Liberty4Ever's 2X4 CNC Router Build Log

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Liberty4Ever's 2X4 CNC Router Build Log

Postby Liberty4Ever » Wed Jan 02, 2013 5:45 am

It's crazy, but I started a CNC lathe conversion, a CNC milling machine conversion, a CNC laser build, a couple of 3D Ord Bots, and now I'm building a CNC router. I'm either going to get an award for the most concurrent projects, or Bart is going to kick me off BuildLog.net for starting too many projects and not finishing them. My excuse for starting projects and not finishing them is that my online business was very busy this year. I had a surplus of revenue and didn't want to pay taxes on it, so I bought the equipment to expand my business so I'd have 2012 deductions, even though my hectic one man business allowed me little build time.

I wanted to design and build my own 2X4 CNC router with an integrated table and dust collection system, and make it beefy enough that I could do some semi-serious machining in aluminum... sort of a cross between a gantry router and a small vertical machining center... but given my abundance of unfinished projects and my lack of time, I decided to BUY a very beefy 2X4 CNC router kit.

The kit manufacturer also sells on eBay (user name: signal-seeker). He doesn't have much of a website, so here's his current eBay ad, and some pictures I'll repost for later when the eBay ad is gone.

http://www.ebay.com/itm/130820766902

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As you can see, this CNC router kit uses Chinese linear rail and Chinese ball screws, and the rest of the design is aluminum. The materials certainly look beefy, and the design looks fairly beefy too. Probably not as ridiculously beefy as what I'd design, but pretty darn good. It's definitely not the cheapest CNC router kit on the market. Far from it. In fact, it's one of the more expensive for its size, but I can say that it's one of the cheapest to use ball screws and linear rail and the other nice features. This is the manufacturer's "commercial" kit. The same manufacturer also sells a kit that uses linear rod and Acme screws that still looks quite nice. I opted for the beefier commercial version, because I plan to run production on it, and I expect my brother will use it a lot for his new business venture too. Of course, I'm sure that most people who buy a CNC router have some sort of serious justification, whether it works out that way or not.

I'll be picking up the CNC router kit on Saturday.

I bought the CNC router kit without the motors and motor drive and I/O electronics for $2500, which is $200 less than the complete kit in the eBay auction. I plan on using (you guessed it) bigger motors. I also had my own preference in motor drivers that I accommodated at the same time. The stock stepper motors were 270 ounce inch NEMA 23 motors. I purchased a complete three axis stepper motor motion control kit with 1090 ounce inch NEMA 34 motors.

http://www.ebay.com/itm/140894283015

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I'll need to drill and tap my own mounting holes for the larger motors. I'll laser cut a drill guide with four NEMA 23 clearance holes, and concentric NEMA 34 tap hole drill guides. I'll make it with two sets of NEMA 34 mounting holes, 45 degrees apart, in case I need to mount a motor at an angle because of clearance issues. I hope the larger motors fit the router table without much grief. That was a bit of a leap of faith.

The motion control kit was purchased on 29DEC12 and should be here in about a week or so. There's no evidence that it's shipped yet.

I went a bit nuts and bought a Chinese 3 HP water cooled spindle.

http://www.ebay.com/itm/200773029466

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I'll never use that much power on a gantry router. The machine is just not stiff enough. I probably should have bought the 1 HP or 2 HP version and saved some weight. The added mass is just more to accelerate when moving the gantry. My thinking was to get a 3 HP sealed water cooled spindle, use maybe 1/2 HP, and it should last a good long time. After receiving the spindle, I had other thoughts. If I was doing it over, I'd probably get a 2 HP spindle. I might make some slightly aggressive cuts for roughing cuts, where a little bit of deflection could be tolerated as long as it didn't start to chatter as that tends to shatter carbide tooling. I'd make lighter finish cuts where I needed to maintain precision. As it is, I expect to layout my jobs so the heavier cuts are in the direction of the longer axis, which I'm calling the X axis. Based on the design, I expect the machine to be more rigid in the X axis, and less rigid cutting side-to-side which would tend to distort the gantry from a rectangle into a parallelogram. If that seems like a problem, I'll probably mount an aluminum plate across the back of the gantry to stiffen it against such bending. If I did, the Y axis may be the stiffer axis, given that the X axis stiffness is riding on one bearing block on each side of the gantry. Too many variables to guess. I'll have to wait and see after it's built.

