Steel frame cnc router design/build

[JAZZCNC]

Looking for some sort of approval (hopefully :-p) before covering all the parts in holes etc

Couple things I see and sure I mentioned this one before.? The Rear plate on the Y axis.? . . . It's not required and adds very little strength and actually can cause you problems with binding the bearings if not perfectly flat and edges of mating plates perfectly 90deg. . . . Drop it and save some money and weight.!!

Next is the Z axis motor arrangement.!! Why have you got the motor fastened to the front plate and sticking out the front.?
It looks to me like you have enough length to the Y axis front plate to mount ball-screw on this and fasten motor other way round. Your rails look shorter than the movement range your ball-screw will allow.
If so and it's longer than your Y axis front plate then just do away with the bottom bearing and shorten screw provided it gives enough screw range to use all rail length. On a short Z axis screw you can easily get away with this and it also makes aligning screw/nut that bit easier.!!

Other way is to have longer Y axis front plate and do it this way, both work.!! . . . Either way Your better off with screw and motor has I've described because it will allow higher acceleration from the Z axis which helps if your planning on 2.5/3D work.!!. . . .No point making the motor/drive work harder than needed.!!


Rest looks ok except that I'm not too keen on the low base frame due to large adjustable bed range.!!. . . .Do you really need that much adjustable range because it's compromising the strength quite a bit.?

[CraftyGeek]

Y-axis rear plate...partly to help keep crap out of the leadscrew etc Thought it would add some extra sideways/diagonal rigidity...can easily drop it.

Z motor - probably didn't think it through quite correctly...with that arrangement, the y axis front plate is considerable shorter than it would need to be to have the leadscrew & motor attached.
The rail lengths are pretty much spot on compared to the screw length - maybe i've got the Z axis linear bearings spaced further apart than needed? (170mm outer face to outer face along the axis). I'll look at swapping the leadscrew & motor to the Y front plate.

Base frame - do you mean raise the lower shelf/surface, or reduce the overall height?
I don't really want to lose much overall height if possible as it will be at a good height for me to work with it at...rather than being low down on the floor like my last mdf machine which was a major pain in the back.
I don't necessarily need all that adjustment - I could raise the lower surface & add more cross bracing to the outer frame?

[JAZZCNC]

Z motor - probably didn't think it through quite correctly...with that arrangement, the y axis front plate is considerable shorter than it would need to be to have the leadscrew & motor attached.
The rail lengths are pretty much spot on compared to the screw length - maybe i've got the Z axis linear bearings spaced further apart than needed? (170mm outer face to outer face along the axis). I'll look at swapping the leadscrew & motor to the Y front plate.

With 350mm Thread length and only 400mm rails then you have loads of excess thread. You only need enough thread for required travel + ballnut length +10mm or so spare.
RM1605 nuts are approx 50mm in length so for 180mm travel then 250mm thread length is plenty.!

Base frame - do you mean raise the lower shelf/surface, or reduce the overall height?

Yes raise it and widen bracing to match. You don't want to rely on bed frame to form main frame strength, obviously it will add strength but better is main frame is strong enough without.!

[CraftyGeek]

Yep - sorry, I had another look at the Z-axis screw....I did shorten it earlier - but it looks like I lost that set of changes & didn't think/notice when I was copying the sizes down above.

Have started revising the layout - its fitting together nicer with the z-axis sorted the right way round :-p

I'll do some more tweaking tomorrow - should have a fully revised version then

[CraftyGeek]

I've been fiddling with it again

Beefed up the diagonal cross bracing on the main frame - all diagonal cross braces are now welded at one end & bolted at the other.
Also rasied the lower surface/shelf - removed the very bottom height adjustment position so it could come up a little further.

I've done a fair amount of tweaking to the gantry & z-axis.
The knock on effect of extending the y-axis front plate to mount the Z motor meant that the z-axis wasn't giving me an optimal range of movement. I had to shorten the height of the gantry (between y rail mounting surfaces) from 200mm to 175mm in order to sort it out - everything is now peachy with a good range of movement & 2mm+ clearances all round.
Making these tweaks along with removing the rear panel looks to have saved a decent amount of weight from the gantry as a whole

Am I safe to start peppering the parts with holes & adding pinions etc ?

Edit: Just spotted that the Z rails could now be longer than needed as well...or the bearings might need moving lower.

[CraftyGeek]

Here's the tweaked Z-axis...ball nut lowered to allow more clearance at the top of the axis & Z rails are now 350mm instead of 400mm.

[D-man]

Personally with you just starting to weld I would urge you to chamfer the two parts to create a 'V'.

Welding can be a tedious venture and without, lots of practise it can take some time to master. So I would not have a gap as you mentioned in image two (I think) as filling gaps with weld is another learning process.

[CraftyGeek]

Personally with you just starting to weld I would urge you to chamfer the two parts to create a 'V'.

Welding can be a tedious venture and without, lots of practise it can take some time to master. So I would not have a gap as you mentioned in image two (I think) as filling gaps with weld is another learning process.

Thanks - think i've got it covered now....been practising a bit on scrap. I'm now at the point where I'm happy to start some of the basic less important pieces to get a bit more experience before getting stuck into anything tricky.

[mart154]

As I understand you are not too far from me. If you like, I could come and give you some welding tips / help over the weekend.

[CraftyGeek]

As I understand you are not too far from me. If you like, I could come and give you some welding tips / help over the weekend.

Thanks for the offer - no i'm not far from you. To be honest, I think i'm ok now - after watching more videos over the weekend & working out what I thought I was doing wrong...I tried again very quickly last night - the result is a presentable weld that i'm happy with. If I get find that I run into problems, I may well take you up on that offer - but for now, I think i'm ok