CNC Router V1.0 (For Cutting Multiple Materials)

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Originally Posted by biketrialsdave

Thanks Jazz! I had thought of something similar but was afraid monting the ballscrew like that would cause problems. Is the general idea of the gantry sides to keep them as short as possible? Well not the sides, but the distance between the top and bottom profile carriages on the X axis?

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Yes if you want the best possible strength then you want short stubby sides but this is only really required if you want to cut hard materials most of the time. Gantry height just needs to be high enough to provide support to the Y/Z axis and resist Twisting/flexing. With this design the height of the gantry supports and takes the full load of the Z axis bearings with just the ballscrew and motor above the gantry.
The red machine in the pictures is twin ballscrew driven and this cuts aluminium no problem with resoanable quality of finish but it's not designed to do this all the time and it would eventually take it's toll on the machine, where has with woods etc it will happily cut 24/7.

With regards to the ballscrew at the rear then IME it hardly makes any difference unless wanting to cut hard materials with deep DOC. Which in this case then you'd want a stronger gantry design. For all wood and lighter aluminium use then it's no problem at all, if it was I wouldn't be using this design.!

To be honest if your wanting to cut all materials then you have to lose something somewhere. If you build for cutting the hardest materials then you need strength and weight, this comes at the cost of speed unless you increase the strength of motors etc and this costs cash.
This is wasteful if your only ever going to cut hard materials 5% of the time. So IMO you get a much better machine if you target the main use and design for the optimum doing this.! . . . Jack of all trades works but truely is master of none and you have to accept this other wise you'll be sadly dissapointed.!

Finally feeling like I may be going in the right direction now! (*awaits comments saying I'm not* =P).

There's just enough room to mount the X axis motor on the inside of the gantry.


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Won't need that top piece it's only adding weight and expense.

Thought you might of said that! Now removed.

I am looking to mount the motor on the inside of the gantry but I'm going to need a long motor shaft or a pulley with a long hub length to get through the 20mm plate and out the other side with enough length. Any suggestions?

It looks as if it will be easier to mount the X axis motor on the outside of the gantry plate (See below). If I wanted to mount it on the inside and still use the FK bearing block then the shaft would be too short to mount a pulley.

Attachment 12853

I am now looking at the Y axis ballscrew mounts in a little more detail. In the screenshot below how is the bearing mount attached to the steel box section? (Does anyone have a link to this build thread btw?)

Attachment 12854

I assume that there's another piece of welded steel plate on the end of the box section? As below?

Attachment 12855

While I am on the subject of the "end plate", I assume some sort of adjustment will need to be built in to allow movement in the Z axis as if I use the epoxy method on the box section then it's going to add some height?

Dave

Yet more questions... this time about welding and distortion.

What is the best technique to use to minimize distortion? I assume I should tack weld each side of the box section before doing full fillet welds? Do I need to do any kind of stress relief to the joint after? I am only practicing at the moment. Picked up an Evolution Rage 3-S to cut some box section and purchased an auto darkening helmet =)

I've also ordered one of these, which I hope will help:

Attachment 12874

Dave

Hi Dave,

Yea tack it all up in sections keeping any eye out for square, once your happy fill them in, alternate the areas your working on so they have time to cool down while you work another area, it's the heat build up your trying to avoid.

If you can clamp stuff down so it's less likely to move or distort, if you want to get really into it, do some googling on preheating, Jody over at http://www.weldingtipsandtricks.com has a pretty comprehensive website and youtube channel.

Where did you get the jig from?

.Me

Speaking as a pretty second-rate welder, I found it really useful to build the bulk of the frame using just one spot of weld at each joint. I then used a series of Spanish windlasses, sash cramps, etc, to pull it all square before going round and building up the welds. Diagonal bracing followed. I cut all the box section as accurately as I could using an angle grinder in a cheap stand but it wasn't perfect. Your cutoff saw might do better. And if it goes pear-shaped (literally!) then there's always the angle grinder to cut the weld to start again - another reason not to weld too much before you're happy with the shape. The great thing about welding is that for something like this, it is very forgiving. I cut one piece on the wrong side of the line, but built back up with weld and ground back to dimension...

Good tips! Hopefully I will get some time over the weekend to practice with my new tools :) Still got a LOT of design work to do...I'm thinking of moving away from the FF blocks + aluminium plate for the Y axis and maybe just using steel channel (or angle) welded to the box section and mounting BK blocks to it? One of my biggest concerns for the whole project is actually drilling accurate/straight holes! I have a pillar drill but it is pretty useless as there is a lot of slop in the chuck.

