528,075 active members*
2,596 visitors online*
Register for free
Login
Page 1 of 2 12
Results 1 to 20 of 26
  1. #1
    Registered
    Join Date
    Jan 2015
    Posts
    27

    Gantry mill with moving gantry for Z-axis

    I'm simply posting to attempt to contribute to this great community. I'm an avid RC aircraft hobbyist, and got into CNC machines to make things for that hobby. I started on a Shapeoko 2 and quickly found out it was garbage for anything but wood or plastic. I then set off on designing and building my own CNC router/mill. I wanted to be capable of cutting aluminum, so I when down the 'mill' path. It has cut some aluminum parts for me. I still need to get a better feel for the speeds and feeds. I also need a better spindle. I have a Sherline on there right now, and the case is kinda wimpy. I went with a gantry that moves up and down to solve what I perceived to be a weakness in most CNC router designs. Most simply have the gantry at a fixed height and move the Spindle down. When one does this, the rigidity suffers when the spindle is deployed downwards. My goal with this design here was to always keep the gantry behind the spindle, no matter the z-axis elevation. This also permitted quite a large increase in the z-axis capacity, relative to other gantry-type machines. The height of the side plates is what determines the z-axis capacity. Those plates I have there let me get about 10 inches of Z travel. I can stand plates up on end in the vise and machine features into the width of plates, for example.

    Here's a video showing the machine moving in all axes:


    Here are some pics:

    This is the front of the machine. It has dual y-axis ballscrews, a single x-axis ballscrew, and the entire gantry moves up and down for the z-axis, so the Z has two ballscrews


    Here is a side view of the machine, showing the gantry plate, and one of the y-axis ballscrews


    Here's a view isometric showing the rear. One can start to see the dual z-axis ballscrews


    Here's a straight-on view of the rear of the machine


    A closeup of the x-axis, showing the headstock and its drive motor. That's a hobby brushless motor. I use a regualr helicopter ESC to drive it and an 18 V power supply. The pulleys from motor to spindle have a 1:2 ratio.


    Here's a closeup of one of the z-axis ballscrews attachment points to the gantry.
    Attached Thumbnails Attached Thumbnails IMG_0519.jpg  

  2. #2
    Gold Member
    Join Date
    Apr 2004
    Posts
    5110

    Re: Gantry mill with moving gantry for Z-axis

    That's an interesting design, reminiscent of some 3D printers I've seen. Is it intended mostly for cutout work, where everything's pretty much happening on a single level? Have you tried it on 3D work, where there's lots of little moves for the Z axis to make?
    Andrew Werby
    Website

  3. #3
    Registered
    Join Date
    Jan 2015
    Posts
    27

    Re: Gantry mill with moving gantry for Z-axis

    I have done aluminum parts that have multiple z-axis moves, but no 3D contour work.

  4. #4
    Registered
    Join Date
    Jan 2015
    Posts
    27

    Re: Gantry mill with moving gantry for Z-axis

    I finally got a video of this bad boy cutting some aluminum:
    https://www.youtube.com/watch?v=6a3MA9a_FA0

  5. #5
    Registered
    Join Date
    Feb 2016
    Posts
    13

    Re: Gantry mill with moving gantry for Z-axis

    Cool! I've been thinking of doing something similar to what you built. How do you like it so far? Is there anything you would do different?

  6. #6
    Registered
    Join Date
    Mar 2014
    Posts
    970

    Re: Gantry mill with moving gantry for Z-axis

    Interesting. Is that a brushless outrunner rc motor? Are you going to cut a cage for it?

    Nice build by the way.

    Edit: yes, brushless. I've missed the first post.

