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  1. #61
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    I just made a quick plan for the prototype buidling. actually I'm thinking of make a new final product bring to market. I don't clearly know the small desktop CNC market will be for this one, but I'm sure this will be something worth.

    okey. here is the planning now:
    a. I will machining the casting parts with my bigger CNC machine. but maybe just manually oprating for no much time to program and some possible temperary adjusting for the first one. The parts have been rough machined already before a year and jsut left about 1mm machining remaining. so I will just need to do the finishing machining.

    b. I have already purchased the ballscrews and linear parts long time ago. for initial prototype, I just ordered rolled type ballscrews of P7 class. Actually they should be enough accuracy for most hobby working especially for the small travel distance. Ofcourse grind type of P3 class ones are also avaliable and better. I ordered some HIWIN linear parts for this building of C class also. and maybe H class next for better. just not decided yet. or maybe just optional.

    c. I decide to develop a small milling spindle unit for this milling machine. I considered much about the electric spindle units and think it should be exchangable both of them. some times milling spindle is best for mill cutting. but sometimes electric spinle will be best for carving. So I planning a milling spindle of ER25, MAX 3000-5000RPM, MAX torque 2N.M, synchronous drive, same OD as electric spindles of 65mm. so it can be exchangable with some 800W or 1.5KW, 24000RPM electric ones.

    d. The spindle driving I want to use a BLDC one of around 0.75-1HP one. I have two reasons for this selection: firstly, the BLDC motor has much better torque and power than AC ones in similiar size; secondary, I have a BLDC driver sample from some engineering side for very long time and never tested before. so, I will do this together^-^.

    e. The axis drive will use the tradional steppers firstly. just easy to apply for initial building and no problem for common usage. I have also thought of the SERVO ones, but I don't want to make it to complex for begining even I have some good resource to get such servo ones. but I also keep it for optional. A further thinking is using GIVIs to buid a full-closed loop servo system. but won't do it now.

    f. A full enclosure is still a consideration now. Actually I will start to design it soon. Since it's just a mini desktop machine, I will make the enclosure in compact size also, but of course, enough for oprating. and all other accesories will be considered also as the industrial machines. I'm not very sure the enclosure is very necessory to everybody. maybe I should build a machine just with a tray of worktable, and a electric control box placing aside? ? just to be decided.

    g. About the electric system, I'm planning to contain the power system, I think should be around 400W capacity for axis drivers. Transformer is the best for best overload capacity. but if I found a good switch power one, I will consider it also. A BLDC driver, or a VFD driver is basic part. The stepper/servo dirvers, I will design to 4 to leave remaining for possible 4th axis next. And the interface board of parallel port using MACH software etc. but some USB MODBUS interface will be a longterm planning. Home switches, limit switches are also contained. Some simple LEDs to show the status with other POWER switch, ESTOP button on control pannel; sys fan, work light, cooling system for electric spindle... Just one by one next.

    okey. just thinking the items above. any ideas just be welcomed. I'd like to talk on any subjects. Thanks again guys.



  2. #62
    Registered Skyfire's Avatar
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    Here are some pictures taken a year before in the casting factory. It's lucky they are still in my camera. The castings were just left outside in the yard. They will look bad with many rust. But believe me, this is very good thing for casting stability.

    The casting surface quality look good. I guess my molds were working well^-^.













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    Hi guys, I picked out the casting parts just now. They have been stored in the corner long time. So have some rust even had been painted before.

    The parts are realy some heavy by the structure thickness of 12-14mm. So the total stifness should be very good on such mini desktop size machine. We will see the result when finishing.

    I will start the machining now and upload some cutting process and finished part then.







    Last edited by Skyfire; 02-04-2013 at 01:47 PM. Reason: correct picture links


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    I did some machining today start from the base part. Only get one part done after half a day by manual operation with a DRO on machine. It's some slowly because need to exchange mill tool, drill tools frequently. but the process is smooth. I totally got 7 base casting pieces now--actually I had just wanted 1-2 pieces for prototype but the supplier totally made 7 sets for me by mistake. so I think I will write a G code program for remains to save time and my energy.