This is the jig I bought, got to be worth a punt at £21!:

http://www.ebay.co.uk/itm/1114096787...84.m1497.l2648

Cheers Dave.

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Originally Posted by biketrialsdave

Good tips! Hopefully I will get some time over the weekend to practice with my new tools :) Still got a LOT of design work to do...I'm thinking of moving away from the FF blocks + aluminium plate for the Y axis and maybe just using steel channel (or angle) welded to the box section and mounting BK blocks to it? One of my biggest concerns for the whole project is actually drilling accurate/straight holes! I have a pillar drill but it is pretty useless as there is a lot of slop in the chuck.

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Anyone got any opinions on the above? I appear to be coming to a point where I'm not sure where to go next. Still not happy with the X motor on the outside of the gantry plate either :(

I wouldn't worry too much about the stepper sticking out the side of the gantry (I'd have called that the Y stepper but there's no hard and fast rules) as it's just basically a metal lump there's not a huge amount to go wrong as you have it. If you can't design it such that it's internal maybe consider sticking a bent aluminium box around it. I managed to squeeze my Y stepper inside the gantry (see here) but it's pretty tight and I expect to be replacing the belt more frequently that usual. That's not quite the final design that I've gone for but it shows the basic layout.

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Originally Posted by biketrialsdave

I am now looking at the Y axis ballscrew mounts in a little more detail. In the screenshot below how is the bearing mount attached to the steel box section? (Does anyone have a link to this build thread btw?)

Attachment 12854

I assume that there's another piece of welded steel plate on the end of the box section? As below?

Attachment 12855

While I am on the subject of the "end plate", I assume some sort of adjustment will need to be built in to allow movement in the Z axis as if I use the epoxy method on the box section then it's going to add some height?

Dave

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Is anyone able to answer any of the above? It would be great if there was a link for the red router listed?

Cheers,

Dave

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Originally Posted by biketrialsdave

Is anyone able to answer any of the above? It would be great if there was a link for the red router listed?

Cheers,

Dave

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Again it's one of mine Dave and no build thread as these where built by me for someone off forum.

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Originally Posted by JAZZCNC

Again it's one of mine Dave and no build thread as these where built by me for someone off forum.

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No problem JAZZ. I'm currently making some changes as we speak. A few questions are now arising:

1. What pulleys do most people go for? XL? Not sure on pitch etc.
2. Is there a way of extending motor shafts so that I can overcome this problem below?
Attachment 12908

3. Is 10mm of motor mount adjustment enough for belt tensioning?

Attachment 12907

Some progress on the Y axis too:

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What most people do is rout out a recess for the stepper to mount in so you've got only maybe 5mm of material where the stepper sits (see here). That way you generally get enough shaft to mount a pulley on directly without needing an extension.

I don't think 10mm of movement will be enough for tensioning, especially not on a long belt. I'd go for more like 25 or 30mm if you can.

#1 Use 15mm wide 5mm pitch HTD pulleys and belts.

#2 Need extensions made on lathe but much easier to use BK/BF bearings inot profile and belt/pulley like shown in my picture on other thread.

#3 20mm slot.

Tonight's updates:

Attachment 12923

Still not 100% sure on the way I have attached the "end plates" as seen below. I.e. using 5mm steel plate welded to the box section and tapped with two M6 threads.


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The stepper in the first two pictures looks large for the size of machine you are building, are the 34s? I would have thought 23's would be enough for a machine of this size, especially if you have slaved motors.

The connection between the gantry screw and the top plate (third picture) looks like a weak point. I'd try and make it thick enough that it covers most of the body of the ballnut.

They are 23's. I think the model I am using has a particularly long body.

I agree with the ballscrew mount. Could make it 20mm plate (from 15) or increase that joint some other way...

Not touched the mechanical design for a while as I got distracted down the route of designing my own stepper driver...

So here's a small update. I'm feeling quite bad for how much this is looking like one of JAZZ's machines! Believe it or not I am not trying to copy you Clive!

I am still not happy with the way I have the Y axis plates attached to the steel box section. Think I need to come up with something better?...

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Believe it or not I am not trying to copy you Clive!

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If you was, I would be more than excited,:pride: but I don't see the resemblance to mine if it is me you are referring too. ..Clive

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Oops! I meant Dean...it's been a long day.

Nice machine though! :)

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Originally Posted by biketrialsdave

Oops! I meant Dean...it's been a long day.

Nice machine though! :)

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No problem with copying my stuff and you wouldn't go far wrong copying clives either it's an excellent machine.!

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Originally Posted by JAZZCNC

No problem with copying my stuff and you wouldn't go far wrong copying clives either it's an excellent machine.!