  7. #7
    Registered
    Join Date
    Jan 2015
    Posts
    27

    Re: Gantry mill with moving gantry for Z-axis

    There's something weak about the spindle housing. I think the way I have it attached is the weak point. I can fix that easily by just making myself another spindle housing that's beefier, and doesn't attach with that 'flange' style mount. The machine is difficult to clean, there's quite a few nooks and crannies that are hard to get to. I haven't figured out a rearrangement to address that though. This machine has 5 steppers. A 5-driver box is hard to find. I have the MX4660 which gives me 4 drivers. I simply paralleled the wires for the two z-axis motors into one driver. The way the MX4660 works means I can't drive those z-axis motors very fast, because it'll lose steps when trying to drive two motors from a single driver. I have a 5th stand-alone driver that I need to wire up to the step and direction pulses. It's just added complexity. The stackup along the y-axis is kinda big, and the cutting tool is far in front of the gantry. I'd like to compact that a little more because it results in deadspace and eats in to the overal travel of the machine. If I go full +Y, the gantry plates are the first thing to hit the backside of the frame, but the cutting tool is far in front of that. Maybe the x-axis ballscrew can be behind the gantry. I haven't sorted that out yet. I love the z-axis clearance. My initial build had just 3 inches of z-axis movement and that was a mistake. With those big tall gantry sides I can move the whole thing up and out of the way to get a vise in there, or a tall part even!

  8. #8
    Registered
    Join Date
    Jan 2015
    Posts
    27

    Re: Gantry mill with moving gantry for Z-axis

    Quote Originally Posted by Azalin View Post
    Interesting. Is that a brushless outrunner rc motor? Are you going to cut a cage for it?

    Nice build by the way.

    Edit: yes, brushless. I've missed the first post.
    I was surprised how well that burshless motor can drive the spindle. I've only had it stall out once when I made an error in movement speed and cutting depth. What do you mean by a cage? cage for the whole machine or for the motor?

  9. #9
    Registered
    Join Date
    Mar 2014
    Posts
    970

    Re: Gantry mill with moving gantry for Z-axis

    For the motor to keep it out of chips and dust.

    Sent from my GT-I9300 using Tapatalk

  10. #10
    Registered
    Join Date
    Jan 2015
    Posts
    27

    Re: Gantry mill with moving gantry for Z-axis

    Quote Originally Posted by Azalin View Post
    For the motor to keep it out of chips and dust.

    Sent from my GT-I9300 using Tapatalk
    Don't have any plans for that, it seems to be in a safe area. If I cut steel it would stick to the magnets though.

  11. #11
    Registered
    Join Date
    Mar 2014
    Posts
    970

    Re: Gantry mill with moving gantry for Z-axis

    What is that black thing on the front of the spindle? Tacho?

    I got a 3kw boat RC motor from hobbyking (probably the place where you get yours from) and modified it for milling machine use. The original shaft was 6mm. Now it is 12mm. I also cut a water cooling jacket for it.

    This motor:




    Turned into this:








  12. #12
    Registered
    Join Date
    Jan 2015
    Posts
    27

    Re: Gantry mill with moving gantry for Z-axis

    Quote Originally Posted by Azalin View Post
    What is that black thing on the front of the spindle? Tacho?

    I got a 3kw boat RC motor from hobbyking (probably the place where you get yours from) and modified it for milling machine use. The original shaft was 6mm. Now it is 12mm. I also cut a water cooling jacket for it.
    ]
    It's a servo signal generator that I use to drive the ESC. The ESC is set to control to certain RPM, it's a CastleCreations ESC, which lets you program it from a computer.

  13. #13
    Registered
    Join Date
    Mar 2014
    Posts
    970

    Re: Gantry mill with moving gantry for Z-axis

    I know what a CC is.

    So its basically a servo tester, some sort.

    Have you been able to activate the governor of the ESC? I'm using a CC Edge 130 amp but I cant enable the gov as it needs an idle-up signal.

    Sent from my GT-I9300 using Tapatalk

  14. #14
    Registered
    Join Date
    Jan 2015
    Posts
    27

    Re: Gantry mill with moving gantry for Z-axis

    Quote Originally Posted by Azalin View Post
    I know what a CC is.

    So its basically a servo tester, some sort.

    Have you been able to activate the governor of the ESC? I'm using a CC Edge 130 amp but I cant enable the gov as it needs an idle-up signal.

