Newbie questions. Planning a new machine.

[space_case]

Hello all. I am at a new place (new state for that matter!) and I have a
workshop that I am itching to fill. I successfully built a CNC foam cutter over a year ago and I want to start a router now. Sorta tired of being stuck in a 2 dimensional world, so to speak.

My main focus will be aircraft molds. RC aircraft and UAVS. I would like to be able to route high density foam and perhaps aluminum. So I need a nice long X axis (is this the convention, say to make a long wing?) and a router and steppers robust enough to handle aluminum billet. I really don't have an idea as to resolution (accuracy ?) Couple of thousandths?. You know, I just want to make airplanes! And molds with nifty joggle gaskets!

-Router? I am having trouble sourcing routers.
-Steppers? How much torque?
-Boards? These seem to be everywhere and not to much of a problem.
-Linear motion? Don't think I will be using drawer slides on this one.
-Software? Cheap is the operative word here...

I would like axes measurements of:

X: 6-8 ft
Y: ~ 3 ft
Z: 1-2 ft

Is my X axis doable for a home built?
Thanks

Kenny

[summers]

Tagging along here as I would like to build a router table with similar deminsions.

[2muchstuff]

Any thing is doable if the funds are there.

X-Axis and Y-Axis:
I have yet to see a drawer slide that long.
Gas pipe with bearings- least expensive, accuracy-ok
Round linear bearings(supported)- moderately expensive, accuracy- better
"THK" style rail/bearings- expensive, accuracy- best
Double Vee rail/bearings- expensive, accuracy- best

Z-axis:
I would go with either the round linear or the THK style due to the short length.

Only your imagination will determine the length. The gas pipe idea can be gotten thru the hardware store. The round linear and THK idea is best gotten thru Ebay. The Double Vee rail must be gotten thru the mfgr. or a bearing dealer.

Stepper Motors:
Torque equals speed to a point. I would start out with at least 450 oz. of torque. Due to the lenght of your x-axis (8 feet), a ballscrew would almost be cost prohibitive for a home machine. You would be looking at a rack and pinion or a timing belt for a drive. You would have to gear down your motor to make either one of these to work. By doing so you would increase your torque but lessen your speed. To get your speed back up, bigger motor. Bigger motor, less gear reduction. Oh what cycle. Increasing voltage to the motor will also speed things up---to a point---
Your Y-axis could be driven by a ballscrew due to it's length with no problem.

Routers:
Everybody seems to have thier favorite brand but Porter-Cable routers seem to be the going thing right now, the bigger the better. They can be found at local hardware stores to specialty wood working stores.

Software:
I can't comment on that because there are so many out there. It all depends on what you want it to do and will the program fill your needs.

[space_case]

Thanks for the info! It look like the X axis will be the tricky part. I had invisioned lead screw as on my CNC foam machine. I will have to go read up rack and pinion and belt/gearing methods. This all sounds challenging.

Will a large Porter-Cable handle aluminum? Without one of the fancy cooling systems I see on comercial machines?

More questions to come!

[2muchstuff]

The x-axis can be very easy. If you have your heart set on using a ballscrew for the x-axis you can use one but I would recommend that it be a fixed screw. One where the nut rotates around the shaft and rides in a holder attached to the gantry, by doing this you can use a significantly smaller diameter screw. Rack and pinion, large commercial machines use this method. It's not hard to set up at all, just keep the rack parallel with the axis rail and tension on the pinion, keeping things meshed. The most common rack comes in a 14 degree pressure angle but 20 degree is what's best, allows a greater force to act upon the teeth before things start to jump and is much smoother.

Gearing can be accomplished in two different ways. One, use a gear box designed to fit your stepper motor. This can be expensive but is the smallest and easiest to fit. Two, use timing belts, pulleys, shafts and bearings. This method is cheaper, takes up more space and takes a little more brain power to fit and adjust. The nice thing about this method is that if you decide to change ratios all you have to do is change pulleys, not entire gearboxes.

