Reply with QuoteWes, typically, when the web site directs you to different sales sites.....it is not a good thing.I don't think these will be inexpensive.
Mike
ps in case I am wrong, let us know!
Hi guys,
I did some more research on zero backlash drive systems today and while looking at chain drive alternatives I stumbled upon a roller pinion gear system that boasts zero backlash. I have not seen the prices of the parts for this yet but the idea looks promising even if a person had to design something similar and machine them themselves. The pinion wheel uses a number of roller pins positioned so the circumference of the pins engages the mating gear teeth much the same as a chain roller. This setup by maintaining opposing contact with two or more teeth at all times is said to eliminate backlash. Here is a link to the site:
http://www.nexengroup.com/nexen/jsp/.../news?id=@9043
So am I getting closer to finding a method to drive the b/c head at a reasonable cost without backlash? I have to check into the cost of this roller pinion/gear setup but the cost is usually the dead end for my pocket book.
What do you think are the possibilities of fabricating something similar?
Regards,
Wes
Wes, typically, when the web site directs you to different sales sites.....it is not a good thing.
Mike
ps in case I am wrong, let us know!
No greater love can a man have than this, that he give his life for a friend.
Hi Mike,
Yeah, I had the same feeling and they did not seem to have any prices available for any of the product they offered so I figured that would be the case.
I thought I would attempt to design something using the same basic idea or a combination of belt/chain/roller pin ideas and fabricate the parts myself. I may have the roller pin discs and gear laser cut and then do all the 2nd ops in my shop and assemble it.
Any input on the feasibility of fabricating something along this line and having an accurate no backlash finished item? Maybe using servos with the drive and belts in a configuration similar to the servo belt drives would make the belt drive more feasible and have better torque?
Regards,
Wes
Wes that is way above my head. Personally, I think Colin's heads would be the least inexpensive.....ifn you count your time. They may not be heavy enough for your app though.
Mike
No greater love can a man have than this, that he give his life for a friend.
Hi Mike,
I think Collin's drives would work great but I just can't justify the cost for a hobby type build. I have done some work with the roll pin/sprocket design and think I'm getting close to something worth giving a try. I have a little more work to do on the sprocket and roll pin boss sides drawings and then I should be able to cut some parts and give them a try. Anyone else done any work on a 5th axis build lately?
Regards,
Wes
5-axis patent drawings for Tri-Tech
Time to time I will post some patents published at www.uspto.gov regarding 5-axis headsOriginally Posted by valio
How about a trunion table for 4 and 5th axis?
[nomedia="http://www.youtube.com/watch?v=w0-tXDEvAqg"]YouTube- New CNC Trunnion Table can be 4th or 5th Axis made by HTS[/nomedia]
I thought about doing a 4-5 axis spindle head, but the inherent loss of rigidity in anything that I can afford makes the choice of a trunion table more feasible. That way I can have a rigid spindle to use for most of my work, and use the trunion table for for more complex 3d work. Is this logical?
Hello,
A trunnion table is another alternative, but the size of the parts that can be done with this is much smaller than what I could do with a B/C head and that is my main reason for wanting the B/C style.
I have a 4th axis that I have already built and I will implement a swiveling Z first so that I will have 5 axis when doing parts on the 4th axis but I still want to complete the 5th axis B/C head for use with my new large router build. Something with a 48" x 48" part size capability would be good for me with 2 ends opened to allow repositioning of longer material blanks. For a lot of work the trunnion table will actually be more robust and may be fine for you.
Regards,
Wes
Hello guys,
I have decided to pursue the design of the roll pin and sprocket mechanism due to claims of no backlash and the fact that the machining looks to be something that us hobbyists might be able to accomplish with some degree of accuracy. I have the parts drawn and ready to start fabrication so it should not be much longer to see if my design and assembly will work. I am attaching a snip of the pin-drive/sprocket parts as I have them currently drawn. I will post pictures when I have some parts cut.
Regards,
Wes
Looks like a nice design Wes. Keep it up. I'll be your first customer!
