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  1. #21
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    Quote Originally Posted by Rockn-Roll View Post
    My criteria for a CNC machine tool is that it have a spindle motor rated at least 2HP on single phase 220Volt and 3-axis precision of at least .001" for around $10,000 that can cut a 5"x5"x5" cube of steel.

    mactech54 generously provided me with a suggestion to look at How-Mau...and after some assistance at finding a modern web site for them I am happy to say that their HM-145X does "appear" to meet those requirements. Spindle motor power is rated at 1.5KW using 220Volt Single phase (or apparently even 110Volt) which is equivalent to 2HP and the rated precision is exactly .001". The table is 24.65"x8.11" with table travel (x,y,z)=(11.81",7.87", 11.81") which will accomodate my theoretical 5"x5"x5" cube. And, the control system is Mach 3 which I have learned is a modern PC based control system. The price tag is $7650. They also have a model HM-241X with a 2.2KW motor (3 HP).

    Edit: I just noticed that in the Electrical section of the HM-145X it indicates a power consumption of 750W...even the HM-241X only requires 1500W. Electric motors are not very efficient...if the spindle motor really is producing 1.5KW of cutting power, then the power requirement would be more like 3KW...nearly double, but the specs from How-Mau are indicating a power requirement of 1/2 the spindle power output. I only minored in physics, but I believe if a machine is only drawing 750W from a power source then the theoretical maximum it can produce is 750W. Perhaps it's a mistake or I'm not reading it right.

    Thanks for the suggestions...keep them coming...I'd like to see if there is another one available that meets my requirements. The Tormach's don't, but thanks for the opportunity to take a look at them. The Okuma's are production machines with at least 10HP and have 3-phase power requirements which are more than what I'm looking for, but again...thanks for mentioning them.
    hiya. a few things to note. ive got a novakon nm145 in my shop. the how mau is a copy of the novakon design. how mau used to make their machines, but there was a falling out. some research on the forum will show that how mau as a company is not the most trustworthy source of machines. their US counterpart might be a little better, but id still watch my step with them.

    ok, that out of the way, on to the machine. as mentioned, ive got an nm145, and also an nm200. these are NOT linear rail versions, but they are basically the same otherwise. the machines are good in general. the 200 series is head an shoulders above the 145 though. the 145 could be looked at as a high end bench machine, the 200 as a low end industrial machine. they come from 2 different factories in china.

    the spindle motor on the 145 is of particular note. the maker of the motors and drives has had serious issues on certain models, and the motors have been not delivering full power. novakon has a fix on the way, i assume other companies using the motors do as well but a fix may be still many months off from the original drive maker as my understanding is they need a complete redesign.

    the 145x will NOT likely do well cutting a 5" cube of steel. the y axis travel is a bit short. you wont be able to comfortably get a tool all the way around the piece. the 145 dovetailed machine might do ok, it has slightly more usable y travel. you would really be better served with the 200 series machine. the nm200(non linear) has a comfy 15" y travel and 24" in the X and alot of clearance over the table for tall workpieces and long tools. the linear version has much shorter travels, but still quite good for the work you need. the linear version will be a little less rigid than the dovetail model.

  2. #22
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    Quote Originally Posted by Rockn-Roll View Post
    I am totally not interested in a used machine
    Then for $10,000 you are talking a desktop machine as I mentioned above

    Quote Originally Posted by Rockn-Roll View Post
    I would need the warranty and support from the manufacturer.
    Check the posts on the respective manufacturer forums in this site. The one which apparently has fewer teething problems, and perhaps better customer support (at least from a reputation perspective) is the Tormach. Anyone that believes that not to be the case please feel free to jump in

    Do not worry about the 2HP and 0.001" because it is not like you have many machines to choose from anyway.

    If you are willing to spend $30,000 get a Haas TM-1.

    Alternatively consider hiring a local CNC shop do the work for you. That may be indeed be your best option.

