Thread: Steel Framed Router
I tend to work and put more value in experience than calculations and I know from my own experiences with helping others that long thin 16mm screws give more grief than the same length 20mm.
If you want to go looking around the zone etc then I think you'll find more unhappy owners of long 16mm screws than you will 20mm.
I know if asked to build a machine with 16mm screws of this length I would re-fuse and recommend 20mm with correct size pitch to suit the intend purpose of the machine.
My proposal to use geared 20-05 was work around to no cheaply available 20-10 and wasn't saying they are the ideal solution just an easy one that I know works thru practicle hands on experience. . . . The right pitch for the job wins every time but theres always other ways to skin a cat.
I'll take real world experinece over calculated theory any day . . . . IMO it's priceless and feel privilaged when someone shares there often hard learned experineces.
Oops, sorry gents, dropped the quote somewhere along the line, what I should have posted is:
When I did the motor tuning on Chip's router we got perfectly good feedrates (can't remember exactly what, long time ago). That's with similar length 16mm screws, but only 5mm pitch so nowhere near as good as 10mm pitch if you're after speed.
How much racking depends on several factors but obviously the wider the machine the worse it gets, wide gantry or wide placement of the bearings the gantry sits on helps reduce this to a degree.
Basicly if you have central screw on narrow machine with wide bearing placement then the racking affect can be controlled to acceptable levels. Wide machines are better suited driven from both sides of the gantry using 2 screws.
Regards work positioning I think you'll find when you see a referanceto 0,0 position it will often relate to work coordinates which are often differant to Machine coordinates.
Excuse if you know this.! . . . Machine coordinates define the overall cutting area of the machine. .Work coordinates define a referance point on your material that you want to start work cutting from.
So say you have 400mm * 400mm cutting area with machine coordinate 0,0 defined in the lower left corner (looking down from the top) and place 100mm x 100mm material in the centre with the cutting start point in the lower left corner of the material.
Then the work coordinate is at 0,0 but it's actual position on the machine is at 150,150. Where you position the work 0,0 coordinate will be determined by where abouts you position the 0,0 in you cad program and the part your drawing.
Often Machine coordinates are positioned in the lower left corner so you'll never have negative machine coordinates, so If your work as negative coordinates IE Circle with centre defined as 0,0 work coordinate then you need to offset the 0,0 work coordinate far enough away from 0,0 machine coordinates other wise the machine will crash into the limits.
Hope this helps if i'm teachng dad to suck eggs then i'm sorry.!
The Following User Says Thank You to JAZZCNC For This Useful Post:
Thanks for your time with the answer Jazz, most helpful! No, not sucking eggs even slightly, I'm in the happy position of knowing enough to know I don't know enough! :-)
I might have clarified what I meant better by substituting the 0,0 for a "corner of the work area" But, yes, I see what you mean. I'm interested in this thread as the design (Rev 872) I'm playing around with uses steel too, most helpful!
I can't see a problem
but your cable and may be vibration on the rail.
maybe box section instead of flat bar
but I'm no expert
if I'm reading the drawing right, is the belt the only thing that will transfer the movement to the gantry, for the gantry to move on the x axis? that would be a problem.
Caveat as above, I'm no expert! :-)
Last edited by mocha; 14-09-2011 at 05:06 PM.
I'm afraid that wouldn't work. As soon as you put and tension on the timing belt it will bend the ballscrew which is obviously bad. The ballnut needs to be supported with bearings and it's own mount. The best option is a pair of preloaded angular contact bearings with the pulley in between so that both bearings resist the tensioning force of the belt. This is what I used. Angular contact bearings are best as they accept radial and, importantly, axial loads whereas standard deep groove bearings don't take much axial load. Having said that I've seen one on youtube that uses deep groove bearings, but it's only cutting foam...
I've almost finished designing one similar to that for 16mm and 20mm pitch screws with 7207 bearings.
By Wejjmeister in forum Gantry/Router Machines & BuildingReplies: 87Last Post: 02-01-2016, 11:45 PM
By Boyan Silyavski in forum Machine Frames & BedsReplies: 0Last Post: 06-11-2013, 04:58 PM
BUILD LOG: Steel Framed CNC routerBy Joe in forum DIY Router Build LogsReplies: 14Last Post: 23-06-2013, 09:45 PM
BUILD LOG: Formed steel cnc routerBy sbams in forum DIY Router Build LogsReplies: 4Last Post: 07-03-2013, 01:00 AM
BUILD LOG: My steel framed routerBy pavlo in forum DIY Router Build LogsReplies: 17Last Post: 06-03-2011, 09:08 PM