*Slight* change in plans...... 6x12 CandCNC

[douglasco]

Dream: 6x12- 6 axis plasma, router, torch w/rolling water table.
Reality: No CAD, CAM or CNC building experience. No Mill, No Lathe. Little $$

I see everyone ends up building a second table or at least doing lots of rebuilding. So instead of pretending to get it right the first time, and wasting alot of time and money, I'm going to try to do a really good job of half-@$$ing it. Also it won't risk falling into the unfinished project abyss.

I just happen to have this boat anchor(pic1,2,3) that i built many years ago before i knew what CNC was and only had a few bucks in my pocket(some things never change).

All my Q's are in red.

Linear rails: 35MM 18.5" of z travel; 86.5" Y travel; one spare 10ft rail and block(for the X?) Never heard of the manufacturer- the carriages have KUSE-35 and INA stamped on the end cap. Google says that is the Schaeffler Group and KUSE is:

"Six-track linear recirculating ball bearing and guideway
assemblies of series KUSE have the highest load rating
of any recirculating ball bearing guidance system with the
same envelope dimensions, and allow very high accelerations
and velocities. Linear ball bearing and guideway
assemblies of series KUSE should be classified between
the traditional linear ball bearing and linear roller bearing
guideway assemblies.
Linear ball bearing and guideway assemblies of series
KUSE derive their high load carrying capacity from the six
tracks of preloaded balls. They can take loads from all
directions and moments about all axes. The low friction
characteristics of this new linear recirculating ball system
allows very high accelerations and velocities."

.............Sounds good to me untill I have to buy more carriages Are you guys using 6 track carriages?
Notice the rail is not thru-drilled so that makes it hard to deal with



I was going to use the motovario(blue) worm gear boxes for my servo reduction, because i can get more and 20:1 shouldn't be toooo slow. The Tech Dept said the motovarios(free) are "only" 10-20 arc min.

Oh and yes that is a swivel plate mounted behind that super-precision router holder. Its actually off the base for a captains chair in a van. Its stamped out of .100" but its very tight. I think i'll leave it to play with.

So in 10 easy steps....

1: Cut off the 8" angle currently holding up the Gantry I beam,
2: Find cheap gear rack for the x and decide what to use for rails.
Was thinking maybe my extra linear rail on one side and v-bearings on
the other.
3: Lengthen the table from 4x8 to 8x12ish and beef it up. Mount rack and rails
4: Add sides onto Gantry beam w/ bearings and/or carriages. Probably move the gear rack to the outside of the ibeam so i can have more room for the cable chain on the inside.
5: Mount a drive onto the Z (maybe just use gear rack?) and put a floating head and torch holder on it.
6: Order the 5 Axis Plazpak package from C&CNC
7: Throw the servos/gearheads on the x,y,z w/Limit switches and wiring
8: Hook up my harbor freight plasma cutter because my old PCM-70 just died (prob not worth sending to the shop, its high freq anyways)
9: Buy CAD/CAM and read the tutorials
10: Throw down some (1/4" bar grate?) for slats and START CUTTING!....in the driveway till i get my water table built


Okay....set me straight.

[douglasco]

I love when procrastination pays off. I skipped my step 1 and went looking for rails today. I found this and just had to bring it home. It is an Esab Gantry that came with an old Burny 3 Controller(w/books), with 35ft of X travel! It has servos on the x&Y. They didn't pay me to take it, but I figured it was well worth the $800, even though its been sitting in the weather for about 6months. I got to drive on the scales when I had most of it loaded and it weighs about 3500lbs, plus the rusty-junk 5x10 cutting table i have to go back to pickup. The Gantry is about 16ft long and actually was a cantiliver setup. It held some sort of optical scanner on one side of the cantiliver and instantaneously duplicated the fullsize drawing it scans in with the 3 torch heads on the other end. (no optical scanner included) There is no y rack for the torch heads because they are connected to the scanner w/a push rod. I feel bad for you old guys, having to do things like this back in the day.

Anyways, I think i'll cut the gantry in half and use the scanner side(75"rack), on top of the x rails/gear/framing. IF, I was smart as you guys i'd be able to reconfigure the Burny controler. So, i'm still going with a CandCNC kit. Its been a long day, more specs and pics to come....Oh i also found a wrecker rollback while i was out(incase you were wondering)

[millman52]

I know people still using that system today to make parts.. I'm sure you can use the framework & other structure to build a fine table. Cantilever design is almost impossible to use for speeds that plasma cutting require.. As others tell me you might as well scrap the Burny controller & servo motors. at least for any conversion. Good luck with your project.

