CNC Building

From FmxWiki
(Difference between revisions)
Jump to: navigation, search
Line 140: Line 140:
The Z axis is finally finished, and this is the result:
The Z axis is finally finished, and this is the result:
 +
<gallery widths=60px heights=60px perrow=7 caption="sunflowers are groovy">
 +
File:img_7806.jpg
 +
File:img_7807.jpg
 +
File:img_7808.jpg
 +
File:img_7809.jpg
 +
File:img_7810.jpg
 +
File:img_7811.jpg
 +
File:img_7813.jpg
 +
File:img_7814.jpg
 +
File:img_7815.jpg
 +
File:img_7816.jpg
 +
</gallery>
[[File:img_7806.jpg|none|thumbnail]][[File:img_7807.jpg|none|thumbnail]][[File:img_7808.jpg|none|thumbnail]][[File:img_7809.jpg|none|thumbnail]][[File:img_7810.jpg|none|thumbnail]][[File:img_7811.jpg|none|thumbnail]][[File:img_7813.jpg|none|thumbnail]][[File:img_7814.jpg|none|thumbnail]][[File:img_7815.jpg|none|thumbnail]][[File:img_7816.jpg|none|thumbnail]]
[[File:img_7806.jpg|none|thumbnail]][[File:img_7807.jpg|none|thumbnail]][[File:img_7808.jpg|none|thumbnail]][[File:img_7809.jpg|none|thumbnail]][[File:img_7810.jpg|none|thumbnail]][[File:img_7811.jpg|none|thumbnail]][[File:img_7813.jpg|none|thumbnail]][[File:img_7814.jpg|none|thumbnail]][[File:img_7815.jpg|none|thumbnail]][[File:img_7816.jpg|none|thumbnail]]

Revision as of 16:05, 24 October 2010

Building a CNC Machine - The Parts

So the big question is what do I need to build a CNC...? Looking at the web, its clear that there are just as many ways of building a CNC, as there are people interrested in this, so what I basically did was to look for what parts that were available for me, and build from those.

Quickly I discovered that getting parts from Denmark were vertually impossible, because there simply is no market for used CNC parts here..., so I turned to Ebay, and found a huge selection of usable CNC parts, just waiting for me.

To be able to dimention the CNC frame, I need to seek out the vital parts that need to go on the frame, this beeing:

- Lead Screws (XYZ) - Linear Bearings (XYZ) - Milling head with ER16 Collet.

Leadscrew / Ballscrews

So I started looking at leadscrews/Ballscrews, and came across this great offer. A set of 3 spindles including thrust bearings at both ends, only a spacer and a nut missing, but Ill manage (-:

These lead screws will set the physical limits of the milling machine.

1.jpg (6254 bytes)2.jpg (7454 bytes)3.jpg (8602 bytes)4.jpg (12021 bytes)5.jpg (13204 bytes)6.jpg (8799 bytes)7.jpg (10102 bytes)8.jpg (8694 bytes)9.jpg (10569 bytes)10.jpg (11131 bytes)11.jpg (10786 bytes)12.jpg (8513 bytes)13.jpg (7627 bytes)14.jpg (9437 bytes)15.jpg (8174 bytes)16.jpg (10144 bytes)

(Used lead screws from Malaysia, purchased on eBay - No Problems)

You might have notised that the pitch on these screws quite high (20mm pr. rotation) which by some persons will be considered very steep, and I agree and thinks it will be torture for the motors to try to drive these screws, resulting in loss of steps, and therefore unusable results. Therefore I investigated the possiblity of a reduction between the stepper motor and the spindle, and I managed to find a way to do a 4:1 reduction with tooth belts. In addition to reducing my motor to spindle ratio, I also eliminated another common problem in DIY CNC world, which is resonance. As the motors work, they make a horrible loud noise when beeing run directly on the spindles, so many use some kind of rubber bridge on the axis to isolate the motors harsh movents from the spindles just slightly.

The motors that followed the kit were 305 oz/in motors with a step degree of 1.8, which give a perfect 200 degrees pr. rotation. If I were to run the motors directly on the spindles, it would give me a resolution of 20mm/200 steps = 0,1 mm pr step (1:1 microstepping mode.). So when I build the 4:1 reduction, Ill have 0.025 mm resolution which will be more than enough for me at this first CNC build. If I find that I need more reolution, the kit from hobbycnc is able to run in the following microstepping modes: 1/1, 1/2, 1/4, 1/8, and 1/16. So in theory, my resolution could be 0,0015625 mm pr Step - But this is way beond the precision of this CNC anyway. And when you increase the stepping division, you are giving up power of the motor.

