I already did that. I created an AutoCAD macro to create the rack profile, and cut a sample from Plywood. Then I decided to use helical R&P instead. I need to try to sell these roller pinions I have in my drawer.....
If somebody was to provide the maths required to create the curve of the rack, and output it to a DXF, would people cut there own? Another thread on here discussed the cycloid gearbox and making your own. Seems people were very interested in that....and guys created a program to spit out the profile in DXF. I love the way the pinion is easy to make in this system.
I already did that. I created an AutoCAD macro to create the rack profile, and cut a sample from Plywood. Then I decided to use helical R&P instead. I need to try to sell these roller pinions I have in my drawer.....
Gerry
UCCNC 2017 Screenset
[URL]http://www.thecncwoodworker.com/2017.html[/URL]
Mach3 2010 Screenset
[URL]http://www.thecncwoodworker.com/2010.html[/URL]
JointCAM - CNC Dovetails & Box Joints
[URL]http://www.g-forcecnc.com/jointcam.html[/URL]
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
I think if you apply an accumulation factor to any measuring device then provided the series of objects that make up the accumulated length each do not vary more than .01mm then the accumulated measurement overall will be very accurate indeed.
This means if you have rack sections 12 inches long and they were precision ground on their ends to within .001" each then who needs the expensive Nexen type R&P when your 20 foot rack would only be out by as little as .020" maximum......guaranteed.
I doubt that anyone (at home) has the capability to measure or check a measurement of 20 foot to within .020".....at the same time any work performed on such a machine would be accurate to within .001" for every 12 inches.
Many years ago I worked with an inside tubular stick micrometer that measured 2 metres in 600mm lengths....it had a calibration certificate from a metrology company that guaranteed the overall accuracy.
As that is an achievable factor, then a segmented rack will be in the same category provided the butted ends are in close contact.
It just means the pinion must make metal to metal contact (spring loaded etc) with the teeth tightly meshed in the rack to eliminate backlash......who expects to get that accuracy on a big DIY CNC router anyway.
Ian..
I believe that the Nexen racks come in 1 meter lengths, with a jig to mount them with the correct spacing. They probably have a small gap between them.
Gerry
UCCNC 2017 Screenset
[URL]http://www.thecncwoodworker.com/2017.html[/URL]
Mach3 2010 Screenset
[URL]http://www.thecncwoodworker.com/2010.html[/URL]
JointCAM - CNC Dovetails & Box Joints
[URL]http://www.g-forcecnc.com/jointcam.html[/URL]
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
I can't seem to find it. I may not have saved it when I got a new PC. Here's a drawing I created with it.
Gerry
UCCNC 2017 Screenset
[URL]http://www.thecncwoodworker.com/2017.html[/URL]
Mach3 2010 Screenset
[URL]http://www.thecncwoodworker.com/2010.html[/URL]
JointCAM - CNC Dovetails & Box Joints
[URL]http://www.g-forcecnc.com/jointcam.html[/URL]
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
Shame, that DWG doesn't help with the design of the rack, and the shape of the curve of the teeth. Thanks anyway.
I used that drawing to cut a sample.
It just needs to be trimmed, as each tooth is a little long at one end.
Gerry
UCCNC 2017 Screenset
[URL]http://www.thecncwoodworker.com/2017.html[/URL]
Mach3 2010 Screenset
[URL]http://www.thecncwoodworker.com/2010.html[/URL]
JointCAM - CNC Dovetails & Box Joints
[URL]http://www.g-forcecnc.com/jointcam.html[/URL]
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
There are different sizes of Nexen rack and pinion, and this is only good for one size.
Gerry
UCCNC 2017 Screenset
[URL]http://www.thecncwoodworker.com/2017.html[/URL]
Mach3 2010 Screenset
[URL]http://www.thecncwoodworker.com/2010.html[/URL]
JointCAM - CNC Dovetails & Box Joints
[URL]http://www.g-forcecnc.com/jointcam.html[/URL]
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
So your macro rotated the pinion and took multiple snap shots to create the path of the teeth, and make spline with those co-ords. I guess you could have stipulated the "resolution". However, I think that this type of operation would not result in linear motion that is proportional to the amount the motor rotates.
That is because at this part of the curve;
the pin in the pinion is not moving at the same proportion as the profile of the tooth. I might be wrong, but I've seen this curve in cycloid gearboxes, and they don't provide constant velocity inside each revolution. I'll have a play with this and see what gives, much appreciated for what you have done.
It basically rolled the pinion, and tracked the center of the rollers. I don't remember the exact details. In the section you highlighted, the segment lengths are about .02mm.So your macro rotated the pinion and took multiple snap shots to create the path of the teeth, and make spline with those co-ords
I then offset this path by the radius of the roller, and converted the straight segments to arcs to smooth it out. It's not 100% perfect, but I think it's very close. It would have been fine for what I was going to use it for. It rolls very smoothly over the test rack I made.
Gerry
UCCNC 2017 Screenset
[URL]http://www.thecncwoodworker.com/2017.html[/URL]
Mach3 2010 Screenset
[URL]http://www.thecncwoodworker.com/2010.html[/URL]
JointCAM - CNC Dovetails & Box Joints
[URL]http://www.g-forcecnc.com/jointcam.html[/URL]
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
Nexen gives out the rack DXF on their site.
Ger21, you still have those roller pinions?
No, sold them about 6 months ago.
Gerry
UCCNC 2017 Screenset
[URL]http://www.thecncwoodworker.com/2017.html[/URL]
Mach3 2010 Screenset
[URL]http://www.thecncwoodworker.com/2010.html[/URL]
JointCAM - CNC Dovetails & Box Joints
[URL]http://www.g-forcecnc.com/jointcam.html[/URL]
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)