Steel frame cnc router design/build

I wouldn't go running full welds round the edges if they are only for decoration and capping purposes. There will be a lot of heat generated for those welds and you want to keep heat to minimum.

Just chamfer the 4 corners and tack weld into place they will be more than stronger enough.

If you must fully weld then just chamfer the edges. If your on your own with no one to hold then buy some cheap magnet clamps to help.

Edit: Gytis . . if your still reading this then go check your email ASAP please.!!

Thanks Jazz - that kind of backs up my first thought.

Another quick Q on the welding front - how much cleaning do you do before welding new mild steel?
I've been searching & keep seeing hugely conflicting opinions - just a quick wire brush & then good to go?

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Originally Posted by CraftyGeek

Another quick Q on the welding front - how much cleaning do you do before welding new mild steel?
I've been searching & keep seeing hugely conflicting opinions - just a quick wire brush & then good to go?

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Well with stick welder then not critical has other forms like Mig-tig etc but still the better you clean the easier it will be to strike up and get good weld.
Just a quick whip over grind or flat wheel is enough just to remove any rust spots etc.

So it turns out that welding is quite tricky to master...who'd a thunk?...more practice & video watching required!

At least pillar drill tests with 10mm steel went smoothly - very happy drilling the stuff, but need some new taps.

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Originally Posted by CraftyGeek

So it turns out that welding is quite tricky to master...who'd a thunk?...more practice & video watching required

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Keep trying and it will click and don't get too stressed if your welds don't match those you see on the videos. Even pigeon shity looking will hold more than you realise. Weld 2 pieces together and then try to break the joint you'll be surprised how much effort it takes even with crap looking welds.!!

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Originally Posted by JAZZCNC

Keep trying and it will click and don't get too stressed if your welds don't match those you see on the videos.

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I'm not stressing over it at all - i'll get it...not convinced i've got the current setting nailed yet. Welding lines & dots on a flat surface are coming out nicely - 'T' joins are a bit of a mess but solid. I think i've only used 3 rods so far...another 10 & I might get the hang of it.
Overall though, I like it - very relaxing to do.

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Originally Posted by CraftyGeek

I'm not stressing over it at all - i'll get it...not convinced i've got the current setting nailed yet. Welding lines & dots on a flat surface are coming out nicely - 'T' joins are a bit of a mess but solid. I think i've only used 3 rods so far...another 10 & I might get the hang of it.
Overall though, I like it - very relaxing to do.

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Relaxing until you blow your nose after burning a few rods and realise you are coating your insides with filth!

If you can get over the annoying accent there is a guy on YouTube called chucke2009 I think who does some handy trouble shooting videos on stick welding. I found them useful anyhow. Practice is key though I think...

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Originally Posted by JoeHarris

If you can get over the annoying accent there is a guy on YouTube called chucke2009 I think who does some handy trouble shooting videos on stick welding. I found them useful anyhow. Practice is key though I think...

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I found his trouble shooting vid at the weekend - that has helped me loads...need to have another quick go, I think I should be sorted after the next practice.
For anyone needing welding help have a look at this...
How To Weld: Stick Weld Troubleshooting - YouTube

I've got a fan set up blowing 'most' of the black crap away from my nose - still got a bit of filth working its way through :-p

Progress report...
Design is still progressing, well on the way now - I should have a more advanced version to show soon.
As the design for the main base frame is finalized, I've bought the steel for the sides & rear brace so at least I can start making some progress on the build. First pieces were cut & drilled over the weekend.

Ok - design progress time:welcoming:

The overall machine...base frame is mostly the same as before except for a few minor tweaks - I'll probably add more cross bracing when its built if I feel it needs it (there's plenty of room)
Attachment 9799

Moving on to the gantry - i've lost count of how many times i've altered the way this fits together...i'm now pretty happy with it - there's nothing offending me there now:peach:
The upper & lower front plates are 5mm aluminium...all other plates/braces are either 15mm or 20mm (ecocast where appropriate).
Attachment 9796