[douglasco]

Yes, I was very surprised. Esab is still selling almost the exact same gantry for the same application. I had no idea there would still be a market for tracing/replication. But oh well, i'm going to chop it in half anyways. Just going to use the scanner half of the gantry(the only side with a drive rack- 6'). Its 4x8 1/4wall + the aluminum Y rail holders and dual 1"steel round rails, so its going to be heavy. But its already drilled tapped and mounted so it will get me up and running quickly. Later i can switch to an aluminum beam and more precision rails(if these don't prove accurate enough) So the original cantilever rollers will be one side of my x and i'll just try to duplicate it for the otherside. Although, i called esab and got a parts manual for it and they want $650 for just one roller. So i'll have to find an alternative, any ideas? If nothing else i'll just use bearings to make a v roller (or use the ones that are already on the torch holders). But it'd be nice because the gantry rollers are slightly cupped to match the 1" round rails. The existing rollers are spread 4ft apart! (So my x has to be 4ft longer then my cut area) I'll just live with it for now and chop it down later. The gantry is going to stay low profile(like it is now) so I was thinking 2ft should be enough. I could make them 1 foot apart and it wouldn't tip, but i suppose the extra distance makes up for the crappy rail system and helps keep the gantry parallel to the X rails(less wobble).

The gearheads are 33.9.1 and are slightly belt reduced ontop of that. Max speed on these new esabs like this is 118ipm. But again, its already done, i'll use it for now, upgrade to the best possible gearhead i can find later. Hopefully i can find the cogs to gear the belt reduction the otherway when i swap the servos. I'm sure i'll have to swap out to the new CandCNC servos because i don't know jack about servo compatibility. Since it was only driven down the middle(cantilever) on a round rail, the former center rail/rack will be split up to be both my x rail/racks. It had 35ft of x run so i've got plenty for my two sides.

I'll use the parts off my boat anchor for the z axis.

Going to order my CandCNC Plazpak 5 this week, so i've got a couple more weeks to procrastinate.

The rack is rusty. I figure i should probably try to have it soda blasted instead of sticking it in my sandblaster, right?

Thanks for the help.
Oh did i mention i bought a high-def cutter.
....it just needs a little work

[millman52]

I used a round rail (1) side only on my table Started building new 5 X 10 table today It has worked well through the 7 months it has been in operation. I used double row ball bearings with no cup in the face to run along the rail. I opted to use a flat rail along the other side with bearings on top & bottom only. I was afraid the gantry would grow enough with the heat of Ox/Fuel burning. To cause a problem with binding if I had "captive" rails on both ends of the gantry

[douglasco]

So thats why everyone is using that dumb flat rail. I didn't even think of that. Is it that big of a deal? I'm sure it is. That really messes up my plan. Hmm...

Anybody gotten away with a "captive" gantry succesfully? I'll have to look at the manufacturer's pics. Mine gantry is going to be very close to work piece so i'd better not take the chance? Think a water table will make it okay? I'm planning on being able to run submerged. Probably not worth taking the chance, regardless.

[Torchhead]

The gearheads are 33.9.1 and are slightly belt reduced ontop of that. Max speed on these new esabs like this is 118ipm. But again, its already done, i'll use it for now, upgrade to the best possible gearhead i can find later. Hopefully i can find the cogs to gear the belt reduction the otherway when i swap the servos. I'm sure i'll have to swap out to the new CandCNC servos because i don't know jack about servo compatibility. Since it was only driven down the middle(cantilever) on a round rail, the former center rail/rack will be split up to be both my x rail/racks. It had 35ft of x run so i've got plenty for my two sides.

(sound of calculator powering up) Okay, let's run some numbers.... The top RPM of the Servos in the PlazPaks is about 3000 RPM. Assuming this is driving a rack and pinon with say a 1 1/2" pinon gear your travel per Rev is about 7.8 inches (adjust up or down for different sizes (diameter) of pinions) So you could see some nice rapids with the 33.9 :1 (reduces the RPM to about 100) with Gobs of torque. If you have the sized pinion I used then your Top speed is around 700 IPM but you don't want that monster whipping along at that rate!. If the pinon gears are smaller than 1.5" DP then the speeds go down accordingly. When you get ready to order you might want to consider using 250 line encoders (stock is 500). We can build it with whatever you want.

