Moving table fixed gantry build

[judleroy]

I have been working on a router for some time now. The machine will be all steel, aluminum, and Iron. Most of the parts for the machine I already have. I will be purchasing a screw drive system and several electronic items to finish the build. The machine is to have a 52in X travel, 32+inch Y travel and 12+inch Z travel. The pics I am posting today only reflect the start of my build and I have accomplished alot more then what is pictured. I will be giving a good inventory of parts both purchased and machined in the next few days. I will need alot of electronics help in the coming days as its a weak point for me. As a little background I have been programming and running cnc machines for going on 11 years. Much more to come soon I promise.

[carvemylog]

Wow, that thing looks solid. Be interested in see what parts you get for it and what the overall design looks like. Don't know how far along you are with the design, but I'm really glad I designed mine on my CAD program 1st. I probbaly redid 5 or 6 times in the CAD program before I was happy with it, that saved alot of time working with the real parts. I didn't go into the detail of drawing the bolt heads, etc, but probably should have cause I had some clearance problems to work out when building it.

[judleroy]

Thanks for the reply. I've spent many many hours in cad designing but know from past experiance that things change constantly for practical reasons during a build of any type. Also I've spent so much time in design and always make changes to my cad as need arises so I figure for now I'll build and then do the cad around what I Build. The table has a 1/2" think aluminum top and the rest is all welded steel tube. The 30"x18" moving table is a SS newport precision measuring plate with 1/4-20 threaded holes on a one inch grid. The work surface or rotary table or even a small lathe
will be mounted to this main plate alowing the machine to adjust to my needs. As it stands two people can slide the table around with effort but cant lift it a quarter inch off the ground. The X axis rails are 3/8" thick angle iron 5"X3.5". They have been milled on the 5" side for straightness. They measure within 2 to 3 thou variance in thickness from end to end and are 64" long. The X axis carriage will ride on bearings similiar to ahren from cncrouterparts design. The bearings very in size by location. The main stay of my design is the 2" bearings with homemade 1" eccentric bushings to allow easy preload to the rails. The bushings will allow about 1/4" adjustment so they should be easy to adjust. Pics of these rails and carriages soon. Thanks Judleroy.

[shridhar]

I will watch this build. Why have you chosen 'Moving table fixed gantry' other than fixed table moving gantry? Don't you feel you need to do surface grinding where LM rail is resting?

[Riceburner98]

Nice! I've got a larger version of that Newport plate that I was going to use as a base for my machine.. Mine was dropped on a corner so some of the glue inside broke, it sounds like a "Plinko" machine from the Price Is Right when I tilt it and the glue pings around inside the honeycomb in there! I also made the mistake of putting it in my car upside-down so I got metal shavings and glue bits all over the place when they came out of the holes. Seems like a very sturdy piece, and it's designed to help stop resonance with the optics that are normally mounted to it. Looking forward to some more pics!

[Andre' B]

"Moving table fixed gantry build "

Commonly known as a bridge mill.

[judleroy]

I choose a moving table fixed gantry (Bridge mill) design because I have had bad and mixed results with a moving gantry. Second is because I think it lets me add and remove accessorys quickly. I own a Hurco BMC30 (Used for many years but is needing repairs to run)that is very rigid and cuts Very smooth cuts so I have seen first hand how smooth of cuts you can get with a moving table. I need a bridge instead of a fixed column to get the 52" of X travel
needed for 4x8 sheets. I opted for no surface grinding because the iron square tube underneath is between 1-3 thou variance along the length and the table moves very smooth with no binding or play. Okay now for more pics.

