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Cutting foam sheets... with a needle!

dkj4linux

Well-known member
Short of modifying and re-printing my endplates yet -- may have a couple more mods to make -- I’ve patched together a wheel/bearing setup that seems workable for now.

I’ve got the wheel bearings back in place (where they belong), with a new bearing spacer…



and made “plugs” to fill the space where the bearings once sat in the endplate…



and, finally, assembled…



I’m wondering now if I might be able to use Openbuild’s mini-V linear actuator “verbatim”… by allowing the 2040 rail/axis to extend sufficiently to allow the motor and idler mounts/housings to sit outside the wheels/workarea. I’d also have to remove the front “notch” where the extrusion passes-through the endplate to provide clearance for the belt to pass through.

I think I’ll go ahead and print a set of those linear actuator parts… as this seem like it could be handy at some point down the road, regardless. I’ve already got @geodave's motor/idler supports and carriage printed and can use those if the linear actuator idea doesn’t pan out.

– David
 

TEAJR66

Flite is good
Mentor
Why not lose the wheels? Let the outer edge of the belt be the "tire". No need to calibrate distance. The printed gear/wheel can be any diameter because the belt length doesn't change.
 

dkj4linux

Well-known member
Why not lose the wheels? Let the outer edge of the belt be the "tire". No need to calibrate distance. The printed gear/wheel can be any diameter because the belt length doesn't change.
Well, Tommy, I just hadn't thought about it too much. I've enjoyed using my FoamRipper -- which uses skate wheels -- so much and @geodave's design is using printed wheels with O-ring tires... It just seemed natural to keep thinking along those lines. Rather than a "rolling plotter" as @geodave is using it, however, I was seeing it more as a alternate gantry for FoamRipper. I'm comfortable with the grippiness, shape, roundness, quality, consistency, etc. of the skate wheels on FoamRipper, I already had some on hand, and since they're actually designed to function as a wheel... it makes more sense to me to use them rather than using the backing of belts -- the material of which is unknown to me and possibly very variable? -- for traction and straight tracking.

At any rate, I'm having fun with it and it keeps me off the streets... yada, yada, yada ;)
 

TEAJR66

Flite is good
Mentor
Well, Tommy, I just hadn't thought about it too much. I've enjoyed using my FoamRipper -- which uses skate wheels -- so much and @geodave's design is using printed wheels with O-ring tires... It just seemed natural to keep thinking along those lines. Rather than a "rolling plotter" as @geodave is using it, however, I was seeing it more as a alternate gantry for FoamRipper. I'm comfortable with the grippiness, shape, roundness, quality, consistency, etc. of the skate wheels on FoamRipper, I already had some on hand, and since they're actually designed to function as a wheel... it makes more sense to me to use them rather than using the backing of belts -- the material of which is unknown to me and possibly very variable? -- for traction and straight tracking.

At any rate, I'm having fun with it and it keeps me off the streets... yada, yada, yada ;)
Glad there's something to keep the likes of you off the streets 😁.

Hope I did not come off as critical. I was just pondering out loud. I envy all of your creations.

Keep having fun brother. And I'll keep enjoying your journey as you share it.
 

dkj4linux

Well-known member
Glad there's something to keep the likes of you off the streets 😁.

Hope I did not come off as critical. I was just pondering out loud. I envy all of your creations.

Keep having fun brother. And I'll keep enjoying your journey as you share it.
Not at all, Tommy. I appreciate all you guys, the regulars, asking questions and offering up ideas... and it helps keep KISS "king" around here. I've always been proud of the "quality" of the ideas shared and discussions that go on in this thread... I think that's why it's stayed alive for so long. It's not just the fun stuff we do but the friends I've made here... this is what's keeping me going.

One of the few things about FoamRipper I've always wished was "different" has nothing to do with its operation or performance. It's simply the "double duty" its work surface provides as a work area/table. With the gantry pushed to one end, the belts are still stretched full-length down the both edges, front and back, of the work surface. They do often get in the way and are pretty easily snagged when I'm using it as an assembly table... as I am now with this new project. I'm hoping that if this new gantry, with the driven wheels, works out and performs as well as the other gantry has... at the least, it will allow me to use the work surface without the belts in the way.