Here's some more math: With 500 line encoders you need 2000 pulse per rev. to get 3000 RPM you need 50*2000 pulses per second (100,000 pps) pushing MACH to the limit. If you keep the speeds to about midrange on the servos then you can live with a 50,000 pulse rate. If you use 250 line then you puls rate drops in half with full RPM at close to the 45,000 pulse rate.

You can change encoders in the future but you don't really need to if you keep the ratios up and use the motor RPM to trade for torque.

You may start to relaize why they used such a high gearing when that gantry start to move (:-0



I would think acceleration of that mass will be the bigger challenge. You need acceleration to get sharp corners on cuts

Just don't get in the way of that gantry when it gets up a head of steam!

[douglasco]

Thanks Tom,
I just want to get it functional, so i can say "hey i did it". If you say 10:1 is the optimum ratio, eventually, i'll have 10:1s. As long as i'm not going to break any of the expensive parts(servos, electronics) then I can live with rough sharp plasma corners until i get around to building it right. Like i said, the gearheads are belt driven from the servo. Just the thought of that makes me want to shoot an engineer. But for now i'll try to use it to gear the 33.9:1 back down closer to 15 or 10:1. As far as the gantry being heavy. Well, it was 16 ft, now its 7, plus it held four torchs with steel Mounts, all the gauges, solenoids, lots of hose and all this was supported on one single center rail, with one gear rack. I'm guessing it was about over 1000lbs. So I think if they were running 118ipm i should be able to run it at 300 (or more).

When i cut the gantry in half, I figured it was just 1" round cold roll whatever for the rails. But they are hardned i guess. My bandsaw barely made a scratch, had to take them out. So i guess i'm going to cut them on the chopsaw(grrr..) and try to clean them up and reuse them instead of just replacing them with cheap steel.

I really don't want to run flat rail, maybe i can build some give into the gantry supports. I see alot of gantry "ends" just made out of a single piece of sheet metal or 1/4". This always bugged me, but maybe that will have the give i need to lock down both sides.

[millman52]

I'm not saying it wouldn't work with a fixed roller system on both sides. I'm sure there are many examples of precision linear rails on both sides of the gantry. Most are probably plasma machines (much less heat radiating to the gantry)

As I stated earlier I use Ox/Fuel & burn lots of heavier materials mostly 3/8" - 1" & some above 1".

I processed a 4' X 8' sheet of 1" today. From it I cut (544) gussets. I have them configured in a "chain cut array". Pierce 1 time & continuous cut till finished. Only having to pause (1) time for an oxygen bottle change. That translates to about 7 hours of continual cutting. The gantry sits apx 6" above 1" metal. After about an hour the gantry is hot enough It will not burn you to touch but you can't hold onto it. So I'm sure over it's nearly 6' length it grows several thousandths.

The cantilever ESABs I have seen in use, have long barrel torches & the rail sits well above the cut table. With a cantilever design the torch rail growing would be non issue anyway.

Hardened round rail would be better than using 1045 CRR like I used on my table. Although it has worked well so far for me it does have a slight tendancy to allow small amounts of debris (dust, sparks, or whatever) to embed into the rail where the bearings make contact with the rail. It hasn't been a huge problem. I have ran fine grit emory over the round rail 2 times in 7 months, to smooth them back up. It has never caused me any problems at Ox/fuel cut speeds. I only notice it under rapid movements & at it's worse only causes some vibration. Never any lost steps, skipping, or rough cuts.

Being the first CNC project I ever tackled. All in all I couldn't be more satisfied. For me & my use It's a good solid design. About the only things I'd change is. (1) spend the money for a hardened round rail. (now that I know how well the machine & electronics work). (2) Sit the round rail & gantry higher off the cutting surface. (3) drop my flat rail (side of the machine I load from) to the bottom side of the outer frame rail. If it were on the under side it would be better protected from loading & unloading the table.

I used a stepper kit from www.CandCNC.com. In my opinion you can't go wrong with their product(s)

[douglasco]

Geez, going thru a whole bottle on one sheet! It would be interesting to know how much yours grows, it might even be .01+

[millman52]

Although the gussets are only 3.875 in the longest single direction. When you include the entire perimeter of the part & connecting cuts to allow for chain cutting it ends up 14" of cut per part. 544 parts works out to be about 635 feet of continuous cut.