Buying CNC mini-mill

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michaelplogue

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So, I've always wanted to have my own CNC setup, and recently I've been having to farm out a lot of small milling projects - for what I consider a pretty heafty price. So I'm thinking it's time for me to go ahead and get one.

I've been looking at the Sherline 8020 setup (2000 model 8-direction mill complete with stepper motors and pre-configured computer & software).

http://www.sherlinedirect.com/index.cfm?fuseaction=product.display&Product_ID=185

8540pic3mms.jpg


My question is this: How difficult is it to learn the software? These come with EMC (on Linux), but it's my understanding that there are several other programs that can be used. Do any of you - who have CNC experience - have any preference to a particular program? I've extensive experience in 3d modelling (3ds Max), and also have a very strong background in programing in VBA. Any tips and advice would be greatly appreciated!

.
 
Matt, recumpence, would be the one to ask.
 
Michael,

If you want to create tool-paths from Max, I came across this: http://www.cnc-toolkit.com/cnc_toolkit.html see also: http://cnc4free.org/index.html

If you want to try with a more suitable modelling program maybe start with the free versions of Alibre Xpress/Alibre Cam Xpress: https://www.alibre.com/assets/alibrecamregistrationinstructions.pdf
 
I kind of wonder, is there anyone on the boards with a un-fully-used CNC that could sell their machine's CNC time?
 
So far, I'd say Bubba is the CNC master here (a few folks have em tho).

Alibre is slick and easy to learn. The trial version allows full-functionality on about ten pieces. (I have not tried an export to a CNC setup.)
 
Thanks for the links guys! It's nice to know that there is a 3ds Max plugin that I could use to get me started quickly. That Alibre looks really nice - will definitely have to consider it if I really start getting into things.
 
awesome, i allways seized CNC-setups to carry pricetags with one more digit than that. The software being open source is something to checkvinto more closely most probably ( aka check the activity on the support site there), but in general this seems like a desirable and also usefull bigboys toy.

the plugin for open source software most gearheds can operate could even get you side-income when being done with your parts, like adaptors for hydraulic brakes on gopeds and such stuff.
 
It will probably take some time to get the software up to speed for the machine you wish to use.

Learning the software should be no harder to do than any other software you've learned so far.

For the most part G-code programming is the same from machine to machine, there are exceptions however. What you will probably want to do is basic moves and cuts, basic drill cycles, and experiment with speeds and feeds until you familiarize yourself with how it all works.

Here is an example of some basic programming.

O1111;
G0S1000M3;
G0X1.0Y1.0Z.1H1;
Z-.25M8;
G1X-5.F3.;
G3X-6.Y2.R.5;
G1Y5.;
G0Z.1M9;
G28Z0X0Y0H0;
M30;

There would be some codes specific to the machine at the beginning of the program to pick up the coordinate system and some other info, but this is an example of G-code programming.

G0....X1.0....Y1.0...etc are all called words. Each line is called a block. O1111 is the program number, the semi colon ends each block. Now, line by line...
G0 tells the machine to move in rapid (fastest speed) to the position defined after it. G and M codes remain active until another G or M code counteracts it. So the first line turns on the spindle at 1000rpm (S1000) in the clock wise direction (M3) as opposed to CCW (M4).
The second line moves the tool in rapid mode to position X1.0 Y1.0 and Z.1 in relation to the coordinates you define during a setup for the part you are working on. H1 is a height coordinate for the tool length.
Third line rapids the tool below the surface of the part by .25, note you should not be directly over the part or you will crash M8 turns on coolant which remains on until the M code to turn it off is read.
The fourth line uses G1 which is a linear interpolation (straight line) move, it changes the traverse from rapid to a controlled feed specified by F3.0 which is 3 units (inches or MM) per minute.
The fifth line changes the G1 linear move to a circular (G2 for CCW or G3 for CW) move, in this case it is making a CW corner on the part for a 90 deg sweep at a radius of .5
The sixth line returns to linear move to Y5.
The seventh line returns the move to rapid to a position above the part, M9 turns coolant off.
The eighth line uses G28 which tells the machine to return to the zero reference point for each axis listed, in this case Three X Y and Z, then it clears the height offset for the tool.
The last line is a command to end the program.

