[harryn]

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.

[Mauser]

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.

[harryn]

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.

[ger21]

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

A machine that wide should really be driven from both sides, which would eliminate the need for the anti-racking system.

I'm guessing the cheap idea of re-purposing a single start veneer press Acme screw for Z might be counterproductive.

Yes, spend the extra $50 up front. If you don't, you'll and up upgrading it soon anyway.

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.

[harryn]

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.

[louieatienza]

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.

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...

[ger21]

The G540 can probably give you close to double the speed of the HobbyCNC too. You get what you pay for.

[Mauser]

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. :-)

[louieatienza]

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. :-)

I run 8-start ACME on my Z axis, and when I shut the machine off it stays put. I suppose partly from the friction of the AB nut, and partly from the stepper magnets? I COULD push the carriage down, but it does take considerable force, whereas rotating the coupler I can move the carriage easily. The carriage plate along with the linear rail, router, and router clamp probably weigh abut 15-20 pounds.

You could buy two G250 drivers, and a breakout board, but the G540 comes in a neat package, has its own breakout board, parallel port and db9 connectors, and enclosed and rack-ready. It would cost you far more in materials and time to do the same, and you'd only have 2 axes! You could run 2 steppers on the long axis (they won't go out of synch unless you push them too hard) and I'm sure there could be some creative use for the fourth, possibly focal adjustment on laser, spool feed for the bolts of material, or even use the 2 axes for a tangental knife head...

[kinghong1970]

Mauser,

i take it that you're building a machine for a friend in the garment industry?
i have been manufacturing garments for over 20 years, specializing in down jackets from SE Asia... most factories there tend to do it manually since labor cost is so low. anywhoo...

I just spent an interesting afternoon in my friend's shop seeing how she and her assistant work. They have giant cutting tables that span the length of the room, and lay out several layers of material and try to flatten them out, and then plan their cuts with heavy cardstock pattern pieces, and cut around them with rotary cutters.

yes, most full sized factories have a very long marker table to save cost and maximize fabric utilization... but this is usually found in high volume factories where i've seen marker tables as long as 40' in length... if your friend manufactures garments in the states and need such high volume table... God has indeed blessed her...

So one important aspect of the job is laying out the pattern pieces to maximize the fabric usage. Being able to do that on a computer and save layouts will be a big timesaver, so finding software to do that will be a requirement.

Gerber/Lectra systems sells programs, glorified cad with decent database software, that can spread markers as well as digitize patterns/grade etc...
but if they have a person with a decent set of brain tween the ears, setting markers manually is not that expensive in comparison to the apparel manufacturing softwares.

here's a quick google search of pattern & apparel making software

i've taken course in GGT a while back... it did have some issues but that was in the 90's... there should be cheaper software around... PAD system is another company that seemed to have a bit more user friendly interface.

The other big surprise is how big the machine will have to be. It will be a Beast. Typical fabric is 63" wide, and although the pieces tend to top out at about 6' long, they can sometimes lay out 12' of cuttings in a go, but 8' would be okay for her too. And I don't have to worry too much about burnt edges, since the sewing machine they typically use, called a Serger, automatically trims off the excess as it stitches.

yes they are large, but to save on fabric waste... and one idea i've seen to help spread fabric before cutting is having another set of rails or another light weight gantry that can ride on your X-Axis that simply has a riser and a hole to hold the steel pipe/rod. then insert fabric rolls (usually comes with paper core roll) and unroll onto your surface.
once fabric has been laid out, then remove the fabric gantry.

iirc, you stated your friend works with spandex... this is highly flamable material and does not react well to heat/flame... be careful.
this fabric also have a lot of stretch... so your gantry should be able to ride quite smoothly to spread fabric w/o tension.

usually, when spreading knit fabrics, they have strips of "needles" that will help grip the fabric and keep it flat. then remove when finished spreading.

and yes, you do have to worry about burnt edges... you REALLY have to worry about burnt edges.

here's a quick process:
1) spread marker on paper
2) spread fabric layers
3) cut fabric layers with paper on top
4) number each layers of cut pieces
etc...

now step 4 is what most high quality factories do... reason is, black is not always black...even on a single roll of fabric. they number it such that a single garment is produced out of a single layer of fabric with pieces that was cut adjacent to each other. if not, they can have production lots that will have different tone of a same color...
i actually had to cancel an order for 20,000 down jackets from Qingdao because of the burned edges and color migration.

also, if the edges can get burned, they can get sealed to each other and also in removing them, the cut pieces will stretch and in doing so, size spec & seams will not be ideal. you can compensate a bit on stretched fabric by feeding control on the serger but... it can lead to puckering and poor quality.
remember, most synthetic fabrics are petroleum by products and when exposed to heat, solidifies to a glop of plastic like polyester... no matter how small... introducing solid and potentially sharp particle into garment factory is not ideal... even in the discarded waste, it will migrate and embed in garment/fabric...

think about this... issue with broken needles.
even the best factories have issues controlling foreign particle in garments... in the production floor, the operator will not be given a new needle unless she brings back all the pieces that assemble an entire needle... so if it breaks into 4, she needs to bring 4, else, no needle, no production, no pay.
and in the inspection phase, japan bound products (sadly not USA) have strict guidelines to pass each garment through metal detector to avoid broken needles...

despite this, there are still cases of broken needles and sometimes, even scissors found in garments... yes.... even scissors... so you're talking about small plastic flakes... burnt edges is really an issue...

cotton otoh, less of an issue, it burns down to ash and serger will remove the edges.... but i will still not accept it... the fume is multiplied many folds in odor when packed and shipped...

sometimes, factories cut orders of multiple colors to save time... so layer qty needed for red, black, etc etc... and cut one time.
if edges burn, then you have issue with color migration. may not seem visible, but sometimes, after wash, you can see it.

furthermore, fumes, smoke, embedded into fabric, will stink.

