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Mike.Mara

Any interest in a guitar specific CNC design?

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3 hours ago, Mike.Mara said:

I think there wouldn't be any issues mounting the rails on their side for this application, but if one person has concerns I feel others will too. That alone would probably make it a non-starter.

Given the limitations of the building materials and budget, I reckon you'll be fine running the rails as you have shown it in your pic. I'd continue on with the design as you have it. The intent is to mill timber, not titanium. And a 600mm wide gantry made from MDF and a bit of Al isn't going to weigh dozens of kilos.

The way you have the rails on the sides also gives you the option of replacing them with Hiwins later on with minimal work to the frame, as they're perfectly capable of being mounted in that configuration too. Probably all you'd need to do is make up some spacer blocks to bridge the gap left by the wider SBR bearings to the gantry sides when they get replaced.

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19 minutes ago, curtisa said:

Given the limitations of the building materials and budget, I reckon you'll be fine running the rails as you have shown it in your pic. I'd continue on with the design as you have it. The intent is to mill timber, not titanium. And a 600mm wide gantry made from MDF and a bit of Al isn't going to weigh dozens of kilos.

The way you have the rails on the sides also gives you the option of replacing them with Hiwins later on with minimal work to the frame, as they're perfectly capable of being mounted in that configuration too. Probably all you'd need to do is make up some spacer blocks to bridge the gap left by the wider SBR bearings to the gantry sides when they get replaced.

Well, Timber and aluminium anyway. That's why I originally went with extrusion as much as possible.

It's a difficult thing trying to design a machine on as tight a budget as feasible so that most people could afford to build one. And thinking about the kind of tools people are likely to have access to.

I personally have a CNC capable of wooden parts and a CNC mill capable of aluminium parts and given Mikro's suggested $2500+ budget, I'd have no issue putting together a damn good CNC router. But most people won't have access to that machinery or that budget. I know I don't have that budget lol.

You could easily put together a machine out of that Openbuilds stuff without needing to make anything, but it's lacking in the rigidity department, although it could be helped with strategically placed steel angle.

I dunno, I was just kicking the idea around... If you think it's worth pursuing, I'll soldier on!

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OK... In the interest of covering all bases:

How do you guys feel about MGN15 rail from China? Because (I know China can be hit or miss for quality) For 2 sets of 700mm rail, 4 carriages a 1605 ballscrew and all associated parts including mount, you're looking at £122 all in ($160.90). Excluding import taxes. Combine that with some cast aluminium for the back plate (or MDF), 2 pieces of small extrusion and a motor mount (pre-fabricated) and you're pretty much there for the X axis. No fabrication so-to-speak apart from drilling a few holes. And with the method outlined by Mikro, that's not going to be an issue. Well within the range of anyone with a drill.

Thoughts?

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2 hours ago, Mike.Mara said:

OK... In the interest of covering all bases:

How do you guys feel about MGN15 rail from China? Because (I know China can be hit or miss for quality) For 2 sets of 700mm rail, 4 carriages a 1605 ballscrew and all associated parts including mount, you're looking at £122 all in ($160.90). Excluding import taxes. Combine that with some cast aluminium for the back plate (or MDF), 2 pieces of small extrusion and a motor mount (pre-fabricated) and you're pretty much there for the X axis. No fabrication so-to-speak apart from drilling a few holes. And with the method outlined by Mikro, that's not going to be an issue. Well within the range of anyone with a drill.

Thoughts?

Only problem with 15mm rails is they do not fit 80/20 extrusion well They are too narrow to get a good footprint on the groove as 80/20 is rounded somewhat at the edges. I know this from experience as I use the 15mm as the side rails on my machine. Main load carried by the 25mm on the bottom. So I would say 20mm min. Unless I'm thinking about the wrong type of rail?

 

BTW,

Z axis is now on, still a lot to do but I am very pleased so far. :) check out my rebuild thread.

mk

 

 

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20 minutes ago, MiKro said:

Only problem with 15mm rails is they do not fit 80/20 extrusion well They are too narrow to get a good footprint on the groove as 80/20 is rounded somewhat at the edges. I know this from experience as I use the 15mm as the side rails on my machine. Main load carried by the 25mm on the bottom. So I would say 20mm min. Unless I'm thinking about the wrong type of rail?

