[Usmanali]

Hello everyone, after a long time searching and reading through many CNC forums online I decided to start my build in late spring this year. And I've been a bit busy getting the machine together. I am by no means an engineer or qualified in any subject, I can just put my mind to something and try to make the best of things. I'm not far from getting this machine moving now but before I do so I just wanted to ask the members on this forum for some suggestions advice or help. Any input is appreciated, I don't mind honest opinions and thoughts even if they sound harsh.

Many thanks. Here is a quick photo attached.

[Usmanali]

And I forgot to ask the questions! Lol

Does anybody have any criticism towards the way this machine has been built? Does anybody see any failure points with regards to the way my carriages are built for the Y/A movement as well as the X axis movement.

Do my gear and rack placement require adjustment? I can adjust the racks so I have full engagement or adjust to leave upto 0.6mm gap between gear and rack.
I will start off by just routing aluminium composite for signage, wood and eventually later in next year metal also.

Gearboxes have a 3:1 ratio
I'm using the eding CNC controller, leadshine drivers, breakout board.
All the aluminium plates are 20mm and the base plate for the Y/A carriages are 25mm

Any more information required? Just ask.

Thank you in advance.

Usman

[Usmanali]

Another pic

[Usmanali]

Another pic

[Usmanali]

Anyone out there? Lol
Here's another pic

I need lots of input!

[Usmanali]

Time for another pic!

[ger21]

Do my gear and rack placement require adjustment? I can adjust the racks so I have full engagement or adjust to leave up to 0.6mm gap between gear and rack.

Most people spring load the pinion into the rack to minimize backlash.

[alan_3301]

Run out of bolts?




Looks very very nice by the way! I am jealous.

[Usmanali]

Thanks Gerry.

I was going that route first. But was trying to simplify it. Do you think software can eliminate backlash alone if the backlash isn't constant along the length of the rack? Other way I can think of now is to just adjust the rack up against the gear to get full engagement, I guess it's gonna have to be tried and tested? Will have to see how much wear it will cause.

[Usmanali]

Run out of bolts?




Looks very very nice by the way! I am jealous.

Haha. Thank you.

Do you think I should fill those gaps with bolts too? That's a very keen eye to detail!! I am impressed.

Usman

[kevincnc]

Nice work, it looks well made. I agree with spring loading, there are several reasons to do it. Do you have cushioned end stops? You might want to use ramps to contact the limit switches to give a little travel to slow down if they get triggered during a rapid move.

[vtx1029]

Pretty sweet looking machine! :cheers:

[Usmanali]

Nice work, it looks well made. I agree with spring loading, there are several reasons to do it. Do you have cushioned end stops? You might want to use ramps to contact the limit switches to give a little travel to slow down if they get triggered during a rapid move.

Thanks. Ur right, that's exactly what I'm going to do. I like that idea of approaching the limit switch in a very nice and smooth manner, I think ill change out all the switches for roller lever type as well.

And yes about the hard stops, cushioning definitely.

Probably get it moving first, and pay someone a visit to make nice looking bits to install those bits.

[Usmanali]

Pretty sweet looking machine! :cheers:

Thank you
Gotta say, I tried welding similar gantry towers like the crp, and failed miserably, lol. Then changed up the design. Keeping the crp r and p kit in mind just in case I have too much problems with my setup! Fingers crossed it should be ok for a short while?

Thanks

[Usmanali]

And another pic.

[Usmanali]

.........which I forgot to attach

[dmalicky]

Very nice machine! I'd say you have really good engineering intuition. (I teach and practice it, 24 years.) A few thoughts--
-The gantry aluminum cross-member may twist during heavy cuts in the long direction (not visibly, but enough for chatter). What is its cross-section and length? It's great you used a closed section, but even it may be on the small side for heavy cutting, given its length. An interesting experiment would be to try heavy cuts with the y-car in the middle of the gantry vs at either end -- it will probably cut better near the ends.
-The frame may shake a little during gantry accel/decell. It's great you bolted it to the floor and 1 of the legs is big in the fore/aft direction. If it shakes, some diagonal bracing would stiffen it greatly.
-Also for high gantry accel/decell, the x (long) axis bearings may be spaced a bit close to each other, which may allow a little tipping of the gantry. But given you have profile rail, this could be really minor.
Maybe more importantly than the above, there is no major weak spot in the machine. That means you're putting the material to efficient use, and it will perform fully up to its potential.

For R&P drive, JFG says a fixed pinion can work great if the rack is aligned well enough to the rails:
http://www.cnczone.com/forums/linear...ed_please.html
I'm involved in a 4'x8' build now and we're going to try for fixed pinions. Spring loading is easier, but it does wear the pinion quickly.

[Usmanali]

Thanks for the comments dmalicky.

The cross section of the gantry bar is 80mm x 160mmand the total length is 2.5 metres.

Adding diagonal braces is a great idea. I'm rushing it now thats why I can't see these things. But the more rigidity the better it is. I don't want to cut fast either, nice and slow is good enough. I probably jog the hell out of it tho!!

[Usmanali]

Forgot to mention, with the rack tight against the pinion, there absolutely no movement at all, no backlash! The backlash is also visible from inside the gearbox, it has a 3:1 reduction ratio which means any slight movement will be noticed when looking inside the gearbox. I removed the motors from the gearboxes so I could freely move the gantry, even with the motors on, if the rack is tight against the gears, even hard pushing and pulling of the gantry and the x carriage, produced no movement, I know it was a feel good factor visually, but ideally I will have this checked with the correct instruments.

And thanks for that link to the jgo page. Gives me confidence.

I think this forum is great, so many people with different ideas, and everybody helping to make it work, the possibilities great.

[Usmanali]

Here's another pic then.....