    That is about it, I think

  3. #23
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    Quote Originally Posted by Rockn-Roll View Post
    The Okuma's are production machines with at least 10HP and have 3-phase power requirements which are more than what I'm looking for
    Yeap, I do not know how much the small Okumas go for, but generally when you think Okuma you think 6 digits

  4. #24
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    Quote Originally Posted by Ed from NY View Post

    If you are willing to spend $30,000 get a Haas TM-1.
    if i was sincerely trying to start a profitable business around a cnc machine, id finance a tm-1. the new version is fully enclosed and has tool changer upgrades available. its also easy to hire someone to run it (its very hard to hire a mach3 fluent machinist). the haas can be run on 220 single phase as well, so it suites garage/shed based shops.

    the big hobby class machines work best a "accessories" to a shop, where you use them often, but the profitability of the company doesnt hinge on their throughput.

  5. #25
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    Every single post in this thread is helping me learn what is available. I have requested a recommendation from the HAAS Answer Man...it does look like I might need to finance something.

    It's starting to look like machine tools are an extremely competitive market...it's not going to be easy to find one to fit my needs. I'm also starting to see that there is no single company that is building both low-end, middle-end, and high-end machines. In otherwords i don't see a company where I can get a $10,000 machine for development...then when I get my patents approved and designs ironed out upgrade to a $30,000 machine for small production runs, then when I get a contract for making hundreds or thousands I can upgrade to a $100,000 machine. It seems that there's a lot of companies making low-end machines and a lot of companies making medium-to-high end machines, but nobody is doing both. Does that sound right?

    In other words I'm thinking it would be great if I could get a machine with a 2HP spindle and table & spindle movement of like 10 inches per minute. Then when I get all the bugs out of my designs I can upgrade to a 5HP spindle with table & spindle movement of like 100 inches per minute in order to quickly duplicate the parts. I wouldn't have to learn a totally different machine. Am I making sense?

  6. #26
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    You're on the right track

    But I don't think that milling speeds scale proportionally to dollars spent as tightly as you're imagining. Yes, you can take heavier cuts with a bigger and more rigid machine with a more powerful motor. But if you're using a small endmill in hard materials, the speed of the spindle might be more important than horsepower, and there will be a certain upward limit on the amount of material that you can take off at a time (expressed as chipload per flute).

    That's what determines the feedrate, not the capability of the machine to go faster, or its price. However, there are various "High Speed Machining" techniques for boosting feedrates, either by increasing spindle speed and taking lighter cuts, or by optimizing heat transfer with coated carbide cutters and carefully calibrated feeds and speeds, so that much of the heat is removed with the hot chips that are flung out. Here's a section of Modern Machine Shop's site that deals with that sort of thing: High Speed Machining : Modern Machine Shop

    Andrew Werby
    ComputerSculpture.com — Home Page for Discount Hardware & Software

  7. #27
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    I've had an epiphany. I'm a computer engineer with 28 years of experience and if a machinist came to me and asked what computer to buy for $2000 I'd tell him that I have no clue because I always build my own, but I could recommend the components that he should buy and help him put it together. So...is this what most machinists do? Instead of bying off-the-sales-floor models they build their own? Should I be looking in the Build Project threads and lining up components to build a decent CNC machine tool?

    Oh...if someone insists on buying from a dealer then I could help him decide on which one, but the machine would never be optimal. For example, if you want a gaming computer then most serious gamers, who don't build their own systems, go to Alienware. Oh...the machines advertised for $2,000 are OK, but they are the most basic systems. And, if you select a $2,000 machine it will ask you to personalize it...and if you select the components so the machine will be the performance machine that they advertise then the price tag climbs to nearly $4,000!

    Also, the dealers throw lots of trial versions onto the systems that keep popping up asking you to buy the retail version...I always recommend a complete wipe of the store bought computer's hard drive and install a fresh copy of a retail copy of the Operating System (OS). In fact, this is my litmus test of systems...many retail computers cannot have an off-the-shelf operating system...some computer components require drivers which are only available from the dealer and only for a specific operating system, or even worse are computers that require an OEM version of the operating system otherwise it won't work at all because some of the computer components don't have everything needed to run the retail copy of the OS...computer manufacturers can get an OEM kit from Microsoft that allows them to turn off OS features.

