Steel Gantry Router - Page 3


Page 3 of 3 FirstFirst 123
Results 25 to 34 of 34

Thread: Steel Gantry Router

  1. #25
    Member
    Join Date
    Mar 2017
    Location
    United States
    Posts
    163
    Downloads
    0
    Uploads
    0

    Default Re: Steel Gantry Router

    Your design looks like it would lend itself well to an idea I have had in the back of my head for a while. Think about this idea for a sec.

    Use a Fab Block as the basis for your table design. https://weldtables.com/collections/f...48x48-fabblock
    It is a welding table base that is constructed from tab and slot pieces. I think it would be a great starting point for a flat surface that has parallel sides and will allow you to build any base on it that you want.

    I think that a welded frame will give you good rigidity the problem is warping introduced by the welding process. These tables are designed to stay flat during welding.



  2. #26
    Member peteeng's Avatar
    Join Date
    Jul 2018
    Location
    dum dum
    Posts
    634
    Downloads
    0
    Uploads
    0

    Default Re: Steel Gantry Router

    Hi Max - They are good but getting them to OZ is a killer cost! Peter



  3. #27
    Member
    Join Date
    Feb 2016
    Location
    Australia
    Posts
    54
    Downloads
    0
    Uploads
    0

    Default Re: Steel Gantry Router

    Gerry,
    - Thanks for the link, I had read that thread about a month ago, maybe will run through it again and compare the findings, there is a huge amount of info in there.
    - Good to know about the DMM's in Step/Dir, I will do some more research into that, Unless there is evidence one way is better I'll likely go with whatever is easiest to set up.

    Peteeng,
    - I missed the question before - I am using Solidworks 2018, which is available to me through work, I also use Fusion360 but it frustrates me a little, though it also has FEA. I haven't done a lot of FEA in Solidworks but will get up to speed in it and try and get some numbers - I will run over your build thread and the one Gerry posted, but what forces exactly should I be checking? i.e a 10n force on the cutter perpendicular to the endmill, tested in each direction?
    - I agree the Z-axis needs a lot of work, I will spend some time studying principles and other designs then get right into it. It's only in very early draft stage at this point - maybe an hours work total so far on the Z axis itself. - it has a long way to go.
    - Thankyou for the link on the commercial router, though it looks like the 600x900 model is $12k, I have emailed to get the price on a 1212, I'm guessing it'll be in the 16-20k area. I have attached some photos of the Z on that machine - the design does not look particularly rigid compared to the advice I've had here, maybe I am missing something? though the design is quite similar to my early draft.

    Hanermo,
    - Thanks for the advice, I live in Australia and the second hand machine market is not great, to get any commercial machine second hand is still $25k+ maybe I need to set up some alerts on ebay and other marketplaces for used machines.

    Tommylight,
    I checked a 1500mm ballscrew at 20mm root diameter (i'll be using 2525 screws) and it came back at 1075rpm as the critical speed. this is using Metric Critical Speed Calculator | Nook Industries
    what are your thoughts?


    Thanks all for your input

    Attached Thumbnails Attached Thumbnails Steel Gantry Router-z1-jpg   Steel Gantry Router-z2-jpg  


  4. #28
    Member peteeng's Avatar
    Join Date
    Jul 2018
    Location
    dum dum
    Posts
    634
    Downloads
    0
    Uploads
    0

    Default Re: Steel Gantry Router

    Hi Stuart - the machine you are designing will be much more rigid then many commercial machines. That's one reason you are doing it I'll reread the Sapele thread. They concluded that the 200x200x6mm is the go for the gantry but they didn't seem to be clear on the conclusion for the Z axis. If you have a design I'm happy to run it in FE, I'd need a step file from SW. The worse case for bending is a push or pull perpendicular to the gantry with the Z axis down. I use a design load of 1000N and the target stiffness is 10N/um ie at 1000N applied the spindle should deflect <1.0mm. If you do not include the bearing stiffness and other contact conditions then I'd aim at 20N/um as your structure will be about 50% efficient. The Sapele thread did mention that they used SHS and when bolted up the linear bearings jammed due to the cupped surface. They had to scrape and fill to get flat. So maybe work with the SHS supplier to get a flat piece or get two tracks milled on it, or at least have a plan B if you can;t get the linears to work. Peter



  5. #29
    Member
    Join Date
    Feb 2016
    Location
    Australia
    Posts
    54
    Downloads
    0
    Uploads
    0

    Default Re: Steel Gantry Router

    When I get a minute to sit down I’ll take a look at the FEA, I’ve done it for single parts, but not assemblies so will have to have a play with it.

    I am going to start putting prices together for the frame, a have a friend who works for a fabricator that might be able to weld the frame up and heat treat it, which would be a big win.

    I figure I’ll continue with the design, while getting rough quotes for all the parts, then go from there. I’ve had a look at a lot of commercial Z axis designs over the last few days and am pretty confident I can get something together that will work well. A lot of the big names just use two bits of plate with 25mm linear rails between them... As Peter said, I think I can do better than that.

    For the X Carriage I’m looking at a 2” 6061 block, milled flat potentially with a groove milled in it for Z ballnut clearance. Then maybe 1.5” 6061 milled flat for the Z. I’m yet to draw it up. But will see how it looks.

    Having read up a bit on Z-axis design, It sounds like the rails on the Z can be quite close together without any negative effect, as long as there is as much distance between bearing blocks as possible.



