Gnu's CNC [New design]

[Gnu]

Hi all!
This is my first CNC build. I bought five THK SHS20 rails and ten blocks from ebay.de at half the price or less. The price was right!
Now I've made a design in Solidworks and I'd like some feedback on it!

The portal is made of 20mm thick and 100mm whide aluminum plate and the table frame is mostly 15mm and I'm planning do put a T-nut plate on it.
The block on the X-axis is LC blocks, long blocks, and on Y-axis I've put two V blocks. These rails and blocks are very very rigid but I'm not sure about vibrations in the aluminum plates. Planning to put some concrete or sand in the table to reduce vibrations. Think I'm going to build some concrete foundation as a table to minimize vibrations. As a matter of fact I have'nt put time on the design under the table. Mostly cus it's not as complicated as the Y-axis. I'll solve the problems when I get there. Hopefully

The Z-axis has a THK ballscrew with 4mm lead and about 90mm of travel. I bought it together with a fixed block and got away with 29 bucks

The X and Y-axis have NSK ballscrews with 20mm lead and about 520mm of travel. I bought them new from ebay and gave 75 each.
Going to use pulleys and belts on all axis. 1:1 on Z and 2:1 on X and Y. Not sure how big motors I should use. I have three bipolar steppers and drivers with 8 microsteps. Think my motors are like 69oz... but we'll see what they can do. Thou the lead is high my motors will go slow and they are stronger when they are slow but I'll probably end up with some 269oz monsters :P

I'm planning to do some aluminum and wood/plastic work. I bought a Kress router and hopefully it's enough.

[DDM]

The design looks good but I'd beef things up a little bit, your gantry looks like it could rack side to side with enough force. The 269 oz in aren't very big but they would probably drive that machine if you didn't try and push things too hard. The 69 oz in isn't probably going to push things without loosing steps.
Keep us posted on the progress.

Carl

[ViperTX]

Nice design....I would not worry about racking unless you're using some really thin stuff for the gantry uprights....anything over 1/2 inch should work great. Personally I would have gone with 2 trucks on the x-axis.....regarding the belts and pulleys...I would save the money and buy some larger steppers and directly couple them....also you could eliminate the linear shaft on your z-axis by going with the direct couple route.

[Gnu]

Originally Posted by ViperTX Nice design....I would not worry about racking unless you're using some really thin stuff for the gantry uprights....anything over 1/2 inch should work great. Personally I would have gone with 2 trucks on the x-axis.....regarding the belts and pulleys...I would save the money and buy some larger steppers and directly couple them....also you could eliminate the linear shaft on your z-axis by going with the direct couple route.

I'm using 4/5 inch plate and M8 bolts to keep it stable. I thought about racking when I made the design, ofcourse it will rack with enough force but I can't see were those big forces should come from.

I was planning to use 2 trucks on the x-axis but when I held those HSH20-LC in my hand I could'nt imagine why I couldn't use only one block. It's only 300mm (12 inch) between the X and Y rails. I't not like using a ball bushing..

Yes I'll probably get some bigger steppers but why not keep the pulleys? with 20mm lead I'll get down to 0.05mm and with pulleys I'd get 0.025mm

[Gnu]

Now I've made some changes to allow two blocks on both X-rails. The gantry side just got wider and I put a plate on top to prevent flexing. What do you think?

[Gnu]

New design

What you guys thinking?
Going to put it all on a concrete foundation with 8 M16 bolts molded in to the foundation. That'll make it easy to adjust the hight.

[luis81]

which is the full reference of your blocks SHS20, which is the preload?