# Nebula Controller Failure :(



## 4DThinker (Feb 16, 2014)

After they sat idle for a few months and survived being moved from one shop to another I finally got around to checking out the condition of our college owned Meteor and Nebula from Probotix.

A student was able to use the Nebula with no complaints last week. Wednesday this week I wanted to show the students how to use the rotary axis so we booted up the Nebula again. Something must have happened inside the unity controller. The right Y motor would not respond to any jogging or g-code command. As such I couldn't Home the machine, and any Y movement would rack the gantry. Attempts to jog the X or Z axis would quickly generate a flurry of limit errors with the occasional E-Stop pressed warning (it never was). 

I've boxed up the controller to ship back to Probotix on Len's advice. Hopefully they can diagnose and repair it. 

Sad am I. That Nebula has caused me a few fits over the 3 years we've had it, but always kept on running. 

4D


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## rrrun (Jun 17, 2014)

No fun, that. Hopefully it's a cheap & easy fix.


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## MEBCWD (Jan 14, 2012)

Bad time for the controller to go down right at the beginning of the semester. 

Could just be dirty contacts in the E-Stop button from sitting for a long time and then reactivating the machine might have caused the error codes. The E-Stop might have been triggered during the move and when reset might not be making good contact electrically. 

Hopefully Len can get you back up and running quickly.


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## 4DThinker (Feb 16, 2014)

As I said in my first post, the Nebula ran perfectly the week before it died. We even homed it then jogged it all around the bed to lubricate all the guide rails/bearings and feed rods. The symptoms seemed like a cascading failure of internal components. 

The e-stop errors only popped up once or twice when I was trying to jog the CNC a little in each X, Y, and Z direction. Ever more odd was that when the controller was turned off I'd see either left or right Y motors spin for a few seconds. 

In any case that poor controller is now on the way to Florida. Our Nebula was one of their first extra wide Meteors. Although it does have Nebula stickers on the sides the name of the LinuxCNC configuration was MeteorXtraWide.ini. The controller was an early Unity model. I think even before they were officially being called the Unity Controller. It had no VFD input (output?) like my new personal controller does. 

4D


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## 4DThinker (Feb 16, 2014)

At this point we've determined that the controller wasn't damaged. The PC running it apparently suffered a power spike that damaged both of the parallel ports. We've had electricians working over the weekends in our new fabrication lab wiring up tools, and my guess is that they caused the surge accidently. The PC had been left on over the weekend so it was the only victim. 

I sent the controller back to probotix, but they couldn't find anything wrong with it. When it came back it caused the same errors on our nebula. Using the configuration app I moved the control path from the first parallel port to the second parallel port. The limit errors disappeared, but the right Y motor would only run in one direction. Swapped the Y motor cables and the flaw moved to the other side. I brought to controller home to try with my personal CNC and it ran perfectly. The only thing left to blame is the PC's parallel ports. We are now on the hunt for a new PC. 

4D


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## BalloonEngineer (Mar 27, 2009)

LinuxCNC is an very stable real time control system, but it’s insistance on doing the real time step generation internally and using parallel port(s) is becoming somewhat of a liability as computers with parallel ports become harder to find. There are lots of old computers that are available cheaply, but they are old and many can be unreliable. 

I wish there was a version of LinuxCNC that could interface to any of the dedicated hardware step controllers (i.e. the Ethernet Smoothstepper). The only such choices seem to be the Mesa cards. There are numerous small, low power (fanless) computers that would be ideal as CNC control computers in a dusty woodshop , but have no parallel port or room for internal cards. I use MACH4 on my machine, with a long Ethernet cord to allow some space between my computer and the CNC.


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## MikeMa (Jul 27, 2006)

@BalloonEngineer When you say small, low power computers, I think about the Raspberry PI (not sure if you meant that small). At a woodworking show last year, a guy had built a small CNC router (think dremel tool) and it was ran off a Raspberry PI, using a GRBL controller. As I dug further, I found that the GRBL wouldn't handle the higher power requirements of the steppers that a larger CNC requires.

There have been a few guys who have successfully come up with hacks for a R. PI, but nothing I would be willing to use long term. The R. PI, and other small computers like that seem like they would be a great solution for running a CNC, but right now options seem limited.


