Liberty4Ever's 2X4 CNC Router Build Log

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Re: Liberty4Ever's 2X4 CNC Router Build Log

Postby Liberty4Ever » Wed Mar 06, 2013 3:56 pm

yasam2002 wrote:Do you have a price list for the components of this beautiful cnc machine?

I cheated and bought the heavy duty router kit, ready to screw together.

Currently on eBay by signal-seeker, the designer and manufacturer:
http://www.ebay.com/itm/261172736081

It's currently listed as US$2700. It might have been $100 less when I bought it two months ago. I asked for it without the motors and electronics, so the seller reduced the cost by $200. My parents are close to the seller, so I stopped by and picked it up to save on the shipping and packaging costs.

I've probably spent $350 or so on the motors and electronics. I upgraded to the largest NEMA 23 stepper motors I could find. It seemed a little underpowered for the beefiness of the mechanical components. Extra speed would be nice, but mostly, I wanted to be able to make relatively deep cuts in harder material and remove more material without losing steps.

The mechanical kit seems complete, and I already had most of the wire and incidentals needed to wire it. I bought a metal cabinet at Sam's Club to use as a low cost electrical panel. I need to buy a subpanel for it to make wiring more convenient. I'll probably buy an aluminum table to screw to the extruded aluminum frame to place under the spoil board to add rigidity to the frame. Once the mechanical part is assembled and the motors are installed, I'll design an integrated table to support the CNC router and a dust collecting enclosure that should also reduce the noise to a less offensive level. I may design a couple of 4 foot fluorescent lights into the top of the CNC router. I like a lot of light.

I decided not to use a recycled Craig's List computer this time, and bought a nice Intel D525MW motherboard that's known to play nice with LinuxCNC, and a power supply and a 60 GB solid state hard drive and a couple of sticks of RAM to max out the memory... so I can watch YouTube videos while routing - HA! Actually, the big RAM memory is so Linux shouldn't need to use the swap partition on the solid state drive and prematurely wear out the flash hard drive. I have maybe $200 in the PC components.

Those prices were from memory, and are approximate. I'm keeping accurate records. When the project is fully assembled, I'll post an accurate accounting of the cost, and include a bill of materials with costs for the various subsections.

It's definitely possible to build a less expensive CNC router. My goal wasn't the absolute lowest cost this time. I wanted to be on the high end with regard to quality (accuracy and long term reliability), but of course cost is always a consideration so I did seek a good value solution.
Apparently, I didn't build that! :-)
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Re: Liberty4Ever's 2X4 CNC Router Build Log

Postby yasam2002 » Wed Mar 06, 2013 5:58 pm

Hope you fiinsh it soon so as to see the nice assembly work :D
Yassine Morrocco.
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Re: Liberty4Ever's 2X4 CNC Router Build Log

Postby Cre8ivdsgn » Thu Mar 07, 2013 1:59 pm

I took a look at the ebay kit and I was... stunned at how inexpensive it was. I added up the costs of the bearing blocks, leadscrews, machined pieces, etc and things just (in my mind) add up.

Until... I looked at leadscrews on ebay! I could not believe the pricing! A full set of (well heck, even for ROLLED thread) three screws with end machining for $139. Supplied new out of a Chinese firm. No, we are not talking THK, NSK, Thomson, INA, or any of the others. But wow!

So I know Liberty can't really tell unless you hook up a laser interferometer or some kind of linear encoder setup, but I am very curious as to the overall quality of these screws.

I feel as though I have been living under a rock. I had no idea things had gotten this inexpensive.

The bearings must be pretty low cost as well.
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Re: Liberty4Ever's 2X4 CNC Router Build Log

Postby Liberty4Ever » Thu Mar 07, 2013 7:15 pm

So far, the quality of the kit, including the imported ball screws, is about what I expected, which is to say it looks pretty good! Yes, the value for Chinese lead screws is now very good. As you mentioned, the overall quality generally isn't quite up to par by US or German or Japanese standards, but for this project, I'd rate it as definitely good enough. Another advantage that's often overlooked in the imported precision motion products is the convenient ordering. Shopping on eBay is fast and easy, and the suppliers are very accommodating. You can get ball screws in any length, and they'll grind down the hardened surface to produce any bearing diameter you need, and they'll thread it however you like. Sketch a rough drawing, email it, and they'll return a quote very quickly, and the custom work is fast and cheap. That'll be very handy when I upgrade some existing machine tools from lead screws to ball screws.

There's nothing too technical in the CNC router. It's a proven design. I did consider buying the components and building my own from scratch (I like projects like that), but lately I can't seem to find the time to do much. I figured my only reasonably path to success would be to buy the kit and integrate the electronics, which plays more to my strengths (I'm an EE, not an ME). I figured that I could probably save about $500 if I sourced the mechanical parts and built the CNC router mechanical systems myself. It didn't seem like a good value. To the extent that I'll use this for my business, I certainly couldn't make a good business case for building from scratch and delaying the project from "late" to "never".

