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4DThinker

2nd CNC purchased for dedicated use?

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I've heard all sorts of wise advice for those considering getting a CNC.  "Buy your second CNC first!" for example. 

I benefit from already owning 2 CNCs, but am honestly considering buying another one.  Not a larger one.  I looked back at the kind of cuts I do most of the time.  Most (90%) were joinery cuts that only took up a small area of my Probitix Meteor (26" x 50" cutting area).  Any project might consist of flat cuts needing my CNC bed configured one way, and vertical cuts needing it set up another way. 

 

Probotix also sells smaller CNCs, down to their V90 MK2 (20" x 13" cutting area) selling for $2999.  For my needs though I can get that price down to under $2000. I don't need their MDF spoil board.   I don't need the cheap mouse and keyboard and monitor they normally include. We have a spare unity controller that just needs a fuse replacement, so I don't need a new one of those. I don't need their router mount as I have a spare left over when I updated my meteor to use a different (larger) router. 

 

I would set this little CNC up on my usual simple base frame, except a little taller than normal.  I'd make a version of my adjustable angle clamping jig that would fill the entire cutting area when horizontal, but rotate down to perfectly vertical when needed to hold boards vertically for tenons or related joinery. I have spare monitors, keyboards, and mice I can use.

 

This smaller CNC will take up less than 1/3 the floor space of my Meteor.  The smaller design actually has a higher maximum feed speed limit (300ipm vs 200ipm of their larger CNCs).  With one CNC always handling the vertical/angled joinery cuts, my older Meteor can be left configured for flat cuts. 

 

4D  

Edited by 4DThinker (see edit history)

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Not having seen one, 4D, I have to ask - does the smaller machine have the same rigidity and accuracy as your larger machine or will you be giving up something to which you may be accustomed?  How about speed - can it be close to the larger machine?

 

David

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13 minutes ago, difalkner said:

Does the smaller machine have the same rigidity and accuracy as your larger machine or will you be giving up something to which you may be accustomed?  How about speed - can it be close to the larger machine?

 

David

The V90 MK2 is made from the same components as their larger machines.  The shorter gantry beam and side rails would actually make it stiffer than the large machines.   The specs show that the max feed speed on this small CNC is 300ipm and all their large CNCs are limited to 200ipm.  The MK2 has less room to accelerate in,  so that 300ipm may never be reached except when jogging.   

 

I can see the potential of cutting some aluminum on the small machine that I wouldn't attempt to do on my Meteor.  I have an interest in making replacement parts for the Z axis assembly which would make it stronger and less in the way of clamps and such when down. 

 

4D 

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I can see the justification for you buying a dedicated CNC just for vertical and angled cuts and I think that the smaller footprint will give you a tighter CNC to machine the critical joinery that you plan on using it for.  Dovetailed drawers and your own decoratively designed joints are just around the corner.

 

As you also say this might help you cut a few pieces of aluminum that were out question on the larger machines.  I know I have done a little aluminum on my Shark HD1 and it can be a nightmare but my Piranha is small and tight so it does a lot better job cutting aluminum parts

Edited by MEBCWD (see edit history)

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We have a Shark HD1 (maybe its an HD2) in the college shop and there is so much play in the router mount that I've demoted it to only cutting 3D parts where there is little material removed on each pass.  This is after replacing the warping plastic gantry back plate with their aluminum upgrade, and making a better router clamp from plywood after the plastic one failed. 

 

The larger Probotix CNCs are limited to 200ips to keep the threaded X and Y feed rods from whipping. Short rods on the MK2 won't whip at 300ipm.   The Nebula and Asteroid use a longer gantry beam that is prone to twisting flex with a heavy router hanging off it and doing aggressive cuts.  I notice on their facebook page a prototype 50" x 50" CNC with a beefier 60mm x 60mm gantry beam.  No doubt to help minimize the potential flex. 

Edited by 4DThinker (see edit history)

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If the gantry arm are straight up and down on the Shark it is an HD1, if they are slanted to the back then it is a HD2 or later model.  I bought my HD! used and I replaced that deeply carved gantry plate with the upgrade aluminum plate and replace the cheap plastic router clamp with an 1.25" think aluminum upgrade.  I also added adjustable bearings because the HD1 did not have adjustable bearings and had too much slop in it.  I also did a whole lot of other modifications to it and looking back now I should have been buying another CNC that was sturdier and got away for the Sharks entirely.  

