[turbotoys]

Just started my build last week - I dont have much time to work on it with kids and work and all but this is what i have done in roughly 5 days. Any input would be appreciated greatly- Im just a newbie but we all have to start somewhere.



I have the gecko drives ordered - I went with the G340's.

I am planning to drive the x- axis with 2 850/oz servos from homeshopcnc- i ordered one motor so far just to mess around with untill i get it all assembled - i got the 500cpr encoder but i think after learning more i should have gotten the 250 instead.

I ordered the rack from mcmaster carr - it is 20degree pa - 20pitch 7teeth per inch - i will be mounting that very soon.

I ordered the linear slides from nook industries - it is the NH25TA with 2 blocks per side with scrapers - C5 precision - T0 preload - hopefully this was a good choice..... I was initially looking at linear rails with full support but the sales guy said these would be a better choice and pretty much the same price point.

I am trying to figure out what reduction to use with these servo motors - I am setting this table up for plasma and routing, anything from foam to aluminum. Hopefully someone could point me in a good direction as to what gearing to use... I was thinking 3:1 or 4:1 but im not sure if i would get high enough feed rate +600/min. there has to be a calculation??

Anyways, it would be great to hear any ideas from all the veterans- If it wasn't for this site with all of the knowledgeable people here i would have never thought this was possible. Thank you everyone

[turbotoys]

Here is what i designed in Solidworks so far. I am designing as I go... The x axis is going to be around 3' depending on how i do the gantry. The main rails are 6"x3"x0.1875" and the rest is regular 3"x3"x.1875" tube - the reinforcments are 1x2's and 1x3's- i am using a 3.5"x3.5"x.25 tube cut in half for use underneath the linear track - your probably asking why? well after i welded the first side up i looked down the tube and noticed that it had a little bow to it so i figured i would use something to align the track as straight as possible- i could have used shim but this way i have a thicker piece of material underneath for threads- 1/4" versus 3/16"th.... I am planning on using this to design molds and patterns so i will need a deep x-axis.

[Mr.Chips]

Welcome to the CNCZone. And thanks for pasting pictures. There will be numbers of people following your work from all over the world. Shortly you will see answers to your questions. Tons of talented feople around here.

Good luck
Hager

[txcowdog]

Wow... for a first time build you really went all in. Very impressive and keep posting the pictures.

[oeffner]

Nice start. I am just getting started with the design of a similar table. 5+ by 9 , room for 4x8 and clamps. I'll be using ls25 rails and cars from NSK as I got a smoking deal on some used stuff
So far other than a lot of rails my build is still a Solidworks dream. I'm going to finish the modeling in solidworks, and run cosmos on it to see if I can identify any problems with the design before I waste any material.
Plan on rack & pinion drive and using a belt geared x and y axis much like on the mechmate .
Please keep us updated with your build ,and the processes you go thru to figure motor sizes drive speeds etc. the rack size you chose is the same as I've been modeling so I hope I can benefit from the hard work your doing!

[TSJ]

I have a similar design in mind. I plan to mount the linear rail to angle iron (3/8" thich, 2" X 2") mounted on to side of the frame. I can cut slots in the angle iron on both 2" sides to get the height to the table top the same the entire length and get the linear rail straight (I will use a piano wire and a wedge attached to a battery/light-bulb as I read about in an earlier post).

I plan to place a piece of sheet metal and a brush the length of the table to keep any sawdust (my machine will be for wood) from falling on the linear rail.

Maybe my design is flawed, no better time than the present to get the opinions of the people that know on the forum.

