The Mrs aint gonna be happy about this little project!

Ok, this has turned in to one of those projects that occupies every waking moment....every sleeping moment! Its doing my nut in but it's a dream that needs to come to reality! Ok ok may be a tad OTT:joker:

I've read many of the build logs and have a decent understanding of what the machine needs to do and what needs to be done in order for the machine/me to acheive it. And if i can get even close to what you guys have acheived i'll be a happy man!
The main functionality is to machine my carbon fibre plates.
Machining ali will be a major bonus.
If i can add an A axis at a later date to machine the likes of a motorcycle fender then even bettererererer!:joyous:

So heres a couple of pics of my current design. This must be the umpteenth version and unless you can see any flaws this is what im going with....

Attachment 6938
Attachment 6939

X axis consists of 25mm supported rails on a box section frame made from 60x60x5mm. Box section will be drilled and tapped for the rails. Bearing blocks will be on a plate 200x100x20mm. This plate will support the Y axis upright supports that are 200mm tall. The plan to date is to have the 2510 screws fixed and use a couple of Jonathan's spinning ballscrews.
Y axis consists of a 1000x130x20mm (may go to 25mm)plate. 80x40 ali extrusion will be attached to the length at the top and bottom of the plate. 20mm supported rails will be bolted to the extrusion to form a C shape with a 2005 ballscrew driving it. The ballnut will run within the C and again i'm thinking of using another spinning ballnut.
Bearings for Y will be wrapped by 20mm ali plate 150mm wide.
X axis support is 150mm wide, 500mm tall and 20mm thick. I plan to have at least 300mm travel on Z. I got some profile rails off ebay that ive since discovered are from someone on here. They weren't suitable for them so im wondering about the suitability for my application. So Z needs a little thinking about.

I've got these steppers from Zapp and plan to use MA860 drivers with a 70v+ PSU.

A 2kw watercooled spindle with flooding at the cutting head will be used to minimse CF dust floating about. Ill also need a vaccum attachement for MDF and the like.

Oh and the bed. Nearly forgot about that. Height is going to be adjustable whether it be a manual job of unbolting and adjusting or using and electric scissor jacks on each corner.

Appreciate your comments/advice.

Cheers
Rob

Quote:

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Originally Posted by r0bsk1

I've got these steppers from Zapp and plan to use MA860 drivers with a 70v+ PSU.

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WHY.?? . . . . far far to big and will restrict performance not gain. To get any decent performance then you'll need far more than 70V and really need to be run using 240V drives.

Personally I'd ask about returning and get something more suited. From what you're proposing using rotating nuts then 3-4 Nm would be enough on 70V. Even 6Nm 34's would be OTT using rotating nuts esp if twin driven X axis, and then still restrict performance compared to 3Nm 23's.!

Bigger is NOT better and on this machine would be restrictive.!!

Originaly i wasnt planning on a 2m X axis and they came up cheap on ebay. Ah well looks like they'll be going back on ebay.

Quote:

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Originally Posted by r0bsk1

Originaly i wasnt planning on a 2m X axis and they came up cheap on ebay. Ah well looks like they'll be going back on ebay.

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I'll stop messing about trying to design the rotating ballnut mount to accommodate both size motors and just make it for the 3Nm nema 24's then? :)
Your gantry as drawn will weigh about the same as mine, so you'll be fine with 3Nm on 70V since that's what I use and the system is virtually identical...

Nema23 Stepper Motor 3.1Nm

Quote:

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Originally Posted by Jonathan

I'll stop messing about trying to design the rotating ballnut mount to accommodate both size motors and just make it for the 3Nm nema 24's then? :)

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Aye! Sounds like a plan!

Is a rotating ballnut on Y OTT too?

Quote:

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Originally Posted by r0bsk1

Is a rotating ballnut on Y OTT too?

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It'll cost more than the standard setup and wont really gain anything if you use a 10mm pitch screw. I hope you've not bought the RM2005 already since RM1610 would have been much more suitable for that length, again due to critical speed.

Nope i've not bought anything else as yet.

Ok so scrap the rotating nut on Y. It should secure nicely on its bearing between the Y rails. I'll have the stepper bolted to a mounting plate and have the mounting plate adjustable on the Y upright to get tension on a belt.

So the old brain cells have been working overtime again......
What if i were to have 2000mm X axis on the moving gantry and Y axis stationary? Would the current setup of 20mm tooling plate and ali extrusion be enough to prevent flex on X over 2000mm?
This setup would suit my current workshop arrangement alot more and would make it easier to load large sheets for machining.