Now, If I could just figure out a way to keep every horizontal surface in my house from piling high with clutter...

Take care, Tommy.

-- David
 

dkj4linux

Well-known member
Okay… got new endplates printed, added a new Y-axis, and ran a few motion tests. I had the accelerations set pretty high initially and it almost did “wheelies” on the floor! I toned them down for this simple test…


Simple Nano-based Grbl 3-axis controller and Pi 3B+ running Jeff’s V1P1 image and CNC.js… runs from the browser on my Chromebook.



I was able to adapt the ERC TimSav’s “skinny” axis to this machine’s Y-axis. Printed a smaller motor mount plate ..



and fancy tensioner somebody out on the FB group did early on...



The belt actually runs inside the extrusion channel and there don’t appear to be any clearance issues where it passes through the endplates.



I’m sorry that the black extrusions don’t really photograph detail very well. I now need to start looking at a Z-axis. I built one I really liked once before but it’s on my daughter’s laser engraver… need to hunt it down again. And, of couse, need to mount all the electronics stuff on board.

Finally, I need to put it up on the FoamRipper’s worksurface… turns it from rolling plotter to gantry?

Later. – David
 
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David, allowing for the dark pics from black extrusions (as bad as my white pix of MPF texture and cuts - black on black and white on white both tough to show details) the mechanism is really intriguing and looks efficient! I'm wondering if I could do something similar in concept with my setup, currently using the eleksmaker stepper/rollers/extrusion with long belts. Having the motor, belt all tightly located seems really efficient. I wonder how well it will manage the cross sheet location of the two Y axis motors? I perceive that one possible advantage of the long stationary belts is consistent cross location. But is perception reality?
 

dkj4linux

Well-known member
Alright…

TimSavX2 is no more. SIL finished his large foam project for his church’s children’s room… and I have no real need for such a machine…



Still have a TimSav to play with…



New horizontal surface to start piling stuff up on…



Go to thinking… what’s better than FoamRipper? TWO FoamRippers! Or, at least, one FoamRipper… and a Mini?



Still have the cutoff door piece from FR… could make a MiniFR. Lots of stuff I do really doesn’t require the full area of FR and this might be a really handy size. At the very least, it’ll be easier to get around it to work on during further development.

Gotta spend the hours of my day anyway… why not piddling with this stuff?

– David
 

dkj4linux

Well-known member
David, allowing for the dark pics from black extrusions (as bad as my white pix of MPF texture and cuts - black on black and white on white both tough to show details) the mechanism is really intriguing and looks efficient! I'm wondering if I could do something similar in concept with my setup, currently using the eleksmaker stepper/rollers/extrusion with long belts. Having the motor, belt all tightly located seems really efficient. I wonder how well it will manage the cross sheet location of the two Y axis motors? I perceive that one possible advantage of the long stationary belts is consistent cross location. But is perception reality?

Here are some better pictures of the Y axis from my remaining TimSav machine... which I modified slightly for TimSavX2 and adapted for MiniFR. This works with 2020 (TimSav) or one side of 2040 (MiniFR) V-slot. All credit goes to Edward Chew, of course.

20200622_100854.jpg


The carriage plate can be doubled up (forground) or single (background)...

20200622_100941.jpg


The fancy tensioner comes from somebody out on the TimSav FB group. It really is nice...

20200622_100927.jpg


The motor can be on stand-offs, or flipped (a little less compact) if necessary...

