. .
Page 2 of 2 FirstFirst 12
  1. #11
    Quote Originally Posted by Kitwn View Post
    And soft limits are there to stop you accidentally crashing the machine due to any one of a dozen easy mistakes. But they only work only AFTER you have used the homing switches to tell the machine where it is.
    That's not quite correct actually. Soft limits will work without a home switch by just hitting Home all, after which home will be where ever the machine happens to be parked. However, it's not advised because then you still crash the machine into the ends. But if your going to fit just home switches then you may as well make them move with the axis and have them double up as Homes and limits.

  2. #12
    Kitwn's Avatar
    Lives in Exmouth, Australia. Last Activity: 18 Minutes Ago Has been a member for 2-3 years. Has a total post count of 231. Received thanks 30 times, giving thanks to others 3 times.
    Quote Originally Posted by JAZZCNC View Post
    ....... However, it's not advised because then you still crash the machine into the ends.
    Precisely!
    I have one set of switches which double up as limit and homing switches. This is very easy to configure in LinuxCNC. Once the machine has homed itself the soft limits will prevent the limit switches from disabling the stepper drivers (most annoying!) even if I get the gantry out of the way by just pressing the LEFT button on the USB Nintendo game controller (er, sorry, meant to say "sophisticated manual pendant") until it stops.

    As Hermione Granger (almost) said "Simple but effective".
    Engineering is the art of doing for ten shillings what any fool can do for a pound.
    Wellington.

  3. #13
    Wow glad to see so many replies!

    Quote Originally Posted by NeoMorph View Post
    Iíve been operating my machine for a couple of years and if there is one thing I would tell anyone who is designing a CNC... think scenarios where things go wrong. How easy will it be to fix or adjust your machine.
    This, I'm def a fan of simple solutions. So I've done my best to keep my design free from unnecessarily complicated solutions. Sometimes it might come at the expense of top notch quality, but then again I'm here to learn!

    Quote Originally Posted by Kitwn View Post
    Welcome to the forum. You'll find plenty of help and advice here.
    You have to make a minimum number of posts (10 I think) before you can upload pictures. have a look at the forum rules.

    Kit
    Good to know. Actually, I was lucky there is such a rule as it gave me more time to consider my design (which now is even more developed) :)

    Quote Originally Posted by AndyUK View Post
    Welcome to the forum :)

    Yeah... this is quite a time-sink (and potentially money-sink) of a hobby.... ;)

    Based on your post title, I'm guessing you were thinking of grabbing one of those pre-made Chinese jobbies off ebay?
    Yup, something like that. And I'd probably been quite happy with whatever I would've got had I not dug into it. Nontheless I figure it won't be cheap anyway (time or moneywise) so I might as well make building one a hobby in itself + I'll have to learn the basics of electronics which I've never made time for!

  4. #14
    As I wait to break the 10 post limit so I can upload a pic of my design for public dissection I'll try posting a couple burning questions I have in this thread.

    1. Partly related to neomorph's comment- in an attempt to keep things simple I've considered using fk/ff ball screw supports mounted directly on the end plates/gantry plates, but this would require the steppers to be mounted with spacers (in between the stepper and the other side of the plate). The other option would be to use bk/bf supports mounted some distance away (on the "inside") from the plates, leaving enough clearance for the steppers to be mounted straight on to the plates. Do both work equally well in practice?

    2. This might be impossible to answer without more details, but I'll give it a go. I currently have planned about 150mm of Z travel which would make the gantry plates roughly 500mm in height as measured from the X (long) axis side mounted rails to the top (ie the plates would extend a further 100mm below the cutting bed). Does this seem OK or would it be advisable to give up some Z travel in favour of shorter gantry plates?

  5. #15
    AndyUK's Avatar
    Lives in Southampton, United Kingdom. Last Activity: 3 Hours Ago Has been a member for 2-3 years. Has a total post count of 218. Received thanks 52 times, giving thanks to others 22 times. Referred 1 members to the community.
    Quote Originally Posted by Juranovich View Post
    2. This might be impossible to answer without more details, but I'll give it a go. I currently have planned about 150mm of Z travel which would make the gantry plates roughly 500mm in height as measured from the X (long) axis side mounted rails to the top (ie the plates would extend a further 100mm below the cutting bed). Does this seem OK or would it be advisable to give up some Z travel in favour of shorter gantry plates?
    You'll always get a stiffer solution with less Z travel, but I wouldn't have said 15cm is unreasonable. Also depends on if the bed is adjustable or not - if not you have to consider the clearance height of any clamps or vises you plan to use. Having said that, it sounds like you're implying a 25cm (500-100-150) tall gantry? Without seeing the design its hard to say, but sounds quite hefty!

