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  1. #21
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    Quote Originally Posted by ilya View Post
    NO! Don't make such a large machine out of wood.

    The bottom line is: don't mess with wood, make it from aluminum or steel.

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    Must be from Russia .
    I agree 100%. I had to get that in there because they know what "real" machines are over there.



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    why would anyone want to spend 3K$ on fire wood?? real machines are built of metal. Glue & sawdust is for presto fireplace logs not cnc machines.



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    Quote Originally Posted by henrydavis View Post
    www.buildyourcnc.com has a new 4x8 machine design that uses roller chains instead of lead screws. Is this guy crazy, or is he on to something? I can't imagine a roller chain could be at all comparable to a highly precise lead screw when moving on the X any Y axis like his machine does (his uses a lead screw for the Z). It looks like the chain will be pushing up on the stepper motor the whole time and wouldn't you think it would lose tension after time? I remember his last machine with the 4x8 option was around $2400. Now he wants almost $3000 for one that uses a bike chain?


    Any input is greatly appreciated.
    the use of roller chain isn't anything new and after experimenting with it a few years ago myself , I'm all for the use of chain drive .

    $3000 for a "machine" that is built with cheap angle and mdf is a bit much , I'm sorry but it is ,

    Last edited by dertsap; 02-20-2010 at 03:18 PM. Reason: probably came across to harsh
    A poet knows no boundary yet he is bound to the boundaries of ones own mind !! ........


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    What constitutes a good deal is a satisfied buyer and a happy seller. If you are satisfied with Patrick's machine then you got a good deal. The fact that www.buildyourcnc.com does actually video a build of a cnc machine does many of us a service and he should be commended. Thank you Patrick for documenting a build in video and making a site for each of us to view. I do plan on making a cnc eventually and like to see everybody ideas and experiences. That way I can come to my own conclusions. That is what this forum is about. Open source is the best way to share ideas and improve upon them.

    Is the voice in my head bothering you?


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    Registered mlabruyere's Avatar
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    Not sure why so many folks are so down on this machine.....it is a hobby and it looks like a nice hobby machine. He's using his own machine to make his kits so it's capable. To address the moisture issue couldn't you prime and paint all the exposed parts?

    Mind you I have never used one of his machines and I figured out that and MDF based machine is not for me. Mine is steel and Aluminum but for folks wanting to get started you get everything you need save the controller and PC.



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    Dont think anybody is calling the machine or patrick, just the construction material.
    The price i suppose is reflective of the time and effort patrick put into the design and R&D.
    Patricks site and dedication to is design and helping others is a fantastic effort and i for 1 applaud him for this.

    Personally i hate mdf, to me it's completely unsuitable for a cnc machine of any substance. . . . It swells with even the slightist amount of moister and it wears very easily and it's also a killer if dust is not controlled.!!

    The thing that would concern me (A lot), appart from the moister issue's and the 3g's, is the longevity of the machine.
    Mdf wears like crazy at any moving joint or pivot point, just drill a hole in some and put a bolt thru it a few dozen times and see if the hole is the same size afterwards.? I know a bit ex-stream but the point i'm trying to make is it's soft and spongy which is not a good thing for a machine that relies on repeatabilty!!
    So to me for 3 grand i would want something thats more than a time limited machine.

    That's my 2 penarth!!



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    IMO, the problem discussed here is not the particular design. The probem is dumping 3 grands for an MDF...

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    didn't he stop using mdf in his newer machines?



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    Registered fatal-exception's Avatar
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    NO! Don't make such a large machine out of wood. It will wander and your precision will suffer badly!
    I second that. I don't know why anyone would think that wood is a good building material for a precision machine. Save up your pennies till you can buy some steel.



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    I'm with ilya on this one, really its about what you are willing to pay for the DIY machine $3k is too much for a disposable CNC machine. MDF will expand and contract according to the moisture in the air, you can poly the parts (i would do it before assembly) but MDF does not have the longevity one would desire in a machine he spends $3k on.