Even though I'm convinced that the spindle motor is way too big, even for a beefy CNC gantry router, I'm very impressed with the spindle motor's build quality. I haven't fired it up yet, but spinning the spindle by hand was a nearly sexual experience. I've never felt such a smooth spinning armature on a motor of that size. The eBay auction mentioned some fancy German bearings, and I believe it. It has a very high precision feel. It was like a 3 HP dental drill. Expensive servo motors don't feel nearly this nice, and the typical router from Dewalt, Porter-Cable, Bosch, et al, feels like it has gravel for bearings by comparison.

The ER20 collet nut was spot drilled in three places where it was dynamically balanced at the factory. I paid quite a bit extra to get some precision ER20 collets with .0002" average total indicated runout. I bought regular non-precision ER20 collets for my milling machine, but they won't be spinning at 24000 RPM like the spindle on the CNC router. At that angular velocity, a lot less runout can result in significant centripetal forces leading to vibration, and I didn't want to accelerate the spindle motor bearing wear or accelerate the wear on carbide cutting surfaces from chatter or vibration. I'm a bit suspicious of the .0002" AVERAGE TIR. Average isn't a kosher way to measure TIR, in my opinion. I think it should be measured as maximum runout, but, whatever. The US made precision ER20 collets were sold in sets for over $200, and sometimes WAY more. The Chinese precision collets looked good and inexpensive. We'll see.

http://www.ebay.com/itm/251198551519

I've also bought some carbide tooling (Chinese and US, to compare), a 5/24V DC power supply to power the control electronics and logic on the machine side of the optoisolators, etc. I have lots of stuff left over from previous builds, where I bought extra E-stop switches, LCD temperature displays (for the spindle coolant temperature), a small coolant pump, solid state relays, prox switches, etc. I still have some minor stuff to buy, mostly some incidental electronics and the support table/frame and dust collection enclosure. I'll wait to design that, after the CNC router is running on saw horses, but I've already bought most of this project.

Here's the Chinese 1/8" carbide ball end mills I bought.

http://www.ebay.com/itm/140444566452

Oh yeah. In my mad dash to purchase as many expense deductible items as possible before the end of the year, I purchased a digitizing probe.

http://deepgroove1.com/probe/probe.htm

I've been reading up on how to do digital probing. Apparently, there's a wizard to do that in Mach 3. I'll be using LinuxCNC, and it's done with either gridprobe or smartprobe, which are just some reasonably simple G code. They write XYZ point cloud coordinate data to a file that can then be input to several different programs to create a surface, which can then be output as an STL, or with information added about the cutting tool, G code can be generated to cut the copied surface on the CNC router. A Linux and LinuxCNC compatible solution for generating G code from DXF, STL, etc. is PyCAM.

http://sourceforge.net/apps/mediawiki/pycam/index.php?title=Features

I'll probably buy a PC and monitor on Craig's List to run LinuxCNC. $100 or less is pretty cheap for a realtime controller with a nice big graphical display.

I like the Logitech K400 wireless keyboards because they can be carried close to the work and used as a glorified wireless pendant for touching off on the workpiece and other up-close precision work.

http://www.logitech.com/en-us/product/wireless-touch-keyboard-k400

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But I also bought four of the JogIt! pendants on KickStarter, configured for LinuxCNC, and they should be shipping later this month.

http://www.kickstarter.com/projects/1651082654/jog-it-open-source-controller-pendant-for-emc2-and

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I'm always overly optimistic about my projects - ridiculously so - but I expect this CNC router to come together fairly quickly. I bought the kit for the router table, and it should assemble in a few hours. It's mostly bolt-together. The Z axis is pre-assembled. Bolt on the stepper motors, wire them to the motor controllers, wire those to their power supplies and the motion control kit is installed. Stock LinuxCNC is good about controlling these stepper motors. Run the stepconf routine, tell it the microsteps and the pitch of the ball screws, and it should be a done deal. You guys can quote this arrogance later in this build log and laugh at me when I run into the inevitable problems. Really, I don't mind.
:)

Then maybe I can finish the more complicated projects - the CNC laser, CNC milling machine and the CNC lathe.