    I took several pictues during the machining to share now. I have to say this is the real begining to build a CNC. just geting more and more interesting from now. But it means hard works start also and no exciting point until now.

    start milling the slot for linear rails:


    drill many holes for screws:


    the first finished base part:




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    About machining, I have some addtional points to say here.

    a. the machining accuracy is very important especially to build a new machine. Normally, if you want to build a machine with a decided accuracy level, you need to make sure the machining accuracy is of a higher level. but it's not very certain now if you are using linear parts. the machining level could be the same as you want to build. or some traditional manual fixing method will work too after initial machining. Human hand is always the best tool until now for building machine---maybe not ture anymore in future, I guess.

    b. the CNC mill machine I'm using in this building, is some much bigger one I developed before. the accuracy on every dimensions are within 0.02mm(0.001"). This had been carefully adjusted and just the same accuracy level I want this build achieve. So that's related to the point I mentioned above on linear part application. So If going smooth, the machining parts will be just usable without scraping or some other post conduct. We will see when assembling then.

    c. I will also need to say, the whole machine structure is not as solid as most people think. Actually it's a "flexible" system. so must ensure some good finishing milling to the castings to avoid unexpected accuracy lost. Every step of the building must try to eliminate possible error to make sure the last assembled machine to be a precision one.

    Cheers. Thanks for reading and welcome any input.



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    Hi everyone.

    I machined the worktable piece today. This is some key important part for whole machine. The milling must be very smooth and the position of all the mounting screw holes must be accurate. So I wrote a simple G code program and machined this piece with MACH software control.

    It's still some boring work by much dirt and chips... but get some comfortable after the milling and drilling works. Here are the machining progress pictures.







    After the rail slot milling and drilling works, I found the top surface and side surface are not very accurate. This will make the next works much hard. So I milled the sufaces with a big surface mill tool.




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    Very interesting thread! I'm happy you came back to show progress.



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    Then I cleaned the worktable part and tried to install the liear rails. It seemed the rails are fit well and mounting holes are exactly the right position. So It's a first succeful step now.

    The worktable is still not good looking now. It will be ground to be shining and will be nice then. But the most important thing is to make the worktable surface very smooth with the error under 0.01mm. Normally, it should be 0.005mm. I don't have a grind machine, so I will send to some machining side work for me later and just leave it as it is now.

    just finish top surface mill:




    try to install the linear rails:




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    Quote Originally Posted by ebrewste View Post
    Very interesting thread! I'm happy you came back to show progress.
    Hi ebrewste, thank you for input. I'm so sorry for pause of this thread over a year for many reasons. I will finish it this time and promise to bring an exciting real benchtop CNC mill. Please keep an eye on this thread.





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    I went back to the beginning post and I don't see the dimensions and travels on that mill. Care to tell us? Great work btw, how much did it cost you to have them cast?



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    Quote Originally Posted by Winterwatchers View Post
    I went back to the beginning post and I don't see the dimensions and travels on that mill. Care to tell us? Great work btw, how much did it cost you to have them cast?
    Hi Winterwatchers, thank you for reading my thread.
    I must forgot to mark the dimensions and travel range before. Sure, I can tell the dimension features.

    The overall dimension will be L*W*H :19"*19"*28.3"(maybe some small difference depending on motor length)

    The traveling was designed to be: XYZ 8"*5"*8", but have some remaining distance so should be slightly bigger than this(around 8.3"*5.3"*8.3").

