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We had a nice Graftec plotter at the sign company I worked at, but when we needed to do very small lettering we cut them on the laser. It took a while to figure out how to cut the vinyl without cutting the paper backing and not melt the vinyl as well...Originally Posted by harryn
New question....
What's the most common shaft length on NEMA 23 and 34 motors? I'm starting to think about the layout of my belt drive idea vs. how thick mounting plates will be.
It's kinda funny, I went and modeled 20 mm and 30 mm V-rail, and once I added them to the model, it struck me how small they seem. I have to watch out, I inherited my Dad's tendency to overbuild things.
I think the Keling website has schematics for both motors. But if you think the 30mm rails look small, wait till you put nema23 steppers on your model!
Heh, especially when I compare them to the S-28 Magmotors I once had in my Battlebot. ($400 (ten years ago) Rare Earth PMDC motors that would put out 4.5 horsepower if you could feed them enough juice.)
I would design in nema 34 motors from the get-go, even if you don't perceive the need for the torque. In the event that things change, it is a lot easier and cheaper to obtain nema 34 motors in higher torque ranges than 23s. They also come with larger shafts.
Also, I am not so sure where this whole rare-earth business dispute is going to end up, and rare earth elements are being designed into solar panels, displays, magnets, cars, etc. Way too much demand vs supply.
The timing belt pulleys can extend past the length of the motor, but don't get crazy about it.
Hmmm, I wasn't thinking in terms of 34's, really, but I guess for the plywood router that could be justifiable (maybe a 23 for the Z-axis). For the laser machine 23's are probably the better choice because they'll have virtually no load.
I was considering going with the HobbyCNC driver board, but I don't know how well that would handle a bigger motor. The 36 or 42 V and 3 amp limits on those boards would really limit getting the torque out of them.
Hmmm, to avoid confusion, I should label the two projects. I've been thinking of them in terms of these names anyway. Because they're so large physically, I've been using "Beast". Let's recap:
"RouterBeast" will be a full 4x8' Plywood routing machine. The current thinking involves a 6" thick torsion box table, 30 mm v-groove rails, "ServoBelt" drive on the X and Y axis, with a cable anti-racking system. I was considering a wide X-carriage with a sort of dual-gantry Y axis with the Router carrier in between for rigidity, but I'm coming around to the idea that it may be more trouble than it's worth (Keeping four rails in alignment!). The gantry will protrude over the non-drive side by enough to allow for a future Lathe. The router carrier design is still in flux.
"LaserBeast" will be a fabric cutting laser table. It needs to handle 65" wide bolts of cloth, and be 8-12' long (eep!). The gantry needs to be light and fast, yet rigid. I'm leaning toward 2" aluminum square tube (not 8020), 20mm V-groove rail, and regular belt drive for the gantry, and ServoBelt for the X-axis. X-axis will be a single-side drive with a pair of rollers at the far end of the gantry to support it. Still trying to figure out the best material for the bed. I won't even start on this one until the first is completed.
So I guess the idea is that RouterBeast will take NEMA 34's for X and Y to help plow the Router through plywood quickly, and a 23 for the Z axis. That would mean probably going with a GeckoDrive or Keling/Automation Technology setup.
I'm guessing the cheap idea of re-purposing a single start veneer press Acme screw for Z might be counterproductive.
LaserBeast could get along fine with NEMA 23's, since it's built for speed, not strength, and heck, the HobbyCNC board might be a fine driver for it.
The lightest gantry is going to be one where the X rails are mounted on top of fixed raised sidewalls at the max Z height, rather than the type where the raised gantry sides move along with the Y and Z axis.
The downside is side access, as many peole don't like leaning over the raised side walls, especially if there is any grease on it.
Some mid range commercial router machines appear to be designed around 75 lb holding force ratings in all dimensions, while DIY designs are often closer to 25. I found it surprisingly challenging to actually design much higher than 75 lbs force in all three axis in all dimensions once you really start looking at the forces on belt or rack and pinion teeth strength in the size ranges we are used to.
If I were buying a drive, I would definitely consider servo belt, as it is a pretty neat concept. For myself, I am not confident enough in getting all of the subtle details right in a DIY approach, but partly that is because I just don't have the tools to keep making changes, if needed.
What I do agree with you is that a belt is a good choice for the Y motion, especially on the cloth cutter. It is one of the few drive methods that you can ensure grease free motion over the cloth.
Square tube is neat stuff, but it is not very straight, or square, at least the pieces I have been able to find so far. Pacific Bearing has an intereting product that integrates a pre-made V groove rail into 8020 sections more precisely than most people could pull it off. I think it is called integrated V or similar. It might be worth a look.
