I haven’t built my Maslow yet but as the cold sets in and my outdoor adventures come to a halt, I’ll have a bit more bandwidth for experimenting…
I saw a mention of a ball screw (I know them as lead screws… are they the same thing?) Maslow that might help to overcome some of the challenges with chain sag/stretch and thought it might be an opportunity to contribute.
You see, I’m installing Maslow on a wall in my shop that happens to lie between trusses, meaning I have over 20’ of overhead space. I’m thinking that this would more than accommodate the height required to have a lead screw extending above the machine.
A lot of you have experience with traditional XY CNC’s which all use these screws; can anyone recommend a source where I can start research on the parts necessary to pull this off? It appears that if I want to keep a 4’x8’ area, I’ll need screws in the neighborhood of 10’ long. (Assuming Pythagoreas was all he’s cracked up to be )
You might consider a Cartesian drive, acme screws top and bottom, plus one horizontal. Grainger might be a good source if nearby or if you have a free ship account (they refuse to cut long items for me, just send them free truck freight).
You’ll need to do some research on speeds vs screw whip to determine what diameter and pitch screws to use. Lots of discussion on CNCZone.com
Building a vertical 4x8 CNC panel cutter was on my wish list before Maslow came along
By Cartesian, do you mean traditional X/Y orientation? I was planning to keep the triangular kinematics since that’s kind of what makes Maslow a “Maslow”
We don’t have a Grainger nearby but I can have freight shipped to work.
At 10ft long you will need a pretty heavy lead screw to not have sag in it. I’ve worked with 26 inch long lead screws on printers, they can sag and bow they are also subject to torsion and sideways force from the lash nut in the sled.
I recently saw a “all lead screw printer fail” . They were only going 1 ft and found XY&Z would rack against each other. The “Samples” were of better quality than the product they took form the production line. I’m in no way saying not to try this. I’m saying proceed with caution.
3D printers move lightweight print heads at (comparatively) high speeds and acceleration without any cutting loads, and use lightweight components to achieve this. My modded kickstarter Printrbot has travel speeds approaching 250mm/sec and 120mm/sec print speeds (using slic3r’s volumetric option for constant speed extrusion, but we digress).
OTOH a CNC router or mill faces heavy cutting loads, with heavy spindles or tables and uses beefy components for (again comparatively) low cut and travel speeds and acceleration. That’s why combo machines rarely work out, completely different mechanical goals.
Dual screw machines are common in the hobby (Shapeoko, XCarve, etc) market, my budget doesn’t extend to the big iron, and can be single (belt driven) or multiple motor driven (like most dual z screw 3D printers). Keeping the screws synchronized can be an issue but it’s engineering problem that’s been solved many times and with varying degrees of success.
Sounds like the machine you mentioned suffers from implementation problems. Screw vs belt is a long running 3D printer argument (beaten to death elsewhere), but for low mass, high speed, low cost belts have pretty much belted screws out of the way.
We’re talking 1 inch/25mm +/- screws here, not T8s or 5/16 allthread. Screw whip (resonance problems at speed) and undoubtedly sag are an issue, but it’s been dealt with many times. Lots of discussion on cnczone and elsewhere, you can spend days reading up on it if you want. Then there’s rack and pinion or simulating R&P with belts, but that’s another show
Edit: Sorry about the multiple edits, Tapatalk mangled my link, seems to be fixed now
I haven’t built my Maslow yet but as the cold sets in and my outdoor
adventures come to a halt, I’ll have a bit more bandwidth for experimenting…
I saw a mention of a ball screw (I know them as lead screws… are they the
same thing?)
a ball screw is a lead screw that has a special nut that isn’t direct sliding
contact with the leads, but has ball bearings between the nut and the lead screw
Maslow that might help to overcome some of the challenges with
chain sag/stretch and thought it might be an opportunity to contribute.
You see, I’m installing Maslow on a wall in my shop that happens to lie
between trusses, meaning I have over 20’ of overhead space. I’m thinking that
this would more than accommodate the height required to have a lead screw
extending above the machine.
