My First CNC, own design, buidling in progress

[balsaman]

Very nice. My guess is the spindle will be the limiting factor for heavy materials. It will be a great spindle for the little wheels you want to make.

Eric

[arie kabaalstra]

the spindle i choose is a normal router, it can take quite a lot of momentum, since the tools for machining wood ( its normal purpose) are quite long, thus generating a lot of momentum.. if it can withstand that kind of force, i think it will even do hardened steel.( not that i intend to, but just in case...)

i did a "test cut" with a standard HSS end mill, 3 mm @ 32000rpm ( cuttingspeed 300m/min) it will "eat" thermoplastics with hardly any burrs..

this is very nice, because this will enable me to make Sheet Styrene model kits.
To do this, i will glue a sheet of styrene ( evergreen ) onto a Nylon plate, with a waterbased glue, bolt the lot on my machine, mill out the contours and Hey presto!!,, parts like brakediscs, wheel spacers, or small parts to create assemblies, like why not even ship models?... mill out the bulkheads, and cover the lot with styrene sheet..

[rhino]

1. WOW! i'll be keeping an eye on this thread and see how well you go. An absolutely fantastic job so far, So keep up the fine craftsmanship!

2. When you talk about construction steel, i presume you are referring to high tensile steels? (eg 4140, 4340, etc) am i right?

[arie kabaalstra]

the construction steel i use is a "plain ol' carbon steel"..

C45 is a steel with 0,45% Carbon, with a tensile strength of about 600 N/mm²
the Cold rolled quality i use is quite precise as it comes to dimensions, i usually don't have to grind of more than 0.05 mm on each side to get it perfectly parallel..
( i could also get flat ground quality, but i'd have to order that, insead of just Jankin' the lot from the steel rack )

it's a pity that there isn't an international materials specification.. for instance, the steel americans call "D2" is called 1.2397, Sverker21, or K110, the last two being factory names from Uddeholm and Böhler.

4140 is a bit like some steel i used for machine parts.. a manganese alloy, nice material. but, since factories like DMG, Bridgeport Mazak, Mas, and all the others i forgot to mention, cast their machineframes from iron, why should i bother myself with alloysteel for a machine?.. that's why i use this steel, it's tough enough to handle the stresses, doesn't vibrate that much, and Ridgidity is provided through the construction of it all.. ( box-like sections ) ..

Just got word that somewhere next week, my guides and ballscrews are going to be ordered... Progress!!!

[arie kabaalstra]

today i made a critical decision....

I decided i wasn't happy with the attachment of the motor, and while glancing at the motor the idea came to me like Archimedes law to Archimedes.. "Eureka!".. the bottom bearing bracket is made from cast aluminium, and its a bit thin in some places.. Furthermore, the only way of attaching it to the machine is by clamping it at the cilindrical part at the bottom, making a clamp-like construction is jeopardising the ridgidity.. not a real good idea then...

SO!.. i thought, why not machine a solid aluminium bearing-attaching bracket instead, basically the same part, but then with a flat section to bolt onto the head of the machine, still with the 44 mm "Collar" to put it exactly in one position, but also with an extra cooling duct, and more ridgidity, i can now bolt the motor to the head frame with for bolts, instead of one to squeeze the clamp...

[erikkate]

Really amazed by your craftmanship.
Good build, keep us posted!

[digits]

Very nice work! You do know you're going to have to mill or turn an alloy body for the rest of the router now - that green plastic really doesn't go with all that perfectly smooth ground steel!

[arie kabaalstra]

Progress today,

i put the new Motorbearing bracket in the lathe, and centered it,



For some inside Thread cutting, Left hand M36 x 1 mm thread for the bearing retainer




After that, the retainer was made, so outside threadcutting left hand M36 x 1 mm



After finishing both parts, the new bracket coudl finally be mounted on the motor



And, the motor could finally be attached to the head, with four socket screws M5





Turning an alloy body?.. how about the first picture in this thread?... a nice and neat casing?..

Maybe i'm gonna drill some more holes in the mill head bottomplate, for cooling with air... Plan is: mill a circular groove in the bottomplate, and four or six holes through it, angular towards the spindle, i can attach an airhose to the motorbearing bracket, and then drill to the bottom, above the groove..

[arie kabaalstra]

And... some more progress today, though it will be invisible to the naked eye..

some guy on a dutch modeling forum had his doubts about the radial runout of the spindle.. how right could he be...

'til he mentioned his concern about the accuracy of the spindle i had no reason to doubt..how wrong could i be?..

So.. Yesterday i took the mill head with the motor, and put an endmill in the collet, then i put a clock on the shaft of the endmill, and turned the spindle.. YIPE!!.. that was not what i expected.. a runout in excess of 0.1 mm ( 4 thou )

Upoon further examination of the spindle, i found that the opening for the collet had a rather coarse surface, and the angle of the collets and the spindle weren't equal..

So here's what i did to fix the problem.. it's not that i bought a bad router, it just wasn't finished..



First, i clamped the entire head on the bed of a CNC lathe, and alinged it with the X-axis

Then, i just machined the spindle to a smooth surface, by putting the motor on, and programming the lathe to machine the inner surface to a depth of 23.5 mm, and a diameter of 10.5 mm ( 0.5 bigger than it was supposed to be )



so, after that, and two finishing passes, i finally got the surface i wanted.. a shiny smooth one, instead of the coarse black surface if first had..



After that, the head was removed from the machine bed, and some programming was done, to get this:



a Collet, so, i put a piece of Toolsteel in the Chuck, and ran the program..



and this is what i got afterwards, an eight milimeter Collet, only the slits still have to be sparked, why am i going to wire erode the slits?.. because i also want a 1.5mm collet, and a Wire erosion machine will make a cut of only 0.3 mm, which will leave plenty of collet surface for a neat clamping surface.

after deburring this collet, i put it in the spindle, and tightened the nut, and i put the 8 mm endmill in again, to check the radial runout.. less than 0.01.. so it got 10 times better... !! even before machining the slits in.. (it doesn't yet clamp the tool !! ). I'm perfectly happy with that..

[martinw]

Dear arie,


Your thread is extraordinarily good. Beautiful photographs, and really well written posts.

Oh yes, I almost forgot the machine.....

NICE

Best wishes

Martin

[thkoutsidthebox]

Wow!

[rhino]

Hey arie, another question,
all parts are machined steel, how do you plan to combat rust? are you going to paint it?

p.s. looking better than last time i saw it.