I'll probably post a picture or two of me transporting the CNC router mechanical kit, but then it's all build posts. I think I'll take a tip from some of you other guys and lean more in the direction of a build vlog - heavy on the video, so you can see the build in greater detail with less of my wordiness to suffer through. Of course, I think listening to my voice may be worse.
Apparently, I didn't build that! :-)
Liberty4Ever
 
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Re: Liberty4Ever's 2X4 CNC Router Build Log

Postby TLHarrell » Wed Jan 02, 2013 9:58 pm

I will defintely be keeping an eye on this one, especially your further adventures with the Chinese sourced components. I am also contemplating a CNC build, but smaller, around 22"x30" primarily for computer case modding parts. While I'd probably tone down the spindle to a 1HP, the ballscrews to ACME, and the motors to +/-300 oz, I'd probably run fully supported rail for the X and Y axis. All the parts basically would be a smaller version of what you're running, so the comparison is perfect.
40w Full Spectrum Engineering 5th Gen Hobby 20"x12" w/ Rotary Engraver
South San Francisco Bay Area - Sales and Support Representative for Full Spectrum Engineering
408-47-LASER - Skype: whitelightlaser-thomas - Facebook: White Light Laser
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Re: Liberty4Ever's 2X4 CNC Router Build Log

Postby Liberty4Ever » Wed Jan 02, 2013 10:47 pm

Late in the decision making process when selecting the mechanical components for the gantry router, I did think of designing my own and sourcing the Chinese ball screws, linear rail and matching bearings from eBay. The Chinese sellers are very competitive and customer oriented. They sell linear rail by the inch ($3.50 per inch delivered, IIRC) and the bearing blocks (about $30 each), and the guys selling the ball screws will cut it to length, and do some fairly detailed lathe work on the ends to create a shaft to mount to a motor, and to make a turned down OD to fit the ID or a bearing. That's a pain to do in a home shop, because the ball screws are hardened and they need to be ground.

It wouldn't be too difficult to source those critical precision motion parts if you wanted to DIY for a full custom design. I added it up and it looked like I'd potentially save a few hundred dollars over the cost of the kit, but at this point in my life, that looked like money well spent, even though I'd have enjoyed designing my own version.

In reality, I'd have probably spent several hundred more dollars and made an even beefier version. If things go well with my other projects, and maybe the solar powered Libertymobile 3 wheeled electric vehicle I want to build :? then maybe I'll build a super CNC router next year. Maybe a 2X4 or 4X4.
Apparently, I didn't build that! :-)
Liberty4Ever
 
Posts: 274
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Location: Lexington KY

Re: Liberty4Ever's 2X4 CNC Router Build Log

Postby lasersafe1 » Thu Jan 03, 2013 3:47 pm

Yeah, having a surplus of revenue just sucks when you have to pay taxes on it... :lol: At least we aren't paying European type taxes (yet), but I suspect this will come to pay for our new socialized healthcare system and out-of-control spending.

A little off topic....
I don't know if you realize this or not, but as a one man shop, you can put aside quite a bit of moola into a simple employee pension (SEP IRA) tax deferred. I have a day job where I can only contribute up to $14,500 a year tax deferred to the 401k, but in my home business, I can have another retirement plan to which I can contribute up to 25% of my home business income tax deferred (up to $50,000). You have until April 14, 2013 to setup your SEP IRA for the 2012 tax year. This is the "business" contributing to the employees account, and it must be provided to ALL employees at the same rate in any given tax year. This is why it is such a beautiful plan when you are the only employee, or a husband and wife team. I only learned about this last year, but it allowed me to reduce my 2011 income by 20%.