20200622_100914.jpg


I'm really not sure what the "cross sheet" location/considerations you're talking about? If you are talking of the two slaved truck/tractor assemblies... that's used all the time on MPCNC, FoamRipper, etc. The common practice is to wire the truck motors *in series*... that way, both motors see the same current and stay in sync. Am I misunderstanding what you are getting at? Probably... :oops:

-- David
 
You got it; a comparison between the typical stationary belt where the gantry moves up and down driven by 2 steppers either at one end or riding the gantry base like mine and your new idea where the gantry is driven at its base with short continuous belts. Which would be better to keep the two motors synched locationwise?
 

dkj4linux

Well-known member
I guess I'm missing something and/or getting dense/dull...

Your Eleksmaker machine IIRC uses fixed-length belts, anchored at both ends, and the motor rides the carriage, pulling itself and the carriage along the belt. Another setup is done with a double-length belt looped, ends terminated/fixed at the carriage, motor at one end, idler at the other... similar to this TImSav axis. Or, the truck setup, driven-wheels, unlimited length, properly-sized closed-loop belts required. CoreXY has stationary motors and super long belts routed in a novel way... can move light loads very quickly but machine size is limited primarily by length of the belts. I'm sure there are others...

A gantry could use any of these drive methods... your choice. First method the motor weight adds to, and moves with, the load... limits quickness of movement. Second method the motor is stationary and the carriage/load might be quite light and move more quickly. With the truck method, the potential length is not limited by belt length (probably something else) but is relatively slow and heavy. CoreXY... 'tis a mystery.

Regardless of the drive method -- and ignoring CoreXY -- a gantry will probably be driven at both ends, so there'll be one driver at each end... and sync must be maintained to avoid racking. Ignoring single motor/jackshaft setups and using a drive-motor at each end... what I was trying to say earlier, I've had ZERO problems keeping things in sync as long as the drive motors are hooked in series and all connections are secure. MPCNC, LowRider, FoamRipper, TimSavX2 hot-wire machine, etc... all have at least one axis with drive motors at each end. Except MPCNC and TimSavX2... which have TWO axes set up that way.

I apologize for the length of this, Mike. I'm sure you know all this but -- since you asked -- my "short answer"... I think what method is "better" or "best" comes down to the tool/load you need to move around. Lasers and extruders need to move rather quickly whereas routers and needle cutters need to move relatively slowly. Look at different belt-driven machines... 3d printers, CNC routers, laser engravers, etc. Pretty soon you'll probably see one method preferred over another... for a particular type of tool/load.

o_O

-- David
 

dkj4linux

Well-known member
More progress on the rolling plotter/gantry...

I printed a couple of plates to mount the RPi and CNC controller boards on the back rail...

20200623_100909.jpg


and then started working on the Z-axis.

After the "discussion" (I apologize if it was unwarranted, Mike... just me being "dense", I guess) about the various forms of belt-drive, I decided to see if I could make the entire machine be belt-driven. I came up with a smaller version of the Y-axis linear stage, to use as a Z-axis. As I don't ever expect to lift anything heavier than a laser, needle cutter, or a pen... I wanted to try using a very inexpensive 28BYJ-48 geared stepper motor that I had used on a couple of projects before. But first I needed to perform a well-known "unipolar to bipolar" conversion/hack on it (you cut a trace on the internal PCB and remove the 5th wire) to increase its torque and allow it to be driven with the little stepstick driver modules used on the other axes. Here it is in action...


I strained my brain to try to simplify the mechanism as much as possible and finally decided on a "shared carriage" assembly... where the Y-axis carriage plate is also the Z-axis carriage plate. So while the Z-axis carriage remains fixed in the Z-axis, the entire assembly moves up and down. I haven't added a tool mount yet but being V-slot extrusion, it's easy to attach stuff to it. The range of motion here is only about 55 millimeters and is limited by the lower end of the Z-axis hitting the spoilboard. I guess I'll eventually need to fashion 2x4 elevated guides for the trucks/tractors to run on if I have thicker materials I need to work on.

Here are detailed photos of the Z-axis assembly. The "hacked" (note the blue plastic piece just hanging...) 28BYJ-48 geared stepper motor, with IIRC a 20-tooth GT2 pulley...

20200624_194147.jpg


Back-side shot showing the stepper motor now driven by A4988 driver (had one sitting there). X and Y are driven with DRV8825 drivers and RPi-3B+ on the left...

