My 1st Router - PEU

[PEU]

Well, Its time to start my log on the long and windy road of building a CNC Router.

It started like this:




but after reading a lot, and I mean a LOOOT of logs here I decided to change to rails and aluminium extrusions.


It will be a fixed Y axis bridge (not as the previous picture), moving X & Z type router

My main problem with everything is that I live in Buenos Aires/Argentina.

Why a problem? you may ask, for example I purchased in USA the following items: thk rails, steppers, drivers, breakout boxes and these things are heavy so postage and customs add to the final cost...


On top of the extra costs, the typical 8020.net extrusions (or similar) are not available here, the only one I found are Bosch Rexroth ones, but with some disadvantages, they are pricey, and they cut to size BUT with a common carbide blade, not the straight & precise cuts that are available in USA.


My purchase logs is as follows:

8x THK SHS15C1SS 317.5mm long $327 (ebay)
3x Xylotex 269oz/in Steppers $162 (xylotex)
3x PMDX-150 driver boards & 1x PMDX-122 $282 (pmdx)
Shipping of these to Buenos Aires $160 (still need to know customs $)

2xNSK 8mm per turn ballscrew 440mm lenght (320mm usable)
1xNSK 8mm per turn ballscrew 224mm lenght (108mm usable)
3x Ballscrew's bearing blocks (Support block + Fixed block) + Nema 23 stepper motor mounting bracket
3x Couplings
$545 shipped to Buenos Aires (all these from Jimsonchan) (still need to know customs $)

Total to date: $1476

Still to go: Extrusions and some machined pieces.


Here is the drawing of the actual Y fixed bridge



The different color at the end of the rails is because I want to use the full usable lenght of the ballscrew, so I will cut a rail and use the parts for extensions. Remember I only have 8 rails & 8 blocks.

The moving table will use 4 more blocks and the z axis will be supported by one rail/block and the leadscrew.


Today I have a meeting with the Rexroth salesman regarding extrusions, the prices I guess would not be cheap

If someone have prices for the 45x45H rails per meter and profile conectors, please let me know so I can compare and/or bargain


As you may figured it out, the working area will be around: 300x300x100mm


I hope this journey ends with a very nice & precise machine

Thanks for looking and of course, comments & sugestions are welcome!


Pablo

[buscht]

peu, You sure are building one heavy duty machine.
A couple of comments, just my opinion.

1. With the way that you are showing the Y fixed bridge, you aren't taking advantage of the aluminum extrusions. You should just mount the THK rails to the flat plate or figure out a way to use the extrusions and get rid of the plate. To me, it seems that you are just adding cost without gaining any benefit.

2. Notice how you aren't attaching anything to the end of the extrusions. Because of this, you don't need 100% perfect end cuts. Buy the extrusions in long lengths and cut yourself.

All in all it is a fine start.
Trent

[PEU]

Hi Trent,

I see your point regarding the plate, as you guessed I want to make the unit as solid as possible, so I can achieve the maximum available precision from the parts used, I added the plate to give rigidity to the bridge, so this way I avoid torsion, and as an added benefit it isolates the leadscrew from the debris generated by the machine.

Regarding the end of the extrusions I drawn it like that because I was told over the phone that the local Rexroth shop didn't have the proper saw to cut the extrusions, but yesterday afternoon I went to talk to them (B.Rexroth local branch) and they told me that if they can't locally, they order the parts cutted directly from Germany at no extra cost if necesary (or machine them after the cut with a mill here)

They gave me the full catalogs and tips on which conectors to use between extrusions , so as you may guess again, im back to the drawing

let me know what you think

The update to the log is that all the parts from the 1st post are on the mail already


Thanks


Pablo

[ViperTX]

It would be somewhat clearer if you kept the colors of your overall view consistent with the other views. Keep the plate, you'll need it the way you're using these...

[PEU]

Hi Viper,

I don't quite understand you colors comment, so I'll best guess it the 1st drawing is no more, so I started from scratch with the second one, so maybe that is the reason for different colors. BTW, I like to use different colors while building an assembly because it helps me to visualize all the used parts and the eventual overlaps.

After the visit to the Rexroth branch I decided to use the 40x40 profile instead of the 45x45 (yes redrawing again )

I have two questions:

1) If I sit the ballscrew supports and the rail on the same plane, the nut of the ballscrew is about 14mm higher than the top of the sliding block of the rail. What is the common practice to cover this gap? a machined piece of aluminium?

I want to keep the machining of custom parts to a minimum, thats why I ask


2)

Im trying to economize a block, is this arrangement a sound idea?




By the way, I found this MARVELOUS site:
http://parts.web2cad.de/asp/PPOW_Entry.asp?language=GB
it gives 3D or 2D cad models of every major manufacturer parts, and yes, these include: Bosch Rexroth, THK, NSK, INA, IKO, and about a hundred more. AWESOME


Thanks


Pablo

[DieGuy]

Skip the extrusions altogether and just add a aluminum plate under the rails as needed to get ball screw past the Z axis plate. This will lower your moment arm and decrease the leaverage from the high riding Z axis. Secondly I don't think you want to use your screw as a supporting member just a drive member. You might want to add trucks under the other end of the Z axis plate

[ViperTX]

Pablo...you could also machine a grove on the bottom side of the top plate, or you could add spacers on top of the rail trucks...or do the opposite on the bottom plate as someone suggested.

Yes the colors are very helpful...have you done another of the overall system?

I don't like how you've cantilevered this last setup.....ballscrew nut is being asked to take 1/2 of the torque applied to that plate.....

What sort of accuracy are you shooting for?

[PEU]

Viper/DieGuy: I gave a second tough on the idea of saving a block as you suggested and you were right, its NOT a good idea to use the leadscrew as a support.

Viper: Well, to be honest at the moment I have five folders containing every rebuild from scratch, and my guess is I will have more I'm not a designer engineer so I need to see the parts and then figure out if they work or not

Regarding accuracy, I want the best possible with the parts I purchased, so this is the ideal:

8mm per turn ballscrew (zero backslash) + 200 steps p/turn stepper + 1/8 microstepping = 8mm / 200 / 8 = 0.005mm resolution

I will be more than happy if I get near 0.01mm resolution


Thanks


Pablo

[PEU]

Im anxious, parts are in local customs, tomorrow or wednesday I may have them

To Moderator, since this is not a wood router maybe its more appropiate to move it to the main section. Thanks


Pablo

[randyf1965]

Wood router refers to what it cuts not what it is made of.......

[PEU]

oops

Pablo

[PEU]

This is the power supply I will be using:



How lucky you USA guys are sometimes, parts alone here are around $35, you can purchase a ready made switching supply for the same money shipped there...


Pablo