Of course, if you are already retired or of retirement age, this is a moot point and you should be spending your earnings on cool "business" equipment. Did you know that coffee and donuts provided at the place of business for employees are 100% deductible? New Keurig machine is a necessity for any small office.

By the way.. back on topic. I just bought a 25" ballscrew with bearing blocks and ballnut from Ebay for $100. It is the same item I paid UGRAcnc $220 last year. It is very good quality for home cnc machines.
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Re: Liberty4Ever's 2X4 CNC Router Build Log

Postby Liberty4Ever » Thu Jan 03, 2013 3:55 pm

lasersafe1 wrote:Did you know that coffee and donuts provided at the place of business for employees are 100% deductible? New Keurig machine is a necessity for any small office.

Keep your drug paraphernalia to yourself, pal.
:)

My retirement plan - work until ten years after I'm dead and things should end up just about even. :)

Seriously, though, thanks for the retirement plan info. I'll be talking to an accountant soon, and will mention the option and get his opinion. I'll probably start buying silver and gold rather than contribute to a 401K that will be nationalized in a couple of years. And that's as far as I'll allow my kook liberty political views to infringe upon the glorious geekiness of BuildLog.net.
Apparently, I didn't build that! :-)
Liberty4Ever
 
Posts: 274
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Location: Lexington KY

Re: Liberty4Ever's 2X4 CNC Router Build Log

Postby Liberty4Ever » Mon Jan 07, 2013 7:56 am

The CNC Router Table Pickup Ordeal

On Saturday, I made the two hour trip to pick up the mechanical kit for the CNC router table. It was more of an adventure than I was expecting.

My sister was sick on Christmas, so our family had our Christmas this past Saturday. I had arranged to pick up my new CNC router kit in Wheelersburg Ohio, which is about 30 minutes from my parent's house, so I could escort them down for Christmas, about a two hour drive to Lexington Kentucky where I am, and another 90 minutes to my sister's house in Louisville. I was about halfway to my Ohio appointment when the left rear tire on my Tacoma blew out at 80 MPH. There was a 3" rip in the outer sidewall, presumably by some chunk-o-metal on the highway that I never saw. I quickly came to a stop, about 30 feet past the entrance to a rest area, so I backed it up and limped into the rest area.

It had been 10-12 years since I've had a flat. The spare was flat, but fortunately I had put the inflator into the truck last week, so I plugged it into the cigarette lighter and pumped up the spare as I tried to remove the flat.

I say "tried to", because the aluminum rim was corroded onto the steel wheel. I put the lug nuts back on, but loosened about .1" each, lowered the flat tire back onto the pavement, and rocked the pickup bed left and right in an attempt to break it loose. No go. I jacked it up and donkey kicked the outside edges of the rim. No go. I lowered it onto the ground, removed the jack, started the engine, and repeatedly popped the clutch in forward and reverse. No go. I jacked it back up, pulled a frozen 4' piece of pressure treated 2X10 out of the truck bed and used it as a wooden mallet. I repeatedly swung it in a 180 degree arc until it violently impacted the outer portion of the aluminum rim on the heavy spoke. No go. I continued beating on it until the end of that dense pressure treated 2X10 was badly splintered. No go, but when I went into full beast mode and cranked up the ultraviolence to 11, I did see a little puff of blackish brown smoke emerge. Progress! I kept beating on it, rotating the wheel 45 degrees or so, and I'd beat on it some more. Eventually, I couldn't get any more smoke, but it was still stuck. I tried the clutch popping trick some more. Nothing. I eventually discovered that I got a little more black smoke if I turned my back to the wheel, spread my legs apart, bent over, and used the 2X10 as a battering ram between my legs. I wailed on that rim for about 90 minutes and finally knocked it loose. I'm tired and sore today.