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## 4DThinker (Feb 16, 2014)

You can run a CNC using a tinyG card and a 12 volt power supply, and any PC with a USB port mapped as a com port. It is limited to small nema23 steppers though. I have done this using salvaged guide rails and steppers from many old printers I stripped before throwing them away.

Right now my college is budget strapped, so they are looking for an old PC they can add parallel port cards to which can run LinuxCNC. We may get lucky and have a useful system for $20 in ports. Or we may have to try several old PCs before we find one that will work. A new PC from probotix is $400ish.


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## MikeMa (Jul 27, 2006)

@4DThinker Look for old lease computers. There is place here who sells them for around $100 with Windows 7 loaded on them. Since a lot of these are actually Vista era PCs, they still have a parallel port on them.


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## artman60 (Nov 22, 2015)

Electricians are #%^&%# $%**^$# (I can say this, I is one). Hope you get the machine up and running soon.


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## 4DThinker (Feb 16, 2014)

I appreciate the suggestion, @MikeMa. We have plenty of old PCs laying around the building, it is just that not all PCs will run Linux/LinuxCNC well enough. So far 2 have been identified as having room for 2 parallel port cards inside. We won't know if LinuxCNC will run properly on either until we try it though. Apparently any with nVidia video on board tend to stop linuxCNC in its tracks. 

4D


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## 4DThinker (Feb 16, 2014)

artman60 said:


> Electricians are #%^&%# $%**^$# (I can say this, I is one). Hope you get the machine up and running soon.


Thanks, @artman60. We do have a several CNC jobs queued up to do and many are relying on the 4th axis we have on the Nebula. Students seem a little too fond of tapered legs for their furniture projects and most aren't experienced enough using a lathe to make 4 that are identical.


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## BalloonEngineer (Mar 27, 2009)

By small computer I meant something like this:
https://www.amazon.com/Fanless-industrial-computer-Qotom-Q190N-S01-celeron/dp/B015H4L200/ref=sr_1_10?s=pc&ie=UTF8&qid=1508468077&sr=1-10&keywords=fanless+pc+-atom+-barebones
(No experience with this one, just first example I found). No moving parts, no fans - no issues with dust. 

I am a believer in having a computer dedicated to machine control, with no other applications, no network access. Once you have a reliable, working system, I see no need for any OS or other updates. If I want to check something online or listen to music, I usually have an iPad with me in shop.

The machines I have seen based on raspberry pi or such are too small, slow and flexible for things I am interested in cutting (wood, non-ferrous metals, plastics). I’m sure that small machines like the shapeoko appeal to some, but I would not be happy with one.


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## 4DThinker (Feb 16, 2014)

I've seen PCs on an HDMI stick (mini PC stick/compute stick/etc.) Which potentially could run a CNC if they had a nice little dock to provide parallel/ethernet/whatever outputs to a CNC controller box. At least one has an ethernet jack on it. My old eyes like a big screen though, and heavy duty controllers don't come tiny, so you're going to have a cabinet of reasonable size anyway. The PC used is probably ideally at the mini-ITX size like Probotix uses mainly to be just big enough for all the parallel/USB/video outputs needed to connect it all together. 

4D


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## 4DThinker (Feb 16, 2014)

The saga continues....

The college had several old PCs we could use for the Nebula. The first one tried seemed to work fine once it was stripped of its drive and add-on video card. A second parallel port card was added. The motherboard had a parallel port on it. We took the solid state drive from the Nebula's PC and put it into this old PC box. It booted up fine. LinuxCNC ran fine. I had to use the configurator app to get it to see the controller, but once done I had control of the CNC... 

All except that right Y motor. Just as it had been doing before all this swapping about, the right Y motor would move back but not forward toward the front of the CNC. 

At this point we have a controller verified to be working fine. We have a CNC with all steppers working fine (The right Y motor works fine when plugged into the left Y jack). We have new parallel and USB cables. The only thing left to replace is the solid state drive from the original PC. 

There is a good chance this CNC was left ON with LinuxCNC running over a weekend when electricians were working in our new fabrication lab. I'm guessing they cut the power at least once, which could have corrupted any open/running files including the parallel port drivers unique to LinuxCNC. 

On monday I plan to format and reinstall Linux/LinuxCNC on the solid state drive. Probotix provides all the needed files/info on their wiki page. 