    I think this is what I'm encountering...some system will sound like it will meet my needs, but when I look at the specs there's something wrong...for example the spindle spec says it's 1.5KW, but the electrical power requirement is only 750KW, or the table feed rate is in .0006" increments, but the precision of the machine is only .0012" with only a vague reference to why there's a reduced precision.

  8. #28
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    Does the $10K budget include all necessary tooling, workholding, etc.? In other words, is the goal to have the first chunk of metal affixed to the table with a tool in the spindle for $10K? Or is $10K just for the machine?

    The precision of the machine is more than just the minimum "step" of the servo (or stepper) motor. Despite all the marketing, hype, theory, and general hogwash, machine tool builders focus on heavy mass distributed across wide large bearing surfaces as the best way to achieve the best performance. A spindle with a gajillion horsepower is useless if it keeps bouncing away from the workpiece because the rest of the machine is built from old lumber and rubber bands. Large chunks of cast iron have been the choice of the industry for their mass, rigidity, and vibration damping characteristics.

    Your analogy to spec'ing a computer is good. To further expand it, if someone asks you to advise on buying a computing device, you could spec anything from a smart phone to tablet to notebook to desktop to server to ..... Cray.

    My first recommendation was going to be to attend the WESTEC trade show but the next one is a year away. The ability to walk among the myriad of machines, tools, software, and people is an excellent opportunity to see a lot of different applications, approaches and ideas in one place.

  9. #29
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    Quote Originally Posted by Caprirs View Post
    Does the $10K budget include all necessary tooling, workholding, etc.? In other words, is the goal to have the first chunk of metal affixed to the table with a tool in the spindle for $10K? Or is $10K just for the machine?
    $10K just for the machine. I won't run out of money...the problem is finding a machine tool that meets the .001 precision with a 2HP spindle motor without any problems. It is starting to look like I will need to build my own...start with a new knee mill and build my own CNC system...the electronics is actually a piece of cake for me.

  10. #30
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    Quote Originally Posted by Rockn-Roll View Post
    $10K just for the machine. I won't run out of money...the problem is finding a machine tool that meets the .001 precision with a 2HP spindle motor without any problems. It is starting to look like I will need to build my own...start with a new knee mill and build my own CNC system...the electronics is actually a piece of cake for me.
    This thread is funny.

    do you know what .001 really is?, you aint going to get that building your own machine for under $10,000 either, as you have no way to build one with out having to send parts out to get cut, let alone find a new one with your expectations for under 10k..
    those little light weight machines wont hold that tolorance from part to part.
    you need a machine with rigidity. sorry but a knee mill wont cut it either.

    lets say if you do find a machine for under 10k, I hope you plan on running it in a controlled enviroment ie same constant temp room. cause your .001 is going to be all ove the place if its not. .001 is plus or minus .0005

    a production machine vs a prototype machine are basically the same. just a production machine has more tool holders( ie tool changer) maybe a faster control, some easier set up time etc etc etc. but the BASE of the machine are pretty much the same it terms of weight and rigidity.

    You want too much for the money you want to spend especially NEW, your best bet is to buy a solid used machine. but then you have storage and power issues. either that or rethink your ".001 precision" statement.

    Delw

  11. #31
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    the nm200 spoecifically isnt pretty good for accuracy. accurate and repeatable to .001" easily within itself.

    BUT, i agree with what youve said in that theres alot more to getting .001" absolute precision than just a good ball screw.

    the thing is, i think most people dont really know what they are asking for when they talk precision (both machine buyers and part engineers/designers alilke).

    the nm200 would most likey handle anything hes expecting precision wise, unless its something that genuinely does need the precision, in which case hes better off farming it out anyway with his minimal knowledge. the machine is the least of the worries, just MEASURING a part correctly is an art on its own.)

    i mention the nm200 here only, because its in a class above the typical small hobby stuff.