[turbotoys]

Ive been pretty busy with work and haven't been able to work on this much but here is an updated picture of what I will be doing with the gantry. It will mostly be made with 3/4" aluminum plate with the exception of the two 4x4 tubes that the linear track will ride on - im not sure if the 4x4x1/4" aluminum will be strong enough - i am considering using steel across there. I dont know how much I have to worry about weight - i am using 2 850 OZ/IN servo motors running 3:1 so i will hopefully have enough torque and speed. I was trying to get a huge x-axis but i ran out of overhead space- so i am left with around 28" - was hoping for 36" but oh well. I am hoping that using aluminum for the x-axis isn't going to give me a lot of problems with deflection. I am building it out of 6061 aluminum - it is roughly 50"x8"x3/4"thick and behind it there is 2"x2"x1/4" tubing reinforcing it. maybe it will just be easier to put a pic up. i will post a picture of it after this post..... anyways, here is what i have drawn up so far.

[turbotoys]

Ok here is the backside of the X-Axis.... the distance between the linear blocks is around 18" - i wanted to make sure i had enough between them to eliminate deflection as best as possible. the plate on the front is 50"x8"x3/4" 6061 aluminum- the linear rail is attached to the 2"x2"x1/4" tubes and that will give some support to it as well. so anyone have an opinion here ? is there a way to calculate deflection on this? do u think maybe i should fill the 2x2's with cement or instead use steel? I'm trying to keep the weight down because once again, being i'm a newbie, i'm not sure how much power my 850 oz/in servos will take - oh im running this 3:1 as well. any input would be greatly appreciated... I was actually hoping to get a little more input on the build..... maybe i have it in the wrong section???? oh and if anyone is confused this is the part that the router attaches to in the picture above this one, LOL

[ahren]

For deflection, try some of the calculators online at engineersedge.com. That being said, it depends on what your Z looks like, and what sorts of load you expect to see on it in order to calculate the deflection in your gantry (X axis).

In answer to your question about the 2 x 2 sections, steel tube will be much stiffer than aluminum (almost 3 times) , and concrete really won't do jack for you except make your gantry heavy (read, slow), so definitely go with the steel tube. That being said, this modification really only addresses standard beam deflection (which should be minimal with this much metal), not torsion of the gantry. To handle torsion, you might want to keep your steel tubes, but mount a 3/8" piece of aluminum on each side of them, rather than a 3/4" piece on just one side. This will effectively create a larger main "tube" for your gantry which will be more resistive to torsion than what you have right now. Torsion is unfortunately difficult to calculate for anything other than a round tube, but you can bet there will be significant twisting forces placed on your gantry with the large Z you have in mind. Hope that helps, and don't get discouraged by the lack of response! Keep posting, and we'll keep trying to help. Big machines are super cool, so I'll definitely stay interested.

Ahren
www.cncrouterparts.com

[ahren]

Oops.

I just re-read your post, and it looks like you're "X axis" is what most people refer to as the Z axis (the part the router mounts to, which goes up and down). You can ignore my advice about splitting the aluminum in half on either side -- this axis won't be loaded in torsion. Still stay away from the concrete.

The bigger question is what is mounted to the bearing blocks? You'll need a fairly thick or well reinforced plate (that your router mounts to) in order to take advantage of your travel unless you're planning on using a bunch of router bits that are 36" long (not recommended). The thickness of this plate, and the reinforcing structure you use on it will be as important as the structure you mount your rails to in order to avoid deflection. If you post a drawing showing this part, I can give some more input on where you may need to shore up / modify your design.

Ahren
www.cncrouterparts.com

[turbotoys]

ok here is what the "z-axis" linear blocks are mounting too. it is all 3/4" aluminum- i changed the upper box a little bit to give me a little wider space between the upper linear blocks.

[ahren]

OK, I see -- looks good, although possibly difficult to assemble and tweak into alignment. I believe your limiting factor now will be the moment load on your bearing rails, but you've done a good in spacing them apart more (which means less moment load and more direct load, which they are better equipped to handle). What are the loading limits for your bearing blocks? The manufacturer should have information on this on their web page.

[turbotoys]

Hmmm these are from nook industries - NH20TA. From the looks of the literature i have on these it looks like the Static moment load is 1,389lb-in or .16kN-m . I used a little bigger ones on the ?bed axis - I used the NH25TA on them and the static load on them are 2,430lb-in or .27kN-m.