[Thermodynamics]

Hey guys, been lurking for a while trying to figure out a cnc machine to build or buy. I am wanting to be able to engrave/mill aluminum and plastics mostly. I have read several posts and reports of machines only being able to cut plastic and wood. What determines this? Just the rigidity of the machine? The problem I have heard with cutting aluminum is that it will vibrate and cause the bit to chatter a lot.

The machine that I am leaning towards getting is either a Lumenlab MicRo or M3, or a Fireball V90 (with a little bit more leaning towards the V90). The V90 has the capability of hold a fairly large router, so it seems (in my mind) that it could have a lot of power and if using the right bit, feed rate, correct depth, it could cut and face aluminum no sweat. Is this a correct assumption? I have faced aluminum by hand with a standard Ryobi router and while it didnt look the best (because it was done by hand), it did, indeed, cut about 3/4" into aluminum(taking off very little at a time, of course).

So, thats my question, what part of a machine determines the material it can cut? I know its probably not a black and white answer, but Im just trying to cram more cnc knowledge into my small brain!

[Caprirs]

Depends on "cut". Sandpaper cuts. So do 6" diameter facemills. The first thing to decide is what you intend to cut, how accurate the cut needs to be, and how long it should take. If the biggest tool you'll ever use is a 1/8" endmill to router shapes in .050" thick aluminum, the machine can be pretty light and flimsy. If you need to run a 1/2" endmill 1" deep in aluminum, you'll need something beefier.

Most conventional mills are heavy and rigid. This dampens vibrations and keeps the tool from bouncing around. A lot of the hobbyist type mills rely on very high spindle speed to compensate for the low rigidity and (relatively) light weight of the machine and take little tiny cuts.

[Thermodynamics]

Well, I am 100% sure what I am wanting to cut in terms of depth and width, but I would assume i wouldnt use more than a 1/4" bit and maybe going down to .5"-.75" (big MAYBE), and that would be just for contours, and probably not channels or anything if that makes a difference. Does that help? Sorry if its vague, I am wanting something in between engraving and full fledged milling, so i guess "light contouring" might be an accurate description.

[Caprirs]

A 1/4" end mill can be run on most of the router tables found on Ebay. The tool would have to run high rpm, require some kind of mist or flood coolant, and take a lot of passes (say .050" ?) to get to the final .75" depth. The finished profile would probably have a measurable taper from top to bottom due to the flexing of the machine. By comparison, a traditional knee mill would be able to run the 1/4" end mill at least a diameter deep per pass and would have little measurable taper from top of the cut to the bottom of the cut. The prime limitation of most knee mills is spindle speed is relatively low.

By a taper, imagine using an end mill to interpolate a circle through a plate. Rigid machines will produce a circle that is the same diameter at the top as at the bottom. Less rigid machines will be deflected by the tool pressing against the work piece and will cause the tool to not be perfectly vertical resulting in a diameter variance from top to bottom. In the case of the router tables, this can be significant for deep cuts. The router table is not intended to cut .75" deep into metal. The knee mill is.

There are bench top machines capable of deep heavy cuts. They are heavy and expensive. Dyna Mechtronics made several bench top mills that would easily run a 1/4" end mill .75" deep. Their top of the line machine, the DM1007 listed for $30K and weighed 1400 lbs.

[Thermodynamics]

Yes, I know what you mean about taper. I am familiar with manual mills/lathes, but this is my first endeavor into cnc machines. I live in a condominium, so space is limited (not to mention the lack of 240V power!). This is why I am wanting a smaller unit.

I am not terribly worried about taper in a hole, honestly. The parts I will be making will be strictly for my benefit and hobbies where great precision is not necessarily needed. I also understand that it will take several passes to get to the desired depth. I probably wont be cutting any holes or channels that deep, I will most likely be doing external contouring to my parts. I was just making sure that i could cut aluminum with a smaller machine even though I shouldnt depend on it for the heavier cuts.

Thanks for the input Caprirs!

[Med-Pac]

Pretty much any router system made out of steel, alum. stock, alum. 80/20 will get you there. As far as cut quality goes, you can achieve pretty good results with multiple roughing passes then do a finish cut to get her done. Tolerance may be an issue....but there again shallow up the pass and play with your feeds. Sounds like you need to do more research. Especially with your neighbors!!!!!!