I'll probably try to come up with some covers to keep chips and sawdust off the ball screws. If I designed it myself, more of the precision motion components would have been protected underneath the table. Otherwise, I like the CNC router design and I'm looking forward to building it and using it.
Apparently, I didn't build that! :-)
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Re: Liberty4Ever's 2X4 CNC Router Build Log

Postby Cre8ivdsgn » Thu Mar 07, 2013 8:09 pm

I like the design of the kit you chose quite a bit.

The leadscrew in the base is protected by the MDF sacrificial board (or whatever gets used). The bearings aren't too protected, but based on the design, you could shield them pretty easily.

When I first realized a 25mm rail, I thought the drag would be severe. But the rigidity of that size... well, if the rails aren't square to start with, a few runs back and forth and the rails will square up all by themselves!

With the spindle you have spec'd out, and some form of lubrication, I think you could do a good job routing out aluminum plate. You could even modify the base rail bearing mount to hold two blocks on a side instead of just the one. If you did that and bolted the base down firmly to a good table, you should be able to route pretty nicely.

I have to admit I am more familiar with Haas CNC VMCs, and industrial routers rather than smaller scale stuff, but based on tool loading for aluminum, I have to think its manageable.

What drove the choice of EMC versus Mach3? I am curious because I have used neither.
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Re: Liberty4Ever's 2X4 CNC Router Build Log

Postby Liberty4Ever » Thu Mar 07, 2013 8:58 pm

Cre8ivdsgn wrote:What drove the choice of EMC versus Mach3? I am curious because I have used neither.

I must admit that some of the decision for LinuxCNC was philosophical. I like open source software. I'm not at all opposed to paying for good software. I'm all about capitalism and I view software as a product like any other. If I enjoy it enough, or it saves me enough time and/or money, I'm quite happy to buy software. I don't mind that open source software is free as in "free beer", but I'm much more interested in the fact that it's free as in "free speech". I run Linux on my notebook PC that I use for regular desktop computing tasks, and I run exclusively open source apps such as Firefox, Thunderbird, GIMP, LibreOffice, etc. It's not a titing at windmills philosophical sacrifice. I'm more productive and my costs are lower with the open source software, and that's been true for about ten years. Whenever I'm using someone else's Windows PC, I'm constantly aggravated and hassled by it. It performs a mandatory operating system update whenever it wants to. There are viruses and worms, even with antivirus software that reduces stability and brings performance to a crawl. It might even falsely accuse me of stealing software. Bleh.

Ignoring philosophical issues, I'd justify LinuxCNC on its technical merits. It runs under a truly realtime version of Ubuntu Linux. Mach runs under a realtime-ish version of Windows. The distinction may not be critical in this simple CNC router application, but hard realtime control is definitely a desirable feature in a CNC machine.

Another huge selling point is the support. There's a common and very reasonable sounding fallacy that people should buy commercial software because they need support and there isn't any for open source software. In practice, I've found almost the opposite to be true. It varies depending on the type of software, but I've generally found it easier to get help from a community of open source users and developers than from the manufacturer of commercial software. That certainly shouldn't be the case. When I buy software, I'm not paying for a shrink wrapped CD. If I was, it should cost under a dollar. I'm paying for the development and support, but it seems that support for most commercial software isn't very good. In the specific case of LinuxCNC, it's excellent! There is a large community of enthusiasts who are very willing to help. The developers try to make it easy to install and use, and LinuxCNC has gotten a lot better in that regard even in just the last year, but integrating CNC software with mystery hardware can be intimidating. There are people there to help. I know there is a community of Mach users too, but from what I've seen, Mach users seem to be more likely to be those wanting to buy a solution and be done with it, so the majority of them aren't as able to help, even if they were as willing. LinuxCNC developers are very active in the LinuxCNC support forum. LinuxCNC user support is readily available online, and for the difficult cases, I've seen examples of one user driving an hour to provide hands-on help to get a newbie off on the right foot.

Finally, and this should admittedly be a minor issue, I don't care for the appearance of the Mach user interface. I suppose it's designed to look friendly, and I suppose it succeeds in that respect, but I'm not a fan of the bright primary colors. LinuxCNC has several possible user interfaces and the user is free to change the front end, but most people use the default Axis interface which looks similar to most modern commercial CNC flat panel user interfaces.