Quote:

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Originally Posted by r0bsk1

So the old brain cells have been working overtime again......
What if i were to have 2000mm X axis on the moving gantry and Y axis stationary? Would the current setup of 20mm tooling plate and ali extrusion be enough to prevent flex on X over 2000mm?
This setup would suit my current workshop arrangement alot more and would make it easier to load large sheets for machining.

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Not understanding here.? You wouldn't want a fixed Y axis with a moving gantry machine.!! . .It just don't make sense?????

Did you mean fixed gantry so therefore fixed y Axis.? If so then you'll have a moving Table design and the X Axis will need to be roughly twice the length required to have same cutting area.! Not good design for large format machine.

Ok ill rephrase it......The 2000mm axis will be parallel to a wall and move away from the wall on the 1000mm axis.
Loading the machine with material will be done in parallel to the wall as this side will be open.
This will not be a moving table design.

I think you're describing changing it round so that the longest axis is the Y-axis and the gantry only moves a short distance? This would make the X-axis (or whatever you want to call it) a 2000mm long unsupported length, hence the question about '20mm tooling plate and ali extrusion be enough' over this increased distance.
I guess it does mean you would only need one rotating ballnut mount. The mass of the gantry is also increased substantially.

Edit, didn't see previous post which explains it when I posted this.

Quote:

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Originally Posted by Jonathan

I think you're describing changing it round so that the longest axis is the Y-axis and the gantry only moves a short distance? This would make the X-axis (or whatever you want to call it) a 2000mm long unsupported length, hence the question about '20mm tooling plate and ali extrusion be enough' over this increased distance.
I guess it does mean you would only need one rotating ballnut mount. The mass of the gantry is also increased substantially.

Edit, didn't see previous post which explains it when I posted this.

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Exactamundo! Is it a basic rule of thumb to have the longest axis supported?

Quote:

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Originally Posted by r0bsk1

Ok ill rephrase it......The 2000mm axis will be parallel to a wall and move away from the wall on the 1000mm axis.
Loading the machine with material will be done in parallel to the wall as this side will be open.
This will not be a moving table design.

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Ok understand now it was the fixed Y axis ref that thru me.!! Well that's ok so long has the long gantry is beefed up enough to handle the length.
20mm plate and what size profile.?
What you planning cutting.?

20MM plate with 90x45 extrusion to mount the 25mm rails on.

I'll cutting carbon fibre and ali.

Oh and my other option is to make use of some 60x60x5 box section if needed.

I've now got the 60mm box section. Its 5mm thick and bleedin' heavy. Should be idea for the table frame.

Appreciate any thought of reinforcing a 2000mm unsupported span. The difference in cost of the 2 designs would be minimal due to the cost saving with only one ballnut mount will go in to tooling plate. I've been quoted £160+vat for 2000x150x25.
Ta

Ok so here's my latest incarnation. Gantry is 2000mm wide. Rails are 25mm.

I've stacked 3 60x60x5 box sections on top of each other and will be welded together. The edges have a 10mm radius on them so will need several passes to secure them.....at least thats how they did in on Discovery's Extreme Engineering on a bridge build:hypnotysed:. Do you think i'll need a backing plate?

Each 60mm section will have 2 supports to prevent the beam falling forward or back. I've used 20mm ali plate for now but may weld box section cut-offs direct to the beam to form a 'T' on the ends instead.

A spinning ballnut mount is bolted to the back of the Y axis bearings.


Attachment 7094

Ta
Rob

From the drawing it looks like the plan is to mount the rails on the top and bottom of the welded box section? If so you'll have problems with how much the steel will distort due to the welding. The rail spacing needs to be very accurate (guessing probably <0.05mm) for them to run smoothly, which is hard to get even before welding. Perhaps consider bolting them to a backing plate instead, since this allows adjustment to get the rails parallel. Also you will get much less deflection on this Y-axis if the ballscrew is placed between the rails. Currently when a force is applied parallel to Y, the Y-axis bearings can deflect in the same direction since there is a long horizontal distance (parallel to X) between the cutter and ballnut/rails.

If you decide to mount the rails on aluminium plate (as in post #15), then yes it is best to use tooling plate, but realistically the tolerances of the bearings are not that good so you would be fine with normal aluminium plate, but definitely not flat bar. If you were using profile rails then tooling plate would be the best option.

The rails are bolted to the box section, even in post #15. Earlier designs for a 1000mm gantry had them mounted on 90x45 ali extrusion which was bolted to a back plate.
I was hoping that tacking the sections together first and then do gradual passes would eliminate any heat distortion but if it's out of spec for the bearing before i even start, well that puts the mockers on that idea. Any idea how 90x45 ali extrusion would cope over 2m?