    Hats off to Patrick, he is very resourceful and I have enjoyed his website, he also has a book available. Patrick, in my opinion, though may be missing some opportunities in offering upgrade kits to make the MDF parts in previously sold kits obsolete. Patrick, you owe me some kick back for that idea.

    Offering a DIY kit made from readily available, cheap stock is not a bad idea, and shows just how easily and inexpensively one can build a CNC machine. However, trying to recoup R&D cost by heavy pricing is a mistake.



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    As someone that found this thread because he's looking at building/buying a CNC router, I find it very interesting, especially the different perspectives.

    There are people that highlight Patrick's machine as "it's a hobbyist machine" and others that say "MDF is not good for precision".

    Precision? How precise must it be? It's a hobbyist machine. Patrick is not marketing this to high production shops. Are talking a difference in precision in that Patrick's is precise to 0.005" and the others (metal frame, etc) are precise to 0.001"? It's hard to take the "precision" argument seriously without any numbers to back up the argument.

    Another person says "cheap angle" or something like that. Is that worse than skate bearings over pipe? (See's Joe's first build)

    In a metal built CNC, don't many designs use angle bolted to square tubing? If so, then isn't your argument really about the MDF and not the angle aluminum/steel?

    To those that say "R&D and website and marketing are a lot harder than people think". True, but this misses the point of the thread in that we're examining the actual quality of the product offered. This argument would be like saying we have to give props to a company that sells $10 box wine with a $3 million superbowl commercial. The commercial and marketing might be top shelf, but the wine is still $10 box wine and tastes disgusting. What matters is the quality of the machine, not Patrick's marketing efforts.

    My conclusion:

    $3k for the 4'x8' is a lot. The electronics cost $500 - $750, maybe $1,000? This still leaves $2,000 for everything else. I don't really know how long it takes to package up a single kit or cut it out of the MDF, or anything else and I could be completely wrong, but $2,000 for the hardware and CNC-cut MDF seems high. I realize there has to be some kind of step up from each model to the next. It makes more sense to me to buy the electronics and build my own with all of the knowledge out there. Yeah, there will be a little trial and error, but in the end, I'll know tons more about my machine and look to myself to fix it rather than emailing Patrick for help. Who knows, maybe i'll end up welding up my table and frame anyway, but I think steel would be heavy for the gantry (please correct me if I'm wrong) and I still suck at welding aluminum.



  12. #32
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    Quote Originally Posted by jallenmorris View Post
    There are people that highlight Patrick's machine as "it's a hobbyist machine" and others that say "MDF is not good for precision".

    Precision? How precise must it be? It's a hobbyist machine. Patrick is not marketing this to high production shops. Are talking a difference in precision in that Patrick's is precise to 0.005" and the others (metal frame, etc) are precise to 0.001"? It's hard to take the "precision" argument seriously without any numbers to back up the argument.

    ...

    Who knows, maybe i'll end up welding up my table and frame anyway, but I think steel would be heavy for the gantry (please correct me if I'm wrong) and I still suck at welding aluminum.
    Looks like this is directed to me, 'cause I was the "other, who said that MDF isn't good for precision".

    Well, if you want some numbers I can give you them. But first, let me clear something: if everything that you'll ever be machining is wood, than the MDF machine will probably be quite OK. At least for a month or two of consistent use (untill it wears itself out). With MDF, you'll probably get a 0.02"-0.03" precision. And don't even think of cutting metals - you'll get so much flex and vibration, that you just won't get reliable cuts and good finish.

    With properly built aluminum machine, you'll get 0.004"-0.005" precision. This is sufficient for machining metals and is plenty for cutting wood. My machine can hold even better tolerances on moderate feeds.

    Is 0.02" precision enough for a hobby machine? You decide. For me this is unacceptable.

    The main point that the MDF sucks for CNC machine is: the material itself is so soft and unstable, it just wont sustain heavy loads and will flex badly. And if your machine is flexing, you can forget about precision and good surface finish.