  6. #30
    Member peteeng's Avatar
    Join Date
    Jul 2018
    Location
    dum dum
    Posts
    634
    Downloads
    0
    Uploads
    0

    Default Re: Steel Gantry Router

    Hi Stuart - Seems there are a couple of treaters in Newcastle or is the oven near Armidale? Peter

    The carriage does not have to be very stiff I've found, But the bearings have to be very close together. In this case you need shear stiffness not bending stiffness. For instance if you put the bearings on top of each other that's great but how do you assemble it or adjust it? A few nightmares in there for you.

    The Z axis is however a cantilever and bending stiffness is king in this part. A typical commercial machine uses 25mm steel plate and its not stiff enough to match your gantry or get to 10N/um. Get some budget figures and concepts and geometry along the way to get a feel for where your going. Everything in the machine is connected and changing something may have far reaching consequences so you need to get thru some design rounds to figure out a few things. Your first objective is to get a functional general arrangement going. By functional I mean you can look at it and say there are no fatal errors that you can see in the design. Then it will be another few rounds to get it really good. Peter

    It would be interesting to know how stiff your ShapeOK is, you'll need a dial gauge and spring scale...

    Last edited by peteeng; 08-12-2019 at 06:40 AM.


  7. #31
    Member
    Join Date
    Mar 2015
    Posts
    5
    Downloads
    0
    Uploads
    0

    Default Re: Steel Gantry Router

    Quote Originally Posted by ger21 View Post
    Looks like it did indeed start with the TinyG, but now uses their own code.

    https://news.ycombinator.com/item?id=17288432
    I'm Doug Coffland at Buildbotics. We did indeed start with TinyG. After three years of development, there is very little of the TinyG code left. Our controller has 4 stepper motor drivers built in. We do not interface with servo motors. On the web interface, the Buildbotics Controller offers the ability to plug a monitor, keyboard, and mouse directly into the back of the controller, this eliminates the need to connect across a network if you don't want to do that. I use a touchscreen monitor in my shop, so I don't need the keyboard or mouse either.

    I appreciate that you have looked at our product. If you decide that steppers will do the job, feel free to send me an email a t dougcoffland@gmail.com. I'd be happy to answer all of your questions.



  8. #32
    Member peteeng's Avatar
    Join Date
    Jul 2018
    Location
    dum dum
    Posts
    634
    Downloads
    0
    Uploads
    0

    Default Re: Steel Gantry Router

    Hi Stuart - Looking at your drive speed. If the critical speed is ~1000rpm and your pitch is 5mm (I'll assume the 2525 mentioned is actually 2505) this means your max feed rate is 5000mm/min which is quite slow for a rapid for instance. But if your happy with 5m/min max then that's fine. Cheers Peter



  9. #33
    Member
    Join Date
    Feb 2016
    Location
    Australia
    Posts
    54
    Downloads
    0
    Uploads
    0

    Default Re: Steel Gantry Router

    Family holidays always slow down the progress!

    Peter, it was no typo, I am indeed looking at 2525 ballscrews, which should give me around 25m/min rapids with the screw at 1000rpm, and realistically it'll be reduced to about 75% of that.

    The servos will be running a 3:1 reduction so at the servos max rpm of 3000 I should have the ~1500mm ballscrew at its critical speed.

    I haven't done the models or calcs on the z yet but I can likely get away with a 2020 ballscrew on the z due to the shorter length of screw and the fact that the higher rapid speeds will not be as important on that axis.


    I'm progressing with the models of the z axis, however time will be pretty limited over the next month or so. I'm fairly confident in my design, however the cost of aluminium stock may impact the design choices - I will send off for early quotes shortly to see where I'm sitting.

    I may have a couple of jobs coming in for my recently purchased laser cutter which will bump up the budget for the router somewhat. Those things print money!



  10. #34
    Member peteeng's Avatar
    Join Date
    Jul 2018
    Location
    dum dum
    Posts
    634
    Downloads
    0
    Uploads
    0

    Default Re: Steel Gantry Router

    Ok - Makes sense now.

    Something to think about if your comfortable in epoxying steel and aluminium together is to make a composite Z axis or carriage. Say you glue 2mm skins on the outside of an aluminium plate. It gains a small amount of weight but gains lots of stiffness, as steel is 3x stiffer then the Al. Once you get more geometry settled and costs you may want to optimise this a bit better. I'll figure out webs vs composite soon. Maybe better then using webs (no). Peter

    Edit - Seems the webs are the go. They gain rigidity far quicker then the sandwich does and the main plate will be thinner as well. If we use a 25mm thick plate as a reference then if we add 20mm thick webs 50mm high it will be 10X stiffer then the 25mm plate. An Al plate 36mm thick with 20x50 webs will be 5.5X stiffer then the 25mm steel plate but less then half the weight of the web steel plate. So need to establish rigidity target and tune the webs to get the min weight and max stiffness. Cheers peter S

    Attached Thumbnails Attached Thumbnails Steel Gantry Router-composite-jpg   Steel Gantry Router-z-axis-jpg  
    Last edited by peteeng; Yesterday at 04:42 AM.


Page 3 of 3 FirstFirst 123

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  


About CNCzone.com

    We are the largest and most active discussion forum for manufacturing industry. The site is 100% free to join and use, so join today!

Follow us on


Our Brands

Steel Gantry Router

Steel Gantry Router