 

That's where I'm at right now, still looking over different choices and options and deciding if I can really justify the cost of another CNC right now.

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It's an HD1 then.  A free donation from Nextwave Automation after I met the owner and his wife at a trade show (in Rockler's booth) and showed them what I was doing for my students with my original Shark Pro. 

 

There are far more options/choices out there now than 5 years ago. More this year than last.  Many companies started in a garage using parts ordered from various sources online and are now in warehouse facilities shipping kits or assembled CNCs all over the world.  Controller options. Stepper options. Software options.   Web apps have appeared to run  CNCs from. 

 

I can see the vast difference between what our industrial Multicam CNC can do and these small hobby CNCs can do.    I can also see how the simple nature of an extrusion framed CNC inspires custom configuring to do things you just can't do with that industrial behemoth. 

 

4D

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The companies making CNC s now are getting more competitive and the quality of some of the machines have gotten quite a bit better than what was available just a couple of years ago.  I'm liking what I am seeing right now with that trend and hopefully all the companies will listen to their customers and build quality affordable machines.

 

You are right about custom configurations to be able to get as much out of these smaller CNC machines.  

 

I think the only limits most hobby machine owners face is how far will there imagination take them.

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An odd thought popped into my head today.  I often have to cut the same file on more than one part.  The Z axis faceplate of Probotix CNCs would be easy to bolt an adapter plate to that could then hold two routers/spindles or even three. Make that plate so that the distance between the 2 routers could be adjusted, and you would have a CNC that could cut 2 (or more) parts at the same time. 

 

The outlet box on their gantries only has one live socket in it, but a second could be easily added.  If the one power cord can handle one large router, then it should be able to handle 2 or 3 trim routers at the same time. 

 

It also doesn't look like it would be too hard for Probotix to make a custom V90 MK2.5 with the X direction frame rails and gantry stretched so with two routers in place you end up with the same cutting room for each as the original  MK2 had for one. 

 

I'll have to look back and see how many past projects could have been done in half the time if I'd had a rig like this.  Many cases pop into my mind as I write this.  The dual bracket could always be removed and a single router mounted, so there would be no functional penalty just because the rig could occasionally hold 2 routers. 

 

Am I crazy?

 

4D

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2 hours ago, 4DThinker said:

Am I crazy?

 

4D

Of course you are crazy, that's why you can think of things like this. 

 

This should work as long as you don't exceed the weight that the gantry will hold safely and keep feed rates within reason.  You would need to make sure your design file keeps bits within the new cutting area of the two or 3 routers.

 

I more thought would be to stack cut small thin parts, maybe 4 or 5 at a time like you would with a scroll saw so you could be cutting 15 parts at 1 time.

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You make a good good point about stressing the gantry beam. Probotix CNCs already have more weight cantilevering off the front of the gantry than most designs do.  Of course the shorter the gantry beam is the less likely the stress would lead to deflection or twisting.  Ideally with two routers one should be mounted on the back of the gantry beam to balance the one on the front.  Not so easy to engineer though. 

 

As for keeping the routers within the cutting area the limit switch stop brackets can be moved inward and the available range can be re-defined in the software. 

 

4D

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Roughly 50%.  That is the percentage of the jobs I do for my students that use the same cut file more than once  Cabinets sometimes have a taper cut on 2 or 4 sides of each leg, and 4 legs per cabinet. Most furniture has left and right sides, which sometimes are identical and sometimes mirrored.   

 

The frequency of mirrored cuts leads me to contemplate what it would take to make the two heads on a CNC gantry mirror each other rather than clone each other's movement.  A lead screw with left handed threads on one half and right handed threads on the other perhaps. When one head moves left the other would be moving right.   Of course the first mistake I'd make would be clamping the right part under the wrong (left) head.

 

4D

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The drive for this could  replace the X axis drive and be mounted on the Z axis bracket.  One step motor with a thru shaft would work with left/right hand threads. but this will add a lot of additional weight.

 

Another way would have an additional head with it's own Z axis that mounts so it uses the X axis screw but runs with a direction change gear system.  The Z axis step motors would be driven together like the Probotix Y axis.