Now I'm looking at the prospect of getting a new set of tires for a truck that *might* have 10,000 more miles left in it, because of the Toyota frame corrosion manufacturing defect, as featured in my tell all website. :)

http://www.TacomaCorrosion.com

I've gotta do something, because I don't want to be stuck on the road again with a flat and the rim corroded to the wheel. The next time, I'll probably be on a steep hill, and it'll be sleeting. I guess if that happens, I'll loosen the lug nuts and do some abusive power slides to the left and right, although the flat tire had so little integrity in the sidewall that I'd have probably rolled the tire off the rim and ruined the rim.

Basically, it's new truck time. I probably shouldn't have spent all of my money on CNC parts for all of my various geeky shop projects. :-)

OTOH, maybe I'll get those shop projects working, offer a few new products for sale, and use the proceeds to buy a truck.

BTW - I think the frame corrosion is causing the unusually bad rim corrosion. Basically, I believe the rusting frame is corroding the rims. It's the opposite of screwing a block of zinc to a piece of metal to protect it from corroding (cathodic protection).



More Stepper Motor Musings

After taking a cursory glance at the CNC router table kit, I decided to get a big NEMA 23 motor to replace the Z axis NEMA 34 motor that I had already purchased. For about $60 for the 570 ounce inch NEMA 23 stepper motor, I'll gain a spare NEMA 34 stepper motor for the X or Y axis, and I'll avoid the need to make the adapter plate that I'd need to mount the NEMA 34 motor to the NEMA 23 mounting plate, which has air where the NEMA 34 mounting holes would be. I'll also lighten the load on the gantry a bit, so the X and Y axis accelerations can be a bit faster for the same force.

http://www.automationtechnologiesinc.com/products-page/nema-23/nema23-570ozin-5a-14%E2%80%9D-dual-shaft-stepper-motor-kl23h2100-35-4bm



A Single Board PC & Solid State Hard Drive For LinuxCNC

I just purchased the computer hardware from Newegg.com. I usually buy a well used PC on Craigs List to run LinuxCNC, but I decided to go a bit smaller and geekier and more expensive on the PC for the CNC Router. I'll mount the mini-ATX mobo in the electronics panel. Hopefully I won't need to actively cool the electrical panel, but I will if I need to. Unlike most of my other CNC projects, this CNC router will run in a dusty environment and I don't want a PC out in the open, sucking up sawdust.

Code: Select all
    Diablotek DA Series PSDA250 250W ATX Power Supply
    Item #: N82E16817822006
    $12.99
      
    Intel BOXD525MW Intel Atom D525@ 1.8GHz (Dual Core) BGA559 Intel NM10 Mini ITX Motherboard/CPU Combo
    Item #: N82E16813121442
    $84.99

    Kingston 2GB 204-Pin DDR3 SO-DIMM DDR3 800 Unbuffered System Specific Memory Model KVR800D3S8S6/2G
    Item #: N82E16820139220
    $12.99

    SanDisk SDSSDP-064G-G25 2.5" 64GB SATA III Internal Solid State Drive (SSD)
    Item #: N82E16820171645
    $69.99

    Subtotal:      $180.96
    Shipping:      $9.72
      
    Grand Total:   $190.68




Today's Arrivals

The three axis NEMA 34 motor kit with the three stepper motors, three motor drivers, three 350 W power supplies, and the parallel port breakout board and cable will be delivered by the FedEx truck later today.

This project should be coming together soon.

I caught myself looking at other CNC routers and kits today, and looking at spindles and stepper motors on eBay again. I have no idea why. I don't need two CNC routers. Shopping for CNC stuff may have become an addiction for me. :(
Apparently, I didn't build that! :-)
Liberty4Ever
 
Posts: 274
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Location: Lexington KY

Re: Liberty4Ever's 2X4 CNC Router Build Log

Postby Liberty4Ever » Wed Jan 09, 2013 11:50 pm

More Motor Madness

I've been busy lately, and some of that effort has been on my CNC router build. Woot.

