Re: Drill path inaccurate but endmill path is fine - Troubleshooting
Ahh. I don't think I have seen the older style then. My other machine is regular roller skate bearing on flat bar. It works great too. Tensioning on that style was a little more hands on. :)
Re: Drill path inaccurate but endmill path is fine - Troubleshooting
Forgive me, but I have my doubts about whether you can expect anything better from that whole design. I am sure it's a fine router, but I think you might need something a bit more solid for milling metal.
Just my 2c
Cheers
Roger
Re: Drill path inaccurate but endmill path is fine - Troubleshooting
Ahren - Well it seems my issue is the bars not being parallel, I measured their distance in 5 spots and had a runout of almost 20 thousandths, I am going through my clamps right now and trying to adjust them all within .001. I didnt see the new parts on the website yet, have they been put on there? Depending on the cost I will probably upgrade. I will send you a message through your website contact page. Thank you for all your help man, great customer service!
Lee - Yeah this is the V-groove setup for the pro machine, it's not too difficult to adjust them, but with my rails not being 100% parallel it was binding when I got to the left of my gantry, and I kind of ran it through back and forth and i think it bent my sled a bit because I couldn't see what was obstructing and binding, so after that when I travel back to where the rails are closer, it is able to be twisted because its no longer as tight as it was.
Rcaffin - So far this machine has cut aluminum without much issue, at least so far within the tolerances I needed, Im now pushing the limits though as I need to be accurate to .001 which is why I am building a new machine like the one I described in my last comment.
Re: Drill path inaccurate but endmill path is fine - Troubleshooting
Yeah, it's when you start wanting finer tolerances that it gets hard. EVERY machine has its limits.
But building a new CNC machine seems to be recommended group therapy here ... :-)
Cheers
Roger
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Re: Drill path inaccurate but endmill path is fine - Troubleshooting
Yeah. The CRP machines can certainly cut many materials. It is the level of precision needed that is the question for any given part or material. I would not consider cutting steel with it, though mine did not skip a beat doing it accidentally. ;)
Some grades of aluminum are certainly in the realm of possibility with these routers. No question there. The level of accuracy is the question. There are ways to achieve a higher level of accuracy than you could normally get using the CAD to adjust some dimensions as well as backlash compensation. That will not work in every situation, but can help in some cases. The size mill needed to machine a 2' long part at one go is pretty large and so would be the price tag. There are a lot of machine builds on this site that is every bit as good or better than commercial offerings. Just depends on how much sweat equity and budget you are willing to put into it. I would be the last guy to say that designing and building your own machine is a bad idea. It's not. It's the dedication and follow through that counts. :)
Here is an image of what my carriage looks like.
Re: Drill path inaccurate but endmill path is fine - Troubleshooting
Rcaffin - I totally agree, this machine really got me through a lot of work, its a solid workhorse. The way I look at it is if I need tighter tolerances I'm heading in the right direction, I just don't have the money to buy a commercial CNC router for 50 grand, so I have to build one as close as I can, and to be honest building the CNC is fun as hell too so I am not complaining!
Re: Drill path inaccurate but endmill path is fine - Troubleshooting
Hi OC
$50k? Not me, mate!
But if you are really thinking of a build for greater precision, can I at least suggest a heavy steel body, solid linear rails and ample double-nut ball-screws. Plus, despite what some say, LOT's of mass!
Then you get to the electronics - which are even more expensive...
Plus the instruments, like meters and CROs and so on.
One can be impoverished for years.
Cheers
Roger
Re: Drill path inaccurate but endmill path is fine - Troubleshooting
Roger- Haha yeah I understand bud, Im just hoping these production jobs I just landed will save me from poverty and pay for these upgrades, I went into detail in my previous comments but I have the whole thing planned out, welded steel frame possibly filled with cement, Stationary gantry supports possibly even a stationary gantry to beef up rigidity, linear guide bearings THK style, Heavy duty precision ballscrews, servo motors preferably AC servos but DC will do, watercooled high torque ATC spindle, vacuum table with VilMil for cutting sheet aluminum. I got the direction I want to go, jsut gotta get time to finish my solidworks assembly.
Re: Drill path inaccurate but endmill path is fine - Troubleshooting
Leeway - Oh I see now, You have the new bearing tension setup, it does look much better than the sleds, I sent Ahren a message on their website, I will probably make the upgrade.
Roger - My goal for the new machine is to stay under 10 grand and be able to hog aluminum sheet, I think it's possible. After seeing this machine cut aluminum with no problems using a 1/8" single flute cutter, I have a feeling I can pull off the ultimate aluminum sheet eater for less than 12 grand including the ATC spindle.
Re: Drill path inaccurate but endmill path is fine - Troubleshooting
> servo motors preferably AC servos but DC will do,
I'm running Baldor INDUSTRIAL DC motors with 512 line encoders and a 3:1 toothed belt reduction to the ball screw. Single step resolution of 0.8 microns. Also a Baldor industrial DC motor for the spindle. In general, even machining steel, none of the motors pulls much current. I KNOW, becasue I have current meters on all motors.
OK, on one occasion I got up to 180 V / 8 A on the spindle, which is close to 1.5 kW - but it's only a 0.5 kW DC motor. It didn't seem to worry about that, unlike so many Chinese motors which go into melt-down at their rated power after 10 minutes.
Um - the American industrial DC motors are a bit more $$ than the Chinese ones, but they do sell very well despite that.
