Thread: Tiddy CNC.

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  1. #11
    Folks. I've been wondering about some more design concepts and I thought I'd ask for some advice. I should start out by saying that my goal is to orient the machine at a relatively steep angle but as I've played around with frame concepts I have no idea how to approach that yet. I've found that one step at a time suits this pursuit in my mind…So I'm hoping for some vertical but may go for regular horizontal. The basic parameters are a 1500mm X, 1100mm Y and currently a Z with a conservative 150mm, plenty scope for changing the Z once I can make some parts.

    So. I have considered three basic options and presented them from a front view and my basic question is how to place the rails and screw so that the Y Axis gantry is best supported with minimal adverse forces being introduced?

    Option A is the most conventional I think? Option B has the virtue that the screws are under the machine, need to take more care over a frame that allows this. Option C seems to put a lot of force on one side of the linear bearing block. Any suggestions, comments welcome. Sorry it’s not in CAD but I'll flesh out the winner into a more detailed model later. Thanks. Tony.
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  3. #12
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ID:	10218Next Steps.

    Hello all. I've made some progress lately. The control system is nearly finished (bar some limit & home switch mounting), and tested on The Z Axis which is just about there. The Y is nearly there, just need to mount the stepper which leads me to the frame. I have looked at many frame's and tried to come up with my own. There were three features I was looking for

    i) I wanted the frame to be robust enough to support cutting aluminium
    ii) I wanted to be extend the rails over one end for over sized jobs (thanks jazz)
    iii) Thinking of the over size issue, I wanted the frame to be tall enough that I could mill out the lock on a door.

    The machine will be inside so I'm looking for welded frame sides with bolted cross members. I also decided I didnt want the hassle of a moveable bed, frankly I want to get the thing built (this year), so left 110mm of Z travel from the tip of the spindle, I think thats enough for general use? I also decided at this stage to have two rails (in orange) welded to the sides as support for the drop-in welded bed frame (purple). With the exception of the top rails, everything else is 50x50x3. I havent costed it yet, will probabily have to revise on that basis alone but wondered if there was any feedback on the design so far. Thanks.

  4. #13
    Just a note there about the Estop button: Buy a brand one. The cheap chinese ones have weak springs and stick sometimes right when you need it. I have el cheapo and it betrayed me a couple of times. For my new build i bought Japanese and the difference is huge. believe me, you will need an Estop button

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  6. #14
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ID:	10227I spent some time today calculating the cost of the steel. Not sure its a useful metric (for discussion) but there are just over 30M in steel box in the design. I was quite dismayed to start checking on the web for pricing only to discover several sites quoting around £350, which was more than I had in mind. Then I came across a company called ISG Steel who routed my call to the nearest depot (I live in Berkshire). Thier quote on a like for like quantity of 50x50x3 steel box section was around half the websites I'd found up to that point, also they were friendly and when I mentioned I needed more than just the one length offered me a discount. From then on in I looked at how to cut the required lengths from 7.5M stock and came out at 4.2 lengths, which was dissapointing. I modified the design to use small 5cm lengths of steel to support the bed on each of the 5 side member points, instead of a continuous rail (Orange in the picture above) and that nicely got me to all the steel in 4x7.5M lengths. Once I asked for a quote including the top rail material of 90x50x3 the whole thing with shipping came to £220. It seems a fair price and much better than many of the websites I found.

  7. #15
    Tony I pay around £26-30 depending on steel prices at that time per 7.5mtr of 50x50x3. This is from local steel supplier so I'd checkout any local steel stock holders because that 90x50x3 seems to be costing quite a bit. My local supplier delivers free because I'm just up road but he only charges £15 for 20mile radius and i'm sure other steel stockist's will be similar.!
    Last edited by JAZZCNC; 25-09-2013 at 07:12 PM.

  8. #16
    Quote Originally Posted by TonyD View Post
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ID:	10218Next Steps.

    Hello all. I've made some progress lately. The control system is nearly finished (bar some limit & home switch mounting), and tested on The Z Axis which is just about there. The Y is nearly there, just need to mount the stepper which leads me to the frame. I have looked at many frame's and tried to come up with my own. There were three features I was looking for

    i) I wanted the frame to be robust enough to support cutting aluminium
    ii) I wanted to be extend the rails over one end for over sized jobs (thanks jazz)
    iii) Thinking of the over size issue, I wanted the frame to be tall enough that I could mill out the lock on a door.

    The machine will be inside so I'm looking for welded frame sides with bolted cross members. I also decided I didnt want the hassle of a moveable bed, frankly I want to get the thing built (this year), so left 110mm of Z travel from the tip of the spindle, I think thats enough for general use? I also decided at this stage to have two rails (in orange) welded to the sides as support for the drop-in welded bed frame (purple). With the exception of the top rails, everything else is 50x50x3. I havent costed it yet, will probabily have to revise on that basis alone but wondered if there was any feedback on the design so far. Thanks.
    Hi Tony,

    I am currently doing my first real build so take my word with a grain of salt but i spend a lot of time considering, redesigning, calculating and so on...

