My new CNC machine, and why I've been so quiet lately
JasonDorie
Posts: 1,930
So as not to take over IDBruce's thread, I've moved this discussion here. I realize this is far off the path of Parallax products, but I also know there are folks on here that are into this kind of thing, so hopefully this isn't unwelcome.
I've spent the last month or so building a new CNC machine. I still have some last things to do, but it's basically up & running.
There's a public photo set on Facebook of the build here: The Machine's Big Brother
This machine replaces a smaller wooden one I built a couple years ago. It's made primarily of steel & aluminum, with some HDPE and MDF parts. It's a rack & pinion drive in X & Y allowing for rapid moves in excess of 900 inches per minute. It was built from plans purchased online.
Jack - I built an air deflector for mine that attaches to the bottom of the router to send the cooling air sideways instead of straight down. You can see it on my previous machine, here: Air Deflector. I also have an 800 cfm dust collection system with a 4" hose going straight from the cutting head, so hopefully that's not an issue. On my current machine I use a Mach3 script to set my Z height based on a small steel plate of known thickness. The tool head is moved downward until it makes contact with the plate, completing a circuit. Since the plate thickness is known (measured with calipers) you set the height to that value, and your zero is perfect - no eyeballing required. I still have to install limit switches on this one, and I plan to do the contact plate too.
I was in the same boat, but with properly seated & tensioned gears, the backlash is very low. Builders of this machine have gotten below 0.001" backlash, which is far more accurate than I'm likely to need. It'll also move about 8 times faster than my previous machine, and is significantly more powerful and rigid.
I found the 3D contour cutting bits from PreciseBits work really well: http://precisebits.com/products/carbidebits/taperedcarve250b4f.asp They're tapered, so not good for vertical walls, but perfect for detailed dimensional carving.
I've spent the last month or so building a new CNC machine. I still have some last things to do, but it's basically up & running.
There's a public photo set on Facebook of the build here: The Machine's Big Brother
This machine replaces a smaller wooden one I built a couple years ago. It's made primarily of steel & aluminum, with some HDPE and MDF parts. It's a rack & pinion drive in X & Y allowing for rapid moves in excess of 900 inches per minute. It was built from plans purchased online.
Jack Buffington wrote: »I would also prefer that it didn't blow so much air down where it was cutting. You are quickly going to find that you are going to have dust everywhere unless you make some sort of dust collector around the bit. I also have some LEDs aimed at the bit so that I can see what is going on while cutting and to be able to properly set my Z depth.
Jack - I built an air deflector for mine that attaches to the bottom of the router to send the cooling air sideways instead of straight down. You can see it on my previous machine, here: Air Deflector. I also have an 800 cfm dust collection system with a 4" hose going straight from the cutting head, so hopefully that's not an issue. On my current machine I use a Mach3 script to set my Z height based on a small steel plate of known thickness. The tool head is moved downward until it makes contact with the plate, completing a circuit. Since the plate thickness is known (measured with calipers) you set the height to that value, and your zero is perfect - no eyeballing required. I still have to install limit switches on this one, and I plan to do the contact plate too.
Jack Buffington wrote: »Have you figured out what your backlash is? I stayed away from rack gear because I was worried about that since I knew that I would want really high precision.
I was in the same boat, but with properly seated & tensioned gears, the backlash is very low. Builders of this machine have gotten below 0.001" backlash, which is far more accurate than I'm likely to need. It'll also move about 8 times faster than my previous machine, and is significantly more powerful and rigid.
Jack Buffington wrote: »One final comment is that I had been having trouble finding router bits for smaller diameter cuts. Specifically, I wanted 1/16" cuts sometimes and the router bits that I was finding would be 1/16" in diameter but would be 1/4" inch long in their cutting length so they would snap off easily. A couple of weeks ago, I decided to try making some collets to use 3/8" and 1/8" diameter shank end mills. That has worked out great. Now I have all sorts of options to play with!
I found the 3D contour cutting bits from PreciseBits work really well: http://precisebits.com/products/carbidebits/taperedcarve250b4f.asp They're tapered, so not good for vertical walls, but perfect for detailed dimensional carving.
Comments
-Phil
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Could you posts some spec's.
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Motor data:
Motor Drivers:
Etc.:
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Before you have to get back to that dry-wall project in the back round.
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Great work!!!
- Software to produce GCode is VCarve Pro, MeshCAM, CamBam, others...
- Motor Control Software is Mach3
- Motors are 380 oz-in, 3.5A. One for each side of the Y axis, one on the X, and one on the Z
- Motors are driven by a single Gecko G540 with a 48 volt 12.5A switched power supply
- The rack & pinion system has a 3:1 toothed belt gear reduction from the stepper to the gear rack
The machine itself is a steel welded base supporting 80/20 aluminum extrusion for the X & Y gantries with angle-iron from Home Depot as the rails. V-bearings are used throughout. The machine is roughly a 6' square, with a cutting area of 4' x 5' in XY, and about 5.5" in Z.
