LumberJocks

Homebuilt CNC Router #2: Simpler, Stronger, Prettier

  • Advertise with us
Blog entry by SPalm posted 10-22-2007 08:30 PM 51350 reads 28 times favorited 40 comments Add to Favorites Watch
« Part 1: A Journey Part 2 of Homebuilt CNC Router series Part 3: Routing Large Mortises »

The next and final version.

I needed to address some of the problems that I noticed from before. Complexity needed to be reduced. Some of the racking and shifting needed to be addressed. I wanted to remove the concept of keeping all the skate bearings so tightly pressed against the rails. And it needed a face lift. So I came up with a new (is anything new?) design.

I kept the leadscrew and motor combination along with the torsion boxes. I got rid of the box below the gantry to let the bed lay flat on the table top. The sides were to lose the stiffeners by using a different strengthening technique. The wrap-around Y carriage was to turn into a flat plate. And I went with V-bearings for the linear rails. These bearings are actually fancier than they look. They have two rows of ball-bearings to be able to take both lateral and radial pressure.

They were to ride on angle iron as the official V-rails were beyond my pocket book.

Photo Sharing and Video Hosting at Photobucket

I spent a fair amount of time trying to find a way to make the gantry wall stronger. I actually tested various plys and MDF combinations. I found out that 3/4 inch MDF skinned with laminate on both sides yielded a very strong panel. I also found that yellow glue was better than contact cement at holding it all tight. This combination actually makes a small torsion box, which is a substrate tightly coupled to skins on both sides. I edge banded them in maple to keep out moisture.

Photo Sharing and Video Hosting at Photobucket
My gantry now looked like this:

Photo Sharing and Video Hosting at Photobucket

I went with dual motors on the long axis to virtually eliminate any racking and more tightly couple the drive mechanism to the bearings. I used wooden standoffs to attach the motors.

Photo Sharing and Video Hosting at Photobucket

The leadscrews where coupled to the anti-backlash nuts with wooden holders on each side of the gantry.

Photo Sharing and Video Hosting at Photobucket

I attached the Y leadscrew to the carriage underneath the Y torsion box to get it out of the way.

Photo Sharing and Video Hosting at Photobucket

I used the removable Z from the last machine and mounted it on this one.

Photo Sharing and Video Hosting at Photobucket

And then added dust collection. A must needed addition.

Photo Sharing and Video Hosting at Photobucket

It was all working pretty darn alright. But there were a few things that I decided to upgrade. The V-bearings for the Y carriage were digging into the edge of the angle iron. I solved this by adding a few wooden strips and mounted the angle iron with the angle facing up. This vastly improved its ride. I had also noticed that sometimes the steel rods and brass bushings for the Z were sticking, so I switched them over to V-bearings as well.

Photo Sharing and Video Hosting at Photobucket

Photo Sharing and Video Hosting at Photobucket

And finally I cut the plate across the front of the machine and added an end vise for vertical board routing.

Photo Sharing and Video Hosting at Photobucket

To those who are still hanging in there: On a different note, before I had the money to buy a CAM program, I needed something to use for test cutting. So I wrote SpiroCNC. I think alcohol was also involved. It would generate G-code for spirographs and other geometric designs. It was kind of stupid fun and is still used a bit by people in that same situation. I did also use it to generate some rosettes.

Photo Sharing and Video Hosting at Photobucket

Photo Sharing and Video Hosting at Photobucket

Photo Sharing and Video Hosting at Photobucket

Take care,
Steve

-- -- I'm no rocket surgeon



40 comments so far

View Dadoo's profile

Dadoo

1766 posts in 2646 days


#1 posted 10-22-2007 08:39 PM

Man, you really impress the hell out of me. Wow. I am humbled. Keep it up.

-- Bob Vila would be so proud of you!

View woodgizmo's profile

woodgizmo

42 posts in 2560 days


#2 posted 10-22-2007 09:38 PM

What an incredible design.

-- Hard work spotlights the character of people; some turn up their sleeves, some turn up their noses, and some don't turn up at all!

View GaryK's profile

GaryK

10262 posts in 2644 days


#3 posted 10-22-2007 09:45 PM

Great project!

Looks like you are using steppers and not servos. Do you have encoders on them?

What are you using for a controller?

Gary

-- Gary - Never pass up the opportunity to make a mistake look like you planned it that way - Tyler, TX

View SPalm's profile

SPalm

4819 posts in 2538 days


#4 posted 10-22-2007 10:20 PM

Thanks guys.

Gary, they are stepper motors so there is no feedback or encoders. Servos are a bit too much for me to handle. The machine is not allowed to miss a step, and it doesn’t. Those motors are really strong. I can barely hold back the gantry when it is moving. They have about 300 oz/inch of torque and 200 steps per revolution. I am micro-stepping them with 16 pulses per step. Each revolution is 1/4 inch (4 tpi), so that is 12,800 pulses per inch. I am still amazed that it all works. The controller is a kit from HobbyCNC.com.

Steve

-- -- I'm no rocket surgeon

View gbvinc's profile

gbvinc

629 posts in 2603 days


#5 posted 10-22-2007 11:55 PM

Nice! With this setup, how many inches per minute is the cutter moving? (avg)

View Thos. Angle's profile

Thos. Angle

4435 posts in 2618 days


#6 posted 10-23-2007 12:41 AM

Good heavens this is fasinating. I just wish I wasn’t so old, I try to figure it all out. But I’m paying attention and learning.

