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smoothieware-powered 6040 CNC Mill

Run a 6040 engraver/mill with an SKR controller
running smoothieware, and get rid of the clunky old Windows PC and parallel port.

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I bought a used Chinese 6040 CNC mill off Craigslist. Included with the purchase was the 1500W water-cooled spindle and VFD, parallel port control box, outdated computer, 15" flat panel VGA display, and a Mach3 license.

I decided to get rid of the PC and replace the parallel port interface with USB so I could run everything from a laptop. I started off with the idea of using a Mega2560 and GRBL. Recently discovered the SKR controller which runs smoothieware and decided to use that instead.

I also plan to add limit switches, touchoff sensor, VFD speed control and readback, spindle coolant pump control, and cutting fluid mister control.

I'll be updating the project logs as the work progresses.

Maintaining Windows and a closed source app on an obsolete computer was a non-starter for me. I loaded LinuxCNC on a Core 2 Quad box, and was able to verify that everything worked.

I wanted to be able to control the system from a laptop USB port. I chose GRBL on a Mega2560. I looked at possibly using a RAMPS shield or something similar. I plan to drive the stepper control board inputs directly from the Mega, so I don't need motor drive circuits. For the end stops, VFD, pumps, etc, I'm going to build my own interfaces as required.

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  • Update for December 2019

    Darryl N12/24/2019 at 16:37 0 comments

    Wow, another year come and gone with no visible activity.  Honest, this project is not dead, and I know that to be so,  because it continues to take up a huge chunk of bench space!

    • I picked up a low cost Smoothieboard work-alike which is a much better solution than a Mega and a screw terminal shield.  32 Bit ARM cortex-M3 LPC1768. MOSFETs. RAMPS sockets. USB and Ethernet.  SD Card. GUI with touch panel.  
    • Baby step 1: wire up the steppers and limit switches, and get the axes moving. Worry about spindle, coolant, VFD, etc later.
      .  

  • Status update for December 2018

    Darryl N12/22/2018 at 03:11 0 comments

    Wow, no updates in over a year, that sucks.  Sorry! 

    After being MIA from HaD for most of this year, I would like to announce "no, this project is not dead".

    Long story short: life and other projects intervened. One project in particular paid quite handsomely, and the gig lasted for several months, but it took 100% of my time and energy.  

    Anyway,  here's the deal on the 6040 CNC project....

    I recently got a mini-mill, a mini-lathe, metal bandsaw, and tooling, so I now have in-house manual machining capability. I definitely intend to continue with the 6040 CNC rebuild, and the new gear might be helpful, but setting up and learning the machines is highest priority right now, and there are many other projects waiting for attention, so the next update on this project could still be a ways off.  

    "Never, never, never give up."  - Winston Churchill

    "It does not matter how slowly you go, as long as you do not stop." - Confucius

  • Status Update

    Darryl N01/19/2018 at 19:44 0 comments

    It's been quite a while since the last update. Sorry about that, but life intervened and I had to deal. I'm hoping to get back to work on this project within the next month or so, so stay tuned!

  • Status

    Darryl N08/03/2017 at 21:21 0 comments

    Just a quick log entry to say 'no progress', sorry!

    Spent last week attending Longmont Startup Week. Did lots of networking for my engineering services company, http://bitheadtech.com.

    https://longmont.startupweek.co/

    LSW17 brings together entrepreneurs, wanna-preneurs, intrapreneurs, creatives, techies, inventors, business owners, and investors of all ages to connect and inspire.  Over the course of five days, multiple networking events, panels, fireside chats, and guest speakers will be hosted at unique venues throughout Longmont, showcasing Longmont’s entrepreneurs in advanced technology, I.T., bioscience, creative arts, culinary, and more.  All events are FREE to attend and provide outstanding learning and networking opportunities.

  • Ditching the Blue Box

    Darryl N07/23/2017 at 06:20 0 comments

    I tried to work out how to fit all the components inside the blue box, but decided that it was just too crowded. Instead, I am going to mount everything on a 24" x 12" wood backboard.   

    Also will make two aluminum panels, one for LED status indicators, the other for machine cable connections. The status panel will mount vertically at the right side of the backboard, the connector panel will sit horizontally along the bottom, with the cables exiting downward.  

    I'm using FreeCAD to create 3D parts and the backboard and panel layouts. I will post everything in the files section. 

  • Replacing the Stepper Board

    Darryl N07/08/2017 at 18:53 0 comments

    I decided to remove the DB25 connector on the stepper board. The rationale was that this would make it easier to reverse engineer the internal parallel interface circuitry, and the DB25 connector wouldn't be needed anyway. I cut the DB25 off more or less flush using an oscillating multi tool, and desoldered the pin stubs. Easy peasy, no muss no fuss.