Now the problem is that not all machines use the same codes. You will likely have to program your software package for the set of codes your machine uses, so that when the software creates the program, your machine will understand it.

You will also need to understand how to set up the work piece, establish a work coordinate system for it, and set up tool lengths in relation to the location of the part.

There are automated cycles that can be programmed such as drill cycles to drill through, peck drill, or retract peck drill etc...

You have much to learn, and you have to know the first thing, before you can do the second.
 
swbluto said:
I kind of wonder, is there anyone on the boards with a un-fully-used CNC that could sell their machine's CNC time?
Click to expand...

Work is getting slow and I find that I have more time since my school load is backing off a little. I graduate in December, and assuming I get a job as an engineer, I will leave machining behind.

But...

for the time being I might be able to produce a part or two. If a few of you guys got together and decided you wanted something made...for example an adapter that allowed a freewheel to be screwed onto a brake mount on the left side for a left side drive setup, and...say 5 or more of you wanted one, I could probably do that.

All it would take is a detailed drawing...
 
TPA said:
swbluto said:
I kind of wonder, is there anyone on the boards with a un-fully-used CNC that could sell their machine's CNC time?
Click to expand...

Work is getting slow and I find that I have more time since my school load is backing off a little. I graduate in December, and assuming I get a job as an engineer, I will leave machining behind.

But...

for the time being I might be able to produce a part or two. If a few of you guys got together and decided you wanted something made...for example an adapter that allowed a freewheel to be screwed onto a brake mount on the left side for a left side drive setup, and...say 5 or more of you wanted one, I could probably do that.

All it would take is a detailed drawing...
Click to expand...

For the detailed drawing, is there a specific file type that would make your load easier? And, is there a program that's readily available that you might suggest to use for me to make it? I'm actually just looking for a one-off piece and I know it might not seem "worth it" for one piece, but I carry the motto everything has a price even if it's high. :wink:

Basically, I'm looking to get some holes cut in 1/4 inch aluminum that's approximately 7"x5", and also a simple cutout of, say a parabola. Here's the basic idea...


 
swbluto said:
Basically, I'm looking to get some holes cut in 1/4 inch aluminum that's approximately 7"x5", and also a simple cutout of, say a parabola. Here's the basic idea...
Click to expand...
You could prolly do that with a drillpress and a jigsaw. (Not fast, but cheap.)

Steel might even be easier.
 
I originally used a jigsaw with wood, but an ordinary jigsaw can be used with steel? And aluminum? Really?!!

Okay, this I have to research.
 
swbluto said:
I originally used a jigsaw with wood, but an ordinary jigsaw can be used with steel? And aluminum? Really?!!
Okay, this I have to research.
Click to expand...
Sure, with the appropriate blade.

I've used woodworking planes to get straight edges on aluminium :)

If you're patient, you can use a drill press to mill large circular holes - just use a nail or screw as a pivot...
 
swbluto said:
I originally used a jigsaw with wood, but an ordinary jigsaw can be used with steel? And aluminum? Really?!!
Okay, this I have to research.
Click to expand...

I took machining in high school and college, but I don't have access to a milling machine or lathe anymore. Instead I make do with basic hand and power tools at home.

A hacksaw with a good blade (bi-metal; Sandvik is a good brand) and some metal files go a long way.

A drill press is handy. I bought the smallest one at Canadian tire for $39.99

To do some basic milling work I use end mills in the drill press (few $ each) and a cross slide vise ($49 ouch).

I've never used CNC but I'd like to learn how CNC's work, do 3D CAD etc, so I'll stay tuned to this thread.
 
a bandsaw and a drillpress are also found in wood shops, just the badsaw´s blade won´t be for metal. if you know someone into home improvement these tools will most probaly allready sit in his garage.
On a side note, german DIY-stores offer custom-cut and drill service on the material they sell there at a small fee, you could most likely bring in your sheet of aloy and a 10-20 dollar tip for the serviceman an you will have this gotten done.
 
swbluto said:
I originally used a jigsaw with wood, but an ordinary jigsaw can be used with steel? And aluminum? Really?!!