Back of the gantry is also skinned with 5mm aluminium - 2 sections to allow easier removal around the Y-axis motor mount block. I did try to fit the motor inside the gantry, but there just wasn't quite enough space...by the time limit/home switches are in place I really don't think it'd fit.
Attachment 9797

Back of the gantry with the rear plates removed for a peek internally. There are a couple of 5mm aluminium plates at either end on the rear of the front faces to help tie them in at the sides (they will bolt to the back of the vertical piece between the main gantry side braces).
The main gantry frame as such is now 75 x 50 x 3 steel box (top, bottom & vertical side blocks)
Attachment 9798

Z-axis - 20mm plate with rails & leadscrew mounted on the back.
Attachment 9801

An attempt at a cutaway to show how the whole of the gantry/Y/Z fits together - its tight in there, but everything has at least 2mm clearance except for the Z anti-backlash nut housing which only has 1mm clearance on the back of the Z plate.
Attachment 9800

X-axis:
2x 1610 leadscrew (1400mm thread length)
SB20 rails - 1500mm
linear bearing spacing - 200mm (outer faces)

Y-axis:
1610 leadscrew (800mm thread length)
SB20 rails - 900mm
linear bearing spacing - 170mm (outer faces)

Z-axis:
1605 leadscrew (350mm thread length)
SB20 rails - 400mm
linear bearing spacing - 170mm (outer faces)

X-axis movement is roughly 1200mm - a smidge under what I was originally aiming for, but acceptable
Y-axis movement is roughly 750mm - a little more than I was aiming for, happy :cool:
Z-axis movement is roughly 180mm - could probably tweak this to gain another 10-20mm.

How does all this look/sound? :suspicion:

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

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Originally Posted by CraftyGeek

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

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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.?

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?

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Originally Posted by CraftyGeek

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.

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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.!

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Originally Posted by CraftyGeek

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

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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.!

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 :glee:

I've been fiddling with it again :rugby:

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. :peach:
Making these tweaks along with removing the rear panel looks to have saved a decent amount of weight from the gantry as a whole :cool:

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.

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.

Attachment 9902

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.

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Originally Posted by 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.

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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.

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.

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Originally Posted by 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.

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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 :fat:

Right given the lack of negative comments on the last revision of my design, i'm starting to move on to the next stage which brings me onto another set of questions...

Gear ratios & microstepping.

After reading around, it seems that the general consensus is that less microsteps are better ie, either use full steps or at most, half steps.
My understanding is that the accuracy of the stepper motor gets lower when the number of microsteps is increased...I think this also has an effect on the torque?

Couple this with the gear ratio from the stepper to the leadscrew makes the choices a little open ended as far as I can tell.
The general flat answer for the ratio that I seem to see is to use 2:1.

I'm only thinking about the X & Y axis at the moment which are both going to use 1610 screws. Belts/pulleys will be 5mm HTD 15mm wide.
Full step geared 2:1 gives a resolution of 0.1mm
Half step geared 2:1 gives 0.05mm
Full step geared 1:1 also gives 0.05mm

0.1mm sounds quite a coarse resolution to me - 0.05mm sounds more like it. So why gear 2:1 & use half step when the same resolution can be had with full steps & 1:1?

or perhaps go for a somewhere inbetween like 1.4:1 (eg 28/20) full stepped = 0.07mm ??

Am I missing something here?

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Originally Posted by CraftyGeek

After reading around, it seems that the general consensus is that less microsteps are better ie, either use full steps or at most, half steps.
My understanding is that the accuracy of the stepper motor gets lower when the number of microsteps is increased...I think this also has an effect on the torque?


Am I missing something here?

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Erm. . . !! You've been the wrong places then.? First you'll struggle to find drives that allow Full step and most start at half.

This is for a good reason. Don't think of MS in terms of increasing resolution but more in-terms of smoothing the motors action.
Full step gives rough action in comparison it's also common for resonance to be a issue if run at full step.
Main reason why you'll see folks run at full step is because they are chasing speed and have slow parallel port so struggle with pulse's needed for higher MS and higher speeds. They are often running low voltage has well.!!

Your PC parallel port will most likely be bottle neck for higher speeds with higher MS. So again you'll probably select the best MS to suit your PP motor/drive combo.! . . . . . If your using Mach3 and you want very Smooth motors and Higher speeds the invest in a Motion control card Like the SS it's well worth the money.