Finger crossed.
4D


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## 4DThinker (Feb 16, 2014)

Conclusion: As I typed up my "I give up" report to Probotix yesterday morning I started to list all the things I'd done to narrow down what might be causing the problem. The format and re-install of Linux/LinuxCNC didn't make any difference. We had swapped out parallel and USB cables for new ones. We had confirmed that the controller and all the steppers DID work, except not when all connected together. We abandoned the PC for fear the parallel ports had been damaged, and the only thing moved into the new PC was the solid state drive. Today proved it wasn't the problem. We had replaced the X and Z limits switches, and...

Not the Y switches. 

Realizing this I walked over to the Nebula to have a glance at the Y limit switches mounted under the side rails. On the right side (the side giving me the problem) one wire was not plugged in correctly to the outer lead on the 2 back-to-back switches. I moved the wire, turned the system back on, and found all the problems (limit errors, flawed stepper response, and e-stop errors) had disappeared. 

I'm guessing a worker (networking or electrician or painter) had been in the CNC room over the weekend when this problem started. They would have moved the Nebula to gain access to the wall or wall jacks behind and beside it. I suspect in pushing it aside the worker could tell he/she might have unplugged the one wire from that limit switch under the side rail. Not knowing exactly which lead it needed to be attached to he/she guessed wrong. 

So another mystery is finally solved. These CNCs are in what is essentially a public area. Access to the room they are in is not controlled. This leads to people using or even just moving them without really understanding the consequences of that action. It speaks to an area where the CNCs designed and built by Probotix could be a bit more people-proof. The X and Y limit switches in particular hang exposed where accidental contact might find them. I don't have a solution (yet), but some sort of box over these switches might insulate them from both dust AND those accidental contacts. 

4D


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## honesttjohn (Feb 17, 2015)

4D,

Didn't you get a limit switch code of some kind on the monitor? That's the first thing I check when something goes wrong. That usually takes care of it. My controls are set in one spot and don't get moved, and they seem to be made to withstand everything I've thrown at them so far. Except the monitor that got knocked to the cement floor 3 times before it broke. Got a bigger one now.

Glad the mystery problem it solved. But yes, there could be a better set up for those switches.


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## 4DThinker (Feb 16, 2014)

We did get several limit switch errors when this problem showed up. As the right Y axis would only move backward, we started testing the X and Z and of course they also created limit errors as soon as we moved them. I'd had problems with the X and Z axes at the end of last semester so those were replaced with new one. The new switches didn't make any difference (we still got errors from them) we moved on to trying other things (cables and ports and ...).

At one point I reconfigured linuxCNC to use only soft limits, so all the limit errors stopped. The right Y axis still wouldn't move forward though. The Y limit switches only popped back into my mind as I was typing an "I give up" email to probotix. I had tried literally every things else BUT those Y limit switches. 

4D


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## artman60 (Nov 22, 2015)

Just an after the fact, thought from the peanut gallery-Would taking pictures of all the wiring/assembly/harnesses etc to document it in a completely working stage, be helpful? Artie


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## 4DThinker (Feb 16, 2014)

artman60 said:


> Just an after the fact, thought from the peanut gallery-Would taking pictures of all the wiring/assembly/harnesses etc to document it in a completely working stage, be helpful? Artie


Knowing how it is supposed to look is what let me spot the problem.... once I bothered to kneel down and peek under the side rails for the Y switches. In the history of the 2 Probotix CNCs in our shop those Y limit switches had never been a problem before. I had no reason to imagine that one might have been re-wired wrongly. Yet that is exactly what had happened... over a weekend when no one should have been using the CNCs. 

I'll know better next time, but hopefully all new-building work is done now and there won't be a next time. I suspect no other Probotix CNC has suffered the odd problems mine have. Mine live in a college where for the last 2 years they've been moved 4 times. They've gone from a classroom shop under my oversight to a larger all-college shop where potentially any student/faculty might use them without going through me.