    Then I grabbed the meter and started beeping out traces. I didn't get very far before I realized that this was going to take a fair amount of time, because there is a ton of discrete SMT parts on the bottom side. Also, there is a good chance of errors creeping in, because, hey, I'm only human.

    This led me to wondering what happens if this board fails. I'd have to buy an equivalent replacement, and if it isn't identical (very likely), repeat the reversing effort, at least in part, and redo the patch wiring. During that down time, I wouldn't have the use of the machine, and that would make me sad. :-(

    So I took a break from reversing and did some googling on this particular stepper board (JP-3163B). Turns out there are a lot of folks out there who have had problems with it missing steps or just plain dying an early death.

    I also noted that single-axis "TB6600" controllers are only $15, and available from multiple sources. So, rather than waste time reversing an obsolete board with no documentation, no drop-in replacement, and possible performance and reliability issues, I decided to plunk down $45 and replace the stepper board with three single axis controllers. The new controllers are scheduled to arrive Monday July 10.

    WARNING: A lot of these lower-cost "TB6600" stepper controllers don't actually have a Toshiba TB6600 chip, they have a TB67S109 instead, which is not as powerful.

    From the Toshiba datasheets:

    abs max motor currentrecommend operating currentclock input freq
    TB66005.0A4.0A200KHz
    TB67S1094.5A3.0A100KHz


    My motors are 3A, and grbl max rate is only around 30Khz, so these should work fine.

    I disassembled one of the units to have a look - Toshiba TB67S109 QFN package mounted on bottom, thermally coupled to heatsink with a chunk of aluminum. No grease between the chunk and the heat sink, so I'm going to add some.

  • Inspecting the Stepper Board

    Darryl N07/07/2017 at 03:29 0 comments

    I pulled the stepper control board out of the blue box to clean, inspect, and identify suitable PCB locations to patch in the Mega2560. There was a small amount of caked-on sawdust, and the heat sink compound was dried up.

    The back side of the stepper board is rather unremarkable. Note the snubber diodes on the left side, directly underneath the motor connectors. Good PCB layout choice.

    I noticed that the corner of the stepper board was "trimmed" to fit the inside corner of the box.

    Also, the heat sink was "modified" to clear the plastic foot screwed into the underside.

    Note, the driver chips are mounted to the heat sink with a triangle head screw, so you'll need a driver tip that looks like the following. I have a driver bit mega-kit that included one Alternately, you could remove with needle nose vise grips, and use Philips head screws.

  • Z Limit Optical Detectors Installed

    Darryl N07/07/2017 at 00:28 0 comments

    Here's a video of the Z axis lower limit optical detector in operation. Upper is similar. On the lower, I had to swap the 3-pin connector to the outside, else the router base plate would hit it on the way down.

    I made the interrupters from 3/4 x 3/4 x 0.06 aluminum angle with some careful bandsawing (14 TPI blade) and hand filing. Yeah, the slot is crooked, sorry. I center punched, but the wimpy carbon steel 1/8" bit still walked around on me. Ugly but fully functional. I really need to order some machinist-quality drills, all I've got is Home Depot Ryobi junk.

    Z axis optical interrupter.

    Locating the interrupter for the Z axis upper limit detector.

    Some commentary on the taps.... The M3 x 0.5 taps arrived late yesterday. Matching set of 3 - plug, taper, and bottom. Comments on http://www.hobby-machinist.com/threads/irwin-taps.55387/ suggest that Irwin quality isn't all that hot, but the package says "Made in USA" and these didn't break off under normal careful usage, unlike the cheapo $40 Chinese set.

    Also got a pretty nice ratcheting tap wrench with knurled grips, since the wrench in the cheapo tap set wouldn't fully tighten on the smaller diameter taps. :-( However, because you have to go in and out when cutting, the ratchet feature is more annoying than useful. Might be convenient when backing the tap out.

  • Frustration and Delay

    Darryl N07/02/2017 at 19:30 0 comments

    A couple of days ago I started installing the limit switches. I went with electromechanical micro switches with roller actuators for the X and Y, two per axis, and optical interrupter detectors on the Z axis, again 2 per axis.

    I got the two X axis switches installed no problems - drilled and tapped 4 M3 x 0.5 holes.

    Alas, tragedy struck on the lower Z axis plate - the tap broke off.

    ARRGGHH!

    The tip is embedded about 10mm deep, with a small <1mm shard sticking out above the surface. I tried spinning it with a vibrating engraver tool, but as the pic shows, all that did was bugger up the aluminum. So instead of fussing with removing the broken tip, I just used one screw and some 3M VHB double sided adhesive foam. No mechanical force, so it should be fine.