-- Thos. Angle, Jordan Valley, Oregon

View SPalm's profile

SPalm

4819 posts in 2538 days


#7 posted 10-23-2007 03:01 AM

Thanks,

My rapids are set at 150 ipm, or 2.5 inches per second. This is the rate that I can move the router around when I’m not cutting anything. The cutting rate is set by the CAM software depending on what conditions are; depth of cut, type of wood, bit RPM, diameter of the bit, etc. Just like hand routing. I am pretty chicken about pushing it, but I could take it up to the rapid rate if I wanted. Doing something like a mortise at 60 ipm or 1 inch/sec is still impressive to watch, for me. I cut something like that with successive cuts, dropping the Z about 3/8 inch per pass. So the simple answer is about as fast as you would cut it by hand.

Steve

-- -- I'm no rocket surgeon

View gbvinc's profile

gbvinc

629 posts in 2603 days


#8 posted 10-23-2007 04:05 AM

Thanks for the quick answer!
What is the max travel on the X/Y and Z axis?
(Can’t wait to start in building mine… it has been on my list for a year now)

View GaryK's profile

GaryK

10262 posts in 2644 days


#9 posted 10-23-2007 04:29 AM

Steve,

Great website. Thanks for the link. Seriously thinking about this. A few questions.

1. Are you plugging this into your parallel port on your PC, or a USB port with a parallel adapter?
2. Does the CAM software just output g-code and then you use a different program to send the code to the controller?
3. Do you know of any software that can take a dwg or dxf file and use that to create g-code?

Too bad about no encoders. If they were being used by the controller it would allow the steppers to skip and not lose their position. I worked with servos in the automation industry and I guess I an kind of spoiled.

Gary

-- Gary - Never pass up the opportunity to make a mistake look like you planned it that way - Tyler, TX

View Sawdust2's profile

Sawdust2

1467 posts in 2744 days


#10 posted 10-23-2007 04:39 AM

”...on my list for a year now” Hmmmmm.

Careful. On an earlier post Steve said he built one version in a weekend.

He’s got the whole thing planned out. You ought to be able to make if before breakfast on Saturday.

I, on the other hand, am going to sit back, pop a root beer and watch ‘cause this is too good to miss.

-- No piece is cut too short. It was meant for a smaller project.

View SPalm's profile

SPalm

4819 posts in 2538 days


#11 posted 10-23-2007 03:12 PM

”...on my list for a year now”

Don’t do it man.
PUT THAT THOUGHT DOWN AND BACK AWAY FROM THE DOOR.

You really have to ask yourself why. What do you want to do with it and how much do you want to spend in dollars and time. For me, I just wanted to do it, and fell into it. I had no expectations or real cost targets. That is probably not a good way to go for most people. I saw it more like the guys who restore an old car. You can’t ask them why or how much. They just want to do it. They spend a bundle and only drive it on Sundays, but I admire them for it. Building it drove my uber practical Dad and my artsy Sister crazy. The first argued that I didn’t need it, and the second argued that anything that it produced would be just look machine made anyway. I am tired of those arguments.

What is the cutting envelope? I haven’t really measured it. The basic size is about 2’ x 4’ because that is what fit in my shop. It can get kind of expensive to keep increasing the size, just like a boat. A lot of newbies want to cut 4×8 sheets, and they soon find out that will cost a lot of money. Remember flex and whip?

My stepper driver card and controller (Mach3) combination uses Windows XP and a parallel port on a PC of at least 1Ghz. I guess that rules out a lot of modern PCs, or you just buy a cheap PCI to parallel port adapter. USB is talked about a lot, but for the DIY it is not there yet. I am pretty sure that a USB to parallel dongle won’t cut it.

The main purpose of a CAM program is to convert DXF, EPS, and other line art type files (for 2D) to a G-code file. The fancier ones also help you pick feeds and speeds along with a simulation. I do this upstairs, copy the G-code file to a flash stick, carry it downstairs and feed it into the machine. A .dwg file is more like a .doc file. It is a design file that contains much more info than is needed. So you export it to DXF from your CAD program. For 3D (think carving) the CAM input file is more like a mesh file. The output is still G-code. Go to Vectric.com and download their demo. It was originally a sign making CAM, but it has a user friendly look and feel and you can get a better idea how this all works.

Steve

-- -- I'm no rocket surgeon

View gene's profile

gene

2184 posts in 2540 days


#12 posted 10-25-2007 09:31 PM

I had just sent you a PM in regards to another forum question, when I saw this. This is truly fantastic. Great Craftsmanship and detail.
God bless

-- Gene, a Christian in Virginia

View Bill's profile

Bill

2579 posts in 2817 days


#13 posted 10-27-2007 09:31 PM

Great job Steve. Keep it up and we will see a new CNC router on the market!

-- Bill, Turlock California, http://www.brookswoodworks.com

View Alexon's profile

Alexon

1 post in 2468 days


#14 posted 12-19-2007 01:49 AM

Hi, I am Brazilian and living in Brazil! His CNC was fantastica, would pass the measures of CNC (X, Y, Z)

View Karson's profile

Karson

34876 posts in 3057 days


#15 posted 12-19-2007 02:53 AM

Great job. Nice design.

-- I've been blessed with a father who liked to tinker in wood, and a wife who lets me tinker in wood. Southern Delaware karson_morrison@bigfoot.com †

showing 1 through 15 of 40 comments

Have your say...

You must be signed in to post the comments.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics

HomeRefurbers.com

Latest Projects | Latest Blog Entries | Latest Forum Topics

GardenTenders.com :: gardening showcase