I would have liked to have the ballscrew mount on the Z axis upright so I would have to remove the middle box section and bolt to a 20mm back plate but then then is no room for the ballscrew mount unless the width of Y is 200mm+ to accomodate the mount as i feel it best to surround the Y bearings. Y ballscrew is currently 100mm off centre from the Y bearings.

You set up index plates on the top and bottom of the box section which not only would help deal with small distortion of welding But also give you a rebated straight edge with which to create a master index edge for setting up the rails with. This also has the advantage of being able to do dis-assembly and certain types of maintenance much much easier. First you have to decide which edge is you master edge and work from that in the actual building. Though bolting works much better in most cases. This is why King bridges that are bolted together from many plates have been know to last over 80 yrs of active use.

Michael

Quote:

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Originally Posted by r0bsk1

but if it's out of spec for the bearing before i even start, well that puts the mockers on that idea. Any idea how 90x45 ali extrusion would cope over 2m?

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I should have been clearer, it might be out too much even before welding, but you can get round that. Instead of welding three pieces together couldn't you start with one or two bigger sections, then bolt them to a back plate? If you have a fastener every 100mm or so you can use them to adjust and remove the bend enough to mount the rails. Two pieces of 90x45 aluminum extrusion to mount the rails on would be fine, or you could use aluminium box section.

Quote:

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Originally Posted by r0bsk1

I would have liked to have the ballscrew mount on the Z axis upright so I would have to remove the middle box section and bolt to a 20mm back plate but then then is no room for the ballscrew mount unless the width of Y is 200mm+ to accomodate the mount as i feel it best to surround the Y bearings. Y ballscrew is currently 100mm off centre from the Y bearings.

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Spacing the Y-rails out 200mm+ to accommodate the ballnut mount would be good as in addition to making the axis much more rigid due to the ballnut being in the optimal position, it will also make make it stronger because the bearings are further apart. However you don't want the rails too far apart without increasing the spacing of the bearing blocks since it risks them skewing/racking. The ballnut mount could be made a fair bit shorter by moving the mounting holes and having only one available ratio without changing the belt.

Quote:

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Originally Posted by m.marino

You set up index plates on the top and bottom of the box section which not only would help deal with small distortion of welding But also give you a rebated straight edge with which to create a master index edge for setting up the rails with. This also has the advantage of being able to do dis-assembly and certain types of maintenance much much easier. First you have to decide which edge is you master edge and work from that in the actual building. Though bolting works much better in most cases. This is why King bridges that are bolted together from many plates have been know to last over 80 yrs of active use.

Michael

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That would be very tricky to do as the box section is 60mm and the rail base plates are 65mm.......unless i've completely misunderstood. I'd have to mount somthing to the side and offset by 2.5 mm. Tricky but doable.....

Quote:

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Originally Posted by Jonathan

I should have been clearer, it might be out too much even before welding, but you can get round that. Instead of welding three pieces together couldn't you start with one or two bigger sections, then bolt them to a back plate? If you have a fastener every 100mm or so you can use them to adjust and remove the bend enough to mount the rails. Two pieces of 90x45 aluminum extrusion to mount the rails on would be fine, or you could use aluminium box section.

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There's no way im going to be able to bend the box section. I'd expect the ali back plate to bend before the steel. However they do "look" straight.

Quote:

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Originally Posted by Jonathan

Spacing the Y-rails out 200mm+ to accommodate the ballnut mount would be good as in addition to making the axis much more rigid due to the ballnut being in the optimal position, it will also make make it stronger because the bearings are further apart. However you don't want the rails too far apart without increasing the spacing of the bearing blocks since it risks them skewing/racking. The ballnut mount could be made a fair bit shorter by moving the mounting holes and having only one available ratio without changing the belt.

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Right so that sounds like the ballnut mount is upright mounted against the Z upright and runs between the Y box section beams. I had i laying on it side poking out the back. The rail base plates would be approx 330mm apart if the mount is 200mm. What could you get the ballnut mount down to?

Here's a quick mock up the ballscrew mount running between the Y rails. All uprights are approx 500mm


Attachment 7105

Back plate is 2190x330x20mm.......quoted.......wait for it........£300 +vat for ecocast!!!:hysterical:
5038 is £205

Back to the drawing board i guess

Quote:

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Originally Posted by r0bsk1

That would be very tricky to do as the box section is 60mm and the rail base plates are 65mm

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The SBR25 rail base is 55mm wide unless I'm missing something?

Quote:

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Originally Posted by r0bsk1

There's no way im going to be able to bend the box section. I'd expect the ali back plate to bend before the steel.

