Luthier CNC

[bluesking]

Minor update today as I have not made as much progress as I hoped.

Cut angles into the side plates using a table saw with a cheap aluminium blade I got from screwfix. Worked perfectly:


Started assembling machine only to realise I still have my paper templates on my aluminium plates. Started peeling these off and immediately realised using spray on contact adhesive was a huge mistake. Paper wouldn't come off. Used a Stanley knife blade to try to coax it off with limited success. Spent most of the day trying to clean the leftover gunk with acetone - managed to clean off half of one single plate (and not very well).

After dinner I realised I have lots of lighter fluid which I use for cleaning gunk off guitar finishes and tools. Thought this may be worth a try and it worked fantastically. Finished all of the plates in about 1.5 hours!

1 Douse the paper with lighter fluid


2 Leave for 1-2 mins to let it soak in and peel the paper off; dead easy


3 Kitchen roll doused in lighter fluid to gently wipe off any gunk - keep adding lighter fluid rather than elbow grease (avoids smearing the gunk around). Here are all the clean plates and extrusions ready to assemble:

[Lee Roberts]

Nice!

What table saw have you got?

I use blades by OX TOOLS (https://www.ffx.co.uk/tools/product/...6Mm-X-30-X-80T), check out FFX if your a Screwfix/Toolstation kinda shopper, service from them has been great, fast to post out to.

Toolstation have these blades as well but not quite the same size offerings, just got one of these for my circular saw as helping bro build a new workshop: OX TCT Circular Saw Blade 184 x 30 x 28T

[bluesking]

Nice!

What table saw have you got?

I use blades by OX TOOLS (https://www.ffx.co.uk/tools/product/...6Mm-X-30-X-80T), check out FFX if your a Screwfix/Toolstation kinda shopper, service from them has been great, fast to post out to.

Toolstation have these blades as well but not quite the same size offerings, just got one of these for my circular saw as helping bro build a new workshop: OX TCT Circular Saw Blade 184 x 30 x 28T

I use the Triton TWX7 with the table saw module (I have the router table module too, which sees a lot of use in guitar building)
http://www.tritontools.com/en-GB/Pro...20Systems/TWX7

Had it about a year and a half and still everything works very well and no rust - happy with it overall.

Thanks for the links - the table saw needs 245mm blades w/ a 30mm mount - the best deal I found was at screw fix for about £30.

[bluesking]

Build started in earnest:

1 Y axis rough assembly


2 Y axis ballscrew


3 X axis assembly beginning


The gantry seems to move on its rails without binding - more by luck than by any concerted alignment effort. I'm not sure what freedom of movement I should be expecting though. It doesn't keep rolling after its been pushed.

Here is a vid of it being moved by hand. Can someone please check if this looks and sounds about normal?
https://streamable.com/u1pd2

Also, I have tried securing the ballscrew nut to the gantry. This seems to work OK, but at both of the extremes of travel, the resistance does go up quite a bit. I think I need to align the ballscrew more accurately to stop this happening. I'm finding this quite difficult - is there any advice you kind folks can offer?

[Lee Roberts]

Sounds and looks about right to me, did you get the rails and bearings from fred @ BST?

I've just been setting up a bed axis lead screw and had the same problems last week, I noticed in your video that there was quite a gap between the ball nut mount plate and the ali extrusion that passes under the machine, I'd say you need to shim that gap to perfection, just take your time and have the plate screws just finger tight so you can see any movement the plate wants to do, its likely you'll need to get down to beer/coke can thickness for shim material.

Then when it looks like you've got it close, run the gantry up and down a few times, do this with the ball screw mounts just finger tight as well so they can find their natrual sitting postion, then start at the floating end of the screw with the gantry down at that end as close as it can go (with-out falling off the rails), tighten the fixings for the ball screw mount at the floating end and then run the gantry up to the fixed end and do the same, creep up on perfect alignment and the ball screw should spin effortlessly as you move the gantry, I've got my X axis (gantry axis) so close doing it this way that i can push the whole z axis assembly from one side to the other with one finger and think that's the standard to aim for on the other axis's.

You can fine-fine tune each with a dial gauge later ;-).

[bluesking]

Sounds and looks about right to me, did you get the rails and bearings from fred @ BST?

Lee, that's really useful advice, thanks a lot, I'll try to follow it. Yes, all the linear motion stuff is from BST.

[Lee Roberts]

Lee, that's really useful advice, thanks a lot, I'll try to follow it. Yes, all the linear motion stuff is from BST.

Well Fred's kit is the real deal so you don't need to worry about it being fake Hiwin linear rails and bearings, the fake stuff doesn't move as smoothly as genuine Hiwin dose, Hiwin is usually quieter as well.

Don't forget to clean them and give a few drops of oil, once everything is setup and running great you can start using Lithium 2 lubricating grease, this lasts longer.

[bluesking]

Well Fred's kit is the real deal so you don't need to worry about it being fake Hiwin linear rails and bearings, the fake stuff doesn't move as smoothly as genuine Hiwin dose, Hiwin is usually quieter as well.

Don't forget to clean them and give a few drops of oil, once everything is setup and running great you can start using Lithium 2 lubricating grease, this lasts longer.

Thanks Lee. I had a go at aligning everything tonight. Definitely improved. Shimming made a difference but still something a little sticky at the extremes. I then tried relaxing all the various attachment points for the ballscrew but this didn't make much difference. In the end I relaxed all of the big 12mm screws holding the 3 main extrusions. This made a significant difference but if I tighten them all up as tight as I can there is still some binding. In the end I tightened them quite gently and this reduced the binding at the extremes to very low levels and the overall frame still seems very rigid. I'm still concerned its not exactly perfect!

I don't really understand what you mean by moving the mechanism with one finger. Certainly pushing the gantry, it doesn't move, there is enough friction to stop any linear force from being converted to rotational motion. For the vast majority of the travel I can just about turn the pulley with one finger - is this what I should be looking for?

I do have a dial calliper and stand but very few places to attach it and not really enough skill to use it. I think I'm going to have to just move on and hope - without any experience it is hard to know if I'm facing real problems or just being picky!

[MikeyC38]

Hi bluesking
When I built mine (see here) It moved by it self once I had pushed gently.The ballscrew was NOT connected for this test so that you can detect any binding in the bearings. However I am using SBR bearings on a supported round rail. These are more tolerant of misalignment than the bearings you are using. With the bearings you are using for the gantry, accurate alignment is a must, I'm afraid, but they are the best you can buy!

[bluesking]

Hi bluesking
When I built mine (see here) It moved by it self once I had pushed gently.The ballscrew was NOT connected for this test so that you can detect any binding in the bearings. However I am using SBR bearings on a supported round rail. These are more tolerant of misalignment than the bearings you are using. With the bearings you are using for the gantry, accurate alignment is a must, I'm afraid, but they are the best you can buy!

Thanks Mikey,
Thing is, even just running a single hiwin hgr 20 carriage along a single rail (hence no opportunity for misalignment), you give it a little push and it moves, but as soon as you stop applying force it stops - no momentum retained. I think this is due to the relatively high pre-load on the the HGR carriages - they just behave that way. Anyway, with no ballscrew connected I think things behave well overall (see my video above). Connecting the ballscrew introduced the problems - though these have been much reduced now - I just don't know what I am aiming for!