 

Then again you could have a linear rail system that mounts to the Z axis and the two heads connect to the X axis lead screw so the heads move independently, one having the direction change gear system to mirror the other head.  This would support part of the weight from the two routers so might be the best route to pursue.  This would definitely not be a quick change system.

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Since you brought up the fact that Probotix uses two Y motors to move the gantry it has me wondering how hard it would be to split the gantry into two cantilevered halves. Doubling up the height of the Y frame rails and using two rails/bearings one above the other should be enough.... maybe. Split the available cutting width of a Comet or Nebula then add a second Z axis to have two independent CNCs within one frame.  Link their controllers so they can both cut identical parts, both could cut mirrored parts from one G-code file, or each could cut their own unique g-code file. 

 

Their Unity controllers already support 5 stepper motors. X/Y1/Y2/Z and A.  Add just one more to have X1/Y1/Z1 and X2/Y2/Z2.  As fun as it is to watch one router/spindle cut one file just double it when two are cutting at the same time. 

 

Or just adding a second X motor on the opposite end and splitting the X feed into 2 self supported halves while leaving the gantry beam intact would let 2 Z axis run the same or cloned cuts for 2/3 the fun. 

 

4D

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I had a closer look at our CNC Shark and it has slanted uprights so must be an HD2.   They did that to better balance the cantilevered router over the center of the under-table gantry cross beam.

 

I also noticed that the Probotix V90 MK2 uses smaller stepper motors than all their larger CNCs.  The Y motors have less weight to move with the narrower gantry.  X and Z have less to move only if a trim router is used rather than a full sized router.   I'll guess the smaller steppers still should have no trouble doing their job or Probotix wouldn't have specified them.  Makes me wonder why they use large steppers on their larger machines if the smaller steppers of the V90 can do the job. 

 

I've come up with a way to motorize the angle adjustment of my adjustable clamping jig.  I can't see any need for it to move dynamically during a cut, but I'd love to be able to hit an up or down button to move it to exactly the angle I need and lock it in position. The angle it is at would show on a small display.  I see a future version with a phone app you can use to tell it to move to any desired angle. For that matter, I expect to control the whole CNC wirelessly with a phone/tablet app in the future.  The phone would also display a real-time view of the cut in progress from a camera installed over the CNC

 

4D

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You do have a HD2 or later model.  They had problems with the HD1 because of the weight of the router being cantilevered so far forward.  They also had "Next Wave Automation" deeply carved into the plastic gantry plate so that just added to the weakness of the system.   I have the HD1 and have done many modifications to it including replacing the gantry plate with the aluminum upgrade, added a third party 1.25" thick aluminum router clamp to replace the cheap .75" thick plastic clamp they used on the machine, replaced the original linear bearings with adjustable bearings and added aluminum angles under the blue bed to help tie together and reinforce the bed and a few other mods.

 

Probotix might have used the larger motors to help handle heavenlier weight loads.  The smaller motors might have been pushing the limits of their specs and the larger motors might allow faster feeds and added torque to handle larger routers and spindles.  There has to be some point where the smaller motors just won't do the job and would limit the feeds and speeds and quality is being sacrificed, they may have found that point and replaced the motors.

 

If you are using the angled platform a lot this might be a good addition but if it is not used very often then this boils down to "a gadget guy looking for something to play with", that's not a bad thing because that is how improvements and new tools are developed.  My problem with this is I'm getting too old and can't find the time do play with things like this but if I had the time ......  For now I'll use a tilt box!

 

Keep use posted on any progress you make with this project it is interesting.

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Yep, my adjustable angle clamping jig gets more use for furniture than the flat bed of the CNCs do.  That is the whole reason I'm consider a V90 to dedicate to that task.  I've accumulated many redundant parts (spare monitor/keyboard/mouse/router mount/router) and may even have a controller I can get working again with a new fuse.  I don't need their MDF bed, tool length sensor, touch plate, or dust collection either.  We haven't located that old controller since we moved into our new fabrication lab but when/if it shows up I'll decide if I still want to buy a V90.  I know one would get plenty of use in our new shop space.  I often teach a CNC joinery elective and one more CNC that can cut joinery will help with the CNC demand then. 

 

4D

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