a little aluminum machine - thk, dremel, keling, etc.

[vacpress]

I finally got a machine working. soon it will be able to cut the parts needed to upgrade it to the intended design. the current machine was 'tossed' together with what i had on hand and a new set of keling inc. 4030 drivers and 425/oz/in motors. i need a new power supply though, to get anything near 425oz/in.. probably different drivers also.. but here are some pictures cuz that is what everyone likes!

This machine is temporary. The last image is the desired design. It will probably get McMaster Rolled ballscrew instead of the ACME ive got now. Too much friction. The machine currently tops out at 45IPM with 4x multistepping on 8 turn/inch screws and largish nema23 425oz/in steppers. These are driven by a 24v 8amp switching(ugh) power supply feeding Keling Inc. 4030 drivers. The screws on the x and y are ACME with anti-backlash nuts, and the Z is a tortured and adapted pump mechanism of some sort. Nice casting. Easy to work with it.. It has a 5-start acme and a 3:1 reduction. Seems to be about .19in/rev of linear motion. I am about to go off on a family holiday and hope to prepare all the toolpaths and files needed to come back and cut the parts for the 3D rendered design.

Ciao, Robert.

[Harpye]

Hi Robert !

Referring your 3D design...
1) Such a long Z axis move and just one ( ok very massive) rail.... - I think it would be better taking two smaller rails/ bars with the max. distance possible!!!)

2) the sides of the y Axis seem very thin to me - in relation of the length ..
possibly this causes an elastic ( parallelogram spring) area that may decrease the precision of you Y axis under load!

3) The X axis fixation to the sides / sliders /plates may be overdefined!
The Y bar has a certain length ( + tolerances) the front- and rearbar of the frame as equal. for you use those metalsheets to fix your sidebars to the front 6 rearbar this construction is not able to eliminate the tolerances without deforming the sideplates...
you wont get exactly the same distance between
(2xsidebars+ 2xThicknessofsideplates+ 2xThicknesofrails+ LengthofYbar+2xThicknessofsliders) = (lengthoffront-/rearbar)in case of tolerances... if you solve the fixation - fron to sidebar in another way so you are able to vary the distance of the sidebars - you can eliminate the difference in distance....

Please take this for constructive critisism - just want to help - so think about it and leave it if you decide to - just an idea!!!



Hansjoerg

[vacpress]

hansjoerg,

thanks for the comments. i agree with most of them. the number of rails is more or less set with 4 12" thk hrw-21 rails.. that does leave one to put somewhere.. there are, of course, a few missing pieces from the rendering. but the point about tolerange stackup.. it would get hairy.. with the cross-bars, trying to shim the whole thing would be unplesant!

i am hoping 80/20 inc. can cut their material 'very accurately' if paid to do so..

thanks for the comments!

[vacpress]

i should note the scale of the whole thing.. it is small! 9.5" working square.. 1.5" z currently. the z right now is really quite a contraption.. i will use a better camera to detail it in a few days.. that will get a laugh.

[Harpye]

Small means more problem ... ( the manufacturable tolerances are a relatively high percentage of the nominal...)

your high quality rails mean very low movement of the sliders around the rails!
Normally it is ~1/100 mm - I don't think that your manufacturer of the bars is grinding them down to length as there are usually tolerances of 1/10 mm.... doesn't fit...

the hinge for your spindlenut of the y axis is very long and possibly elastic by the holes you lightened it and the possible movement of the slider around the y axis may force the y spindle to bend ...

If you keep this solution -perhaps try get the spindle nearer - to the rail..


Hansjoerg

[ZipSnipe]

Hey Vac , very nice design, I especially like the z axis, and I think the long rail for it will be find as long as its no using the full length, that way when your milling to the table you would have more z axis biting into the z rail which should give ya some rigidness. Also the bracket in the back of the z axis is that one or is there going to be two?(two being better obviously) Keep up the good work !!

[Graham S]

Originally Posted by Harpye Small means more problem ... ( the manufacturable tolerances are a relatively high percentage of the nominal...)

But that does not matter because assuming he does not want the precision of the machine to scale down too then a smaller machine will be easier. I would rather cut something to 0.01mm when it is 10mm long than 10m.

The small size of the machine also means that what may seem like a large over hang etc is not so large. As a "dremel pusher" its probably stiff enough.

The lightened bracket is doing its job of a bracket in the wrong direction, it doesn't take much to keep the nut in place in the vertical direction but it should be braced in the direction it is being pushed. Something more like a T or L section would be better.

I also would not bank on the side pieces being cut accurately enough.

Graham

[Harpye]

Graham .... Stabler??? RC Groups Micro section???

Ok Graham ... you are right with this argument ( precision is easier to keep in smaller parts) . But over definition means always to force parts under tension together....


Hansjoerg

[Graham S]

That's me Strange, I recognized your name, I assumed it was from the CNCzone but now I remember otherwise.

Graham

p.s. "why reach for speed" would sound better

[Harpye]

HI Graham ( thanks for the hint - that's me - always the same problems with the English language.... )

I thought that I 'd seen a modified Proxxon mill on your website...

I 'm still new on the CNC site of life... last year at the end of october I made teh decision to build a mill and it is still not finished ( scratchbuild as most things I do) - just one or two threads away..... today I milled my first part ... and I'm still happy...


Hansjoerg

[Graham S]

Sounds excellent, I've been into CNC for a while but have more components and unfinished projects than I do machines but I'm working on it.

Graham

[vacpress]

I did some more work on and with the little machine. I am totally redesigning the other machine so that the frame can be adjusted and dosent rely on the stock to be within better than 1/16 or so.. i also have realized i can easily use my table saw and a jig to cut the 80/20 material to length. it may not be super accurate, but at least they will be very close to the same length. You can see in the diagram compared to my current wiring that I am not quite done with the planned controls. I am going slowly as the opto-input board and the pendant (not detailed) are in progress as well. having the machine to help make these parts is invaluable. The part being cut in the photo was my first 3D tool paths attempt - in green foam, 1/8" flat end mill. 45IPM. Not bad. I really need a 36v power supply though.

now, the pictures. Sorry they came off my cellphone.