A lot of you have experience with traditional XY CNC’s which all use these
screws; can anyone recommend a source where I can start research on the parts
necessary to pull this off? It appears that if I want to keep a 4’x8’ area,
I’ll need screws in the neighborhood of 10’ long. (Assuming Pythagoreas was
all he’s cracked up to be )
actually, you will need ones a little longer (the maslow uses 11’ chains by
default, and would help to be a little larger)
you need to pick something that will stay put when there is no power (not a
screw with a steep enough pitch that it moves under the system’s weight)
are you going to anchor the screws from rotating and rotate the nut? or are you
going to anchor the nut from rotating and rotate the scres? remember that both
anchors need to pivot (this doesn’t eliminate the need for the pantograph arms
or similar)
You might consider a Cartesian drive, acme screws top and bottom, plus one
horizontal. Grainger might be a good source if nearby or if you have a free
ship account (they refuse to cut long items for me, just send them free truck
freight).
That would be a very different machine than the maslow
You’ll need to do some research on speeds vs screw whip to determine what
diameter and pitch screws to use. Lots of discussion on CNCZone.com
you are desinging a new machine, you need to include motors, etc in your
discussion.
I’d be tempted to try and keep the current motors if I went that route, although even with 1-4 it would be seriously slow (a couple lifetimes for a 4x8 lithophane with my 0.030 ballnose, probably). Probably enough torque to go back to a fixed workpiece and just move the garage. The next step up, and probably worth it in terms of development time would be the usual steppers and something like grbl, TinyG(2), Augie, etc. Like @dlang says it’s not even close to a maslow.
Personally I’d keep the chains since the effort and expense to make a screw driven Maslow doesn’t seem worth it to me. Not enough improvement. That doesn’t mean it’s not worth it to somebody else, of course plus it’s an interesting exercise.
Couldn’t find 10 foot acme at Grainger😱, but it’s about $70us at McMaster for 12 footers and probably that much more for shipping. 10’ allthread is available from Grainger, I’ve bought it from them, and if you stuck with the stock motors (and a major firmware rewrite) probably good enough. Heck, if I had time I’d try and build one just for fun.
Ballscrews would be so spendy that they’re not especially practical.
More than a chain? Also, remember that these will be nearly vertical, not horizontal like a traditional XY machine.
Thanks for the clarification. I could see a difference but couldn’t discern a reason.
I’m thinking the screws would be anchored and the nut would be surrounded by a sprocket or pulley that the motor would drive. That assembly (sprocket/motor/encoder/bracket) would all pivot together at a point convenient to the math. (Co-planar to the nut, I’m guessing)
For a proof of concept, I would probably go with allthread. Maybe some 0.75 x 10 or maybe even 0.625 x 18.
I could re-use the stock motors but like Moose said, the speed would be obscenely slow. It would probably be worth the effort to find a motor/encoder that works with the existing driver and simply calculate a new drive ratio to match/get close.
Just thinking out loud here: I don’t think the rod would be prone to whipping/deformation between the router and motor (At least not at the speeds we’re talking about) but in cases close to the upper corners, where most of the rod is payed out beyond the nut… that will have to be dealt with.
I just had a ridiculous vision of a machine with cages that extend 10’ beyond the top of the machine, providing balance and support for the rods as they leave the nut on the top side. Now I have to draw it. where’s that Sketchup link…
If you can get this to work, you are no longer completely dependent on gravity
(the rods are stiff and can push the router, not just pull or let gravity work),
so you could increase the speed a LOT. so you will need to worry about the rods
whipping.
I would like to throw my hat in the ring… So first of all I have a large surplus of ball screws linear bearings timing belts.
Every kind of motor you can imagine.
I’ve been thinking about using linear bearings putting the truck on a bearing so it can swivel.
Then you can use a timing belt like a rack and pinion.
You can glue the belts to the bottom of the rail and use the timing pulley to pull it up and push it back now you have a rigid rail for each of your arms…
A hoop mounted to the end of the rail to be affixed to a bearing that way your rails are always pointing at the direct Center of your router bit.
I’m thinking like a slip ring or a thin wall bearing or Lazy Susan kind of a thing.
I’ve also thought of doing a Cartesian type setup that would use the Maslow as it is but to help with precision positioning.