For a common stepper based system like this CNC router, LinuxCNC should be as easy as installing the operating system and application from the CD, wiring the inputs and outputs to the parallel port I/O board, selecting the stepper based CNC router configuration, tweaking the config for the number of steps per inch on each axis, and running LinuxCNC. Stay tuned and see how comically wrong that boast turns out to be! :D
Apparently, I didn't build that! :-)
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Re: Liberty4Ever's 2X4 CNC Router Build Log

Postby Cre8ivdsgn » Fri Mar 08, 2013 3:19 pm

I just was going over the rest of this log and something struck me.
BenJackson said that the BASE_PERIOD becomes irrelevant when using the Mesa 5125/7176. Perhaps I am mistaken here and he is referencing the servo versus stepper flavor?
If the BASE_PERIOD is no longer a factor, what can you get the max step rate up to?
My head is mush these days, but I was plowing through the LinuxCNC info and the example for working out max stepping rates and the BASE_PERIOD is drive hold time + latency time. The only way to avoid this is if LinuxCNC offloads the whole Accel/decel ramp profile to the Mesa hardware. I see that Mesa has a SoftDMC package... ahhh, I think I see. It does offload things to the Meas card and its profile generator. The while kit and kaboodle for the Mesa hardware rings up at 199+89+cabling costs.
I still can't see what the mesa card max pulse rate can be.
Also, if dual leadscrews were used on the Y (base of router), could the A axis be configured to drive the second motor?
The whole Mesa thing has really opened up some interesting possibilities!
Sorry... thinking out loud here!
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Re: Liberty4Ever's 2X4 CNC Router Build Log

Postby Liberty4Ever » Fri Mar 08, 2013 4:39 pm

I purchased the MESA electronics for my (as yet unfinished) CNC lathe project. It uses servo motors. There is certainly a limit to MESA's equivalent of the base thread, with a limit on servo response time or step rates to a stepper motor, but the FPGAs used in the MESA electronics are so fast that I think they'll never be the concern. I also bought the MESA electronics for a big servo based industrial job that was nearly completed when the company was sold and the project was scrapped. That really hurt, considering the blood sweat and tears (and MANY late nights and all nighters) that I put into that for nothing while my own CNC projects gathered dust. I was very favorably impressed with MESA electronics and their interface to LinuxCNC. Peter also provided excellent customer support, answering my newbie questions. The MESA experience was so good that I'm almost looking for excuses to use their products in my CNC projects, but I just couldn't justify it for this simple stepper based CNC router.

You wouldn't need to (or want to) use the A axis to drive the second motor on a dual motor Y axis. If using stepper motors, just wire the motors in series or parallel as appropriate and drive them as a single motor using a larger stepper motor driver. Or run the same step and direction signals from the parallel port to two stepper motor drives, each driving a separate stepper motor. Dual stepper motors for the large axis on a CNC router is a common practice. If you're using servo motors, you'd need to be more careful to make sure they aren't fighting each other. Run a single encoder back to LinuxCNC as the position feedback. You might be able to wire the motor windings of each motor in series or parallel and treat the two motors as one larger motor, but I'm not sure about that and currently too sleep deprived to have an intelligent opinion.

MESA is also great for adding a LOT of inputs and outputs, way beyond what you'd get from a parallel port or two. MESA can be configured with remote I/O too, which is very handy. Power it remotely, and you only need to string a CAT5 cable for a serial data link to control an entire board full of I/O.
Apparently, I didn't build that! :-)
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Re: Liberty4Ever's 2X4 CNC Router Build Log

Postby Liberty4Ever » Tue May 28, 2013 10:06 am

http://youtu.be/iiuTNsUVC0A
(lame 30 second motor jogging video)

YouTube isn't letting me edit the video description. :-(

I finally wired enough of the electronics that I was able to jog the X axis using LinuxCNC at a little after 3 AM. I'm liking the JogIt pendant. It's very handy.

I bought the larger NEMA 23 stepper motors, stepper motor drives, stepper motor power supplies and the DB25-1205 optoisolated parallel port breakout board as a kit from a Chinese company on eBay. There was no documentation. It's not rocket science, but there should have been a minimal system schematic of these components, both for the optoisolated power supply version and for using the PC power supplied outputs to the optoisolated inputs on the stepper motor drives.

Apparently, the stepper motor drive's ENABLE signal actually disables motion on that axis. Unwired, there is an internal pullup to enable motion. Wiring +5V to the ENABLE+ signal and 0V to the ENABLE- signal disables motion! It took me a couple of minutes to debug that undocumented feature. Something must have been lost in the translation.

Now that one axis is debugged and moving, I can wire the rest of the electronics, mount the electronic control panel on the side of the router table base and dust collection enclosure, permanently wire the motors and fluorescent lights and power cord, mount the spindle motor and finish wiring it, calibrate the motion in all three axes, run the 4" flex hose for the dust collection system, install the water cooling for the spindle motor and cross this project off as #1 in my Summer Of Projects.

2) Build my very simple CNC Sherline Mini Lathe.

3) Finish building the back yard shed.

4) Build the CNC laser.

5) CNC conversion for my Grizzly G1006 benchtop milling machine.

6) CNC conversion for my Clausing 10X24 lathe.

7) Finish assembling my two Hadron ORD Bot 3D printers.

It should be a fun Summer Of Projects. Most of the parts are purchased for the other projects. Just need to get a Round Tuit.

I'll post a longer video with technical info describing my LinuxCNC router project when it's finished, with a lot of building tips and problems I had that you should avoid.
Apparently, I didn't build that! :-)
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