    I'd like to talk some about the castings too. I can't remember the exact cost when casting but the total weight is around 90kg(198lbs), so roughly the net casting cost then should be around $120. Castings, you know, is not a big cost part of a precision machine. If you don't require good material, it can be even cheaper. But if you want some real things like meehanite, it will be much more expensive.

    glad to talk, cheers~



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    Excellent work on this. I have enjoyed reading so far. I would imagine machining the castings like this in a non production environment would probably cost well over what the actual casing costs.
    In a production setting, the castings are probably cheaper as well.

    That doesn't mean that it isn't worth the extra cost though. Especially since it will receive far more attention than a production frame might.
    Keep up the excellent work. Love seeing pictures of everything.

    Lee


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    Quote Originally Posted by LeeWay View Post
    Excellent work on this. I have enjoyed reading so far. I would imagine machining the castings like this in a non production environment would probably cost well over what the actual casing costs.
    In a production setting, the castings are probably cheaper as well.

    That doesn't mean that it isn't worth the extra cost though. Especially since it will receive far more attention than a production frame might.
    Keep up the excellent work. Love seeing pictures of everything.
    Thanks Lee. You are right that if prepare everything for just build one machine it will be a big cost for many tools and materials you may not use any more. Fortunately I have most tools needed for machine building and only need some milling tools purchased this time.

    I had been R&D side in some former machine projects. You guys may not know me but must know some projects I did before. I started to build machines on my own since last year. Normally I will just send sketch to my machining suppiers to get the parts. But for this building, I have a CNC mill just big enough to do this project completely by myself.

    I just want to do something abnormal this time. Make everthing original from myslef, original ideas, original works by my own hand and form a real good thing at last. I want it to be better and some different than current other benchtop mills. Not conversion, not copy, just most reasonable banlanced and system designed. I want it to be perfect you know.

    Thank you again for attenton. welcome any talk. cheers~



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    Gold Member LeeWay's Avatar
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    The mill I am using for production is built on an aluminum backbone. No, it won't hog off steel, but cuts it very well. It does lack the structural rigidity of a cast iron base, however with precisely installed precision parts, it is quite capable of producing good parts. It isn't afflicted by the mass a larger machine would have on the parts. IE wear.
    You are using basically the same type precision parts and adding the mass and strength of cast iron. IMO I think that is the best of both worlds.

    Lee


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    Quote Originally Posted by LeeWay View Post
    The mill I am using for production is built on an aluminum backbone. No, it won't hog off steel, but cuts it very well. It does lack the structural rigidity of a cast iron base, however with precisely installed precision parts, it is quite capable of producing good parts. It isn't afflicted by the mass a larger machine would have on the parts. IE wear.
    You are using basically the same type precision parts and adding the mass and strength of cast iron. IMO I think that is the best of both worlds.
    Hi Lee. I think we are touching a very basic question about machine. The structural issue is elementary for a machine start from the initial idea of a building.

    First, nothing is absolutely best but does something fit for you mostly. Aluminium structure doesn't mean weak and no precision if having good structural design and thick material and good machining, assembling. The actural problem is: do you apply any heavy cut with distructive cuting force?

    The whole machine structure is actually a flexible system, including the machine body and cutting tool, workpiece. so that's why we always need finishing machining to get accurate size. If always cutting smooth, I guess a hard wood structure will work well too. So, if you don't have distructive cuting app. the machine will definately keep accurate and work well.

    Acutally a casting iron structure means high rigidity to resisit the impact cuting force under heavy cut. the initial accuracy maybe the same, but the point is to keep the accuracy under hard work conditions.

    Even the real big industrial CNC, must avoid the distructive cuting as well. Every heavy impact of the tool will cause accuracy lost. So we always try to build machine rigid, and on the other hand, use it carefully.

    I just had a very bad tool knock today. the reason is I made a mistake in the G code by forgeting to input a "M3" code to start the spindle before cuting.
    So the big tool--a 16mm alloy end mill touched the workpiece and broken in half by the feeding torque. That's really big accident and if the machine structure isn't strong enough, the accuracy of the machine will be fnished.