  12. #32
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    If you have any thoughts about the availability of new CNC machine tools with a precision of .001" cutting a 5"x5"x5" cube of steel for less than $10,000USD then please post. I don't want to get into a discusion about precision, accuracy, or whether my skills are up to using it or not.

  13. #33
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    Quote Originally Posted by Rockn-Roll View Post
    If you have any thoughts about the availability of new CNC machine tools with a precision of .001" cutting a 5"x5"x5" cube of steel for less than $10,000USD then please post. I don't want to get into a discusion about precision, accuracy, or whether my skills are up to using it or not.
    There is none, well unless you face one side then flip the cube 5 more times and indicate each part in, however your going to have to use a pretty wide face mill and lap each face after you cut it to locate on it. thats one way to do it,. your specifications indicate you been reading too many books/posts on what real machine will do and want the same performance in a package for under 10k. thats gooing to be hard to beat, Personally if your good at building computers it might be a wise idea to stick withit so you dont get too disapointed buying something that you think will work only to be disapointed

    Just like me asking for a gaming computer that will be as fast and as reliable as the expensive ones but on a $500 budget.

    but a simple answer to your question is anything will work, how much time do you want to spend making it work. for example most machinist can do it on a cheap ass bench mill with a 3/8" endmill and then some sand paper on a granite plate. I however wouldnt waste 10k or less to do it, I would send them to a shop that has machines capable of doing the part and pay them to do it.


    Delw

  14. #34
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    Quote Originally Posted by Rockn-Roll View Post
    If you have any thoughts about the availability of new CNC machine tools with a precision of .001" cutting a 5"x5"x5" cube of steel for less than $10,000USD then please post. I don't want to get into a discusion about precision, accuracy, or whether my skills are up to using it or not.

    Help us understand what you mean by .001" precision? Does that mean +/-.001" final part accuracy? Does that mean +/-.0005" final part accuracy? Does that mean .001" programmable steps in the control/servo/stepper/encoder? All of those are very different.

    How do you intend to measure the final part? Calipers? Video? Coordinate measuring machine? As mentioned, what kind of temperature controls will you have in place? Steel has a coefficient of expansion of 7.3 E-6 in/in *F meaning if your 5" steel part changes 25 *F, it will grow .001" in all three dimensions. Can you control the workpiece, the machine, and your measuring tools that closely?

    Machine tool builders will claim a machine has an accuracy of .xxxx" and a repeatability of .xxxx" but those numbers are without a load, e.g. no cutting forces. Positioning the axes accurately and cutting accurately are not the same thing. Further, those claimed accuracies require idealized conditions such as a temperature controlled room, a solid unchanging foundation for the machine's base to sit on, etc. It may be required to laser calibrate the machine to map the pitch error and backlash of each ballscrew to assure the machine can position as accurately as possible. This would not address rigidity though.

    There are a lot of brand new full size VMCs costing over $50K that cannot hold +/-.0005" when reaching 5" deep into a steel part. The machine is not rigid enough to have the tool extend that far out of the spindle without deflecting.

    I worked for a machine tool builder. They built benchtops and full size floor machines. The cheapest benchtop was $30K and could not realistically reach 5" into a part. The full size machines went up to $80K. For a 5" deep cut in steel, I would recommend the $80K machine and some expensive tooling.

  15. #35
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    Quote Originally Posted by Rockn-Roll View Post
    I don't want to get into a discusion about precision, accuracy, or whether my skills are up to using it or not.
    unfortunately you need this discussion before thinking about buying any machine. too many people go out and buy equipment before knowing how to use it, then realize they have bought entirely the wrong thing.

    your own skill is 90% responsible for an accurate part, not the machine. on top of that you need tooling that will meet you needs.

    what are you making first of all. a block of steel is very vague. what type of steel? is it hardened? stress relieved? what are the critical features? flat surfaces? shoulders? bolt holes? round bores? do you need to mill down through the whole 5"? do features on the front and back need to be aligned with precision?

    basically, under 10k, the nm200 will do as good a job as you can reasonably expect. the machine itself will be square within a few thou per foot and has a general precision of .001" or better and no backlash so its repeatable which is usually more critical. its nice and rigid and has 6000rpm and 3hp so it will cut steel very easily with the right feeds and speeds.