Hello,
I finally got the parts for the pin wheel drive lasered out of HRS and a couple pictures of the parts. I will begin 2nd operations and assembly asap, but wanted to post the pictures to show that something is being worked on towards the 5th axis. One shot shows each item and the second is with the parts orientated similar to how they will fit when assembled. I guess I will find out fairly soon if the design will even fit and function at all. Take a look. Oh, the sprocket did not cut very well and it will be redone soon, but it will work for the proto anyway.
Regards,
Wes
Lookin Good Wes, I looked into this system for my rack and pinion for the X axis but was quoted somewhere near $300-400 per meter....I nearly fell over
It should work well......I still think you need a greater ratio howeverperhaps two stages with what you have....shouldn't take up too much extra room.
I've finally assembled my B/C head....pics soon.
Liam.
Wes,
Is the pin diameter slightly larger than the radius at the bottom of the notches on the large sprocket? My meager understanding of gear mesh says that if it is the same or smaller, there can be some backlash as the direction of rotation changes. The pins should always have a small gap under them and only make contact in the slopes of the teeth, even after some wearing in. This is assuming that everything is in perfect alignment otherwise.
CarveOne
CarveOne
http://www.carveonecncwoodcraft.com
Hi CarveOne,
Right now the holes for the pins are cut a bit under-size to allow for reaming to the final size. I have to take a closer look at my drawing but I'm sure the holes look smaller than the arc on the teeth, but they will be reamed and then the dowels will be press fit. Also the way this mechanism works there will be 3 teeth in contact all the time if I built it right, and the extra 2 teeth(one on each side of the tooth engaged are supposed to keep the backlash in check. I have a lot of work to do to get to a point where I can even see if the parts as they are made will work correctly. Thanks for the input on the gears and how they engage etc.
Regards,
Wes
I don't know if I'm correct or not, so see what you can find out about the physics of this system. If the pins are exact size of the radius it may not have backlash, but any wear on the pin or sprocket may change that. How long it takes to wear enough to make any difference I don't know. It's just that there has to always be positive engagement to have no backlash. It's an interesting idea to me though. Just three tooth engagement huh? Seems like that would introduce some bumpiness. Show us what results you get, good or bad.
CarveOne
CarveOne
http://www.carveonecncwoodcraft.com
Hello,
I did a revision to my previous sketches for the B/C parts to compensate for the pin wheel sprocket design. Here is a snip of what I have drawn so far. Will try and get started on cutting the aluminum parts soon.
Regards,
Wes
Hello again,
I got off my rear and got the pin wheel assembled today. I need to replace the screws with some socket head or button heads a little longer and drill and tap the set screw retainers for the shank, but it all went together much as planned. I also got another sprocket cut with better results on the teeth but have not picked it up yet. I need to cut the other parts to begin the assembly of the drive to see if and how well the pin wheel and sprocket will work. Here are some pictures.
Regards,
Wes
Hey Wes, that is good news. Are you going to have the gear hardened?
Will it matter?
Mike
No greater love can a man have than this, that he give his life for a friend.
Hi Mike,
The teeth have a slag coating on their edges from the laser cutting that is itself pretty hard, so I don't think it will need to be hardened. I am going to try this steel assembly for proof of concept and design testing and feel that a double reduction will provide a better ratio so I will see about using 6061 T6 aluminum for the next revision if this works.
I just picked up the newly cut sprocket and the teeth are looking a lot better on the surfaces that contact the pins. There are still some rough edges on the outside diameter of the teeth but I don't think that surface will be in contact with the pins. I took a pic of the sprocket to try and show the better edges. I will use this 2nd sprocket for the trial assembly. At this point there are a lot of variables that I am not sure about but I think finishing the assembly will provide me a lot of information.
Regards,
Wes
That's looking pretty good now. Starrett makes a very fine cut finishing file for lathe work that works very well for removing burrs in steel parts. It can remove anything that sticks up without gouging other areas with file marks. The file is about 1/2" wide and about 6" long. I have a couple of new ones that were donated to me by a friend who didn't need them after closing his machine shop. I couldn't be without them now, and need to look them up to see where I can get replacements.
Looking forward to see how well this works.
CarveOne
CarveOne
http://www.carveonecncwoodcraft.com