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    Hi guys. I just finished another part of Y slider today. It's something more complex than the base and worktable. the slider needs milling the linear slot, many screw holes and ballscrew mount surface both sides. And the point is, must make sure accurate perpendicularity between both sides. Or the X-Y travel may be never adjusted to be vertical. so this piece costed me much more time to make sure of this. I'm thinking that I should make some frock clamping tool in next machining to help locate the slider exactly on the mill worktable.

    Anyway, it's done now. here are still some pictures of this part. still working under CNC control. It will be a disaster to deal with so many holes and surfaces manually.







    look some comfortable now:




    Last edited by Skyfire; 02-05-2013 at 01:54 PM. Reason: comments correction


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    I'm getting some tired these three days machining by myself. so I'm planning to a inital assemble the worktable and slider module from tomorrow to confirm they will fit together with linear parts and ballscrews etc well. This will be some easier job to make some rest.

    I will machine the rest parts of column and spindle box 1-2 days later.

    I just found several fomer pictures taken on some my machining supplier side to share with you guys.

    the Machining of machine worktable is something interesting:

    the first machining of the T slots will be milled using a horizontal type mill machine. And using three tools together to be more efficient.


    start cutting...




    then mill the T slot on vertical mill with a T slot milling tool.


    finished worktable part




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    And another picture of milling a machine base on a real CNC center with ATC. This is the best way for batch production. I think I will put the machining works to this one when have some real production of this benchtop machine. Or, I maybe build an ATC machine for myown.
    Anyway, the ATC is very helpful to make machining easier and fast. I realized this much more than before now since every part will need to change tools at least 3-4 times and you must wait beside. So.. maybe this is the next plan...



    Thanks for reading again.



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    Hi guys. I'm updating now but not much work done today. I just watched a movie Cloud Atlas. It's an amazing movie very long almost 3 hours. Maybe you guys watched too.

    I just formally installed the linear parts to another worktable milled yesterday. I will show how to install th linear rails correctly, but of course, not the only correct way. In the guide books of some famous brand linear parts, It will be a detailed part to show how to install the rails.

    okey. start now:

    Firstly I just fasten one of the rails randomly to a rail slot. but must pay attention to the arrow printed on the rail top to the reference wall of the slot. The linear rail is not straight at all when it is free. so must be adjusted after mounting. Here I use a stone ruler of top acuuracy as the refer standard. The stone ruler accuracy is normally about 2.5-7um and never changed as iron rulers. So it will be best to be the standard to build a 10um class machine. That's the simple rule of machine building---the refer standard must be higher magnitude.

    There are several ways to fasten the screws. The guide book from linear part supplier may suggest fasten from one end to the other and give a standard of fasten torque. I like to fasten the middle screw first--that's not big issue. You can find your way to be best. Anyway, I adjusted the first rail to under 0.01mm error to the stone ruler with a dialgage. It's not too difficult because the reference wall is straight enough so no need much adjusting works, but of course this work need some skill and experience, and patience.


    Next, use the first rail as the standard to munt the second rail. leave one linear block on each rail and measure the distance changing between two blocks to be always the same. This way we can make sure the two rails are completely parellel. One issue must pay attention: the blocks all have two side different. One is ground, one is not. Must use the ground side as the measure side.


    after the two steps above, the linear rails are installed succefully. Now just install all the 4 linear blocks. and check every screws fastened well. The last step: add the small plastic green cover to every screw hole. It's not just for looking nice. the reason is that, without the covers, when the block moves fast across the screw hole, it will generate big air resistance here.

    Here is the fnished worktable with linears. looking much nice now and make me a little excited.




    Last edited by Skyfire; 02-06-2013 at 03:00 PM. Reason: edit pictures
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    What a project! Looks awesome so far though!



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Show how to build a CNC machine from the very beginning to the end

Show how to build a CNC machine from the very beginning to the end