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We're only talking small fractions of a milimeter which doesn't require that much force. Both will bend a little bit...

Quote:

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Originally Posted by r0bsk1

What could you get the ballnut mount down to?

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About 160mm if you're happy being limited to only using 1:1 or 1:2 ratio without changing the belt. Don't quote me on that though as I need to draw it first!

Quote:

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Originally Posted by r0bsk1

Back plate is 2190x330x20mm.......quoted.......wait for it........£300 +vat for ecocast!!!:hysterical:
5038 is £205

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It would be fine with 1/2" thick plate, but that doesn't really change the conclusion as it's still expensive.

Quote:

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Originally Posted by Jonathan

The SBR25 rail base is 55mm wide unless I'm missing something?

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My Bad, been looking at TBR rails

Quote:

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Originally Posted by Jonathan

We're only talking small fractions of a milimeter which doesn't require that much force. Both will bend a little bit...

About 160mm if you're happy being limited to only using 1:1 or 1:2 ratio without changing the belt. Don't quote me on that though as I need to draw it first!

It would be fine with 1/2" thick plate, but that doesn't really change the conclusion as it's still expensive.

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To be honest I'm seriously thinking about going back to the shorter gantry as in my orginal designs. I'll need to weigh up the pros and cons.....

Due to a change in plan i've settled on a 1200mm for both X and Y. Ill be using 2 lengths of 60mm box section on a back plate with sbr25 rails to form the Y axis. Y is mounted on the X bearings near enough at the mid-point of the Y bearings. I've not drawn them in yet but ill put some diagonal pieces in to support the Y uprights against the X bearing plates.
Would taking the Y uprights below X bearings and box section and linking up with the opposite side of the X bearing plates offer significant more support to the X bearings?
Y bearings appear to be a little out of position. Everytime i move 1 bearing, they all move! I must have grouped them somehow. Going on the bearing blocks are 65mm i have a 20mm space between the 2 which make 150mm from one end to the other on each Y rail. Is this spacing sufficient?
Is it best to drive Y on the main Z back plate or can i use the shorter Z back plate? I'd like to protect the Y screw from any debris.


Attachment 7198
Cheers

Just a quickie in prep for building a PSU. I've got 5 MA860 drivers rated at 7.2A each driving 3.1nm steppers.
When I come to use all 5 stepper they wont all be maxed out at once. What rating of transformer should i be looking for?
I'm looking at 1200VA 2x50 at 12A each. Wire the output in parallel and get 24A. Yes this is below 7.2x5 but would i ever exceed that machining wood/composites/Ali?

Bit of a hand waving explanation here, but in short...The the motor coils are rated for 2.1A, and you'll put them in parallel so 4.2A per motor. Due to them not drawing anywhere near full power most of the time, you can design for about 2/3rds of that, so 2/3*4.2*5=14A. 50V, so P=50*14=700W. So you need the nearest size transformer, or combination of transformers above that rating - so most likely 800VA. Plus some capacitors and a rectifier. I've currently got a 500VA and 325VA to power 5 or 6 of those motors.

Quote:

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Originally Posted by Jonathan

From the drawing it looks like the plan is to mount the rails on the top and bottom of the welded box section? If so you'll have problems with how much the steel will distort due to the welding. The rail spacing needs to be very accurate (guessing probably <0.05mm) for them to run smoothly, which is hard to get even before welding. Perhaps consider bolting them to a backing plate instead, since this allows adjustment to get the rails parallel. Also you will get much less deflection on this Y-axis if the ballscrew is placed between the rails. Currently when a force is applied parallel to Y, the Y-axis bearings can deflect in the same direction since there is a long horizontal distance (parallel to X) between the cutter and ballnut/rails.

If you decide to mount the rails on aluminium plate (as in post #15), then yes it is best to use tooling plate, but realistically the tolerances of the bearings are not that good so you would be fine with normal aluminium plate, but definitely not flat bar. If you were using profile rails then tooling plate would be the best option.

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With reference to the section marked in bold, you simply cannot make such a sweeping statement, ive just welded my complete 7x4 and i used my dual dial guages one the gantry was clamped and ready to weld and there is no diference in the distorsion after welding or certainly no more than there was before the welding. If you weld it in the correct fashion and you have used a jig to hold the pieces, then it is fine. I will admit that if you use a 2mil rod on an old stick welder crank up the amps and weld 2mm box together you will have problems but a modern mig used to tack the items together before finishing the welding of it turns out fine, im not saying Its better than Ali, just that if care is taken during the welding of steel box no more surfacing and leveling will be required than before you welded it. Obviosly when mounting the rails onto the gantry you will have to do some remedial leveling work but its just not difficult, I will show you how ive done mine in the next week or so and it certaily ticks the 0.05 accuracy box you mention with ease


Rick

Ah the ruddy motor windings! New i was missing something. Ta

Even before welding, it's questionable whether steel box section is accurate enough to mount round rails on opposite faces, so no matter how good the welding is it's not a good plan. It certainly wouldn't work for profile rails without further machining or shimming.