 

BTW,

Z axis is now on, still a lot to do but I am very pleased so far. :) check out my rebuild thread.

mk

 

 

I thought the exact same thing so I went with 20mm rails. :lol: It also probably would have been a pain to get them centred correctly without all sorts of calibration tools. Since you've done it, am I correct in that thinking?

Well... With the 20mm rails, I've managed to scour the internet and find parts you can get anywhere, so we're good there. And the best part, nothing has to be perfectly square as long as you work from one reference edge. So it doesn't matter if you don't have the tools, and all you'll need is a drill and some type of saw. (So far, on just the X axis).

I'm heading over to your re-build thread now! Looking forward to seeing it. :D

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5 minutes ago, Mike.Mara said:

I thought the exact same thing so I went with 20mm rails. :lol: It also probably would have been a pain to get them centred correctly without all sorts of calibration tools. Since you've done it, am I correct in that thinking?

>snip<

Yes it was a pain in the ass. and yes it required me using dial indicators, patience and shims on the carriages to blocks, to square them up.

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1 minute ago, MiKro said:

Yes it was a pain in the ass. and yes it required me using dial indicators, patience and shims on the carriages to blocks, to square them up.

How many hours did you pour into doing that?

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5 minutes ago, Mike.Mara said:

How many hours did you pour into doing that?

Doing my long axis. That is my X axis took me about 45 hours of work to get 4 rails aligned with 8 carriages. 2 are 15mm and 2 are 25mm sets.

Had to use my 123 blocks and dial indicators to get it right.

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2 minutes ago, MiKro said:

Doing my long axis  X axis took me about 45 hours of work to get 4 rails aligned with 8 carriages. 2 are 15mm and 2 are 25mm sets.

Ouch! I mean I know it'll pay off in the end but damn that's a lot of time. <_<

 

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Just now, Mike.Mara said:

Ouch! I mean I know it'll pay off in the end but damn that's a lot of time. <_<

 

Yes but without a good foundation the rest is junk. This thing is rock solid now.

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1 minute ago, MiKro said:

Yes but without a good foundation the rest is junk. This thing is rock solid now.

Agreed, the more time you put in now the less problems and time later. Glad to hear it's all going well! Have to put up a video of it when it's alive again.

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2 minutes ago, Mike.Mara said:

Agreed, the more time you put in now the less problems and time later. Glad to hear it's all going well! Have to put up a video of it when it's alive again.

I will. :) Today is cleanup day again. Time to get everything cleaned up and reorganized before the next step. :)

 

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6 minutes ago, MiKro said:

I will. :) Today is cleanup day again. Time to get everything cleaned up and reorganized before the next step. :)

 

Good to hear! Hopefully everything runs smoothly from here on. :thumb:

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1 minute ago, Prostheta said:

I feel like I'm late to the party. Because that's how I roll, I guess.

Lol, not that late... There's still plenty of time to butt in and give advice :thumb:

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27 minutes ago, Prostheta said:

I literally have zero advice on CNC. Just never had enough time or resources to be more hands-on with this field.

That doesn't mean you cant be of help, dimensions of use, budget ect. Or jigs... Jigs are always useful!

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Well... This thing looks tiny with a body on...

yTbRqoY.jpg

Just an idea of course, feel free to shoot it down if needs be ;). All parts needing to be made are just drilling, and depending on your suppliers, cutting.

This one is done in extrusion because... Well it's just easier to line parts up on it. MDF can be planned around it.

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28 minutes ago, Mike.Mara said:

Well... This thing looks tiny with a body on...

yTbRqoY.jpg

Just an idea of course, feel free to shoot it down if needs be ;). All parts needing to be made are just drilling, and depending on your suppliers, cutting.

This one is done in extrusion because... Well it's just easier to line parts up on it. MDF can be planned around it.

Center cross extrusions only need to be half height. only ends and sides need to be full height. Also  80/20 will cut to dimension if specified as well as drilled and tapped if need be., so that should not be a problem. As far as cutting AL, a good chop saw setup correctly with the correct blade will cut any of these. This is what I use on my 12" saw.      Non Ferrous Blade

mk

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9 minutes ago, MiKro said:

Center cross extrusions only need to be half height. only ends and sides need to be full height. Also  80/20 will cut to dimension if specified as well as drilled and tapped if need be., so that should not be a problem. As far as cutting AL, a good chop saw setup correctly with the correct blade will cut any of these. This is what I use on my 12" saw.      Non Ferrous Blade

mk

Good to know! Saves a bit on cost.