1. pic is 1 of the 3 DC brushless servos I hope to use.
2. is an example of the eccentric bushing with bearing mounted to test piece and 2 pinion reducers I'm thinking of buying rack for to drive the X.(Will be modified)
3. are of the k-motion board I'm hoping to use to control the machine.
4.The supply and board all mounted together in cabinet.(supply is 54v 13amp). Also pc power supply attached to K-motion.
5.Is the 1/4" thick I-beam I will cut to 66" long to be centered and bolted to the underside of the table. It will be used to support the gantry uprights.
6. are of the blocks to be drilled and tapped to mount the i-beam to the bottom of the table and the upright supports to the i-beam.Also some angle to be used with the gantry slide.
7and8. are the rest of the eccentric bushings needed, a 2.4-1 ss. timing belt pulley set to be mounted to the sherline cartridge spindle shown and in a 24,000rpm router
to give me 10,000 rpm max at the spindle.(I hope to control the router speed with a ac frequency converter).
9. is the beginning of the Z axis. Its a 3/4"X6"x10" pc of aluminum mount to two 24" long 20mm rails with four blocks.
10.is the two 64" long angles to be used as gantry rails.(they have had 1/4" shaved off of the 5" side 60" long by a cnc mill with 60" max cut so the should be very straight).

I will try to update and answer any questions as often as possible. All feedback and opinions are appreciated. As a warning this build will still need a good bit of time to completion. I will try to start posting cad models as the machines design is closer to being finalized.(I know basicly what I want but not the exact dimensions that things will end up being). Thanks Judleroy

[svenakela]

I like steel builds.
I have a steel CNC but with a moving gantry, and it's crazy sturdy.
But if you go for a fixed gantry, why not increaze the Z-axis? I miss a couple of inches every now and then. You can avoid all flexing a moving gantry machine suffers from.

[judleroy]

These are rough cad drawings of what I'd like to see done within the next week. Note the drawings dont show the support blocks that will hold things together but they will be added. I will probably end up adding legs or some other support directly under the uprights. I agree with the need for more z clearance and have adjusted to get closer to 15". Thanks Judleroy

[judleroy]

I've gotten a little sidetracked over the last few day's. I bought a small piece of 1/2-13 threaded rod and am trying to duplicate something like the dumpstercnc nuts. The one i'm making to test is make of brass and aluminum with a heavier duty spring then what is used for the dumpster nuts. If the test nut works I will be ordering 1/2-10 5 start or 3/4-8 4 start acme threaded rod. The final nut will be made from bearing bronze. The test nut will be finished in the next few days and I will post pics. The questions I have are...
1. Do you guys think the 1/2" rod is big enough?
2. Does anyone know of any reason the dumpster design won't work in bronze.
3.Does anyone know of a antibacklash nut design out of bronze that would work instead of the dumpster design.(I love the dumpster design its simple and seems to be well proven).

Thanks in advance for any help. If you have any suggestions feel free to throw then at me. Judleroy

[judleroy]

As a note I will be driving the nut with a timing belt pulley not rotating the screw so whip should'nt be a problem.

[FandZ]

Originally Posted by judleroy I've gotten a little sidetracked over the last few day's. I bought a small piece of 1/2-13 threaded rod and am trying to duplicate something like the dumpstercnc nuts. The one i'm making to test is make of brass and aluminum with a heavier duty spring then what is used for the dumpster nuts. If the test nut works I will be ordering 1/2-10 5 start or 3/4-8 4 start acme threaded rod. The final nut will be made from bearing bronze. The test nut will be finished in the next few days and I will post pics. The questions I have are... 1. Do you guys think the 1/2" rod is big enough? 2. Does anyone know of any reason the dumpster design won't work in bronze. 3.Does anyone know of a antibacklash nut design out of bronze that would work instead of the dumpster design.(I love the dumpster design its simple and seems to be well proven). Thanks in advance for any help. If you have any suggestions feel free to throw then at me. Judleroy

Is there any particular reason you don't want to use a derlin anti backlash nut? The reason I bring it up is if you send Joe a sample of your screw he can make it for you. His prices are reasonable. I know you plan to spin the nut instead of the screw (a fantastic solution) but I'm sure you could get a gear to mount up to the flange of the nut. I'd contact dumpster cnc before you invest too much time. Why slow you build up over a 20 dollar nut?