We discussed budget (more than I thought, but she's been pricing big machines), and it will have to be moveable, because light industrial space in Seattle seems to be entirely in the hands of really flaky landlords who like to change the terms of their leases without notice.

how movable of a machine she's thinking? these suckers are HUGE!!!
i saw 20 of these in italy... solid machines... dunno here... can you make it "modular"? hmm....

One issue that came up is what to use as a table. I see a lot of the engravers like to use the expanded hexagon mesh (where to buy?), but I don't know how that will be for the fabric. I wonder about using heavy plate glass. Would the laser pass through with very little energy transmission, or would it blow up?

again, check the fabric she's going to cut... reason why garment factories still use oscillating blade is because it can cut all types of fabric... regardless of composition.

oh, vacuum... yes... it'll help.
spread fabric layer, spread plastic sheet, vacuum to hold pieces... even while cutting, they do a good job at cutting.

good luck.

Al

[kinghong1970]

quick google on laser cut fabric...

http://www.lasercutfabric.com/

i suggest you contact them and find out if they can cut multiple layers.

from the looks of the images in google image, most laser cutting machines have a very shallow or fixed Z... hence, cutting one layer at a time...

wonder if you can put this on a conveyor belt...

[ger21]

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.

The majority of large machines built here use dual motors with no problems. They won't get out of sync, unless you push them to the point of stalling, or have some type of electrical or mechanical failure.

[Mauser]

The majority of large machines built here use dual motors with no problems. They won't get out of sync, unless you push them to the point of stalling, or have some type of electrical or mechanical failure.

Since one thing I was considering for the RouterBeast was the possibility of a lathe on the side, I wanted to keep the A channel available for that. I know that it doesn't work well to have two motors on the same driver, but what about the same step and direction signals into two drivers? Obviously one motor would need to be wired differently to turn in the opposite direction.

(On the other hand, with the servodrive at the bottom, there would be room under the edge of the table to tuck the motor under there so it wouldn't interfere with the lathe and wouldn't need to be reversed.)

[ger21]

You can always add another motor and drive, although you may need to add another parallel port.
My biggest concern with using 1 motor to move the gantry is that you end up with a 4x8 (or bigger) table suspended by the ends. Even if you can make it rigid enough so it doesn't sag, it willhave some flex and vibration, which can affect cut quality.

[Mauser]

That's what I liked about the cable system, unlike the tables that run one leadscrew under the center, or running a shaft across underneath, the cables won't interfere with legs, which I'd like to set in a bit for just that reason.

Speaking of flex and vibration, has anyone tried filling their torsion boxes with anything like concrete or sand to make them heavier and less likely to vibrate?

[louieatienza]

That's what I liked about the cable system, unlike the tables that run one leadscrew under the center, or running a shaft across underneath, the cables won't interfere with legs, which I'd like to set in a bit for just that reason.

Speaking of flex and vibration, has anyone tried filling their torsion boxes with anything like concrete or sand to make them heavier and less likely to vibrate?

Hate to bust your bubble, but this is pretty commonly done, maybe moreso in the metalworking section. A common thing is an "epoxy granite," mixture of epoxy, gravel, and I believe sand. Accoding to the metalworking guys, the more common analysis is that more mass raises the resonant frequency of the machine; it's the lower resonant frequencies that are hopefully attenuated.

[PaulRowntree]

Accoding to the metalworking guys, the more common analysis is that more mass raises the resonant frequency of the machine; it's the lower resonant frequencies that are hopefully attenuated.

Hmmm not sure how that would work. Adding mass will shift the resonances to lower frequencies if everything else is constant. In my work you lighten things up when you want to shift to higher frequencies. With F=ma, a given force (eg rapid gantry shift in direction) will cause the heavier object to move less, and seem more stable.
The key phrase may be 'everything else is constant', since the epoxy/granite mixes will also add stiffness, which will shift the resonant frequencies up.

[louieatienza]

Hmmm not sure how that would work. Adding mass will shift the resonances to lower frequencies if everything else is constant. In my work you lighten things up when you want to shift to higher frequencies. With F=ma, a given force (eg rapid gantry shift in direction) will cause the heavier object to move less, and seem more stable.
The key phrase may be 'everything else is constant', since the epoxy/granite mixes will also add stiffness, which will shift the resonant frequencies up.

Egad you probably got it right. Mixed up stiffness and mass.

[Mauser]

I think you've got both factors going. Heavier items will move more slowly, and take more energy to get them going at any amplitude, but the epoxy increases the rigidity, which increases the resonant frequency. I guess the best result is one that makes the natural amplitude by weight incompatible with the natural frequency via stiffness.

[Mauser]

Man, there's nothing like doing a Sketchup model to force you to think of the less "sexy" parts that you still need to take care of....

Got my tax refund. More than enough to fund this build.