    So looking at your idea i could not help but share my thoughts, even if they are quite influenced of my current design. I hope it helps though. Sorry, i dont mean to hijack your thread

    What i don't like at your idea is that the diagonals actually don't reinforce the profile where the rails are.

    I went on my design from 60x60x4 to 100x100x3 as i was faced by the same problem as you, great lengths and a lot of cutting and soldering.

    So here i just twisted a bit my design to accommodate it to your measures and needs. Much less rails, much stronger, much simpler to execute and cheaper, as much less weight. I would like to hear what others say but i am quite sure is strong enough for routing aluminum, not scratching.

    All in all there are 17.8 meters of 100x100x3 x 9kg per meter = 162 kg

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    My thoughts about bead and gantry:

    I made my gantry design to be from 2 pieces of 100x100x3 soldered together, just to have in mind when considering the following.

    For me to build a machine and later to upgrade it is not OK, i mean what you say for your Z depth. Please take a look below for my solution to this.
    My Z plate is 500mm long. My useful Z travel is 200mm, but i will limit it to 180mm. However the idea is the bead to be deep but over it to have a cheap wooden structure 100mm high to serve as a removable table. So now the working area is raised and there the aluminum or normal jobs will be cut. The table can be made from a couple of MDF sheets glued together or whatever scrap. Even from ribbed inside wooden structure to weight less and easy removal.

    So with everything soldered i would have quite versatile machine/ in fact its not for me the machine/ .


    Of course you can add 2 x 1600mm rails and make the bed removable, but i don't see a reason for it as you can remove the wood bed instead and keep everything much stronger. I believe on my design there is no need to add anything or change anything, as even it looks simple is thought to withstand forces from all directions. The only thing that comes to my mind that can be bettered is to place everything at asymmetrical distances to avoid frame vibrations further

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    If you use Sketchup i will be happy to send you the file with the table i draw with your dimensions so you can play with it.

    I hope that will give you some ideas .

    PS. One key part of that design that i forgot to mention is that there are plates that fix the rails supporting beams. I will lasercut them, but they can easyly be fashioned from something else. They play the role of not permitting to the beams to vibrate left right, looked from front and also seal the profile end.

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    Last edited by Boyan Silyavski; 25-09-2013 at 09:42 PM.

  9. #17
    Silyavaski. Thanks for taking the time to modify your model with the dimensions I am looking for. I have to say your frame design does look so much more solid than the one I designed. The one one constraint I have is that I need to move the machine in the house so I cant have it all welded. I can see though that if I made the cross members you have proposed as bolted rather than welded, this might work. I'll have another look at the Z height and see what that means for the rail height. Thanks again. Tony.

  10. Tony - it may be worth seeing if you have another local steel yard near you. My local supplier charge £4.1 +VAT per meter for 50x50x3 (£147.60 for 30m) as a base price & charge less than that if you order a reasonable quantity. I also get them to cut some of it to size for me - depending on quantities, they charge 50p per cut or less...this means I can fit it in my car & pick it up myself removing the delivery charge as well as saving me time cutting stock to size.

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  12. #19
    You guys are lucky to live in UK. Here in Spain i think in kg. Roughly any profile costs 1kg=1euro at the big warehouses. Unfortunately no near where i live and they don't cut to size. As i don't have a band saw i have to order from the local metal shop. If you befriend them they cut to size and sell it for 1.50 the kg with the work. if you don't know them they sell it for 2euro per kg and you pay the cut extra and that if you are lucky that they pay you any attention...

    Hence my designs are influenced by the KG and by the 6 meters length. Guess who i will be bringing some beer tomorrow

  13. #20
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ID:	10243I've been caught by the CNC bug again :)
    Silyavski emailed me a model in Sketchup to play with which convinced me to ditch Visio for my drawing and start again in Sketchup. As I tried to explain to my wife "the guys on the forum made it stronger, cheaper and lighter", which is I guess the power of good design. Trying to manage the constraints of cost and size I ended up going for 80x80x3 due to an inherent constraint with my Y Axis (which is built), which then left me trying to get the frame out of only two lengths of 7.5M stock, which led me in the end to cut the legs down to 350MM from 500MM. I phoned around today and a local Steel supplier quoted me £50 ex Vat per 7.5M length of stock. Now that its down to just £138 with VAT and delivery I'm happy. Bonus is the machine can be carried through a doorway so no bolting. So thats my current plan. Thanks for all the input, any other comments welcome.

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