Quote:

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Originally Posted by Ricardoco

it certaily ticks the 0.05 accuracy box you mention with ease

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How do you know?

Quote:

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Originally Posted by Jonathan

Even before welding, it's questionable whether steel box section is accurate enough to mount round rails on opposite faces, so no matter how good the welding is it's not a good plan. It certainly wouldn't work for profile rails without further machining or shimming.



How do you know?

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Because ive measured it.

Quote:

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Originally Posted by Ricardoco

Because ive measured it.

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What did you measure from and to and using what instrument?

Quote:

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Originally Posted by Jonathan

What did you measure from and to?

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Do you want to know how i measured it or where i measured it?

Well it's been a while since i last update due to other commitments but i've finally mounted Jonathan rotating ball nuts (oooooeerrrrr missus!), built the 70v PSU with 24v safety system and got it moving with 860 drivers and 4Nm steppers. Not moved it using Mach3 yet but only used the pendent that came with the BOB.
Just working out the idea of a pneumaticaly controled table height if/when the pneumatics arrive. That's what my recent wanted post is for :peaceful:

Ok this is a bit of a strange one.....
I have 2 screws for an axis. They move independently using the pendant in both directions but when using Mach3 to jog the axis using the keyboard something odd happens!
At this point i haven't slaved the 2 sides together. A side of the axis moves up and down fine. B side moves up only. When i try to jog side B down it seems to release the holding voltage and spins free.
I have to tap the key to jog side A down slightly and then side B will jog down.
Side B then moves in both directions but side A will only move the 1 way.
Has anyone else had experience on this?

Ok am I getting this correct your trying to jog 2 motors on same axis at same time independently and keep them in sync.? . . . To be honest If connected to gantry your just asking for trouble and bent ballscrews.!!!. . . . Anyway are you sure your not just stalling the B motor by racking the gantry or axis.?

If the B axis just moves in one direction intermittently then I'd check you Dir connection at the drive it could be loose.!!

You could have dodgy keyboard. To test if things are ok try using MDI commands for each axis if they move ok with G-code commands and they move with pendent then chances are key board is playing up.? The pendent will use the same Axis commands the keyboard does so to mach it's no different, they are just key press's.

Have you tried removing pendant and see what happens.? They could be clashing.??

I've not slaved the 2 side together yet just so i can confirm each side is working correctly. I've no tightened things up yet so there's enough slack in the gantry to allow independant movement of each side.

The pendant plugs directly in to the BOB, not the PC so commands as different and with this working i though jogging via Mach would be fine.

Well it turns out that the pendant does conflict with keyboard jogging commands. If i unplug the pendant it it's fine and both side jog via the keyboard. They're now slaved together and all is good in the world for now and i can tighten things up.

Quote:

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Originally Posted by r0bsk1

I
The pendant plugs directly in to the BOB, not the PC so commands as different and with this working i though jogging via Mach would be fine.

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Mach doesn't know or care what's sending the signals, it could be keyboard, pendent thru the BOB or just set of buttons on a control panel.? To Mach they are the same, It's just watching for inputs and acting on them to do the assigned tasks.

Quote:

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Originally Posted by JAZZCNC

Mach doesn't know or care what's sending the signals, it could be keyboard, pendent thru the BOB or just set of buttons on a control panel.? To Mach they are the same, It's just watching for inputs and acting on them to do the assigned tasks.

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Mach doesnt need to be running or the PC can be off for that matter to move the axis via the pendant. However you cant slave 2 axis together with just the BOB without wiring 2 drivers to the same output which isnt the best of ideas. So that rules out the pendant working independantly without the PC and/or mach. Its not a big issue but was a nice to have.

Quote:

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Originally Posted by r0bsk1

Mach doesnt need to be running or the PC can be off for that matter to move the axis via the pendant.

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Ok I see.! So the pendant has a pulse generator built into it. Think you'll still be able to use the pendent but you'll have to set the Jog mode to shuttle mode so it uses the MPG(manual pulse generator) to output the pulses while jogging not Machs pulse engine.? .. . . I'm not 100% on this but think I'll be close.!!