4D


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## artman60 (Nov 22, 2015)

4DThinker said:


> Knowing how it is supposed to look is what let me spot the problem.... once I bothered to kneel down and peek under the side rails for the Y switches. In the history of the 2 Probotix CNCs in our shop those Y limit switches had never been a problem before. I had no reason to imagine that one might have been re-wired wrongly. Yet that is exactly what had happened... over a weekend when no one should have been using the CNCs.
> 
> I'll know better next time, but hopefully all new-building work is done now and there won't be a next time. I suspect no other Probotix CNC has suffered the odd problems mine have. Mine live in a college where for the last 2 years they've been moved 4 times. They've gone from a classroom shop under my oversight to a larger all-college shop where potentially any student/faculty might use them without going through me.
> 
> 4D


That is the reason I’ve come to pick Probotix as my future cnc. They stand up to all the different students, learning how to use a cnc machine. I’l probably make my share of mistakes, but i’ll be the only student making them on my machine. Now I gotta just find a way to come up with the funds for one.


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## beltramidave (Jan 6, 2016)

Interesting. Glad you finally got it figured out. I had been following your journey, but didn't have any suggestions for you (that you hadn't already tried). I agree that the Y limit switches are very prone for accidental issues. I just had issues last week with those on one of the machines I oversee...

Dave


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## 4DThinker (Feb 16, 2014)

Figured out, lubed up, and back to use today. Very nice to have both of our Probotix CNCs working as today both were being used to cut parts for student projects. Between now and the end of the semester the dedicated room they are in will be very busy/dusty/noisy/productive. 

4D


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## 4DThinker (Feb 16, 2014)

One thing this episode reminds me is that over the years I've been using the Nebula it has always suffered from limit switch errors/warnings when we've tried aggressive cuts in dense hardwoods with it. Vibration bounces open the switches. Probotix has come up with a "soft limits" option in their configurator that should stop the switches from stopping a cut. That doesn't eliminate the vibration, but they are also working on that problem. They have recently been showing (on facebook) photos of a new 60mm x 60mm gantry beam that is thicker walled and considerable stiffer than the current 30mm x 60mm beam they use. I don't know if/when this will become the standard beam on all new Nebulas or Asteroids (or all their CNCs) but they imply you can get the taller beam by request on any new CNC you order from them. 

4D


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## honesttjohn (Feb 17, 2015)

4D

Will that also give a little more Z axis height??


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## 4DThinker (Feb 16, 2014)

honesttjohn said:


> 4D
> 
> Will that also give a little more Z axis height??


The new beam alone doesn't add more Z height, but they also have taller side brackets that DO lift the gantry up for more Z height. 

4D


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## SteveMI (May 29, 2011)

4DThinker said:


> One thing this episode reminds me is that over the years I've been using the Nebula it has always suffered from limit switch errors/warnings when we've tried aggressive cuts in dense hardwoods with it. Vibration bounces open the switches. Probotix has come up with a "soft limits" option in their configurator that should stop the switches from stopping a cut. That doesn't eliminate the vibration, but they are also working on that problem.


I have read about increasing the voltage levels for limit switches to eliminate false openings. 

Steve.


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## 4DThinker (Feb 16, 2014)

The spring/flex in the switch parts seems to fatigue over time, meaning they become easier and easier to "bounce" open the older they are. I can't see any way more voltage would change the metal to stiffen it/slow down this fatigue. Of course more heat and some solder could close them permanently, but that would defeat their purpose.  I suppose some increased voltage might arc over a small gap though. 

There are other types of proximity switches, but I'll guess they would be too expensive in the numbers needed for each CNC axis.
Their soft limits option uses the switches only to find "home" where it looks up the axis extents to keep the head contained from there on. The axis extents can be found and edited in the nebula.ini file (or whatever name is used for your configuration). I change mine to reflect the actual distances my head can move in X and Y directions. It is slightly more than the default setup permits. 

4D


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## beltramidave (Jan 6, 2016)

Each axis limit switch has a debounce variable in the HAL file. This is mainly used, I think, for signal interference. Could possibly increase the setting a little and see if it helps issues caused from vibration.

# debounce the y-axis switches and connect them to signals
net switches-y1-raw	<= parport.0.pin-11-in
net switches-y1-raw => debounce.0.0.in 
net switches-y1 <= debounce.0.0.out
net switches-y2-raw <= parport.0.pin-12-in
net switches-y2-raw => debounce.0.1.in 
net switches-y2 <= debounce.0.1.out
setp debounce.0.delay 10

Another option possibly would be to remount one limit switch on each end of the bed and put the switch target on the bottom of the gantry (where switches are now). This would require some additional wiring, though.