    Now, some notes about welding steel. Keep in mind that after welding the frame should be heat-releaved. Otherwise it will deform after some time due to stress in the weld joints.

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    My DIY CNC router plans at www.8020CNC.com


  13. #33
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    ilya,

    How many MDF machines have you ruined? You seem to be very knowledgable about MDF so it seems like you are speaking from actual experience rather than just the qualities of MDF in general.

    Did you use MDF before your aluminum machine?
    Have you tested an MDF machine?

    You stated "for me this is unacceptable". The advice you are giving about how MDF is so horrible seems to be based upon what is acceptable to you, yet that doesn't come out in your advice. You don't say "MDF is no where near acceptable for my applications." you simply dismissed MDF as a possible material for the build for anyone.

    I appreciate your advice, and I've come to the conclusion that metal is better, but wood (not necessarily MDF) is acceptable for some applications.

    My problem is that you've hit on one of my pet peeve's. I really dislike when people use their own situation in which they make a decision and apply it to the rest of the world as if the rest of the world, in every possible situation, is exactly the same as their situation. In this case, wood is not good enough for you, so your advice is (as I interpret it) that wood is not good enough at all and no one should use it (although you did say in your latest post that "You decide.").

    Do you run a commercial shop ilya?



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    jallenmorris,

    First, I've never said that wooden machine is bad in ALL cases. If you read my posts carefully, you'll see that I argued that spending 3k$ for MDF-based machine is a wise decision. And basing on a particular budget (and henrydavis, the topic starter, seemed to have this money to spend) it's better to consider an aluminum machine.
    I'd like to stress, that I dismissed the MDF based on the conditions, discussed in THIS thread. For me, it's obvious that you'll get much better performance from the aluminum machine AND spend the same amount of money you'll spend for MDF kit otherwise.

    Now, I haven't built any MDF machines. Why? The answer is simple: I'm using my machine for milling and engraving soft metals. The general rules say that a machine will not reliably cut any materials that are harder then that the machine is built from. I've browsed through a lot of forums and discussed this with dozens of people. In my case, it just didn't make any sence to dump additional $$$ for something that won't accomplish the goal.
    However, seeing how the aluminum machine works, I can actually predict how MDF will behave under the same conditions. And, as you might guess, the prediction is not in favour of MDF.

    Actually, this is quite funny - I've never thought that anybody will demand the explanation why MDF is inferior to metals. This is so obvious you don't even need to build an MDF machine.

    And keep in mind, I'm talking about just 1 aspect of MDF - the lack of rigidity. However, there are other caveats like climate dependance (it will change its dimensions depending on humidity), machining tolerances (not nearly as good as metals) and wear resistance to name the few.

    So, to answer your questions: no, I haven't built any MDF machine. Because this didn't make any sence to me. No, I haven't ruined any MDF machines because I haven't built any. No, I haven't tested any MDF machine in real life, but i DID run some simulations in the CAD software and I made some assumptions based on the general MDF qualities.

    If you wonder where did I get the numbers for precision, they were quoted in several sources and by several people on different forums. So these numbers can serve as a general guide of what can be achieved with a wooden machine.

    I'm sorry if I sounded to you like I applied my situation to everyone. This was not the case, and is just a misunderstanding. I repeat than nowhere did I stated that "nobody should use MDF"or the like.

    I don't run any commercial shop yet. I'm doing this as a part of my hobby (building audio gear)

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    ilya,

    If you're building audio gear, are you cutting wood as in the speaker box? Are you milling metal? If you're cutting wood, I think the 0.02 or so would be sufficient. People all over build with normal carpentry tools and people can't do traditional carpentry to accuracy of 0.02" (maybe I was just sloppy when I used to build speaker boxes).

    Can you point me in the direction of some kits that are metal based? MechMate is one I think I remember seeing discussed.

    What are the estimates for costs to build the Mechmate machine? Thanks.

