Jim,
Take a look at the way I got the R&P mounted in my build log. I am using Ahren's parts and you will noticed that there is only one way to mount everything to make it work right. You will also realize that your gantry bar, will not have a lot of contact surface on the carriage. I added a short piece on top of the carriage longitudinal to it so I can get 3 bolts on the carriage. The carriage is very thin so this 12" piece I have over it gives it 1 1/2 " thickness compared to the carriage's 7/8" thickness.
Steven (van)
Hey Riceburner98 .. didn't know you were on this forum also!! How are the A/C controller coming along?? I actually just sold my lamborgini kit car 2 hours ago!! making room for the CNC router and my wood working. Gonna miss my buddies on kitcentral.com
slats and gear wheels
router was built in 2007 year
maybe working as router or plasma cutter
new gear
Last edited by Bartuss1; 02-13-2010 at 03:20 AM.
Ah ok I see, it appears as though Im going to have to switch the top of my table to use 3030 instead of the 2020. There just isnt enough room for the rack to mount it seems. Good eye, thanks for that!! Im thinking of using some of those 80/20 right angle braces on top of the carriage and into the gantry beam for more support. Im trying to keep the center of gravity of the beam as low as possible for a more rigid design but if need be I can add a piece as you did on your buld. By the way nice looking machine!!Originally Posted by nguyenst
Jim,
Got your email -- it looks like you answered your own question with regards to the extrusion style to use. A benefit of using anything in the 15 series (3030 included)is that you can use my rack clamps to make things bolt together really squarely.
I do agree with Steven that the R&P for the z-axis is a lot more trouble (and expense) than it's worth. You'll get better control and similar speeds with a 5 start ACME solution, and the thread angle on ACME makes it such that back-driving usually takes quite a bit of force, so you don't need a brake or worm gear to hold the axis up when power is off.
I would also suggest (for cost and simplicity) that you use my carriages and the rack turned sideways for your gantry -- that way you don't need the funky bracket coming off the back (which worries me -- this needs to be stiff, as the entire motive force for your z-axis is being transmitted through this), and you can use regular cold rolled steel for the gantry rail without having to grind 45's on it.
Best regards,
Ahren
Nice looking machine Bartuss!! I like the gear reduction units you built, are the working as expected??
The AC controllers just keep going...They soak up all my time (and $!), which is why I haven't gotten much farther than CAD design and ordering some parts for the new machine. I hope to do a replica car some year.. Don't have nearly the space for the car or a mill of your size though! I like the guys over at Kitcentral, they do some great work. I'm building some circuit boards for a couple of them as I type this.
Not sure I follow what you are saying about the gantry. Are you talking about the Y axis? I think I will change over to your carriages for the Y if thats what you meant but Im not sure what you mean about turning the rack sideways. How would it all mount if I did use the carriages on the Y and your R and P drive??
Thanks!!
Jim
yes, already 3 years
Last edited by ger21; 02-13-2010 at 05:51 PM.
Revised (again)
Ok Ahren I think I know what you meant, at least I hope so!! Take a look see and tell me what you think now. Im using the carriages on the Y with your R and P parts too.
Im still working on a way to brace the gantry beam to the X carriages, I dont think the 80/20 right angle brackets are going to work unless they make alot larger one. Maybe they do I havent looked yet to be honest.
Jim,
Yes, that's exactly what I was thinking on the R&P mounting. As for connecting the carriages, you definitely want to use 5/16-18 shoulder bolts that go through the long holes in the carriages -- the heads of the shoulder bolts will ride in the t-slots on the bottom side of the gantry beam, and pass through the carriages, where a hex nut is fixed on the other side. This is a fantastically strong connection, and costs all of $0.35 of hardware. Make sure to get the right length carriage bolts (I believe it's 2 1/2", but I need to check) so you don't interfere with the pulley on the motor of the R&P, but there is room for this. You can add in brackets as well if you like, but I think you'll be impressed with how strong of a connection you get from the shoulder bolts.
Ahren
www.cncrouterparts.com
How is the carriage oriented when using the R and P? Does the wider or narrow side face the R and P?
Jim,
You have it drawn correctly in your model. You want the R&P plate parallel to the wider face of the carriage.
Ahren
www.cncrouterparts.com
Reworked Z Axis
Ok Ahren, you've sold me on these linear carriages!! After looking over all the build logs on your site and scouring the pages here Im hooked on the whole system. The R and P, the linear carriages, rack clamps. I love how everything is modular and works with each other. Also I got rid of the need for special machining of the Z slide that I would have had on the older design from yesterday. I guess I had Mechmates in mind when I did that and just thought it would be a good way to go but I like this new design better.
Question for you Ahren, on my new Z slide do you think one extended carriage on each side as I have it shown here, or two of the short carriages on each side the hold the Z through its entire path of travel? Do you think the 8" length of the ext carriage will be enough? I think it will but wanted to ask anyway.
I know in the pics the Z and Y motors look really close and may be touching but when I go to do the actual build I can play around with measurements to insure that doesnt happen. I may have to move here, slide there, extend this or that but it shouldnt be a big deal.
Also I know there were questions before about the Z slide falling down when power was cut but there is a really simple solution for that. A gas spring will hold the Z in place and costs about $15. They also greatly assist the stepper motor in that if you have a 20lb spring theoretically the motor only has to move 20lbs. The way the spring is mounted its keeping pressure to lift the Z car up so now the motor doesnt have to. When the Z is going down the motor is only pulling against the 20lb spring. In theory anyway. I only know this works just fine on all the Mechmates so I know it will work here too.
So thoughts??
Jim,
Glad the system is going to work out for you. I think the extended carriages will work well for your Z. I think the R&P will also work for this with the spring -- it just seems more expensive than a screw-driven solution, with not much benefit given the short travel, but it's your machine!
Best regards,
Ahren
www.cncrouterparts.com
Yeah you may be right.
I guess the main thing I was trying to avoid was having the router itself cantilevered out so far away from the gantry. So many designs I have seen has this and I just didnt think it looked right. Do you know of a screw driven option that fits nice and tight against the gantry like mine? And costs less than what I have proposed? I would love to see it and adapt it to fit mine.
Another thing was if you wanted some gear reduction of some kind on the Z the R and P easily allows for this too.
So while Im not married to the R and P on the Z just yet it does look better to me for some reasons but I would be very interested in a screw driven Z that didnt stick way out from the gantry.
Anyone??
On my Y-axis I will duplicate the design of the X-axis and keep the orientation of the R&P identical on both axis. I can do this because I am using the double gantry design so the X-axis and Y-axis are the same. This also solves the problem of having the router cantilevered too far out since it's gonna be supported on both side by the double gantry. I should have more progress this week when my rails arrives.
Ahren,
got the carriages I ordered for the Z-axis, as usual, superb quality!!
Steven,
Glad the parts are working out for you. Looking forward to seeing this thing running!
Ahren
www.cncrouterparts.com
Just to show you guys, depending on your machine, you can fabricate mounting parts for Ahren's R&P stuff:
Mark
Re: 80/20 Gantry Beam Prototype
wendtmk's in post 39 Your frist photo you show 3030 extrustion with your linear rails mount to machined aluminum spacer strip.
Do have you have any othere photo ie a close up view of your rail mounting to 8020.
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