Without much current running through those switches, it doesn't take much to open the contacts.

Just some thoughts...

Dave


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## 4DThinker (Feb 16, 2014)

Your idea is appreciated, Dave. At the moment the "soft limits" option in their configurator has solved the switch problem for now. We had devolved to using a jumper to bypass the X switches after homing the machine at one time in its history. Soft limits does essentially the same thing. 

The Z switch is the one I've had to replace the most often though. My students tended to bring the router up until smashing it before jogging the head around. I'd find the switch's internal bar/lever bent after a while. 

4D


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## beltramidave (Jan 6, 2016)

The Z limit is a tough one to access too..

The soft limit is a nice idea, but if you were to lose steps because something bound up or whatever, the PC is going to keep counting and eventually you will crash because your limits will not be there to protect you from a hard stop. Hopefully though, someone will figure it out and stop it before that happens...


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## 4DThinker (Feb 16, 2014)

So far the I've never seen any of the 3 Probotix CNCs (one my own) I oversee loose steps. When limit switches are active hitting one stops the machine (without losing track of where it is) before more damage can be done. The CNC Sharks (one mine and one in the same room as the 2 probotix CNCs) don't have limit switches and losing steps (by bumping into a hard limit during a cut) is a danger we've encountered more than once. 

Yes, a coupler could come loose. That hasn't happened yet. The steppers probotix uses are very reliable and positioning is very accurate and repeatable. I suspect I'll be buying another one for the college before I retire. One with taller gantry sides and the new 60x60 gantry beam. We'll retire the old Shark then as we only keep it to do taller 3D projects that won't fit under the meteor/nebula gantry. 

4D


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## beltramidave (Jan 6, 2016)

Yep, well aware of the capabilities of the Probotix machines as I oversee 1- Comet, 2- Meteors and 3- Asteroids as well as using their controllers, PC and motors to build a couple of XY positioners and my first DIY machine. Great product with awesome service!! Haven't seen the 60x60 gantry yet, (I don't do FB).

Was real close to buying an Asteroid for myself, until I saw the 4x4 FLA Saturn. Got that instead...

Dave


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## 4DThinker (Feb 16, 2014)

I simply wouldn't have room for a 4' x 4' CNC in my personal shop, and where I work they now have a 5 x 12 multicam than handles all the large sheet work. Our small CNCs seem perfect for all the quick and dirty furniture parts we encounter. The 4' length of both is rarely used but gives us useful sections when I've split the area into 2 or three different work areas (flat, vertical/angled, and rotary on our Nebula). My personal meteor is on taller legs than I've got the college CNcs on. Came in handy yesterday when I could cut some end-grain joinery on parts that were too long to fit under the school's CNCs. 

I have figured out a way to cut on the ends of even longer parts, but that takes re-mounting the router to a horizontal position. Not worth doing until someone wants to make a tiny house using all CNC-cut joinery on the 2x framing. 

That will be a whole new adventure. 

4D


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## beltramidave (Jan 6, 2016)

I envy you and your joinery talents. I have been trying to master dovetail joints (cut vertically) the last few days, without much success. Think I have watched every video ever made, but can't seem to get it right. Have tried Vectric's Dovetail gadget, but just don't like the overcut corners.

Any advice or files that you care to share would be appreciated. I mainly use VCarve Pro V9, but have AutoCad as well. Want to make some drawers for a dresser. Coming from working in a cabinet shop (elect. maint.) and seeing how easy it is for them with all their specialized machinery makes it even more frustrating that I can't accomplish it on my own.

Dave


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## 4DThinker (Feb 16, 2014)

Dovetail joints are one of the most challenging I encounter as even Aspire can't render what a dovetail bit cuts. 

There are half blind and through dovetails, as well as french dovetail slots and tapered french dovetail slots. I occasionally do half blind mitered dovetails too. I've made a few samples of ramping dovetail joints between boards meeting at a sharp angle. I always start with a vertical section view of the bit I'll be using to show me how wide it cuts both at the bottom and at the top when it passes through wood at the depth I've set it to. What I do next depends on the type of joint I'm making. 