Personally I wouldn't run under 1/4 (800ms) and prefer to run nearer 2000MS which gives much smoother motor performance.
Often your PC and drives coupled with how much machine resonates will mostly determine the best MS to suit for machine.
Every machine tends to have it's own resonance which can affect how the motors/drives perform so you'll probably end up playing with differant settings that suit your machine best.? . . . BUT. . . I can tell you with great confidence you won't run them at Full step or very likely 1/2 has the motor performance will be rough in comparison to higher MS with possible resonance issues to boot with 1/4 or 1/8 being more likely your best option.

Regards the ratio then 2:1 will double torque and resolution of 10mm pitch screw so you won't have any issues here if you do this. It will half the speed thou.!!
If your mainly cutting woods.plastics etc then I suggest running 1:1 for the speed. If your cutting mainly Ali then I'd suggest 5mm pitch and 1:1.

If you want a balance of both then 2:1 would be ok but really not required with 10mm pitch screws if using 3Nm motors with enough voltage (60-70Vdc).

The drives I have at the moment have full steps on them...so I don't know any different in that regard. They have full, 1/2, 1/4 & 1/8 - so it looks like I should just use 1/8 step & forget about it.

I hadn't considered the torque side of things.
If my intention is to mainly cut wood/mdf & then aluminium plate/sheet occasionally....given that i'll be stuck on a low voltage (24v) for a while before being able to upgrade the driver/psu combo do you think that a ratio in between might be a better option? So I don't sacrifice too much speed, but still get a torque boost.

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Originally Posted by CraftyGeek

I hadn't considered the torque side of things.
If my intention is to mainly cut wood/mdf & then aluminium plate/sheet occasionally....given that i'll be stuck on a low voltage (24v) for a while before being able to upgrade the driver/psu combo do you think that a ratio in between might be a better option? So I don't sacrifice too much speed, but still get a torque boost.

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No I'd stick with 10mm pitch @ 1:1 has you'll be speed limited with 24V so the extra lead of the screw will help here. With 3Nm motors torque won't be an issue really unless really heavy gantry or running 2 x screws from one motor.!!

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Originally Posted by JAZZCNC

With 3Nm motors torque won't be an issue really unless really heavy gantry or running 2 x screws from one motor.!!

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I am going to be running the X-axis with 2 screws & one motor....also the motors I have at the moment are 1.8Nm. Not ideal I know - but its what I have to start with.

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Originally Posted by CraftyGeek

I am going to be running the X-axis with 2 screws & one motor....also the motors I have at the moment are 1.8Nm. Not ideal I know - but its what I have to start with.

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Oh dear your stuffed.!!!. . . Lol

Well in this case then your really bating uphill and may struggle bad With those small motors.? . . . So with only 24V then I'd suggest running 3:1 to increase torque and suffer the speed loss.
When you have larger every thing then drop back to 1:1. . !!

Make sure the motors are wired in parallel not series has well else your double stuffed when speed rises. . .Lol

What drives are you using.?

I bought the drivers years ago when there wasn't anywhere as much choice at the cheaper end of the market:
Single Driver

Also have the LPT quick connector from there as well.

I plan on replacing it all when the machine is running....but that will be a way off.

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Originally Posted by CraftyGeek

I bought the drivers years ago when there wasn't anywhere as much choice at the cheaper end of the market:
Single Driver

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Ah ah . . . Mr Rout-out CNC Well I better keep quite then or I'll get banned again. . . Lol

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Originally Posted by CraftyGeek

I plan on replacing it all when the machine is running....but that will be a way off.

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Ermm. . .Well all I'll say is try to Make it sooner rather than later.!!:hopelessness:

What is the vertical distance between the linear rails on ur y-axis?

JazzCNC

Where would you recommend as a source of rails and RM1610 ?

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Originally Posted by Old Silver Fox

JazzCNC

Where would you recommend as a source of rails and RM1610 ?

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BST automation, Aliexpress, Fred. http://www.aliexpress.com/store/314742