Routers:
Porter-Cable 7518: 3.25 hp, 5 speed, 4.2" body
Porter-Cable 7519: 3.25 hp, single speed, 4.2" body

Both routers have autoject collets, 21,000 rpm top speed, short distance from collet to bottom bearing. I checked on the cost of just the motor versus the whole thing, get the whole thing, there is not that much difference in price that way if you need a router you've got it. Shop arround, prices vary quite a bit on the web, some even offer free shipping. As long as you have the correct feed rate and cut depth you shouldn't have a problem cutting aluminum. Cutting anything though I would recommend that a small stream of air be directed at the cutter for chip removal.

[2muchstuff]

I forgot to add, using rack and pinion on both sides of your x-axis's will increase the positional accuracy by reducing the torque factor applied on the y-axis gantry by driving it from one side only. This is easily acomplished by connecting both rack pinions via a drive shaft. To reduce the weight of the shaft you can use a steel tube with a solid bar fit into and welded to both ends of the tube to which the pinions are fitted.

[space_case]

Wll, I certainly know more now than a few days ago. I am pricing MIG welders on ebay and I am taking a welding lesson next weekend. I am going to have to be slick designing the frame as I have a workshop with a normal sized door for access and I am renting the place. I could certainly make a more robust frame if I had a garage door.

Any sources for these rack and pinions? Or simple drawings? I have found and read 'descriptions' of the system, but have not found any insightful illustrations.

Tahnks for getting me started, 2muchstuff.

[2muchstuff]

I could go on and on where to find stuff but I think for the size that it would take to list them in this post you would be better off by typing "rack and pinion" into the search box at the top of the home page. In the meantime I will try to find pictures of rack and pinions being used. I don't know how much time I will have due to the fact that I'm going back to work on Monday after having a unexpected week off.

[space_case]

Hey, don't worry about it. I made the mistake of using google instead of this site. Hope all is well.

[2muchstuff]

In a nutshell, last Monday a lower molar felt funny and went to the dentist, was on antibiotics by noon. By 5 pm swelling started to appear, by noon tuesday my right side of my face from eye to ear to jaw to half of lip was swollen out to a good 2". By 4:30, an oral surgeon knocked me out and they pulled two teeth and one other that needed to come out on the other side. They called it a facial abcess, I looked hideous. Hey , better living thru pharmacuticals, Vicadin's are great. Now mother inlaw is in hospital. One nice thing about being off is being able to spend the time on this great forum.

Being off has gotten me thinking about what is the cost difference between rack and pinion and a fixed ballscrew. I have been trying to come up with a simple way to afix an XL timing pulley to a hollow tube (screw goes thru it) with an angular contact bearing on either side (gets clamped in frame, x-axis) and then followed by a ballscrew on either end (one fixed, the other adjustable to adjust out the backlash). I still fancy the idea of how a ballscrew will multiply the amount of steps per inch and the amount of torque.
I think that homeshopcnc has 5/8" rolled ballscrews for a $1.20 per inch. At 80" thats only $96.00, not too bad. Then you only have to secure it at either end versus the entire lenght for the rack.

[Erik]

Hello Guys, Erik here. I am not quite sure were to post this question to get opinions etc....so I guess I will start here and perhaps someone can direct me to the right forum or answer my question.
I am a former Davenport guy with 3 years experience in setup/run/maintain.
I was laid off from it almost 4 years ago.
I currently have a newfound ambition and excitment to get back into machining, but instead of davenport, CNC lathe to start then mill, then program, etc. etc. etc.....
In whoever responds to this post. with whatever experience you have (please state)
how "hire-able" am I to a shop? how much am I worth$$$
...The old/new guy on the block

[space_case]

You are going through one of those periods, now it's your MIL. I'm sure everthing will work itself out. Hope you don't look like a member of "Alvin and the Chipmunks" for much longer...

There was a dispute on a thread I found over a 1" ball screw being large enough for an 8" axis. So 5/8"???

link

MAybe speed was a big player in this instance. I am not trying to win any races, only build quality composite aicraft parts.

I think I am also a ball screw/anti-backlash nut kind of guy.

But I have a lot of reading/thinking to do.