardwood, mainly. I tend to focus on 3D carving; I rarely run any sheet goods except for fixturing. Either way, the main idea here is to make as much sawdust and noise as possible.

I will also be cutting low tolerance aluminum plate, for making fixtures and in-house tooling. May use it to make some better parts for my older, smaller router. Sure would be great if the lead screws were actually aligned on that thing. The screws are eating themselves after 4 years of use. I cant decide if I need to fix that now, or if it can wait 6 months.