  16. #36
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    Question 10k machine

    Look… I’m more into the full sized commercial milling and turning CNC machines, so bear with me here.(chair)

    Just for the fun of it, I looked at a few of the larger hobby machines and the Tormach machines and product packages looked like something that might fit Rockin-roll’s price and requirements for now. Their PCNC770 standard package without the 4th axis and a few other accessories may just fit your budget.

    It would be new and under warranty… a big plus. Rockin-roll you live in CA and they have a distributer in southern CA. Go see a demo… For that matter do not buy any machine without a satisfactory demo.

    Is there some reason these machines have not been mentioned?

    BTW-As a machine shop owner 10k can be eaten up really fast having protos made. Especially without good CAD prints.

    Steve

  17. #37
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    Quote Originally Posted by scadvice View Post

    Is there some reason these machines have not been mentioned?
    they have been mentioned..... several times.

    the 770 is their ligher weight machine though with lower torque higher speed spindle. since he's hogging out steel the pnc1100 would be more valid.

  18. #38
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    This thread is to supplement my own independent research and to benefit from the experience of machinists who may already know of a machine that would meet my needs.

    But, please let's stick to the focus of my thread...which is to obtain suggestions on machines that meet the .001" precision requirement (which I will explain in this post), have a minimum 2HP output from the motor (if the machine only draws 750Watts like the How-Mau HM-145X then the spindle motor cannot output 2HP and makes me suspect every spec on the machine is fabricated crap…I might consider 1.5HP such as the Tormach PCNC 1100 as long as it’s obvious that the motor output really is 1.5HP continuous i.e. requires a 3KW continuous power input), and have motion in the X, Y, and Z directions necessary for cutting a single face of a 5"x5"x5" cube (position the cutting tool anywhere on the 5"x5" area perpendicular to the spindle and drill down 5" then route to size and shape…no not all at once…be reasonable I’m only offering $10,000 not $100,000) made of A36 steel and the machine itself costs less than or around $10,000.

    I'm using more criteria for selecting a machine than the criteria I'm mentioning in this thread...in fact I'm learning about more criteria that I had not thought of every time I look at another machine. I started this thread hoping that the members here at CNCZone.com can help me narrow the list of choices using just a few criteria and explain some of the new criteria I find and don’t understand...and thankfully some of you are…thanks! I’m learning a lot and progressing steadily toward identifying what machine tool I need and where to buy it as well as what options I might need. It does look like a CNC machine for cutting a 5"x5"x5" steel work piece with a precision of .001" can be bought for less than $10,000 so it's just a matter of making sure I'm looking at all my options and selecting the best one. I must have looked at over 50 machines online so far and may need to look at 50 more before I'm satisfied that I have assessed all my options as well as understand all the specifications so I can make an informed decision.

    As for my ability…I graduated in 2007 with a B.S. in computer engineering with minors in math, physics, and mechanical engineering from California State University - Sacramento with 5 awards for academic achievement (5 semesters with an A average for all coursework) which included classes taught by engineers currently working at Intel. But, my original major that I declared in 1989 was mechanical engineering and I took all the lower division courses for that degree including materials and processing (The only reason I couldn’t finish my degree was that I ran out of money)...yes that means I've been checked out on all the machine tools available back then and unfortunately they had just obtained a CNC machine and they had not had time to figure out how to get it working yet or incorporate it into their curriculum other than to just show us the machine, but I spent several weeks on a lathe and several more on a horizontal mill. I did my first semester CAD on a CADKey terminal then used autocad in my second. The machine tool instructor was very thorough and demonstrated what the machines do when they are not setup properly as well as how they behave when they are.