So the linear bearings would basically float and just be a way to keep the router on track while still using the same chain drive.
In fact you could probably use one rail across the top with another rail in the middle hanging down in a “T” configuration.
This might also allow for some anchoring at the base of the Maslow to keep everything tight.
Just some thoughts to drive everybody crazy.
I do have some small ball screws and could put together a quick demo Machine to test the viability of such a solution…
Any thoughts?
I don’t understand what you are meaning about combining ball screws and belts,
diagram please?
others have talked about using ridgid screws instead of the chains, the problem
is where do the screws go when the sled moves to an upper corner? that takes a
LOT of space
building a cartesion machine is possible, but at that point it’s not really a
maslow any longer.
I’ll draw something up.
I think a Maslow is what you make of it right?
I’ve still got a Maslow shield and motors and firmware…
Anyway, the idea would be to use a Cartesian set up as a guide. Not to drive the axis, just to keep the movements more precise.
I’ve got lots of stuff to play with, it’s NOT the cheap way to go.
But I’d like to see how much I can wring out of the design…
try it, but we’ve discussed it in the past and you are going to have problems
with the frame racking when the sled is in one corner and trying to move the
entire frame
what is the precision that will be added if the frame isn’t restricting the
movement?
Frame racking…
Is it due to flexing of the frame?
I’m using extruded aluminum, think 80/20.
I’m also using an aluminum sheet for the backing with a 1/2 dense sacrificial foam board.
However, I just ordered some porous particle board a guy showed me. He uses it as a vacuum table.
It works AMAZING in his 4x10 router table.
I’m thinking that on top of the aluminum seals the back with spray adhesive around the edges?
If you have a 8’ horizontal beam, and it’s on rollers on each edge, but only
supported by the sled, then when the sled is all the way over on the left side
and pulling up, the weight of the beam to the right of the sled and the give on
the rollers will cause the beam to tilt slightly. This will cause the rollers to
bind up and be harder to move, which will cause the beam to tilt more until
something breaks loose (and in the meantime, this will be affecting the movement
of the sled, causing more accuracy problems)
if this beam is powered on both sides, it’s kept straight and you don’t have any
problems. But at that point you have a conventional cartisian machine that may
use some maslow parts, but not a maslow.
That isn’t to say that it won’t be a good machine, and if I had access to
sutable parts, I would probably build a corexy machine using high power motors
(either DC motors with encoders, or something like odrive to power brushless DC
motors)
Ok, first Im still using the drive and positioning system, as is.
I was thinking that i could use the linear rail as a way to “guide” the movement of the router in a more precise way.
Bear with me for a minute.
I would use a VERY rigid rail, because I have it…
I would mount one rail across the top, basically between the motors, with dual trucks. I would then use another rail again sturdy configured like a pendulum so now I have a giant “T”.
Then I counterbalancing maybe using bungee cord, I think the resistance would have a dampening effect and keep the router from swinging which I think is probably where most of the problem is.
To address the problem that you spoke of if I was doing a more typical Cartesian setup, I would not have a long horizontal bar I would have a shorter vertical bar with two longer rails on top and bottom.
That way the forces aren’t necessarily twisting the Gantry as it were, and I don’t think you’d have any binding.
And again and that kind of a situation I would have two trucks to mount the Gantry piece on to spread the load.
I usually use two trucks on the longer fixed axis…
When I get home I’ll lay some stuff out on the floor and take a couple of pictures to give you an idea what I’m talking about.
I’ll probably just start a new post.
Also because I’m using Extrusion anyway it’ll be really easy for me to make a frame and demonstrate the different configurations.
I’m not trying to reinvent the Wheel by the way I’m trying to stabilize the Maslow as it is. And while I’m going to be using timing belts and pulleys instead of sprockets and chain, I’ll be using the motors in the same configuration everybody else is.
In other words I’m not going to power the rails or motorized them I’m just using them to guide and stabilize the router and give some rigidity to the frame.
I don’t suppose this much help to a project is trying to build an inexpensive router except if I can demonstrate/proof the concept and show that it has merits there may be a cheaper way to achieve the same results using a simpler roller skate bearing and inexpensive Rod type integration.
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where’s that Sketchup link…