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designing stage of a cnc plasma/router

01-31-2011, 12:37 PM
i'm very interested in building a cnc plasma/router machine.

i just joined cnczone and they have a waiting period or i'm waiting on an admin to ok me to post...

so to the point..

budget $2000

i'm planning on building a 4x4 cnc plasma machine/might try to also use it as a router if its doable on the cheap...

i am trying to do this at home with what i have here, i have a mig welder, tig welder,plasma cutter, 4x6 horizontal bandsaw, drill press, also a friend told me to come get his mill/drill and i can use it... i also have access to a small mill and lathe at a friends house, but i dont want to use his stuff if i dont have too, you know how it is..

after researching different builds, what i've come to find out is most of the money is tied up in the slides and the electronics..

planning on building the frame of steel, also the gantry of steel,, possibly aluminum to make it lighter but not decided yet.. also using rack drive as i think this is the cheapest.. the z axis will probably be acme screw drive..

heres what ive come up with for slides for the gantry as of now... i'm not so certain my slide idea is going to work, i'm including a sketch of my idea.. after looking at it i dont think the bearings would hold up too the vertical load.. i think that i somehow need to square the bearings up to handle the load.. this is the simplest idea that i've come up with so far.. the slides would be made of 1 inch angle iron on the table, and the go with 1 inch angle iron or aluminum on the gantry.. was planning on using the abec7 sealed skate bearings mounted with shoulder bolts/ or hardened stripper bolts.. the slide assembly would be 6 inches long using 4 bearings/2 bearings on each end, or could even go up to six bearings for increased side load bearing ability

i need to keep the slides as simple as i can and adjustable to make up for wear later on, i can use shims for adjusting...

for the electronics:
a friend of mine is a hoarder and works for a plant that has the salvage auctions.. he has scored an old Burny cnc contoller and the servos and gear reduction boxes from a cnc plasma that they had retro fitted.. he told me i was welcome to use them... i figured i would use them to start with... possibly later on use the power supply, drivers and then possibly use mach3 or linux-emc2 for the controller software... i'm not worried as much of the electronics right now, as i'm focusing on the design of the table and gantry as this is where a majority of the budget will be i think..

appreciate any ideas..


01-31-2011, 03:48 PM
I think it might work but would probably be hard to keep in tune. I prefer round bar slides and if I build another I will use them on it. You can use a ring at each end with three adjustment screws at 120 degrees from each other. That will make adjustment quite easy. You can get drill rod in up to an inch I think fairly reasonably. I noticed at Alro steel they had stainless bar at about 1.25" dia that would work pretty well too.
Whatever method you decide to use make sure you have plenty of adjustment in all directions. Where are you getting your rack and pinions from? When I priced them they were quite expensive. Sure wish I could pick some up cheap, I would change the feed on my table.

01-31-2011, 08:22 PM
i think it was Moore Gear where i was told to look at the rack gears..

---------- Post added at 09:22 PM ---------- Previous post was at 08:43 PM ----------

thise is about the cheapest way that i've seen as far as a system youcan purchase... you have to buy the 1/4 " crs plate yourself, whatever size support rail you use you have to accout for 1/2" per side overhang.. so if your main rail was a 1 1/2 heavy wall square tubing you would get 1/4"x2 1/2" wide crs... i am also considering this, but am still open to design ideas..

i like thompson shaft, but with a unsupported rail you will have a fair amount of deflection unless you double up on the shafts or use like 1 1/4 or 1 1/2 diameter shaft.. Dbl up running two 1" dia thompson shafts on each side would be nice, but that would be pricey.. even if you use the supported shafts, they are extremely expensive..

i dunno, think i'm gonna dig around on cnczone some more and see if i can come up with some more ideas..

01-31-2011, 08:39 PM
I have a set of plans for one using 1/4" plate bent into channels. I think it was Mech Mate. They no longer offer the plans for free but I can send you a copy of the free plans I got when they were available. Might be worth a look.

02-01-2011, 12:29 AM
i have the mechmate plans.. i found them posted some where on the net :/

the place that has the skates i was talking about is CNCRouterParts (http://www.cncrouterparts.com) this is the skate i was talking about in the previous post, i forgot the link. http://www.cncrouterparts.com/images/Extended%20Linear%20Carriage%20ABEC%207.jpg

also mcmaster carr sells 20pitch rack undrilled for like $40 for 4ft, or predrilled for $60 McMaster-Carr (http://www.mcmaster.com/#rack-and-pinion-gears/=au6scf)

---------- Post added at 01:19 AM ---------- Previous post was at 01:17 AM ----------

the bolts in the skate/truck are also eccentric so they have basically cam style adjustment..

---------- Post added at 01:29 AM ---------- Previous post was at 01:19 AM ----------

i think these are pretty cheap for what your getting. i might just end up going the is route, unless i figure out something cheaper and easy to fabricate/machine..

02-01-2011, 01:19 AM
I would go with a gear belt, I used belt drive on my CNC. The belts that I used are very small, but you can get larger belts that suite your needs. When you think about it most car engines use belts for engine valve timing. You will also get much faster movement from a belt setup. MY 2 worth.