    Especially helpful, in my opinion, was the many hours I spent in the machine shop practicing on the machines (which oddly enough very few students did even though there was an abundance of scrap) and watching the instructor experiment with the machines himself. For example I recall him setting up the mill so that the spindle was turning at its slowest possible speed so he could watch the chips as they are formed. He showed me how the speed of the feed and depth of cut changes the shape and consistency of the chips and how they relate to the precision and surface finish of the part (nice helical full length chips result in a good finish...randomly twisted and inconsistent length chips result in a poor finish). If you set the machine up properly you don’t even need a chip removal system…the darn things just spring off the machine onto the floor by magic.

    He also demonstrated cutting in the direction of the feed and in the opposite direction of the feed and we discussed why the machine behaved in certain ways depending on the direction of the cut...both from a finished part perspective as well as from a materials engineering and physics perspective (cutting in the opposite direction is effectively machining the chip away from the part...the surrounding air doesn't resist the chip moving into it...while cutting in the same direction as the feed is effectively machining the chip into the part...the chip is compressed onto the part causing deformation of the surface which results in a poor finish). This is stuff I learned over 20 years ago and still remember it because I have a deep understanding of it…or maybe it’s just second nature to me…decide for yourselves. Heck I admit that I could be wrong, but I doubt it…though if you see a flaw in my understanding of machining then let me know.

    But, it’s not just education that I have under my belt…I was a fleet mechanic for 3 years and if you add up all the time I’ve spent on my own mechanical projects it would come to 2 additional years…mostly hand tools and power tools…but some welding, sand blasting, painting, and drill press operation. I’m 53 and have been fixing or improving mechanical and electronic parts since I was 11…there’s loads of stuff that can be learned just by doing even if it’s not doing exactly what the next project is going to require. Machine tool operation is not rocket science and I don’t expect my first cut to be perfect…I plan on getting a lot of scrap to practice with before attempting my first finish piece. But, like I said…this thread is just for members that have an idea of which machine I should look at (my needs are somewhere in this thread)…and as far as my skill is concerned…if I don’t know it now then I’ll know it after I’m satisfied with my first part especially with the knowledge base that I see in this forum.

    Anyway...onto the precision requirement. When I indicate that a machine needs to have a precision of .001" that means the machine can be dead on with a precision of zero which is virtually impossible and nobody in their right mind (like me) would expect one to be dead on...or it can be off by .001". Yes...you can interpret this to be +/-.0005" if you want, and if I was providing dimensions for the mechanical drawing of an assembly then I would specify the tolerance at +/-.0005". But, when I look at a CNC machine tool I also mean that it needs to have a minimum increment of .001". Plus, the .001” precision encompasses every aspect of the machine which can restrict the accuracy of what cuts I can make for example the ways and ballscrews. Unfortunately, manufacturers never provide everything that is needed to determine the net precision, so I have to go by what is given to narrow down my options then contact the manufacturers for specifics. And, there is industry specific specifications that I don’t know about. For example, the Novakon nm200 specifications indicate a Spindle Positioning Accuracy of +/-.0005" and Repeatability of .00025"...OK, but that's just one degree of tolerance for one direction of one component...the repeatability for the X and Y positioning is not given and the accuracy is only stated for the ballscrew to be “P5”...whatever that is...my web searches aren't finding a definition of this spec., so if anyone knows what “P5” precision means then I’m open to learning. The ballscrew pitch on that machine is given as .196" and the stepper angle is .9º which seems to indicate that the smallest feed increment is .196" * .9º / 360º = .00049”, but that apparently is only true if the ballscrew is a Single Start which isn't specified. Does anyone know where I can see what the specification is for a P5 ballscrew i.e. what the positioning tolerance or backlash is? I suppose for machine specific information such as whether the ballscrew is single, double, or triple start (is this also called the lead?) I can search the machine forums and if I can’t find it start a thread on it…and/or contact the manufacturer. My goal right now is to identify which manufacturers produce a machine that appears to meet my requirements.