Cheers
Roger
Re: Drill path inaccurate but endmill path is fine - Troubleshooting
Roger- I was looking at the Motors on AutomationTechnologiesInc.com : Either this DC kit for 1500$ http://bit.ly/1STC7ro : Or I might build my own setup using one of these AC servo option, AC is a lot more money but I assume its worth the money, I would probably go with 4 sets of the 750W AC Servo/Driver package for 565$ each. Which would be 1500$ for a full DC electronics kit, the AC would cost around 3500$ to 4000$ all said and done, although maybe 3000$ with the AC servos because I probably wouldn't need to go dual drive on my y-axis so I could go with 3 motors, Im heavily leaning toward a stationary gantry with a moving table on 4 linear rails with 8 bearing blocks. and one monster ballscrew down the middle
Re: Drill path inaccurate but endmill path is fine - Troubleshooting
> this DC kit for 1500$
Oh YES. Very, very nice! I have a few spare DC motors like that and they are SO smooth. MUCH better than cheap Chinese VFDs which burn out. I note the specs on the motors: Continuous Current: 7.8 A, but
Peak Current: 40 A. Overload is no problem!
Stick an encoder on the end - ah, I see they already come with reasonable encoders. Nice.
I suggest a 3:1 toothed belt reduction to the end of the ball screw, with double pre-loaded bearings (eg angular contact), and modern toothed belts, not the old imperial XL style which has some backlash. GT2, 16 mm wide, would be nice.
Fixed gantry with YZ movement, and a travelling X table? Yeah, I have seen a number of very pro machines like that (also rather $$). If I ever rebuild, I would very likely be going that way too.
Just as a thought - would you consider going bolted with dowels rather than welded, for the key parts? NO thermal stresses built-in that way. Bolt, really align, THEN dowel. Alternately, visit your local graveyard and knock off a large heavy granite tombstone as the base. Well, how about a ceremonial stone-mason, anyhow? I discussed this with a local guy and he was quite sure he could go up to about 8' and FLAT. Add granite ribs underneath for extra stiffness.
Dreaming ...
Cheers
Roger
Re: Drill path inaccurate but endmill path is fine - Troubleshooting
Roger
- Yeah the DC kit looks sweet, that is what I will most likely run with, also I figure I could grab that and if I still need more power I can upgrade to AC later when I can afford a quality AC setup.
- I like your idea about the dowels, I was also thinking about using precision made brackets for all the places a weld would be needed, something more solid than the average 90 bracket. I am worried about thermal related twisting in the steel, I would also like to find a better alternative to the whole pouring leveling epoxy deal, that looks like a pain in the ass. Id rather take my material to a machine shop and have them true up all my stock.
- I am really leaning towards fixed gantry, only concern I have about that is the room Ill need for table travel. I only plan on a 3ft x 4ft work area, maybe 4x4. For the table travel I figure 4 linear rails with 8 bearing blocks should be plenty solid, and a fat boy ballscrew down the middle.
Re: Drill path inaccurate but endmill path is fine - Troubleshooting
Severely biased opinion, based only on my own experiences: modern DC motors with skewed windings are seriously undersold. They are as rugged as all hell - far more rugged than AC or BLDC or stepper.
IF you get brackets welded up, get them thermally stress-relieved at the same time. Then get them machined square.
Room for table travel - yeah, I know. But you can stick an A axis on one end and LEAVE IT THERE!
Just my 2c.
Cheers
Roger
Re: Drill path inaccurate but endmill path is fine - Troubleshooting
Quote:
I just don't have the money to buy a commercial CNC router for 50 grand
A commercial CNC router may not be the right tool for that job either.
I use a $100,000 router every day, and it's not made for cutting aluminum.
Re: Drill path inaccurate but endmill path is fine - Troubleshooting
Right. A nice laser cutter might be the best machine for cutting thin aluminum. I use my plasma cutter to cut thin sheet and it works pretty well. Of course it is not a finished part when it comes off the plasma cutter.
It really comes down to what the part is size wise and the finished part requirements.
Aluminum can be cut with lots of woodworking and hand tools as well.
Re: Drill path inaccurate but endmill path is fine - Troubleshooting
Yeah ideally I would use a YAG laser to cut these parts and then make a fixture on the CNC to chamfer the holes. I don't have access to a YAG laser and we already are maxed on budget so we cant make the cost any higher. I gotta do what I can with my own tools. Here is a photo of the parts I'm making, they are cut from .125" aluminum sheet. All the larger holes need a 0.015" chamfer, these cable combs as we call them hold wires together in computer mods because its become popular to sleeve each psu cable individually. Here are some photo examples.
http://i.imgur.com/jWEhaN7.jpg
Here is one of my computers you can see what they are used for on the cables coming up from under the graphics card in the front, this computer has the older model snap in style but people prefer these low profile ones that are installed during the sleeving process. Most of the time they are made from plastic but we are doing aluminum because they are much more durable and aluminum is also very popular with pc modding giving a more modern industrial look, once we are full swing production well also anodize them.
http://i.imgur.com/17CeRwU.jpg
Re: Drill path inaccurate but endmill path is fine - Troubleshooting
What are the small holes for?
Re: Drill path inaccurate but endmill path is fine - Troubleshooting
Small holes are for aesthetics basically, but allow the option to run fiber optics to light up the cables.
Re: Drill path inaccurate but endmill path is fine - Troubleshooting
When I built my PC last year, I practiced sleeving for a few days, and bought all of the supplies, but never finished it. It's been under my desk with the side panel off all year. ;)