Linear bearings

The Linear bearings were also found on Ebay, and was found after the leadscres were recieved, because if all the leadscrew length is to be used, its important to find the correct linear bearing. This is naturally because you need to have 2 bearing blocks spaced on each bearing rail. The further apart, the more stable the construction will be.

img_7744.jpg (150226 bytes) 2 at the top, these are the linear bearings for the Z-axis. img_7746.jpg (138708 bytes)img_7740.jpg (164881 bytes) The long bearings at the bottom are the X-Axis bearings. Im only missing the Y-axis bearing, I found one that are 21" 5/8, in length which is just perfect... However the Danish Post service has much to be desired.. Still not arrived after 15 Days in Denmark...

Ordered it the 29 Jan 2008, and today its 05 Mar 2008... And they are still not here... But I have the tracking number, so I know they are not lost.... I guess...

Belt reduction

This is how I obtained the 4:1 belt reduction. I located an Amarican dealer of alu. tooth belt pulleys and belts. Im impressed about the quality - but they didnt come cheap either!!! but unfortunately were my only option. - The shipping were the most expensive!


img_7741.jpg (159530 bytes) Pulleys ordered directly to fit the axis of the motors.

img_7742.jpg (87183 bytes) Pulleys for the lead screw, I need to make a cylinder piece to make the 12mm hole fit the leadscrew 10mm end.

img_7743.jpg (104962 bytes) The Belts.. Ordered some spares..

Milling Head.

As for the milling head, I ordered everything for this from an existing product: the Taig milling machines has an exceptional good milling head, and you can get it with ER16 collet, which is a standard. So finding milling bits (Pro or hobby) will not be a problem.

Peatol Machine 19 Knightlow Rd. Harborne Birmingham B17 8PS England 011-441-21-429-1015 "www.peatol.com" -> They dont have email, so you will have to grab your phone...

And these are the parts I recieved:

img_7753.jpg (24037 bytes) 2 x ER16 standard collets in 2 different sizes, perfect to start up with.

img_7755.jpg (23716 bytes)img_7754.jpg (31955 bytes)img_7756.jpg (25023 bytes)img_7759.jpg (26422 bytes)img_7760.jpg (25233 bytes) The milling head with pulley, dovetail mounting plate and motor mounting plate.

img_7757.jpg (31067 bytes)img_7758.jpg (26557 bytes) The motor inclusive the pulley and drive belt.

The motor os 220 VAC. 0.18 KW. 1390 RPM.

The above items makes it so much easier to build the CNC, as it is off the shelve items, and spares can be purchased. And the mounting system is easy and the ER16 headstock is commonly available, so there will be no problem finding different tools for this collet system.

If in need to do so, the headstock can be removed from the dovetail mounting post, and placed horisontally, and the ER16 collet removed and replaced with a chuck off the shelve, and you have a Taig lathe...

If the result of the CNC turns out good, Ill add the 4´th axis to the CNC, which will be a second horisontal headstock controlled by a gear reduced stepper motor. this way its possible to make parts that were vertually impossible on the 3 axis machine.



Building a CNC Machine - The Frame

Building the frame is about to be realised. I have recently discovered the very potent and extreamly easy Google Sketchup 3D drawing program, and therefore made a 3D model of all the components I have collected till now, and se how I would visualize the CNC at current stage.

Please not that the drawing is not finished, as I dont know the extual dimentions of the Y axis as I dont have them yet.. But they will come. - And the gantry will be mounted where it is now. it will be more to the center..

CNC2.JPG
nail]]

Please ask if you would like the Sketchup file (.skp), and have a look through the 3D drawing your self.

First G-code controlled moves.. making a simple square in mid air..

Yes, the first cut was done today in Aluminium, I recieved the endmills I ordered from Ebay, and they a 4 flutes endmills.

The result of the first cuts, sorry about the focus, but the camera is not good at taking pictures of objects close to the lens. I think the result os ok, but my final verdict will come when I have a solid metal plate as X-Plane, instead of the 10mm wood board that I currently have!!! but it cuts, and its the wood that gives way when I turn up the speed of the axis.. Enjoy:

IMG 1399.JPG
IMG 1401.JPG
IMG 1406.JPG
IMG 1407.JPG
Yes I know its not much, but its only the 10mm cut at the end of the bar. (-:


Some tests with weight on the X plane: in the first video im running with velocity of 153 mm/2 and an acceleration of 500 mm/s^2. The load on the x-plane is from a solid cast iron flat + sulid metal fixture (21Kg) and 2 weights waying each 5 kg (10Kg) so that is in total of 31 Kg. (Not coundig the plane, metal wise and the linear bearing trains.)