The motion control kit arrived with the three 1090 oz in stepper motors, motor drives, three 36V @ 350 W power supplies [edit - they're 60V @ 350 W power supplies] and the optoisolated breakout board and parallel cable. It's all very nice. I knew I should have waited until having the CNC router table parts in hand before ordering the motors. I knew I'd need to do some work to mount NEMA 34 motors on the table that was made for NEMA 23 motors, but after taking a look, I decided I didn't feel like doing the work to make motor mount adapters. I took the coward's route, and ordered the biggest, baddest, beefiest NEMA 23 motors that I could find, Automation Technology part #KL23H2100-35-4BM.

http://www.automationtechnologiesinc.com/products-page/nema-23/nema23-570ozin-5a-14%E2%80%9D-dual-shaft-stepper-motor-kl23h2100-35-4bm

I ordered three of these. I'll just use them as a drop in replacement for the 1090 oz in stepper motors in the kit I bought. I'll set the current limits on the stepper motor drivers accordingly. The power supplies and stepper motor drivers are now significantly over rated for these motors, so hopefully they'll run cool and last a good long time. I might even be able to use passive cooling on the sealed electrical enclosure and not overheat the electronics. We'll see. Instead of the 1090 oz in stepper motors which would have been 4X the torque of the stock motors that would have been supplied with the CNC router kit, I'll have 570 ounce inch motors that have twice the normal torque. I also got the dual shaft version. That was a tradeoff. The shafts on the back make the motors longer and they'll stick out even more. The second shaft is also another place where sawdust and other debris might enter the motor. But on the plus side, I can add large diameter knobs and turn the axes by hand if I want to do that, without needing to boot the computer so I can jog the axes. I now have three beefy 1090 ounce inch NEMA 34 motors as spares, but I'll probably use them for other projects... like a 4th axis on my CNC milling machine project, a part catcher on my CNC lathe project, a bar feeder for my CNC lathe project, etc.

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The LinuxCNC Control PC

I got a box from NewEgg.com today. The outside of the box is imprinted "MAY CONTAIN AWESOME". In this case, it does. It's the dual core 1.8 GHz mini AT Intel Atom D525MW motherboard, 2 GB of RAM, a 250 Watt ATX power supply, and a 64 GB Sandisk solid state drive for my CNC router project. No crappy old Craig's List PC to run LinuxCNC this time. I spent the extra $130 for shiny and new awesomeness. I just finished plugging it all together. Time to plug in a monitor, keyboard and mouse and install LinuxCNC.

For the last few years, I haven't been able to find the special wall wart power adapter for my very nice La Cie USB DVD drive, and I stubbornly refuse to buy another external optical drive because the power adapter will show up as soon as I do. So I had no way to install LinuxCNC and its real time Ubuntu operating system from a live CD. I assembled the Atom mobo, RAM, SATA SSD, and ATX power supply and plugged in the LCD, keyboard and mouse (temporarily donated from my CNC lathe project). It booted Kubuntu just fine from an 8 GB thumb drive. I had been carrying that Kubuntu rescue drive in my pocket for several months and had never tried it. Based on that quick success, I decided to use Unetbootin to make a bootable USB thumb drive and install LinuxCNC from there. But that required a trip to buy another USB thumb drive. I should probably buy a six pack of those things!

http://blogs.saic.edu/axisofoutput/2010/09/17/cheap-cnc-linux-pc

http://unetbootin.sourceforge.net

Anyway, I think the PC part of this project is mostly a formality at this point. Note the tiny 64 GB solid state drive at the end of the red SATA cable, and the thumb drive plugged into the USB port, where it booted Kubuntu.

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To Do: Boot from the thumb drive, do the memtest for a couple of hours to verify the 2 GB of RAM and see how warm the CPU heatsink becomes as part of a mini burn-in test, install LinuxCNC to the SSD so it'll boot from there, and it should be a done deal. Plug in the parallel breakout board, attach the power supplies, stepper drivers and stepper motors and test the motion. Unless you hear otherwise, all of that stuff went off without a hitch. I'll probably make the required First Motion video with stepper motors spinning on the dining room table.
Last edited by Liberty4Ever on Fri Jan 11, 2013 4:29 pm, edited 1 time in total.
Apparently, I didn't build that! :-)
Liberty4Ever
 
Posts: 274
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Location: Lexington KY