    So far the best match looks like the Tormach PCNC 1100. In fact, my biggest concern was that it uses the PC parallel port which based on my 28 years of experience as a computer engineer is completely unacceptable as a reliable communication medium. However, I did some research and found a post by Art Fenerty which indicated that the parallel port is being used as a pulse generator for the PC based controller signal output to trigger the input signal for the positioning motor drivers. While this does alleviate my concerns about the parallel port being used as a communication device I am still concerned about the reliability of using the port as a pulse generator output to control a motor driver where there can be absolutely no data loss at all. In fact, the Novakon spec sheet indicates that, "Due to the fluctuation of current through the VFD, there can be a variance from the Mach3 output to the actual spindle output by up to 10% + or -." OK...that’s bad…but does that include the position accuracy? If so then to eliminate this 10% variance will I need to go with a newer CNC system like FlashCutCNC, Fanuc, Siemens, or AutomationDirect?

    @delw: I’ve already spent over $10,000 for machine shops to turn my existing priceless oem parts into scrap metal…I’m through dealing with machine shops. I need to have someone with my education and mechanical skill running the machine tools.

    @Caprirs: I’m encountering the same issue with the machine specifications offered by manufacturers…they aren’t giving me the complete tolerance either. You have some good questions. The Tolerance I’m looking for on positioning a part under a tool is +/-.0005”, but the deflection of the tool under load can be up to .001” as long as it’s consistent so I can compensate with operational and finishing techniques. I have an I.T brand dial gauge caliper with .001” increments which I’ve calibrated using gage blocks and can read to within .00025” from closed to 6” which I’ve had since 1985 and an Etalon 1” micrometer with .0001” increments and a Fowler dial indicator with .001” increments, so my measuring precision is a little bit better than a hair past a freckle…and with the number of freckles I have I can do OK even with that measuring system…plus recently I’ve been able to measure by how many wrinkles a part is +/- a wrinkle or two. This is another reason why .001” is my required precision…I can easily tell if it’s within that spec, but difficult to tell if it’s better than that unless the part is less than an inch. But, you are probably right…I should invest in a larger micrometer while I’m at it. The other reason for the .001” precision requirement is for interference fit parts…I’d rather minimize my internal stresses and .001” is small, but .002” is fairly large (if both parts are off by .001”) but won’t damage the parts, while two parts that are off by .002” each would result in an interference fit with a .004” overlap…geez…internal pressures in the ton range I can do without.

    I also have several Xilinx FPGA devices that I can program any time I want to control up to 100 systems simultaneously and a complete National Instruments measuring system and I know how to make use of practically anything available from digikey, mouser, or NewarkInOne (just to name a few electronic device suppliers), so I think I’ve got everything I need to measure anything I’m making.

    The temperature and chip removal which I plan to use is the Vortex cooling system (the flood coolant systems look like a bloody stinky mess). I already have an air compressor which provides 20cfm at 100psi and is quieter than my shop vac (I spent over a month researching air compressors before I found jennyproductsinc). If necessary, I could design and build my own automated controller using an infrared heat sensor to control the coolant flow and maintain a constant temperature on the part…warming it using the hot output before starting the cut then gradually feeding in the cold output and mixing to maintain a constant temperature. I designed and built similar devices in my physics lab when I was in school…should be fun. But, I seriously doubt that I will need to go that far…making consistent thickness full-sized chips with good ambient air flow and chip removal should be sufficient to prevent heat from raising the temperature of the part and maintain good accurate cuts.

    I hope you aren’t suggesting that I should make 5” deep cuts…that’s just plain crazy for prototyping and one-off parts. I’m not in a rush to make parts. It would be just fine if the chips can’t be more than .010” thick and I’ll probably start out that small and increase only when my skills can maintain good precision. All it looks like I need is a 2HP spindle with part positioning at +/-.0005” precision and a loaded tool deflection of no more than.001” and I believe I can manage the heat and chip problems.

    @ihavenofish: The reason I’m being vague is because when I first mentioned an example of what I was going to do with the machine the first responses were that the parts were available for less than $300 which means they have no clue about Corvette Stingray wheel hubs…check the first posts…I removed this detail from my original post so that members could focus on the machine tools which is why I’m here and not on a corvette forum.