One half of a through dovetail joint can be cut with a straight end mill. Both halves are cut with the boards clamped vertically. 
Both halves of half blind dovetails are done with the same dovetail bit. One half is cut with the board clamped vertically and the other half with the board laying flat.
The french dovetail slot or tapered slot is cut on boards laying flat, while the male part is cut one the end/edge of a board clamped vertically.
Doing half blind mitered dovetails both halves are clamped at 45 degrees and are done with the same dovetail bit. 
For ramping dovetails one half is clamped at the angle between the 2 boards. The other half is clamped at half (or is it double?) that angle. 

Generally I'm keeping track of both the bottom width and at-depth width when laying out a vector path for the bit to follow centered ON the line. I often realize I've made a mistake and how to fix it before saving the toolpaths to cut the joint out with. When my sample cut doesn't fit tight it usually means my dovetail bit wasn't exactly the width or angle it claimed to be. 

4D


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## beltramidave (Jan 6, 2016)

Thanks 4D for the info. I am mainly interested in the thru and blind dovetails. Some of my issues are that I am using a bit that I had laying around and am unsure of the angle, think it is either 14 or 15 degree, 1/2" dia. I was also experimenting using some 1/2" plywood which seemed to tear out badly. My last test was in some poplar, which did cut much better.

GWizard told me I should be running my spindle at 8k or less with a feedrate of 129ipm. Does this seem right? I tried it that way and also up to 12k @ 60ipm. What are your recommended feeds and speeds.

I think I am on the same track of toolpathing as you described, so I will keep plugging away. Thanks for your help.
Sorry for hijacking your thread!


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## 4DThinker (Feb 16, 2014)

Unless I remove the center of the dovetail cuts with a straight end mill I keep my feed speed under 60ipm. Larger dovetail bits I may slow down my router spin rate to 12k or so. We just use routers with a variable speed dial 1-5 or 1-6 so I'll set them on 3 or 4 for larger diameter bits. 

I will only use plywood for the flat cut of half blind dovetails. I never use plywood for any vertically clamped finger or dovetail cuts as (you've discovered) it will tear out too easily. 

4D


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## 4DThinker (Feb 16, 2014)

BTW, you don't have to be a facebook member to see the photos Probotix has posted.

https://www.facebook.com/probotix/p...971063415323/1540079426037806/?type=3&theater

Just click on "not now" when asked to sign up or log in.


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## 4DThinker (Feb 16, 2014)

Speaking of joinery, I came up with a sample I'm calling a tapered tenon array. The goal was to make a joint with considerable holding friction when it was together, but was also easy to tap apart. Thus the tapered tenons. I may regret showing it to the students as it is time consuming to cut, and takes careful vector layout to end up with a good fitting joint.

Our 4th year students have to design and make small furniture projects that can come apart to fit into a UPS suitcase box. The tapered tenons are an experiment. Wood may compress and shrink/swell to make a good fit seasonal. The students can glue the joint together once they've proven it doesn't need to be glued. Many are foreign exchange students who will keep the project in that UPS box to ship it home. 

4D


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## BalloonEngineer (Mar 27, 2009)

4DThinker said:


> Speaking of joinery, I came up with a sample I'm calling a tapered tenon array. The goal was to make a joint with considerable holding friction when it was together, but was also easy to tap apart. Thus the tapered tenons. I may regret showing it to the students as it is time consuming to cut, and takes careful vector layout to end up with a good fitting joint.


We’re getting a little afield from the original topic here, But this is a similar concept developed by that paragon of fine woodworking, Ikea: :wink:

How Ikea's New Joinery is Advancing Their Design - Core77

The CNC enables new concepts, and I appreciate those like @4DThinker who are willing to share their ideas.


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## 4DThinker (Feb 16, 2014)

I've been aware of what Ikea is doing since it was first published. I like their table design with the joint and appreciate that their prototype shop has leeway to experiment. Of course they can afford to have custom cutters made for production of that joint while our college budget keeps getting cut and even called back each year. Tuition keeps rising to compensate and administration wonders why enrollment is going down. 

Since we added CNCs to our fine furniture fabrication lab (on my recommendation) I've been able to solve many joinery challenges that would have led to "Go back to the drawing board" advice before.