The motor driver uses 10x micro stepping, so including the gear reduction you get 1908 steps per inch in X & Y. I currently have it set to do rapid moves at 900 inches per minute. It can go significantly faster than that, but it's already scary at that speed.
I'm using a Hitachi MV12 router as the spindle. It's somewhat unique in that the variable speed controller in it attempts to maintain a constant speed, not constant power, so it won't slow down when cutting like so many others do. It's also much quieter than the Porter Cable I was using on my previous machine.
As for your rapids, are you losing steps for real, or is it resonance? My wooden machine rapids at about 160ipm using 5-TPI acme threads. I couldn't get even close to that before I added dampers to the motors. The G540 has resonance compensation built in, but if you're running a hobby board you may have to go a little more old-school, like this: http://solsylva.com/cnc/dampers.shtml
They look a little funny, but they work amazingly well. My wooden machine will cut HDPE and MDF at 100ipm.
For those reading this who are considering building their own CNC machine, you should know that a laptop is not a good choice to drive your machine. I tried a laptop at first and was getting only about 20 inches per minute at top speed. After a lot of head scratching and internet searching, I determined that something about the laptop's bios or chipset was optimized for low power consumption. This caused the pulses coming out of the parallel port to be uneven in their spacing which the stepper motors didn't like very much at all.
I am getting ready to build a small mill myself, but it will be very unusual for a very specific purpose. It's very interesting to see how the design compromises make other mills very inappropriate for the project I am attacking. You will eventually see it here, since it will be Parallax powered in more ways than you're likely to expect. But first I have to prove it works. As far as I am aware nobody has ever built a precision CNC mill to cut mumble mumble whatever.
-Phil
You could bet on this at the Hard Rock, but if you do don't take it for granite.
-Phil
I used a indian slate,it was very brittle.Due to its layerd rock composition.So you cut some perfect and they would fall apart anyway.
You're having greater success and better progress than some of us.
What would it take to have you cut parts for us? Of course, you would be paid for materials, set up time, cutting time, shipping, and some kind of mark up so it would be profitable.
My guess is that you making parts would cost a lost less that the enineering shop in the industrial part, as they have much more expensive equipment and higher overhead, etc.
Are you already doing this?
I'm not already, but it was one of my goals in making the new machine, so if you have something you'd like made certainly feel free to contact me. I've still got some testing to do with this machine to verify it's square and cutting correctly, but so far everything appears to be right.
$500 - the rack & pinion parts, gears, adapters
$500 - assorted hardware (V bearings, Unistrut steel, Z-axis drive screw, anti-backlash nut, collet, bolts, washers, etc)
$400 - steel for the base
$250 - extruded aluminum beams
$200 - Hitachi router & aluminum mount
So the hardware probably comes in between $2500 - $3000. I'm sure I'm missing something, but that sounds about right. You could do it cheaper by sourcing things 2nd hand (I wasn't trying to save money) or go significantly more expensive, if you wanted to beef it up.
Software I had already for the most part, though I did buy Vectric V-Carve Pro. I had Cut2D before and was quite happy with it, and they offer an upgrade path. I've been very happy with their software.
The software I had from my previous machine: Mach3 (controller) - $175. MeshCAM - $175. Cut2D - $150. You could use EMC as the machine controller for free (it runs on Linux), but I chose Mach3 because it runs in Windows.
To be clear, this isn't my design - I made it from plans available at http://www.joescnc.com The plans are $100 and come with access to a support forum for other builders of the machine. There's a wealth of knowledge in there - lots of people have modded the machine to different sizes, there's a cast aluminum version available, various options for making it more rigid, and so on. The design is solid and it's well supported in the forums. Kinda like the Stamp & Propeller.
Have not seen you in the forums for a while. How is everything working out?
Bruce
http://www.rockler.com/product.cfm?page=25376
My current machine, which is a Frankenstein CNC (not quite homebew, not quite store-bought), is considerably smaller.
You could build one heck of a homebrew machine for the price of that one. Just my point of view.
Bruce
Bruce - the machine is running really well. I've been doing relatively small stuff with it so far, but have a few larger projects planned. I'm very happy with how it turned out. The Facebook album I posted earlier is public and gets updated as I build new stuff if anyone is curious.
I forgot all about that facebook page... I will have to check it out later today. Of course I am curious.
Bruce
I'm playing with different materials to get a feel for cutting speeds, but I have a pretty good handle on it already. If anyone wants parts cut for a project, it is now officially for hire - PM me.
Check out the photos around this one:
http://www.facebook.com/photo.php?fbid=10150377152963973&l=412486409f
Video of the process:
Also, I saw your photos. What part did you have to weld? I've made that mistake before. Especially with TIG; it's so quiet and clean it's easy to think "I can weld this small piece real quick and get away with short sleeves".
I had to weld the base of the machine together - it's all 2" square steel. The weight helps absorb the momentum of the cutting head as it moves around.
I'm totally in awe of what you've accomplished with this project. Congrats on a job well done!
-Phil