1250 x 1250 cnc router (from scratch)

[Danielroyal25]

Hi, here are a few more screen shots of the model. Done a lot of work on it, but still a few more hours to go... Please let me know your thoughts as i would much rather make the changes now than down the line. I have still got to add diagonals / gussets onto the frame to strengthen it up. What are peoples thoughts on the X pulley set up (i have left the cross bar unsupported so material can be slid through), ways to mount X ball screws and set up of motor / pulleys on Y axis?

[kingcreaky]

nice work. i can see some time has been put in to these drawings.

Pretty confident the guys will tell you to mount the Z rails the other way round.. so the Y plate holds the bearings and the moving Z has the actual rails if you understand? see my machine

I suspect the pro's will suggest more strength under that bed.

To be honest, I took all the useful pointers from the guys on here regarding strength and rigidity and resonance with a pinch of salt..I use 6mm steel box section and 50x100x6 ali for the gantry.... every one of my mates told me its over-engineered.

Now, I sh*t you not. It is only now my machine is working I understand what they were talking about. Its literally got to be SOLID AS A ROCK otherwise you watch the thing flex when cutting hard wood let alone Ali. Your only down the road... Come and watch mine do it before you spend any money

[JAZZCNC]

Pretty confident the guys will tell you to mount the Z rails the other way round.. so the Y plate holds the bearings and the moving Z has the actual rails if you understand? see my machine

If you look again Matt you'll see he's got it correct way round.!. . . BUT . . You have put the Ballscrew upside down with Fixed end at bottom. You want fixed end bearing near motor.

To be honest, I took all the useful pointers from the guys on here regarding strength and rigidity and resonance with a pinch of salt..I use 6mm steel box section and 50x100x6 ali for the gantry.... every one of my mates told me its over-engineered.

Now, I sh*t you not. It is only now my machine is working I understand what they were talking about. Its literally got to be SOLID AS A ROCK otherwise you watch the thing flex when cutting hard wood let alone Ali. Your only down the road... Come and watch mine do it before you spend any money

He really does shit you not.!! . . . Don't under estimate the forces they are high and if you want high Precision and accuracy then the average, and even well tooled up DIY-er can't over engineer.
Build it strong and don't be afraid of weight when it comes to gantry.? Better to have rigidity and sacrifice speed thru using larger motors than end up with flexy resonating gantry which gives crap finish.

[Danielroyal25]

Yeah I am the same really, thinking that the framework can be fairly rigid (nothing too over the top) but not seeing many cnc routers in the flesh it's hard to judge how much force is actually created from them. The idea was to try and create some storage for sheets etc under the bed (as workshop space is limited already) but this can be sacrificed by adding some more support struts etc to beef up the frame.
i was worried about keeping the weight down too for some reason? But as its going to be in the same position in the workshop and weight is a key factor for reduction of resonance and improving quality of finish those worries are out of the window.
still unsure whether to go with alu or steel tho...
matt - my gantry design is based on 2x lengths of 50 x 100mm 6mm wall aluminium in a L shape config. And 60 x 60 x 4mm wall alu box for the frame. Based on your machine would you change the material of the gantry?

[Danielroyal25]

Still yet to post the build images... But Was cutting some oak today and all was going well until the grub screw holidng the pulley to the stepper motor on the z axis come loose almost scrapping the material!
what do most people use 1 grub screw or more, any locking compond, keyways?
i checked the others before starting the machine again and they were all loose. They are stainless steel m4 screws but being so small the Allen key just rounds off if they are done up too tight.

[JAZZCNC]

Minimum of 2 screws and I always use Lock thread on both shaft and screws. If you have trouble and can remove motors without needing to remove pulleys then get the Red compound that grips like shit to a blanket.! . . . . Just be warned you'll never remove the pulley again thou.!!

On ballscrews file a small Flat on shaft for one screw to land on.

Keys ways will stop pulley spinning but won't stop grub screw coming loose and pulley falling off.!

Really this isn't uncommon and for first few weeks/months it's good idea to keep going around machine checking screws etc until everything as settled down.

Now I'm answering no more questions until I've seen this bloody machine in one piece rather than load of aluminium parts and chips on my floor/bench which you've had now for best part of year. . Lol

[Lee Roberts]

Still yet to post the build images... But Was cutting some oak today and all was going well until the grub screw holidng the pulley to the stepper motor on the z axis come loose almost scrapping the material!
what do most people use 1 grub screw or more, any locking compond, keyways?
i checked the others before starting the machine again and they were all loose. They are stainless steel m4 screws but being so small the Allen key just rounds off if they are done up too tight.

Hi Daniel, try some blue lock-tite on the grub screws, also make sure your using the flat type screws not the pointed type, you could also use some thin brass sheet or shimming stock (steel, ebay?) to make some disks that live in between the screw and the shaft so as not to mark the shaft with the screw or if the pointed type, you could use a drill bit to make a matching divet on the shaft that the point of the screw will fit into.

Keyways are nice but for this you just need to support the grubscrew rather than the rotary motion, a little of the blue should sort it.

.Me

EDIT: Didn't notice there was a page 5 of this thread...it looks like you have enough ideas and the machine is coming along nicely!

[GEOFFREY]

Surely small flats on the shaft in the grub screw area should stop that. I always thought "two screws were better than one"!!! G.

[EddyCurrent]

I have two M4 hex grub screws 90 degrees apart on the pulley boss, one screw has a flat end that tightens onto a flat that was filed on the ball screw, the other has a point that digs into the shaft. One I've had the machine running a while and all is fine, some loctite will be put on the screw threads. Good quality screws and an allen key that is not worn means the hex socket does not round over.

[Danielroyal25]

Here are a few images from the build. I wont go into too much detail with text, but if anyone has any questions just let me know and i will give more detail.
I am really pleased with how it has turned out, considering it is the first machine i have designed and built. Huge thanks to everyone for the help!!!

Things i would do differently next time:
Not use cheap Omron relays! i had around 3 faulty ones which caused a head ache fault finding.
Get the dust extractor set up before surfacing the bed!!!
oversize the control box, as the wiring become a little messy and cramped
make the bed heigh adjustable
add rail adjustment to aid levelling
use epoxy to level the rails

Things still to do:
fit limit and home switches on all axis
finish the dust extraction system including dust shoe
loctite the pulley and grub screws onto the motors
calibrate the spindle speed

Putting the hours into the design was worth it. The assembly went well with the machined parts, the frame went together well to with only a couple of holes needing opening out. Slotting parts and adding adjustment in the design was beneficial for setting up and assembly.

It has taken near enough a year from design to working machine (working weekends and the occasional week night).

Anyway, enjoy the pics...