Yeah I have a sliding compound mitre saw capable of aluminium and steel :D.

Tool links are going to be very useful if anyone wants to build it after it's done. Feel free to link any other tools you think people will need and I'll archive them to go along with plans. Since you've built yours from scratch, you most definitely know the tools needed better than I do. I spend most of my time waiting on delivery of tools I didn't know I needed lol.

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14 hours ago, MiKro said:

Only problem with 15mm rails is they do not fit 80/20 extrusion well They are too narrow to get a good footprint on the groove as 80/20 is rounded somewhat at the edges. I know this from experience as I use the 15mm as the side rails on my machine. Main load carried by the 25mm on the bottom. So I would say 20mm min. Unless I'm thinking about the wrong type of rail?

I'm using MGN15 knockoffs on mine, but I'm also using the smaller 3030 metric profile extrusions. There's plenty of meat on the smaller extrusions for the 15mm rail to sit on. Although, how well the 3030 extrusions will work over a much longer frame such as yours may need some re-thinking.

Quality of the rails and bearings seems decent. I had one carriage out of 12 that felt quite 'crunchy' when under load though. I initially thought I'd have to order a replacement until I decided to disassemble it and found it just had some fine steel shavings stuck in the ball race channels. While that doesn't really point to fantastic quality control on the part of the manufacturer, provided you don't mind pulling things apart it was completely salvageable without having to make a claim with the seller or order more parts. You get what you pay for. Despite what many people think of the Chinese auctions, the sellers who have been in the game for any length of time do actually want to help you if things aren't what you expect. 9 times out of 10 they will attempt to rectify things if you approach them reasonably with a fault in one of your purchases.

 

11 hours ago, Mike.Mara said:

yTbRqoY.jpg

It does look big. You sure you want to make it big enough for the worst case, or just big enough to cover most reasonable situations ;)

I will say that if you want to make it bolt-together firendly, also consider how each component can fit together without resorting to odd sized spacers and shims. The combined height of the rails/bearing blocks vs the X axis leadscrew mounting brackets are one example.

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8 hours ago, curtisa said:

It does look big. You sure you want to make it big enough for the worst case, or just big enough to cover most reasonable situations ;)

I will say that if you want to make it bolt-together firendly, also consider how each component can fit together without resorting to odd sized spacers and shims. The combined height of the rails/bearing blocks vs the X axis leadscrew mounting brackets are one example.

Yeah, I'm thinking maybe Mikro's first suggestion of 900mm may have been a more reasonable number... I was aiming for something that could handle anything up to through neck basses but the cost difference is huge and as one of you guys suggested, there are ways of doing that on a smaller machine without needing half your workshop for said machine. :lol:

I have been scouring the internet specifically for parts where everything matches so we didn't run into that issue... It took a fair bit of time trying to find a motor mount that would work lol. So far, the only spacers that are needed are 5mm under the ballscrew nuts along the X and one 10mm spacer for the ballscrew nut mount under the bed. There is one more for the motor mount at the back end of the machine but I've yet to come up with a reasonable solution.

So far except for 4 aluminium (Or MDF/PLY) parts everything is off-the-shelf and bolt together. After all the kinks have been worked out and everyone is happy that it will work as planned, I'll get working on an MDF version.

Even if no one builds it (myself included) at least it's a fun venture into design and theory. And also a place to look for ideas into design what with Mikro's design, this design and yours if you fancy posting some pics?

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19 hours ago, Prostheta said:

Workholding is probably a more useful extension of my jig-making obsession.

Workholding is a very important safety factor with CNC. Nothing worse than scrambling for your E-stop when things are shaking loose because you thought, "that'll hold". Not to mention if something shifts the time and material wasted.

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5 hours ago, Mike.Mara said:

So far, the only spacers that are needed are 5mm under the ballscrew nuts along the X and one 10mm spacer for the ballscrew nut mount under the bed.

As long as you've identified them, it's a good start. Down here at least, 5mm and 10mm 'things' can generally be found that can substitute as spacers - aluminium flat bars and acrylic plastic sheets can be had in those sizes.

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