Re: Liberty4Ever's 2X4 CNC Router Build Log

Postby Liberty4Ever » Thu Jan 10, 2013 5:34 am

More PC & LinuxCNC Installation

Installing LinuxCNC onto the 64 GB SSD (flash hard drive) from the 8 GB bootable USB thumb drive went off without a hitch, after I stopped by Walmart and bought an 8 GB USB thumb drive. Flash memory is around $1 per GB now, which is insane... in a good way! It's also amazing how small an 8 GB thumb drive is now. I put the realtime Ubuntu operating system, LinuxCNC, and the other bundled applications on this tiny thing with about 7 GB to spare. I should have copied a Buckaroo Banzai DVD on there, in case I'd like to watch it sometime while I'm out and about. :)

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I like the little Intel Atom D525MW single board computer. No hassles at all, other than the obvious of not having a CD ROM to install software, but that's hardly a bug. More like a feature. I intentionally configured this system with no optical or magnetic drives. The only moving part is the cooling fan in the power supply. And that reminds me, the processor ran a cool 50 C without any active cooling. I just had the board sitting on the dining room table with the rather generous CPU cooling fins sticking up into the still air. I may opt for a fan when it's mounted in the CNC router's electrical enclosure.

I ran the LinuxCNC latency test, with pretty respectable results for such a low power CPU. Kudos to Intel for efficient computing. That's important in an application like this, because a lot of waste heat will make it too warm in the electrical panel. I ran glxgears, opened an empty spreadsheet, and recorded sound to tax the system while the latency test was running, for worst case latency numbers. Then, while all of that was running, I opened Firefox to hit the hard drive and the CPU by launching the large application, causing about a 10,000 ns jump in the two jitter numbers to about 27 usec for the servo thread and about 17 usec for the base thread.

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I'm digging the 64 GB SSD. I'm not much of a power PC geek anymore, so this is my first SSD. It's fast! It takes 23 seconds to cold boot the PC into the realtime version of the Ubuntu operating system, auto load the LinuxCNC application and pull in the configuration for the CNC router... ready to make some parts! This is probably going to spoil me, and I'm going to want integrated PCs with SSDs on all of my CNC machines. Heck. If I ever rebooted my Linux notebook PC, I'd want an SSD in it too!

I haven't really kept up with PC hardware lately, other than reading a bit about it, occasionally. I was very pleased that I was able to quickly go to NewEgg.com, put together an order for four items, and when it arrived I was essentially able to plug it all together with the cables that were provided and It Just Worked. From my PC hacking experiences 15 years ago and earlier, I expected the usual grief, running around trying to find a weird cable or something. Not so.

I originally had 4 GB of RAM (two sticks) in my shopping cart for $26, and I ended up deleting it and getting only one stick with 2 GB of RAM. I figured that should give LinuxCNC plenty of RAM, and normally it would, but now I regret not spending the other $13 and getting 4 GB. With the SSD, I really don't want the operating system swapping RAM off to the swap partition because it'll accelerate the wear on the flash drive. It may not be a problem, but the extra $13 is cheap insurance. I'm going to install some 3D CAD software on this machine as well, and probably some CAM software as well, and it'd be good to have a lot of RAM to avoid the need for hitting the swap partition. I'll pick up another 2 GB or RAM soon.

While I was picking up the thumb drive at Walmart tonight, I also grabbed a $30 Logitech K400 wireless mini keyboard with a glide point pad on the side to take the place of a mouse, which is difficult to use in the shop. The K400 is small and light enough that in some cases, it may make a good wireless pendant.

Image

My three new big & beefy NEMA 23 stepper motors will be here tomorrow. I have some other stuff inbound as well, such as the 5/24 VDC power supply for the logic and I/O power on the other side of the optoisolated breakout board and some ER 20 precision collets. The cool Jog It! LinuxCNC pendants should be here in a couple of more weeks.