A machine that wide should really be driven from both sides, which would eliminate the need for the anti-racking system.The current thinking involves a 6" thick torsion box table, 30 mm v-groove rails, "ServoBelt" drive on the X and Y axis, with a cable anti-racking system
Yes, spend the extra $50 up front. If you don't, you'll and up upgrading it soon anyway.I'm guessing the cheap idea of re-purposing a single start veneer press Acme screw for Z might be counterproductive.
Also, don't underestimate the motor size requirements of the Z axis. Many people find that the Z axis is the one that loses steps most often, due to being underpowered. The Z axis is the only one that's fighting gravity, so quite a bit more torque can be required to lift it rapidly.
Gerry
Mach3 2010 Screenset
http://home.comcast.net/~cncwoodworker/2010.html
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
Making a large cloth cutting machine that is movable will be a big challenge. I wonder if there is any way to make this a roll to roll based design ?
A sort of crazy option is to "make the room the machine". Have a floor poured with self leveling epoxy and lay the cloth out directly on it. This is actually not that expensive to have done.
Make a gantry the width of the room, mounting the X rails on the walls at say 2 ft hight, shimmed out of course to make it straight. When it is time to move to a new building, take the main machine parts with you, and worst case, you have to buy a new Y gantry width.
The main point, is to avoid constructing a table if none is really needed.
You may find for the router, to plow through plywood with speed, that you'll probably need a relatively powerful spindle. That usually means heavier, and you might find you may need NEMA34 for the Z. At the very least, you might get a better torque curve compared to a NEMA23 with the same stall torque rating, and you could run off the same power supply as the X and Y steppers.
For the laser, you might get smoother performance with a G540, as the HobbyCNC is a unipolar drive; it might not be the best solution for a high speed belt drive system...
The G540 can probably give you close to double the speed of the HobbyCNC too. You get what you pay for.
Gerry
Mach3 2010 Screenset
http://home.comcast.net/~cncwoodworker/2010.html
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
Wow, those are some great replies!
harryn: Hmm, I was thinking "Architectural" square tube for the LaserBeast gantry, with 20 mm rail on either bottom corner and the mirror/lens suspended directly underneath, and some diagonal arms going back to the X end of things to keep it square. That sort of stuff is usually pretty straight and stiff, since it's designed to be pretty. Not as hard as some aluminum, but between the size and the light load, it should be okay.
The problem with 8020 is that it actually isn't flat on the sides, it's designed to spring a little where you bolt it. But I've seen the rail you're talking about, and I might consider it. I need to check some of the local parts suppliers and see what's available.
(gotta finish these drawings!)
Ger21: I've been wrestling with how to do the drive from both sides. It would either be slaving another motor, or getting a drive rod all the way across the gantry and running long belts to drive the ServoDrive, which would introduce some of the slack the ServoDrive is supposed to eliminate.
With a machine this long, running a drive rod under the table means less support under the table and possible bowing with the legs all the way at the end, a 9-10' span. I was figuring a cable system is the way to get force from one side of the gantry to the other.
There's no way to win, really. A drive rod could twist or whip, cables can stretch, and dual motors can get out of sync. One thing the dual gantry idea was supposed to help with was to make the connection between the two sides (is there a good name for the X-axis part?) stiff enough that it would also prevent racking.
Re the Z-axis: I hadn't thought about the lifting portion being an issue. With a single pitch screw, backdriving from gravity isn't such a problem, but speed is. Multi-start acme screws give better speed, but they can be backdriven. Has anyone tried using springs to help support the carrier? Heck, it could even eliminate backlash by biasing the carrier up if they were strong enough....
Anyway, most kits seem to be 3 or 4 of the same motor. So perhaps that's how I should go.
harryn again: Not really. With stretchy cloth like Spandex, evening out the tension that's already built into the roll is one of the issues even with hand cutting it. It's one of the reasons I was concerned about honeycomb tabletops, because the chance of a snag while sliding the cloth around could ruin the part.
As for the physical plant, moving tables is the least of T's worries. I've seen her in a whole lot of different warehouse spaces. (What is it with Seattle Commercial landlords? They're NUTS! The latest one is trying to rip her off on Utilities, and she just got there! She may move again before i build this.). She's got probably half a dozen cutting tables at least as big as the machine will be, and about as many industrial sewing machines. I've helped move them. That pizza was EARNED.
But that does make a point about making it easier to take apart and move.
louieatienza: Point taken about differing drive power requirements. The G540 might be a bit much for a 2-axis machine. Maybe some other breakout board and two individual drivers. Any suggestions?
Ger21 again. Point made. Speed is the object on the laser. Especially if she can only cut one or two layers at a time. She usually does six by hand, and for really big stack-ups, she has a device that puts a giant motor oscillating on top of a foot long blade that ends in a shoe that slides under the fabric. It's so sharp though that she's scared of it (and rightly so, it makes ScarySharp look Bronze Age).
As for routers, I was going to just start with one of my PC 690's and a SuperPID.
I'm getting a fat tax return this year. I'm going to run out of excuses soon. :-)
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