  6. #16
    Sorry, I might have been a bit unclear in my description, essentially the gantry plates would be roughly 60 cm in total height. But what matters, I suppose, is that the gantry would be 18cm + two round linear rails mounted top and bottom adding a further 5cm or so to the overall height of the gantry. While the space between the non-adjustable bed and the bottom of the gantry (including the rail) is 20 cm, the free height from the tip of a typical router bit on a mounted spindle down to the bed is 15cm (when Z is in its top position). Hopefully that cleared thing up a bit!

  7. #17
    You should have very clear what you would like to do with that machine. But IMO the best machine for a starter is CNC mini mill. Smaller area but a real machine, not a toy. And will not lose resale value so much. And can make real parts. very good for learning.

    Worse thing to buy is crappy Chinese machine and God forbid a belt driven machine.
    project 1 , 2, Dust Shoe ...

  8. #18
    Quote Originally Posted by Boyan Silyavski View Post
    God forbid a belt driven machine.
    Here we go again.! . . . Have you ever built or used a belt-driven machine.?
    For a small router, (or even a basic large machine) then belt drive is a very good solution with high efficiency and low backlash that's reasonably cheap and easy. Yes, maybe not ball screw good but much better than other methods like R&P or cheap leap screws if done correctly. . . . .Don't knock it until you've tried it.!

  9. #19
    Quote Originally Posted by Juranovich View Post
    1. Partly related to neomorph's comment- in an attempt to keep things simple I've considered using fk/ff ball screw supports mounted directly on the end plates/gantry plates, but this would require the steppers to be mounted with spacers (in between the stepper and the other side of the plate). The other option would be to use bk/bf supports mounted some distance away (on the "inside") from the plates, leaving enough clearance for the steppers to be mounted straight on to the plates. Do both work equally well in practice?
    Yes either works fine. Also consider attaching the motors to the screws with belts as it provides a few advatages. It Lowers resonance, allows a ratio and gives flexabilty in location so can turn motors inwards and keep width narrower.

    Quote Originally Posted by Juranovich View Post
    2. This might be impossible to answer without more details, but I'll give it a go. I currently have planned about 150mm of Z travel which would make the gantry plates roughly 500mm in height as measured from the X (long) axis side mounted rails to the top (ie the plates would extend a further 100mm below the cutting bed). Does this seem OK or would it be advisable to give up some Z travel in favour of shorter gantry plates?
    With out seeing your design then yes it's not easy to say but 150mm Z travel is standard on router machines I build and 500mm length plates is about right so your not far away.

  10. Quote Originally Posted by JAZZCNC View Post
    Here we go again.! . . . Have you ever built or used a belt-driven machine.?
    For a small router, (or even a basic large machine) then belt drive is a very good solution with high efficiency and low backlash that's reasonably cheap and easy. Yes, maybe not ball screw good but much better than other methods like R&P or cheap leap screws if done correctly. . . . .Don't knock it until you've tried it.!
    100% agree.

    Double belting reduces a lot of the stretch too. I glued my lower belt to the aluminium and it really improved the accuracy too.

    It all depends on what materials you want to work with. Woods and plastics and cast aluminium (yeah, ALWAYS go with cast if you donít want to get tons of aluminium welding to your endmills) then belt driven machines are great for learning the ins and outs of CNC... plus itís cheaper to fix if you have a horrible crash that would warp the screws and ways of a non-belt driven machine.

    I had one incident where a glitch decided to rapid in the long axis (X axis on my machine) at crazy speed and it slammed into the limit sensors (thank god I put them in spring mounted blocks) before ramming the hard limits. Then it was skipping gears before the limit switch went ďeh what.. WHAT THE F???Ē Before shutting the machine down.

    Thatís not so say it was slow to respond... it was just that the incident developed so darn fast that it accelerated into the stops like a crash test dummy machine. If it had been a screw driven machine I would be looking at stripping the whole thing down due to warp... and the cause? A glitch in the gcode plus me messing with the X max rate and inputting 1500000 instead of 1500.000.

    CNC baby steps. Belt driven machines are good to learn on as replacing belts is cheaper than replacing ball screws. Now imagine that crash happening to a screw driven machine???? 😱🤯🤬

    Butttttt... donít think that the eBay machines are good value unless you are ready to possibly throw away all that money. Better to buy a machine from a reputable seller in your country who can help.

    It may cost a little more but if anything goes wrong they are there to help. I had a bad CNC xPro controller which was exchanged after trying to get it working with the supplier. No cost to me... and sorted FAST!

Page 2 of 2 FirstFirst 12

Thread Information

Users Browsing this Thread

There are currently 2 users browsing this thread. (1 members and 1 guests)

  1. NeoMorph

Similar Threads

  1. Academic research on CAM CAD software/ Help please
    By lorenzo0572 in forum CAD & CAM Software
    Replies: 3
    Last Post: 03-05-2014, 11:08 AM

Bookmarks

Posting Permissions

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