    Also, do you have any pictures you can show of the stuff you built? Maybe that would be a new thread since it's kind of off topic.



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    jallenmorris,

    I'm machining 19" aluminum front panels for audio devices. I don't build speakers, guitar combos etc. My machines work area is neither big enough, nor I'm really interested in this kind of stuff.

    You can see some pictures of the panels on my site

    I've made another unit with a much finer engraving, but haven't managed to put the pictures yet.

    I agree, 0.02" is ehough for carpentry work. But is horrible for engraving metals.

    As for kits, check out www.cncrouterparts.com for free plans. The sell the kits as well AFAIK

    My DIY CNC router plans at www.8020CNC.com


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    Quote Originally Posted by jallenmorris View Post

    My problem is that you've hit on one of my pet peeve's. I really dislike when people use their own situation in which they make a decision and apply it to the rest of the world as if the rest of the world, in every possible situation, is exactly the same as their situation.
    Ah ah dont make me laugh your country and mine for that matter, are the masters at inflicting there will on everybody else.!!

    The main points are that MDF is rubbish for building a accurate CNC machine and $3K for a machine made from sawdust is utter stupidity.

    My pet peeve is when people who have never built a machine try to argue or contridict others that HAVE and are only trying to help others that HAVEN'T from making a expensive mistake that they will REGRET.

    YES i have run a commercial shop and can tell you i,ve never been approached by any Commercial manufacturers trying to sell me a machine built from MDF.!!

    MDF as it's place in a shop and thats on the bed for a spoil board and thats it. . . Or . . .in the stove as fuel.?



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    I thought that I saw he was selling the dxf plans as well for $300 or so, maybe he is much smarter then you think.....?

    In this world of instant self gratification, where size matters, it seems to me that (just maybe) he is a marketing genius.

    just sayin' ....



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    Why are some people mad that hes selling hes machines at whatever price?
    Hes not forcing anybody to buy hes machines. I think some people just don't like the fact that hes making money out of something all of us on here can do. Also hes videos are the easiest cnc machine anybody can build that actually works with just basic tools, and they are for free. I built hes machine and from the same machine i cut the parts for the Joecnc2006.



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    Quote Originally Posted by trats20050 View Post
    Why are some people mad that hes selling hes machines at whatever price?
    Hes not forcing anybody to buy hes machines. I think some people just don't like the fact that hes making money out of something all of us on here can do. Also hes videos are the easiest cnc machine anybody can build that actually works with just basic tools, and they are for free. I built hes machine and from the same machine i cut the parts for the Joecnc2006.
    I'm not mad at him or anybody for selling anything that they worked hard to develop or design, I just think the people paying 3K for compressed sawdust are mad.!!

    MDF is ok and perfect for a cheap entry level machine to learn CNC and if used intelligently like what you did then can be justified, but 3K is not what i call cheap and if used wisely 3k can get you a solid machine well beyond entry level.

    The whole point of this thread and title was "buildyourcnc.com cnc any good"
    Both Ilya, me and quit a few others have answered the Q by saying that Patricks design is fundamentaly ok but the chosen material MDF is rubbish for the purpose of building a QUALITY and ACCURATE machine that will last, plus the price is ridicuosly high for a mdf based machine.
    We are not, well i'm not anyway, putting patrick or his design down in any way. . . . Good on him for sharing his experience and helping others.
    But from what i can see his experience is mostly with MDF and this were the others that have built machines from steel/aluminium are trying to help and share their experience.
    If like me they sit back in disbelief knowing how hard it was to get a machine setup and accurate using REAL materials that some one would even contemplate building a machine from MDF expecting it to be accurate and strong enough to last long enough to justify the price of glue n bolts holding together.

    SO to anybody starting out do your self a favor and listen to the one's who have walked the walk and dont just talk.!! . . . . . if you want a short term disposable machine then use MDF if you must BUT if you want a long lasting stable accurate machine then avoid MDF like the plague.



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