20200624_194008.jpg


Frontal shot of the Z-axis assembly and the shared carriage plate, with wheels front and back...

20200624_193953.jpg


Z-axis "carriage" is just a little block capturing the belt ends and bolted to the Y-axis carriage...

20200624_193942.jpg


Another shot of the hacked 28BYJ-48 stepper motor and just enough belt clearance inside the extrusion...

20200624_193930.jpg


And finally, the entire 3-axis machine, sitting on the cluttered work bench...

20200624_204614.jpg


I'm pretty sure I'll have to have a guide of some sort to keep the wheels tracking in a straight line... I noted a little drift in some earlier "to & fro" tests. Maybe just "fender skirts" or "curb feelers", attached to the axles on both ends, and extending slightly below the work surface... and the tractor-to-tractor spacing adjusted accordingly.

20200624_205509.jpg


I'll need to adapt a pen-holder to attach to the Z-axis and hopefully start running a few tests. I'll start first with the obligatory MPCNC crown and hopefully then a few of Jamie's rulers. It's been a fun build.

-- David
 

Wildthing

Well-known member
More progress on the rolling plotter/gantry...

I printed a couple of plates to mount the RPi and CNC controller boards on the back rail...

View attachment 172835

and then started working on the Z-axis.

After the "discussion" (I apologize if it was unwarranted, Mike... just me being "dense", I guess) about the various forms of belt-drive, I decided to see if I could make the entire machine be belt-driven. I came up with a smaller version of the Y-axis linear stage, to use as a Z-axis. As I don't ever expect to lift anything heavier than a laser, needle cutter, or a pen... I wanted to try using a very inexpensive 28BYJ-48 geared stepper motor that I had used on a couple of projects before. But first I needed to perform a well-known "unipolar to bipolar" conversion/hack on it (you cut a trace on the internal PCB and remove the 5th wire) to increase its torque and allow it to be driven with the little stepstick driver modules used on the other axes. Here it is in action...


I strained my brain to try to simplify the mechanism as much as possible and finally decided on a "shared carriage" assembly... where the Y-axis carriage plate is also the Z-axis carriage plate. So while the Z-axis carriage remains fixed in the Z-axis, the entire assembly moves up and down. I haven't added a tool mount yet but being V-slot extrusion, it's easy to attach stuff to it. The range of motion here is only about 55 millimeters and is limited by the lower end of the Z-axis hitting the spoilboard. I guess I'll eventually need to fashion 2x4 elevated guides for the trucks/tractors to run on if I have thicker materials I need to work on.

Here are detailed photos of the Z-axis assembly. The "hacked" (note the blue plastic piece just hanging...) 28BYJ-48 geared stepper motor, with IIRC a 20-tooth GT2 pulley...

View attachment 172836

Back-side shot showing the stepper motor now driven by A4988 driver (had one sitting there). X and Y are driven with DRV8825 drivers and RPi-3B+ on the left...

View attachment 172837

Frontal shot of the Z-axis assembly and the shared carriage plate, with wheels front and back...

View attachment 172838

Z-axis "carriage" is just a little block capturing the belt ends and bolted to the Y-axis carriage...

View attachment 172839

Another shot of the hacked 28BYJ-48 stepper motor and just enough belt clearance inside the extrusion...

View attachment 172840

And finally, the entire 3-axis machine, sitting on the cluttered work bench...

View attachment 172842

I'm pretty sure I'll have to have a guide of some sort to keep the wheels tracking in a straight line... I noted a little drift in some earlier "to & fro" tests. Maybe just "fender skirts" or "curb feelers", attached to the axles on both ends, and extending slightly below the work surface... and the tractor-to-tractor spacing adjusted accordingly.

View attachment 172843

I'll need to adapt a pen-holder to attach to the Z-axis and hopefully start running a few tests. I'll start first with the obligatory MPCNC crown and hopefully then a few of Jamie's rulers. It's been a fun build.