    Problem is, I can't continue because I don't have another 3mm tap. It was part of a cheap tap/die set. Lesson learned: spend the money for high quality individual taps. I ordered some good ones online, should arrive this coming Wednesday July 5.

    Meanwhile, I'm going to work on patching the Mega2560 into the stepper board and hopefully get the motors moving under GRBL.

  • Got Parts

    Darryl N06/28/2017 at 22:30 0 comments

    Elegoo Mega2560 R3, DC-DC converter modules (create 5V supply from 24V), variety of circular aviation style connectors, 20x4 backlit LCD, 22mm LED indicators, USB panel mount extender cable, 12V air solenoid, optical limit sensors, microswitches, 0.187 tab terminals for the microswitches, and a screw terminal shield for the Mega2560. I <3 Amazon prime.

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Discussions

agp.cooper wrote 06/30/2017 at 04:11 point

Hi Darrryn,

Here is mine:


Yes Toshiba TB6560AHC. I don't have the datasheets that I collected to workout the switch settings but here is schematic that looks very familiar:


But your board is a much latter version (but the switch setting should be the same!).

Many people have had problems with breaks in the supplied cables. Until you understand how the fault plays out you will think the stepper drivers have an intermittent fault. So be careful. This is a very common problem from my research.

How does it play out! Two hours into a job and the machine loses it! Later it is just erratic.

---

Pushing the machine by hand does not really tell you about how hard you can push the machine. I think I got more than 1 or 2 mm error pushing my machine hard (as hard as the spindle/steppers would take).

Backlash adjustments don't work well here as the error depends how hard you push the machine. 

In the end I had to plan for conventional and climb cuts to compensate depending on whether if is a hole or a cutout.

And you may want to plan for a finishing cut as well.

When cutting aluminium use a one flute bit or it may/will gum up.

It really helps to use a cutting fluid (canola oil is fine) on metal.

Also cut very shallow until you discover the limits of you machine even for wood.

I have cut hardened steel by using canola and very shallow passes, but not recommended

Much of the recommendations on the Internet are for professional machines!

---

On my machine I cut a rectangle in the bed to show the cutting limits and a second rectangle 10 mm inside that. It makes it easier to align the work piece.

---

Did I tell you that the bed was not actually level!

AlanX 

  Are you sure? yes | no

Darryl N wrote 06/28/2017 at 18:38 point

Interesting, thanks for the comment. 

The frame on this unit is beastly - frame with motors weighs about 60 lbs. Uprights are 14mm thick aluminum plate.  NEMA 23 57mm 3A steppers. 14.3 mm lead screws. Motor cables are 4C AWG 18 with PVC jacket.  Spindle cable is 4C AWG 16 with jacket (IEC 60227 IEC 53 RVV). Stepper drivers are Toshiba TB6560AHC, bolted to a 120 x 123 x 17 mm thick finned aluminum heat sink (about the same size as the stepper board).  The heat sink is screwd to the box as well.  

Is your unit the same as this? 

TB6560 datasheet:

http://www.mouser.com/ds/2/408/TB6560AHQ_datasheet_en_20141001-771503.pdf

I've used real machine tools with sub-mil tolerances, and I know not to expect too much from this.  I measured the spindle end play at about 0.15 mm (6 mil) under moderate hand pressure (1-2kg). My main usage case is routing 2mm thick aluminum instrument panels (slowly), plus the occasional odd low-precision metal or ABS part I might need to fab.

Here's a good blog article on cutting aluminum on one of these machines.

http://blog.cnccookbook.com/2012/03/27/10-tips-for-cnc-router-aluminum-cutting-success/

  Are you sure? yes | no

agp.cooper wrote 06/27/2017 at 15:45 point

I have one of these things but I run a low power (80W) air-cooled spindle.

Most of the cheap laser printers are Nano-Grbl based. That is pretty straight forward swap out.

---

For my machine I run CNC-USB that drives the parallel port.

The frame is not up to driving it hard. Take it easy or nothing will be true (or even close!).

The cabling is crap and I had to replace mine (in my case it drove the spindle into the bed!).

The steeper drivers are under-heat sinked so driving hard and long in hot conditions will also be a problem. I downed the power setting of the drivers boards and reduced the 1/16 micro stepping (what is the point on a machine like this?) to 1/4 step.

The power supply to the spindle motor is "live" so make sure you unplug the box before doing anything. My soldering iron got a big shock (and the RCD) even though the box switches were off!

---

I don't recall the stepper motor power requirements but I am tempted to drop the box and use a DRV8825 CNC shield for the Nano. The only reason I have not done this was I don't have a spindle power supply and speed controller (really the spindle is off or flat out!).

---

Any best of luck, AlanX 

  Are you sure? yes | no

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