    @all: Just for the record my two front rotors and hubs cost me nearly $1,000 and I could only find one supplier in the world for the hubs and they do not have the required rivet holes to hold the rotors in place plus together they are off by as much as .005” every 3” which means the parts were made by someone with decent skill on a cheap Harbor Freight, Smithy, or Grizzly, or someone with the skills of a 10 year old on a $10,000 machine such as a better quality Grizzly or Novakon nm200 or Tormach PCNC 1100, or perhaps even someone with the skills of a dog on a $40,000 machine, or perhaps they just didn’t care and skipped a few procedures when making the parts like fastening the vice down thinking, “I’m a skilled machinist so I can just hold the part down with one hand while I eat my lunch with my other hand.”

    I don’t think anyone really needs to know why I want a machine tool with a 2HP spindle motor that can make cuts in A36 steel with .001” precision for less than $10,000 that has minimum tool/part positioning of 5”x5”x5”…the details initially confused some of the members who thought they were being helpful by discouraging me from getting a machine tool at all. I will also use the machine tool for making things that are in my head, so it’s impossible for me to be anything better than vague about what part I want to make with a machine tool with a 2HP spindle motor that can cut a 5”x5”x5” piece of A36 steel with .001” precision (did I mention this before?). Some of you have been very helpful with suggestions on 2HP Spindle motor machine tools that can cut a 5”x5”x5” piece of A36 steel with .001” precision…thank you. I hope more members will post their suggestions.

    Oh…and also during my research I located a device which takes a single phase 230V input and provides a 3-phase 230V output, so it really doesn’t matter if the 2HP Spindle motor is 3-phase.

    Hopefully I’ve included everything in this post that is needed for members to make suggestions on what machine tools I might want to consider which have a 2HP spindle motor with 3 axis movement of 5”x5”x5” and rigidity such that it can cut with .001” precision (even if I have to make .010” thick chips at feed rates of 10ipm) in hot rolled A36 steel bar stock. But, it’s becoming obvious that if one of you has a question or concern about me or my thread you won’t hesitate to post regardless of how crazy it sounds or how much it might offend me.

  19. #39
    Join Date
    Jan 2007
    Posts
    1389
    after reading this the simple answer to your problem is.

    A GRINDER

    from what little bit you describe your parts need to be ground, no ifs ans or butts about it.

    BTW most if not all machines have .0001 increments

    your definately way way over educated for the job, and its hindering in both common sence the ability of what machines can do.

    Delw

  20. #40
    Join Date
    Oct 2005
    Posts
    672
    My degree is a BSME. The info I learned in the formal classes and lab at Univ. of Arizona did not correspond well to the real world. Surprise.

    Before spending your money, I would suggest getting away from the academic environment and visiting a few machine shops. Ask the people who are spending the money on the machines, running the parts, inspecting the parts and see what they think.

    A basic rule of thumb I have learned is that if the "required" precision is .001", then the machine and the measuring tools must be an order of magnitude better. Thus, if you want .001" in the final piece, the machine must operate to .0001" and the measuring tools should have resolution of .0001". This is because of the statistical variances from all the factors beyond your control (or the machine tool builders control).

    Your above example of a stepper motor with .9* steps and a .196" pitch screw. Let's assume the machine has an encoder and runs in closed loop. The minimum step is .00049". However, the screw can rotate +/-.00048" before the encoder signals the control that the screw is out of position by one step. In this instance, all the allowable tolerance in your part is already being used by the position error of that axis. And this ignores backlash, machine deflections, tool deflection, temperature variations, etc.

    My principal concern is having a tool project from the spindle 5". That's a long reach even for a full size machining center that costs $100K. On a benchtop, that's so far, I'd be amazed if the tool will even cut. My guess is the tool will chatter and bounce, no matter how slow the feed and no matter how light the cut. I have no doubt those benchtops can drill 5" deep. It's the profile milling that would be a problem. I am not suggesting the machine would be cutting along the entire 5" axial length, perhaps only .01" at the tip. However, being that far away from the spindle bearings is likely to result in more deflection that is acceptable.

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