mini cnc milling

[endlasuresh]

I have searched a lot in google and here too but i dont get fine answers.I am thinnking to build a mini cnc milling for engraving.I need for my company purpose.I readed on websites but they didnt given exact size of the parts and how to make it
well can anybody give me the dimensions and building information etc

thanks in advance

[Fastest1]

How big of an area do you want to engrave? What material do you want to engrave?

[endlasuresh]

thanks for asking this i too want to know size etc.
let assume 200mm square maximum of area.I want to engrave on copper and iron plates if possible.also on wooden
Can you give some example how much the weight it can handle ?

[JD_Mortal]

You should build a 1-foot square work area... The space it consumes will be expectedly twice that size. For engraving, you want to obtain the greatest precision as possible, which translates into wider bases for each moving axis, and tight tolerances for every aspect of the machine. Luckily, though the parts will be more expensive, they will also be a lot smaller, so not out of reach of a decent budget.

The purpose for having a 304mm (12-inch/1-foot) working area, is for mounting and room to allow the tool-mount to travel edge-to-edge in the 200mm work area. The size of the machine will occupy nearly twice that size, when you include the rail-sizes needed to stabilize and mount the tools and each axis, and the motor protrusions. (Obviously, larger machines, the motor protrusion is a non-issue, but on smaller machines, the motor is apparently larger due to the smaller work area.)

For rails, I would suggest a length that is 300mm on your two flat axis directions X-Y, and a 100mm might work perfect for your Z axis, which moves the tool up and down.

You want to keep the rails as close to the working surface as possible, and as close to the tool-center as possible. This will reduce unwanted stress and reduce inaccuracy that large machines have to contend with. Eg, If your tool should be mounted with enough clearance for your largest part, and no more. Keeping your mounting points of the spindle/drill and the axis close to the work surface.

The most important part of keeping high precision in an engraver, is a good spindle/drill. You don't want a cheap drill that has any motion when you push on the mounted bit. If it moves, you will not have a "true center", and your bit will spiral and wobble as you are trying to engrave a nice clean line. This also goes for your bits. You need to make sure the bits are perfectly centered in the collets and have a true centered tip. Uncentered, it will create spiro-graph patterns where you want to have nice clean lines, and will end-up breaking the bit if it catches off-center on a hard piece of material.

The good news is, you can use motors as small as 1 amp and power in the 12-24v range, with a high gear-ratio or screw-ratio, somewhere in the ballpark of 12 tpi or 25 tpi, to give you nearly microscopic precision of the drive-system, and more torque than you will ever need for carving.

Now... what is your budget like?

[endlasuresh]

thank you very much i am getting some good hints hope i would build my cnc milling.soon
my budget is around $1000 anyway i have friends who have some of the components like stepper motors.The one which i needed is spindle and trying get nice one will post here if i found in the market since online are costed twice.
mortal
can you let me know how much this type milling can handle weight of the plates.

I will reread your post again since theirs a lot of good information in your post tahnks again.

Regards
Suresh

[johnohara]

Nice summary JD_Mortal. There are times when it's best to just sit down and listen. Your post was one of them.

~John

[JD_Mortal]

Originally Posted by johnohara Nice summary JD_Mortal. There are times when it's best to just sit down and listen. Your post was one of them. ~John

Thanks John, I don't often get compliments like that... (I will try not to over-speak.)

The weight you will be able to handle will depend on your design...

Solid rail glides (linear slides) that are only 12-inches 300mm, will handle a lot of weight. The thickness of the guide-rod glides, and the pillow-blocks or bearings, will determine your maximum weights.

Design-wise, you can use a fixed-table with a moving gantry, and then the weight is not an issue at all. Your table strength will determine what weight you can stack on top of it. The moving gantry will essentially slide along the sides of the item you are carving, while the axis hovering above your item will control the spindle left/right motion.

There is no advantage to having a dual-moving table. That design was contrived for fixed-milling spindles, such as drill-presses and fixed-spindles that would stay stationary above the milling surface. For accuracy, you want to avoid dual-sliding tables. They have to be stacked on top of one another, which pushes the axles further from the milling area.

Using a moving gantry will allow you to align the gantry rails flush with the milling surface. That is as secure as you will get on the gantry, related to precision.

The most precise gantry axis, (y), would be a setup which has rails that go in front of, and behind the spindle, like an "H" with the "-" being the spindle-mount. The (x) rails would be at the top and bottom of that "H", that is looking down on the completed design. That whole span being mounted as low as possible to the surface you are milling. The dual-rail will bring the focus of the precision to the center-line of the spindle, thus, your only misalignment will be on the y-linear path. (The fact that the spindle is directly between two rails, translate rotational forces into the spindle rotation, thus, they are not present. If you only had a rail behind the spindle, rotational forces would pull the spindle left and right on the y-liner travel. The same force that your wrist would have, if you held the drill out in front of you, as opposed to holding it with two hands, close to your chest.)

With that budget, focus a good deal on the linear slides, as those will be your biggest core element, for precision etching. (Other than the spindle.)

There are a bunch of "complete mounts", which include the glides, rails, bearings, screw, and mounts, for a decent price on ebay. You just have to mount it to something flat.

With your smaller size structure, you could easily use 20' of rectangle-shaped aluminum extrude, 1.5x3.0 inches, and a hand full of mounting brackets. I would not go the MDF or wood path for framing... due to the nature of wanting that etching precision desired.

You are lucky to have that good of an initial budget...

Like this, but on a smaller scale... (Imagine your spindle mounted through a hole in a table-slide. The Z axis mounted to one side of the table, moving the spindle up and down through the hole.)

[hemsworthlad]

JD: I know i've given you grief in other post's for being overly complex but by the same token i dont mind saying what a great post.!!. . . this is a perfect example of a great and helpfull post. .

[endlasuresh]

Solid rail glides (linear slides) that are only 12-inches 300mm, will handle a lot of weight. The thickness of the guide-rod glides, and the pillow-blocks or bearings, will determine your maximum weights.

thanks again
Ill choose the nice one from shops.you have answered for the motor too but still i have doubt
does this motor will handle to move glides
Low torque small size Stepper motor with 5 wires interface. Can be used in unipolar & bipolar mode for small applications
# 1.8 degree step angle. - 200 Steps per Revolution
# Holes on 4 corners for mounting
# 12 V 150 ma.
# Weight 160gm
# Size 38x38x30 mm.

[RomanLini]

# Weight 160gm # Size 38x38x30 mm.

No! That motor is very small! 38mm frame is a size 14, they are only good for use in hard drives and similar tiny things. It is also very low torque.

You need larger motors, size 23 (56mm or 60mm frame).

[endlasuresh]

I have checked online and their are available but my selection is 3 phase motors.I looked some of the sites but they have been 4 phase motors.I will take good motors with high torque.also please tell me is this cnc machine can do drill the holes just like in this image.
I know the size and the it depends upon machine but i may want clear thing since i mention engraving.So i would be using for both milling and engraving.
It is very important since i have a lot of work that i would spend money for this things