    Sent from my GT-I9300 using Tapatalk
    Yes, I used the Castlelink software on a computer. I had to use a special programmer that plugs into the ESC. Might be a different feature of this particular ESC that let me do RPM control.
    https://www.amazon.com/Castle-Creati.../dp/B000BOG8V0

  15. #15
    Member
    Join Date
    Jul 2018
    Posts
    1716

    Re: Gantry mill with moving gantry for Z-axis

    HI RIU _ i'm looking at building a lifting gantry type machine like this. Any long term issues or errors to avoid with the lifting Z? Peter

  16. #16

    Join Date
    Jul 2019
    Posts
    21
    Quote Originally Posted by peteeng View Post
    HI RIU _ i'm looking at building a lifting gantry type machine like this. Any long term issues or errors to avoid with the lifting Z? Peter
    Hi Peteeng,

    I have gone done this road except, I used a single ballscrew in the centre as I thought 2 motors + ballscrews could problematic. Also depending how wide your gantry is it definitely is harder to aline than a fixed gantry although mine seems to be working fine.

    There isn't too many commercial machines like this that I can find and if they are only on very large machines and fix the gantry.

    Ritzy

  17. #17
    Registered
    Join Date
    Jan 2008
    Posts
    1105

    Re: Gantry mill with moving gantry for Z-axis

    Ritzy,

    Nice. I've been considering doing a single central screw like you have done.

    I am thinking about doing a rotating nut. Means motor for Z is fixed.
    7xCNC.com - CNC info for the minilathe (7x10, 7x12, 7x14, 7x16)

  18. #18

    Join Date
    Jul 2019
    Posts
    21
    Quote Originally Posted by pippin88 View Post
    Ritzy,

    Nice. I've been considering doing a single central screw like you have done.

    I am thinking about doing a rotating nut. Means motor for Z is fixed.
    Hi Pippin,

    Is the advantage of that you don't have to lift the motor+ballscrew weight?

    I have to counterweight mine either way as it is quite heavy..


    Do you know why there aren't many commercial machines like this? I can only think that the clearance under the gantry might become a problem especially for 4/5th axis work.

  19. #19
    Member
    Join Date
    May 2011
    Posts
    790

    Re: Gantry mill with moving gantry for Z-axis

    Quote Originally Posted by Ritzy321 View Post
    I have to counterweight mine either way as it is quite heavy..
    One nice thing about the "dual column rising gantry moving table design" vs a "dual column rising gantry without moving table design" is that it's easier to mechanically counterbalance the gantry.

    For what you've done, you could go with gas struts, preferable ones with little to no dampening.

    The machine I'm currently designing and collecting parts for will have 600mm of Z travel, so for me, gas struts were out. I decided on mechanical counterbalances on each column. I picked up 4 new surplus Martin Idler sprockets on eBay to use with #40 roller chain. I can make the gantry as heavy as I want to now. But it requires extra linear rails to guide the counterbalances on the back of the columns.

    Interesting what you've done with the single drive in the center. Very innovative. I wonder if you will have any issues with racking? Still, it solves the problem of having to home both sides. I wonder if you could find some longer rails for the front of the columns and space the bearing blocks further apart if that would help with racking at all? You've got extra space on the columns for longer rails. Plus then you could use the rails you already have to guide the counterweights on the back side if you decided to go that route. Just an idea.

    Lots of interesting concepts in this thread. Very nice.

  20. #20
    Registered
    Join Date
    Jan 2008
    Posts
    1105

    Re: Gantry mill with moving gantry for Z-axis

    Downside of a simple counterweight is that you have increased inertia to deal with.

    It is simple and cheap though.
    7xCNC.com - CNC info for the minilathe (7x10, 7x12, 7x14, 7x16)

Page 1 of 2 12

Similar Threads

  1. Fixed gantry vs moving gantry
    By scott0999 in forum DIY CNC Router Table Machines
    Replies: 11
    Last Post: 01-31-2014, 06:14 AM
  2. 2nd Build - Steel Tube, Moving Gantry Style, Mill / Router
    By InventIt in forum Vertical Mill, Lathe Project Log
    Replies: 73
    Last Post: 02-26-2012, 08:15 AM
  3. Trade offs between Moving Gantry and Moving Table
    By gregmary in forum DIY CNC Router Table Machines
    Replies: 11
    Last Post: 04-22-2011, 07:48 PM
  4. Gantry: planning to design moving open gantry
    By rdcd in forum Mechanical Calculations/Engineering Design
    Replies: 0
    Last Post: 11-14-2009, 10:52 PM
  5. Moving Table vs Moving Gantry; Dremel vs Router
    By chuckknigh in forum DIY CNC Router Table Machines
    Replies: 32
    Last Post: 03-28-2007, 02:48 AM

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
  •