80/20 Gantry Beam Prototype

[Jkountz]

Well when you're snowed in for a week and nothing else to do it sure gives you plenty of time to design new stuff. This is my latest creation, a whole slew of stolen ideas from here at the Zone!! The main gantry beam is to be of 80/20 size 3060. I couldnt find a Sketchup model of that particular size so I just drew it as a solid beam but it is actually 3060. I ran the deflection caculations and with a width of 60" (more than mine here) and 3060 in size with a load of 50 lbs the total downward deflection was .001 and Y direction was a little more at .005. Both numbers are good to me and Im waiting to talk to the good folks over at 80/20 to see if they can help me take cutting forces into effect but it looks like a single piece of 80/20 is going to work fine for this new design. I did the numbers at 50lbs but I dont think it will be that much, maybe.
The Z slide is shamlessly taken from the Mechmate design so it should be good to go. The sliding Z plate will of course have to be machined flat and true but thats minimal.
I was going for a really light, streamlined design without a lot of unnecessary parts. Im getting there but I keep looking at this thinking there could still be an easier way. Thoughts?
As usual please look it over and see what you think, comments suggestions please!!

[DIYaholic]

Nice work. It does look more "streamlined". Why the change from a double rail gantry? I'm assuming the rail plates for the v-rollers are steel. That would certainly decrease the amount of deflection, or did you account for that in your calculations? Have you ordered parts and when do you plan on starting your build?
Just wanted to say good job.

Randy,

[Bartuss1]

If you turn off the electronics, engines will not hold, the axis Z of the fall

[Jkountz]

Well honestly Randy I havent decided yet which way to go. I like the idea of the double beam gantry but I was looking around at some other designs and just wanted to try something different.
Bartuss, Im not sure how the Z slide stays in place but I know this is how the Mechmate routers are built and it works for them so I have to do some research on that. What holds the Z in place on any other routers when the power is off?

[Bartuss1]

Self-locking bolts or pneumatic actuator

[Jkountz]

Ok I just re-read the thread over at the Mechmate forums and it seems the Mechmate guys use a gas spring, kind of like the things that hold your hood open on a car. You just need to match the weight of your Z slide to the right gas spring. This holds the Z car in place when power is turned off. Should be an easy enough mod for my design I would think. More pics to some soon!!

[DIYaholic]

So, will you be ordering the gas spring from Lamborgini, or is this a budget build and go for one from a Yugo? lol.

[Jkountz]

Funny!! Actually Mcmaster Carr has a good one that looks about right.
http://www.mcmaster.com/#9432k64/=5sbzb1

Should be fine in the 20 lb range.

[nguyenst]

I like the design, it looks clean and compact. For my current build, I'm gonna stick with the double gantry design like the mechmate just because it is actually different than what everyone is doing on this forum. The single gantry is much simpler though.

The mechmate uses the gas spring as a counter balance against the forces of gravity. The motor they used also has built in gearing of 7.2:1. I would think this would also help to hold the z-axis in place with such a high gear ratio.

The rack and pinion design allows for much faster speed but I don't know if it's worth the extra issues that you run into like Baruss1 mentioned. Since your travel is so limited, a screw drive seems to be much simpler for the Z-axis. If you incorporate some kind of worm drive into your gearing, that would solve the problem of the Z-axis falling when the motor is powered off.

Keep the ideas coming!!! I'm building mine right now but am changing the design everyday as I go.


Diyaholic,

funny you mentioned lamborghini... me and the other builders at kitcentral.com are using the gas springs from McMaster Carr for our Lamborghini kit car!!

Steven (Van)

[eigstein]

how do you propose to grind the V-edges on your rails ?

sincerely,

rjs

[Jkountz]

Steve do you have a build log going on? Id love to see your design for a double beam gantry!! Also what did you mean by my limited Z travel? Right now I will have about 7 inches under the gantry of Z travel, is that what you meant?

RJS, I havent decided if I will grind the rails myself or just purchase the V track for the V bearing rollers. If I grind them here I have a plan for a jig to use with my 12" disc sander that may or may not work, still working on that. If not there is always the Mechmate "skate" that seems to do a good job of grinding them properly.

[nguyenst]

I posted the link to my build log in your 'Aluminum Mechmate' thread but here it is again...

http://www.cnczone.com/forums/showthread.php?t=99181

What I meant about the Z-axis is that there is no advantage to using a R&P design on the Z-axis since the travel is short enough that you don't need the speed of the R&P system. That is the advice I got from Ahren, the seller of this system. He is a member of this forum and a very informative guy.

With that said, I would not frown on using R&P on the Z-axis, if you can make it compact. Your design looks very compact especially with the Y and Z motors mounted together. Since I am using of the shelf components, the R&P drive system I purchased is very large. In the future, I will opt to buy a stepper motor with a built-in reduction gear like the ones the Mechmate folks use.