My First CNC Router

[nlancaster]

So I have been interested in machining and CNC for a few years now. And almost started building one of these CNC routers a few years ago but the price was just a little out of reach then. Well steppers and controlers have come done in price quite a bit in the last few years and it is time to build one.

Work area will be 26x52x7, with an A-axis coming later after the machine is working properly.

Going to keep a parts list with prices right here at the top of the thread for anyone that wants it.

$489.87 Keling 4-axis kit with 495oz/in motors (Includes $30.87 S&H)
$9.57 GT (3mm) Pitch, 150 Teeth, 9 mm (.354) Wide Neoprene Belt
$10.75 GT (3mm) Pitch, 200 Teeth, 9 mm (.354) Wide Neoprene Belt
$20.62 2 x GT (3mm) Pitch, 60 Teeth, Polycarbonate Timing Pulley With Aluminum Insert ($10.32 ea)
$60 24 x AXS 1614-2RS Bearings .375x1.125x.375 ($2.50 ea)
$25.08 6 x AXS R8-2RS bearings .5x1.125x.3125 ($4.18 ea)
$55.98 2 x 4'x8'x3/4in MDF Home Depot ($27.99 ea)
$23.99 1 x 4'x8'x1/2in MDF Home Depot
____________
$695.95 Total - updated 10/12/07


And here are some renders of the nearly completed design.

As you can see I am going with belt drive on all axis because I like having the steppers hidden away on the inside of the machine. Not hanging out ready to be hit buy someone moving things in the shop and not paying attention.

I know this is a more complicated way to do things. And will be proto typing one drive axis before actually building the rest of the machine to make sure my design works.


Please give me feedback you have.
Thanks,
Nick

[Eurisko]

Very interesting design, Nick.

Please post some renderings of the A axis when you have time.

I'm also curious how you'll drive the X axis. I'll be using 1/2-10 acme threaded rod, and am not quite sure how it will behave on a long span (48 inches).

My only suggestion would be to enclose the drive belts, just for safety.

[nlancaster]

I will be using 1/2-10 2 start acme screws on the x and y axis. Enclosures for the belt drives will be one of the first things the machine cuts. I have yet to design the A-axis but I have 10 inches of clearance below the y-axis carriage and a total of 7-inches of Z-axis movement. When I design the A-axis I will post some pics of it, but the building of the base machine will come first. If you want to see aproximatly what I am going to do look here at Lionclaw LC-50B

I am not sure if I can build the machine stiff enough for 10 inches of clearance, that is why there are so many holes at the top of the gantry sides. All flat surfaces of the machine will be laminated with Counter top laminate like spalm's machine is, as seen here. I will be drilling all those holes so that if I have to reduce the height of the Y-axis I can just move it down without having to rework anything.

Thanks for the response.

[LeeWay]

That looks like a promising design. I don't think you will have much room for the machine to rack on the X. The shape of the rails will help to prevent it. I run a single 48" ball screw on mine with good results. I can rapid at better than 350 IPM, but have it set at 270 IPM.

I can see only one suggestion. On the Y axis, if you move the motor outside, you would gains some travel. If the X doesn't interfere, then you are good there. I have all three of mine on the outer ends and use as much travel as possible. Mine are direct drive though. You could leave the Y motor inside with a different angle on the mount. It might then miss the Z.
I look forward to seeing your progress and good luck with it.


Nevermind on that. It looks like it would clear the Z.

[acondit]

Hey Nick,

It's looking pretty good.

I got my vacuum bag working and glued up my gantry side pieces.

Alan

[nlancaster]

acondit, yeah vacuum baggin on a flat surface seems to be the way togo. I am contemplating building my table from a vacuum bagged block of foam, instead of the built up torsion table we normally see on here. I have build many RC airplanes with foam core wings and they are incredibly strong. I have seen 2 guys jumping up and down on a foam core RC airplane that was supported 100inches apart, they jumped 6 times before it started to break, and had to jump twice more to complete the break, and it was only 3 inches thick at its thickest point. That will probably be plenty strong for a CNC table, without the resonating booming noise a hollow box could produce.

Leeway, yes it would clear the y-carriage by .25-.5 inches depending on how far out it is adjusted for tensioning of the belt.

[nlancaster]

Recieved the first parts today. Living in Portland Oregon area we have Mcguire Bearing right in the middle of town. I got all these bearing for the same price as VXB without having to pay any shipping.

On a second note I have since seen some inexpensive angular contact bearings but only in 12mm, and I can't seem to find angular contact bearings in inch sizes. Does anyone know a source for inch angular contact bearings that don't cost a bloody fortune?

24 sealed .375x1.125 inch bearings for the linear rail trucks.
6 sealed .5x1.125 inch bearings for the acme screws.

sorry about the picture quality, bad lighting.

[harryn]

Hi, looks like a good design.

This is sort of a generic question - why do people build these routers up with the angled uprights ? It seems like it would be stronger and easier to build with straight up sides. Is this just to reduce mass, look cool, or something I am just missing ?

Thanks

[OzarkCNC]

Elementary.. It is to take advantage of the X axis travel and even out weight distribution.

By having a slanted upright, you change the CENTER OF GRAVITY of the router, plus you gain X distance at the 0 end.

I am a newbie, but I think I am right?

[nlancaster]

Well the uprights could be straight rectangles and still get the full x travel. I mainly did it with the angled uprights because it looks better. There would be reduction in weight with the angled uprights, which is never a bad thing. I have long studied design as a hobby, my father was an Industrial/mechanical designer for 27 years. All thru history you will find things that were built that look good. One example, arguably one of the best looking fighter aircraft of all time, the North American P-51 Mustang fighter of World War 2. One of the designers was interviewed after the war and stated that the airplane looked good because they set out to make a good looking aircraft. The first models of the aircraft placed in the wind tunnel showed that the better looking of the preliminary designs really was a better design. I have always found that I like using something that looks good. A good looking car, boat, RC airplane, or power tool, will always be purchased first all other things being perceived as equal. So I am consciously trying to design a good looking machine, within the limits of feasibility and performance. That is why most of the edges of the machine will be rounded over, it just looks better and your edges also last longer. We will see how that pans out.

[harryn]

Hi Ozarkcnc, I am not sure if you are right or not, but I am new to this as well.

The slant I am talking about is on the router side of the gantry. At least so far, I cannot see how it impacts X motion, and the center of gravity change seems small, but maybe you are right.

[spalm]

Hey nlancaster, nice looking design.

On the question of the gantry tilting back; it does look nice, it moves the center of gravity to the center of the uprights, and increases the reach of the router to the rear of the table. One thing that it prevents though is being able to clamp vertical boards to the front of the machine and route on their edges. This may not be a concern, but it does allow some interesting designs. I guess you would have to move your long screw and motor slightly off to one side to allow wider boards (?), and maybe mount the motor at the rear of the machine. Allowing 8 inch boards would probably be sufficient to dovetail drawers etc. (I would recommend dual screws anyway.)

How are you going to get preload on your linear bearings? I don’t see any adjustment ability, at least on the long axis. One method that I used recently is to split the rails and be able to spread them apart, rather than trying to press a cantilevered truck against them.

Steve