4D


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## 4DThinker (Feb 16, 2014)

Alas, the Fall 2017 semester has ended. The rotary axis on our Nebula was key to the success of a few student projects. Having a talented student employee handle many of the CNC job requests did ease up on my personal CNC work load, but didn't come close to eliminating it. A quick check of the files I have on the USB drive I carry around at all times has 54 unique Aspire files and 3x that many toolpath files with a fall 2017 date stamp on them. This is after I filter the CNC requests and turn many students away as their requests can often be done more easily/efficiently on other machines. 

I've come up with a good way to connect leg parts that have to appear as if they pass through a table top or shelf, but it is a challenge to create toolpaths for when the leg parts are tapered and pass through the shelf at a compound angle. Drafting techniques I learned several decades ago in high school are how I solve these CNC joinery challenges. It appears current architectural college students aren't being taught drafting as I learned it though. CAD yes, but not problem solving using drafting techniques.

We also have concluded our Nebula is not as accurate as our Meteor is. When both halves of a joint are cut on the Meteor we can get repeatable precise fits. When the same files are used to cut one half on the Meteor and the other half on the Nebula the fit is less predictable. 

I've put in a request to upgrade both CNCs to air cooled spindles, and add a new Comet to replace an old CNC-Shark. The Comet we want would have the new taller gantry sides and larger gantry beam from Probotix. That should make it a machine capable of cutting taller 3D furniture parts, and perhaps stiff enough to cut aluminum parts. 

4D


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## honesttjohn (Feb 17, 2015)

That air cooled spindle would be a godsend for you.

If (I mean when the accounting dept approves my request) I get another machine I would probably go with a Meteor. That would do everything I've done so far.

Keep pounding on them!!!


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## 4DThinker (Feb 16, 2014)

I'm also considering buying one of the Probotix V90-MK2 CNCs for myself. Also with the taller gantry sides and stiffer beam. I'm contemplating how to mount it on a frame that will let me change how far it is off the floor. We occasionally get requests for using the CNC to cut tenons on the end of lengthy frame parts. My Meteor's bed is 42" above the floor. A comfortable working height for myself. The college Probotix CNC beds are 36" above the floor. Sofa frames and bed frames come up occasionally. I even had a request for cutting tenons on the ends of a 48" long bench plank this semester. For this type of work a large bed isn't required. Just plenty of room under the bed. Scissor jack? Heavy duty adjustable shelf brackets? Probably not tunable magnetic repulsion.  

4D


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## MT Stringer (Aug 15, 2012)

I didn't look up the specs. How big is the frame for the V90?

The adjustable height work table/dual router work center I built is based on a RV scissor jack from Harbor Freight. I bought that model because it had the bolt head welded on the jack so a drill with a socket can easily operate it.

Maybe you can make something similar that would fit your frame. Might take two jacks so you can easily level the frame from each end.

Seems like even in the simplest form, you could jack it up (or down) and pin bolts through predrilled holes. That should be pretty easy to do.

Here is the link to my project.

http://www.routerforums.com/show-n-tell/46562-adjustable-height-workstation-router-table-more.html

Hope this helps and gives you some inspiration.
Mike


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## 4DThinker (Feb 16, 2014)

MT Stringer said:


> I didn't look up the specs. How big is the frame for the V90?
> Mike


The V90-MK2 is 26.36" wide x 22.28" deep. Very nearly .5x the area of their Comet CNC. Add the length of a stepper motor to each direction: http://www.probotix.com/wiki/images/7/76/Machine_footprints.jpg

Your table project looks great! My goal for the MK2 project is to leave the area under the bed frame clear though. That is where projects will get clamped/hung. I'll replace the whole bed area with a custom version of my adjustable angle clamping fixture.

4D


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## 4DThinker (Feb 16, 2014)

It appears the Delrin lead rod nut on our X axis (gantry) may be due for replacement. The Y axis nuts may be next. Probotix describes them: The Delrin anti-backlash nuts are designed to wear and may need to be replaced periodically,...

The Nebula was the most used CNC for the 2 years we were in temporary shop spaces. The nuts may be where the precision of our cuts is getting reduced. It looks like the stepper(s) will have to be unscrewed from their mounting plates, couplers loosened, and stop rings loosened from the lead rods to allow the nuts to spin off the end of the threaded rod. The nut mounting block with the limit switches attached may have to be disassembled so that the steppers don't have to have to be cut free to get out of the way. 

A puzzle I'm not looking forward to.

4D


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