Second video I didnt write down the data, but its probably not far from the above - Using EMC Stepconf program to cycle the plane

X - Axis frame.

The frame tubes have been recieved, and I just got the angle brackets, so I can start to weld up the X-frame:

Img 7781.jpg
Img 7782.jpg
Img 7783.jpg
Finished welding on the brackets.to the top tubes.
Img 7784.jpg
Img 7785.jpg
Using a polished solid table plate as "true flat surface" on top of the metal "true flat" you see above. This is because I dont have a "true flat surface" of this size, so Ill have to do with what I have. It actually turned out ok, but the final trimming will be done when the linear bearings is going to be mounted.
Img 7790.jpg
Img 7789.jpg
Img 7786.jpg
Img 7787.jpg
Img 7788.jpg

Making threads to hold the x-axis thrust bearing, and making the motor mount, to also accomodate belt tention adjustment.

Img 7791.jpg
Next will be mounting the linear bearings. The top of the x-frame will not be machined to true flat due to its size, but instead the linear bearings will be mounted on nuts that is individually welded on to the frame, so the linear bearings will be tightent on to these nuts. The nuts are adjusted and alligned carefulle before welding. This will come soon... But first the moving x-surface needs to be made and mounted on the rail trains.
IMG 7857.JPG
IMG 7858.JPG
Making connectors for each motor on a front plate for easy and controllable access.

Y - Axis frame

IMG 7833.JPG
IMG 7843.JPG
IMG 7834.JPG
This is the Raw Y-frame mounted on the X frame, just for measure and checking for compatinility. It seems perfect for holding the Z axis.
IMG 7841.JPG
IMG 7842.JPG
IMG 7844.JPG
IMG 7845.JPG
IMG 7846.JPG
Preparinng the Y-Axis rails by fitting small welding pads with thread in it on each rail hole. onec fittec it wil be layed down on the frame, and spot welded and checked.. and finally wielded firm on all pads.
IMG 7847.JPG
Now the rails have been mounted on the Y-Frame.
IMG 7851.JPG
IMG 7848.JPG
IMG 7849.JPG
IMG 7850.JPG
IMG 7852.JPG
IMG 7853.JPG
Trying the Z-axis on the Y-frame, nd se if it fits.. it fits perfectly..
IMG 7854.JPG
IMG 7855.JPG
IMG 7856.JPG
Trying the complete Y-frame on the X-axis. Please note the mounting brackets at the bottom of the Y frame to add stiffness to the mounting point, but also to make the hight adjustable if needed some time in the future..
IMG 7860.JPG
The bearig holder clamp for the Y-frame..

Z - Axis frame

Img 1279.jpg
Img 1280.jpg
So the frame will be made up over a set of box tubes, that is very solid, and light. this will be rigid enough for the Z-Axis.
Img 1281.jpg
Img 1282.jpg
The box tubes is cut out to hold the top and bottom ends - 16 M6 threads were cut to make the frame rigid.. The hole at the top til hold the ballscrew.
Img 1284.jpg
Img 1283.jpg
Img 1285.jpg
Img 1286.jpg
Img 1287.jpg
Img 1288.jpg
The structure assembled.
Img 1289.jpg
Img 1290.jpg
Img 1291.jpg
Img 1292.jpg
Img 1293.jpg
Mounting the linear bearings, and a bearing clamp for the leadscrew end support. On the backside you can se the holes that is used to access the screws for mounting the linear bearing.

The Z axis is finally finished, and this is the result:

Img 7806.jpg
Img 7807.jpg
Img 7808.jpg
Img 7809.jpg
Img 7810.jpg
Img 7811.jpg
Img 7813.jpg
Img 7814.jpg
Img 7815.jpg
Img 7816.jpg
Img 7812.jpg
Here you see where the limit switchedis going to be placed. They are not mounted, because from now on this item is going to be carried areound and trial fitted many places, and those fragile plastic switches breaks first time I place the Z axis on its back.. will first be mounted when the Z axis has a Y axis to go on to.
Img 7817.jpg
Fully extracted upwards.(The CNC motor is mounted at the top of the Z-axis)
Img 7818.jpg
Fully stretched downwards.(The CNC motor is mounted at the top of the Z-axis)

The total Z-axis including the 220V motor and the part that needs to be static on the Yaxis weighs about 14 Kg. From the feel of moving the motor when the toothbelt is on, I dont think it will be a problem to move the Z-axis up and down - if it does I have some good ideas to how to eliminate this.

Ofcource there will be some minor things to do like brackets for the motor power connector so it will not wave around, and wire guides for the switches etc., but this will come at the final part of assembly.

IMG 7861.JPG
Some misc. pictures...
Personal tools