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Your so kind. But I wouldn't go that far:tickled_pink: ..Clive

I think the end is nearly in sight!! :excitement:

All steel plate is currently 3mm ("Y axis "end stops" and end plate attaching bed), should I make this thicker? Will there be any problems welding it to 3mm thick box section? I have a friend who works at a laser cutting place so I'm hoping to get those pieces cut there.


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Any comments on the above would be appreciated =) I think I need to start looking at places to get the aluminium milled soon!

I've been a bit distracted with designing my own stepper drivers but going to put that to the side until I have the mechanical design all done.

I think it would be better to extend the Z axis rear plate to meet up with the bottom plate, like this; it's not shown on this photo but my ball nut fits on the inside of that plate.

Attachment 13312

3mm plate is too thin I reckon, I used 10mm flat bar for brackets, maybe 6mm would do, see what others say about it.

Thanks for the input Eddy!

Well it's been a long time since my last post and since then there have been some large changes... Now, I am fully awaiting the groans and face palms when I say this....

I have decided to return to using aluminium profile for the frame. The reasons being:

1) My welding skills are not quite there. They aren't bad but I envisage a lot of trouble trying to get things square and aligned correctly.
2) I now have free access to a water jet which I plan to cut beefy steel brackets from to connect the profile together with.
3) I have re-evaluated what I will mainly be realistically cutting and steel may be OTT!

Anyway, enough excuses. Here's the latest design. I would really like to get the ball rolling with the custom aluminium parts. Am I best posting on the job request page and going from there?


http://www.mycncuk.com/attachment.ph...id=13543&stc=1
http://www.mycncuk.com/attachment.ph...id=13544&stc=1
http://www.mycncuk.com/attachment.ph...id=13545&stc=1

Dave

Job request can be found here: http://www.mycncuk.com/threads/7974-...-my-CNC-router

I really need to pick this project back up! Been having some thoughts recently and have come to the realisation that what I really need is a machine capable of cutting aluminium more than anything else. I'd really like to mill enclosures for my many electronics projects. Perhaps I need a re-think on the complete design!

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Originally Posted by biketrialsdave

I really need to pick this project back up! Been having some thoughts recently and have come to the realisation that what I really need is a machine capable of cutting aluminium more than anything else. I'd really like to mill enclosures for my many electronics projects. Perhaps I need a re-think on the complete design!

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The design you had wasn't too far away from cutting aluminium. It could benefit from a better/stronger base and the the linear stage for the Z axis isn't really up to aluminium but the general layout of high sides with gantry sat on rails is perfect for aluminium. Gantry design is nice and strong enough for aluminium.
If you sat that lot on nice piece of machine tooling plate or better still Granite base the frame would be sound for aluminum. Ditch the linear stage and put a conventional Z axis with decent rails etc and your sorted.

Some encouraging words there, thanks Jazz! When you say "sit the lot on machine tooling plate or granite..." which bit are you referring to?

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Originally Posted by biketrialsdave

Some encouraging words there, thanks Jazz! When you say "sit the lot on machine tooling plate or granite..." which bit are you referring to?

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Your design doesn't show any base and looks like it sits directly on table.? So I mean put EVERYTHING on solid flat foundation.

Ahh I see, yes your right. I'm not 100% happy with the useable z height I get either. I think I will redesign the z axis but may also have to increase the height of the gantry sides. I could do with finding a 'cheap' solid solution for the bed too...

Not sure if to consider coolant at this point either!

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Originally Posted by biketrialsdave

Not sure if to consider coolant at this point either!

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Yes 100% consider it and also cable routing etc.

Cutting aluminium correctly will need a minimum of blown air and idealy minimum qty coolant ie: Fogless mister. Don't need full flood but better if can have it.

I think an aluminium bed with t-track bolted to it looks like a good idea. Just need to find some for a reasonable cost!

I may of found a cheaper solution. "MakerBeam" is a 10x10mm extrusion and relatively cheap. I was thinking something along the lines of this:

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For the bed plate itself (shown in green). What would be the most cost-effective solution? The dimensions are 725x825mm. Steel or aluminium? What thickness would suffice?

I might of solved my bed problems! Look what I found in the skip at work today (along with other goodies)... It's 6mm steel plate. The dimensions are perfect for the machine to sit on. The raised area in the middle also looks perfect for mounting a bed (aluminium plate or t-slot plate perhaps?). My only concern is how flat and level the plate is. I was thinking it doesn't matter too much if I skim the aluminium plate (or whatever) with the machine once it's built?Attachment 16387