Okay, this I have to research.
Click to expand...

I've been using woodworking tools for a bit of simplistic metalworking lately. For most things, the difference is just in the cutting edge, not the tool itself.

In a semi-related note: What's a small-ish, cheap, possibly used manual mill cost nowadays? Anything I'd use it for wouldn't need CNC precision and I could theoretically convert it to CNC if I ever had to.
 
Link said:
In a semi-related note: What's a small-ish, cheap, possibly used manual mill cost nowadays? Anything I'd use it for wouldn't need CNC precision and I could theoretically convert it to CNC if I ever had to.
Click to expand...

From about $500. Here's an example:
CT133.jpg

http://busybeetools.ca/cgi-bin/picture10?NTITEM=CT133

The prices go up and down every month just like airline tix, so one can keep an eye on the market for a while.

I'm not sure if going with the cheapest is a good strategy though. Check with someone who does machining for some advice.
FYI: I asked a friend who does demos of machining equipment about the CNC mill mentioned at the start of this thread. He said it might do for model work, but it would be better to get a more substantial machine for general purpose use, and then if CNC is needed retrofit it.
 
michaelplogue said:
That Alibre looks really nice - will definitely have to consider it if I really start getting into things.
Click to expand...
Got promo email today: Alibre 2 for 1 pricing.
http://www.alibre.com/email_lp/0609.asp
 
swbluto wrote:
I originally used a jigsaw with wood, but an ordinary jigsaw can be used with steel? And aluminum? Really?!!
Click to expand...

I have used my woodworking plunge router (handheld) to machine aluminium using a carbide bit. The fine shavings are very messy but it does work, and the tool doesn't seem to have suffered at all. I don't know what grade the ali is, probably not a very hard one.
 
I too would recommend the micromill or minimill as a CNC base. You want the most iron as possible. This makes a stiffer CNC machine. The aluminum sherlines, are just not as sturdy and will flex when you try to machine bigger stuff. They are great for small precision work, but I think you will be disappointed when try to do steel or larger aluminum parts.

Here is link to my micromill conversion. I was looking at the sherline at one time and I’m glad I went this route.
http://www.embeddedtronics.com/micromill.html

The software I would recommend is mach3.
 
jag said:
From about $500.
Click to expand...

Eeesh...I'd rather not...

So instead I'll slap together a ghetto CNC table. I really only need to cut out flat pieces for now, anyway. A set of steppers are on the way.

Anybody got any recommendations for drivers? I'll be using a screw to move the tables as opposed to a belt. A 1.8° step motor combined with a 32 thread-per-inch screw gives me a theoretical 1/7,200" resolution (which I don't think typical bolt and threaded rod tolerances would actually allow for), which means I don't really have much use for microstepping. Since I don't, I could put together a basic one from an IC if I had to. Anybody know if there sort of a standard that CAM programs use for their outputs on the serial port or whatever?
 
Micro stepping was developed to reduce harmonics; it's not really about resolution. With full steps, stepper motors lose power when they start vibrating and getting fundamental frequencies at certain speeds to the point where they become useless. It's a way of trying to get the motor to run smoother. We ran into this problem when we first started playing with CNC stuff. It was frustrating when at certain speeds we had no torque to even move the table. We had to create our own drivers to avoid the problem. It really never goes away, but was greatly reduced. We also wanted a driver that could go up to 3amps. Most drivers we found were around 2.5amps at the time. We also created a servo driver for ultimate performance; these have optical feedback and run ultra smooth. They don’t suffer the harmonics that develop with stepper motors.
 
I use a micro mark 1/10hp coping/jig table saw.they have all kinds of equipt. for SMALL precision stuff.I picked up my table w/blown motor for 12$ on eb.They have blades for all things.Also have used local tech colleges in area,most times free.they do the cutting.They also love making cicuit boards and anything "nano".They specialize in nano tech here because of Cray and circuit board manufacturing co's.in town.Thats where their jobs will be.There also is a guy who makes cns for metal work in Menominee(wisc)20 mi's away.he advertises in pop sci.I think they are pretty inexpensive compared to those w/military specs.
 
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