Jog It! Pendants for LinuxCNC or Mach: http://dtrobotics.blogspot.com/p/downloads.html
Apparently, I didn't build that! :-)
Liberty4Ever
 
Posts: 274
Joined: Wed May 30, 2012 1:49 am
Location: Lexington KY

Re: Liberty4Ever's 2X4 CNC Router Build Log

Postby Liberty4Ever » Thu Jan 10, 2013 9:57 pm

A Few More PC Configuration Details - Power On Boot & Hyperthreading

I wanted the PC to automatically boot into LinuxCNC. It was easy to configure Ubuntu to run LinuxCNC with the proper configuration file for my CNC router, but I had a bit of trouble trying to get the PC to boot when power was applied. The standby power LED would light on the motherboard but it wouldn't boot. I could press F2 on the keyboard and force it to boot that way. If I kept pressing F2 I could get into the BIOS setup, but I didn't immediately see where to force a power on boot. I pulled up the motherboard's manual and found which jumper pins were used for a front panel mounted power on push button switch. I could short the pins and it would boot, but keeping them permanently shorted prevented it from booting, as if it was held in a reset state. It needs the low-to-high transition to initiate the hard reboot. I looked in the BIOS again and was a Power option for recovery from power failure. I changed it to always reboot after a loss of power. That did the trick. Now, when I turn on the power supply, the PC automatically boots and runs LinuxCNC. I'm still digging the fact that it goes from power off to ready to roll in 23 seconds. That flash SSD is awesome.

While I was in the BIOS, I also turned off hyper-threading. I reran the latency test and it seemed a little better, but not much. I was able to get about 17us in a few minutes with a lot of "abuse" with programs running and fully loaded with glxgears, etc., and after several minutes with some really bad load abuse, I was able to get about 25us of worst case jitter. It's not great, but it's plenty good enough. 100us would probably be too much jitter for reliable realtime response. The finer the pitch on the screws (or the greater the gearing reduction ratio between the motor and the screws), or the more microstepping you're using, the lower you'll need the jitter to be. I'll consider 25us to be the worst case, and I think I'll be fine. It's pretty good for such a low power processor.

The motherboard was designed for passive cooling. It has an efficient processor and a lot of heat sink, so the motherboard can be used without a fan on the processor heat sink. It's sufficient to place the motherboard in a chassis with adequate ventilation. As long as the ambient air is reasonably cool, there is no need to blow high velocity air over the D525WM's processor heat sink. When I was loading up the processor to get the worst case latency, the fins on the processor heat sink didn't even get warm.



New Stepper Motors Are Here

My three new Kelling KL23H2100-35-4BM NEMA 23 stepper motors arrived this morning. Automation Technologies is in an adjacent state to me and they ship immediately, so I get my orders from them very quickly. The motors look very good. They're the biggest NEMA 23 motors I could find, but they're a lot smaller than the large NEMA 34 motors I originally purchased. The NEMA 23 motors will be much easier to install with no need for custom brackets, and they should still have a lot of torque. Holding torque doesn't tell all of the story though. The longer a stepper motor becomes, the more the torque typically rolls off with high frequency stepping. In other words, these longer NEMA 23 motors will be better for preventing the spindle from back driving the screw and causing the axis to move when it should be stationary, but won't offer the same percentage of torque improvement when making high speed axis moves. I still haven't run the numbers to predict ball screw whip, but there's a chance that the ball screws will be whipping (critical speed) before the torque roll-off occurs, making the high speed torque limitations of the longer motor a moot point.

There are various ball screw calculators online.

http://www.nookindustries.com/ball/BallCalculators.cfm

It's sometimes faster to design using a chart. Here's a critical speed chart for metric ball screws. You need to know the diameter of the ball screw, the distance between the bearings, and how the ball screw is anchored on each end.

Image
Apparently, I didn't build that! :-)
Liberty4Ever
 
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Location: Lexington KY

Re: Liberty4Ever's 2X4 CNC Router Build Log

Postby BenJackson » Fri Jan 11, 2013 12:52 am

You could always pick up a Mesa Electronics 5i25. $89 in qty 1, and your BASE_PERIOD becomes irrelevant. I can help you convert your config -- I just went through the process myself.
BenJackson
 
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Joined: Fri Apr 15, 2011 6:13 pm

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