-- David
Guinness you are. That looks like you could set it basically up for any size you wanted , virtually unlimited .
 
Very cool! And you answered, at least in part, my comparison question between the continuous belt drive (yours) vs the stationary belt drive (mine). Same precision in drive direction, but drift possible 90 deg. With continuous? Probably need better descriptive terms for each, eh?

On a related topic, any philosophical comments on attachment retention methods? Fastner type, size, location methods for instance. I am finishing a "router" cutter attachment to add to the laser and needler and probably don't have the best retention setup.
 

dkj4linux

Well-known member
Finally cleared off the work surface and verified all axes were moving properly and in the right directions.



I then tested the rolling plotter/gantry with a 3D test of all axes. I used the default code snippet from this Gcode Simulator and, with only very minor changes, was able to run it successfully on this GRBL machine. It changes from metric (mm) to imperial (inch) and and back in mid-stream and even changes planes (X-Y, X-Z, and Y-Z) before returning to starting point.


Here are screenshots of the code snippet and path…




Onward to the crown!

– David
 

dkj4linux

Well-known member
Very cool! And you answered, at least in part, my comparison question between the continuous belt drive (yours) vs the stationary belt drive (mine). Same precision in drive direction, but drift possible 90 deg. With continuous? Probably need better descriptive terms for each, eh?

On a related topic, any philosophical comments on attachment retention methods? Fastner type, size, location methods for instance. I am finishing a "router" cutter attachment to add to the laser and needler and probably don't have the best retention setup.
Thanks, Mike. I"m pretty sure it's me and the difficulty I have picturing things in my mind if I'm not directly focused on it.

I'm afraid I don't have any particular ideas for mounting a router on your machine. I'm not doing anything nowadays that involves excessive noise, messy debris, heavy lifting, or manual labor... i.e. pen-plotting and laser engraving are more my speed. But if you really want some good ideas for mounting different tools on your machine, I'd suggest going over to the V1Engineering forum and lurking for a while... and Thingiverse has tons of add-ons for MPCNC. Folks all around the world are mounting all kinds of tooling onto their MPCNC and LowRider machines... and with some creative CAD you should be able to adapt a suitable tool mount to something more compatible with your machine.

-- David
 

dkj4linux

Well-known member
Alright! Made a pen holder to fit my Z-axis…

20200625_191829.jpg


And printed the MPCNC crown. This was my first attempt and the machine was just free-rolling without guides of any sort. There is “drift” as the tractors make their way, to and fro, and the closed shapes… well, they didn’t close :(

20200625_191849.jpg


So I added a guide rail on the side toward where the machine was drifting and repeated the test…


20200625_203840.jpg


This time the gap between closed-shape start and end points was much smaller… but it's still not perfect

20200625_203708.jpg


I’ll continue to play with it and see what I can see…

Later.

– David
 
So I now have “training wheels”!





With training wheels in place, I plotted the crown again. It’s “nice”… but not perfect.



Thinking initially it was probably just the dog demanding my attention… I finally came to my senses and decided to look further for sources of slop. Started wiggling the gantry around and it’s immediately apparent that I need the usual eccentric spacers (that I conveniently left out) to snug things up…


Overall, I’m pleased with the smooth operation of the entirely belt-driven gantry… just need to tighten things up a bit and I think it’ll be a decent enough gantry for plotting and laser engraving.

Now to fire up Onshape and print some eccentric spacers I found on Thingiverse…

Later.

– David
 
So I get by with just one printer nowadays and once I get past a new machine’s basic construction it’s… [wait for it!]… spacers, Spacers, SPACERS!!



Alright! With new spacers, eccentrics, and a carriage plate to accommodate the eccentrics... I got it all installed and reran the crown plot. Much better… now all the closed shapes closed up nicely.



It’s still not the sturdiest of machines but this is the heaviest load it’ll see and I’m good with the improvement. I now need to run a few of Jamie’s rulers to check the calibration… and then start looking at a laser mount.

– David