Hope that helps ya,
Mike

[Thermodynamics]

Yes I agree, I definitely need to look around a bit and get a better foundation. I am trying to fight the "That is so cool I want one now!" urge on buying a machine and make sure its the right one for the job/me.

[LUCKY13]

The V90 appears to a bit more robust machine between your choices. All though the other seems capable ( for what they are) and it appears to have a pretty good following with forum and plenty of involvement.


The Lumenlab though looks like its main structure is the aluminum base plate it is built on. I would feel better about it if the plate was 3/4" thick ( atleast 1/2").


In a machine this size though its kinda hard to tell. The Lumenlab even though it apears to be of very little structure its base can not twist in anyway. Now the mounted pillers holding all the hardware could. I think really I would have to have both machines in hand to really see which had more stability.


WIthout doing so, I would have to go for the V90. One, if it did need some structure stabilizing added it would seem to be not much a problem to add it. And you would have a machine to build the pieces with if needed ( well that would be the case either way). Adding a aluminum base plate to the V90 would be a plus and if care was taken it all could even be made flat and square to where closer tollerance machining could be done.

You see it never fails, not matter what you think you want to do with your machine you sooner or later realize you want to do more ( its CNC so much more can be done). Doing upgrades to the machine in hand is a good first step and normally results in a good learning expeirances. Then the next step come buying a bigger machine or even building one ( not imposible even with a machine cutting the parts of this size). Once you learn the does and dont's of the machine you have bought you understand more about what is needed to achive more.


Looking at it from that point of view the V90 has the ability to handle a bigger spindle. This will allow you to push limits more, and make good add on parts to help the machine itself (bracing, differnt spindle mounts, coolant, aluminum base plates, vises and other tooling and on and on).


Here is a little router that would be worth looking into. I dont know how much you was willing to spent but getting the most you can afford will pay off later for you in a big way. Lets face the more you can do with your machine, the more you will do. The Keling link I will post also has very good proven electronics kits (, controler, power supply). The router has Ball screws all ready on it and I would think better rails than the others, plus its all aluminum and comes with the steppers.


CNC Router Keling Technology Inc

If for some reason that dont take you right to it just look at the listings on the side of the home page for CNC router. I believe for the money this is a lot better setup than you have posted. Plus Keling has been with us for a long time and there service is very good. They even have a section in the forum with dirrect feed back with them if needed. Its a little plain Jane on the looks if you know what I mean but that easy enough to take care of yourself, you will have CNC so decorative covering or such would be a good project. I looked into both the listings you posted pretty good but then it hit me about this router. They just added it to there line up and few months ago or so. Now you have to buy your spindle which could be a router or even one of there spindle kits which are much more than just a router. Even if you had to save a bit to reach for something like this I feel it would be a better machine. Because you will , you start doing the work you have in mind and then it start growing when all the friends start wanting little side jobs here and there. The extra ability of the machien will pay off, plus I think this machine will hold better tollerances than the others and be able to run at a faster rate ( believe me a slow machine will get old fast). You dont need a hotrod machine but one with single thread screws and nuts will not come close to one with Ballscrews.

I would guess there is even more good machines out there but Keling has been offering good parts and service at a price for so long I feel good about going with them. I have nothing to do with them, except buying parts from them myself. They are not perfect but they will stand behind there stuff good. There is a few venders on the forum that is this way and I have bought from many of them. Keling is hard to beat from a hobby standpoint.

Jess

[Thermodynamics]

Lucky,

Thanks for this info, I will definitely look into those machines. It is a bit more than the others, but it seems more robust as you mentioned, but is still in my budget.

I have thought about making more parts for a V90 with a V90, as in, replacing the MDF with HDPE or aluminum to make it a bit stiffer in the future.

I like the Lumenlab a lot and have seen many videos posted by the makers and its pretty impressive. They have cut aluminum easily as well as HDPE with deep cuts. However, there is a long lead time for those machines right now. On their own forums, there has been a discussion about one of the owners getting pretty sick lately which has slowed down their production considerably. Nothing against him, he obviously cant help it, but i think it would be best to get another machine with comparable capabilities and not inundate LL with more orders.