Luthier CNC

[bluesking]

Following on from my introductory/ideas thread - http://www.mycncuk.com/threads/12712-School-me-on-the-best-machine-for-big-hardwood

I have now finished an initial design for my CNC for guitar building. I had the following requirements:

- Optimal performance for fast and smooth cutting of hardwood with large bits
- Minimal machine weight (1 person carry, or easy to dismantle)
- Minimal tooling required to produce - I have access to a CNC but no experience and little desire to work with Aluminium
- Adequate size to produce guitar bodies and necks - bass necks and neck-throughs are not part of the core requirements
- Relies on low-risk mature technologies (parallel port, Mach3)
- Sensible cost

I drew inspiration from two existing machines:
1) Wal's build - http://www.mycncuk.com/threads/11266-3-Axis-900x500mm
I liked the simplicity and robustness of the mechanics on this machine. It is for bass guitars, so similar requirements.
2) The obsolete K2 CNC 3925 - https://www.youtube.com/watch?v=LLNeA1oUCGc
I have seen quite a few videos of this machine performing wonderfully in guitar building. Seems to have been a popular choice for woodworkers and particularly luthiers in its heyday. Nothing else I've seen compares (short of a HAAS). Not impressive mechanically but has fully convinced me that a servo drive is what I want.

Attached are some pics of the mechanical CAD model. There are a couple of features which aim to meet the requirements:
- Performance is met using servos, and gearing for all axes is required. 1605 ballscrews used throughout with pulley drives. 20mm linear rail throughout. heavy duty 45x45 extrusions throughout.
- 3kW air-cooled spindle. Mainly decided on due to the K2 machine. I'm reluctant to use water-cooled as don't want the faff of pumps and water near my dried woods - after VFD control I'm also running out of capacity on the basic parallel port breakout board. I'm a bit worried about the noise - I use handheld routers a lot - I hope that an air-cooled spindle will be a lot more quiet - does anyone have any experience with one?
- For weight, I rely mainly on extrusions, using plates only where necessary. All plates are 15mm thickness. Machine size is kept as small as possible.
- The work envelope is big enough for all guitar bodies and necks, including angled headstocks etc. It is not big enough for most bass necks or neck-through guitars. If I have the spare space and the need I will upgrade the machine - easily done, until then I will be tiling any occasional bass build - I wanted to ensure I could easily tile work so avoided a raised support around the work area.
- I'm using openbuilds steel Nema 23 mounts as these allow me to get easy belt tensioning without requiring me to make bespoke aluminium components. Apart from the side supports, only rectangular plates are used so they can be bought pre-cut. Everything else can be done with only hole drilling and tapping.

The electronics and motors are based on my research into the K2 machine. I will be looking to use this 3 axis servo kit from the US as it uses the same drivers and slightly higher spec servos as the K2. Not a bad price and contains most of what I will need.
https://www.automationtechnologiesinc.com/products-page/cnc-3_axis_4_axis_kits/3-axis-nema23-350ozin-60v20a-psu-g230x-gecko-driver/

I already acknowledge a few limitations/challenges:
1) Using servos will not be straightforward however I am ready for the challenge and have some relevant control systems education
2) I gather 2 ballscrews for the major axis would be preferable. Unfortunately I am reluctant to take on the challenge of synchronising the control loops of 2 servos, and the belt tensioning complexities and mechanical synchronisation of a single servo driving 2 screws. I'm therefore sticking to a single screw - it seems to work fine on the K2 at least.

Would love to hear any feedback or suggestions at this point as I'm feeling about ready to jump in!

[Clive S]

3kW air-cooled spindle. Mainly decided on due to the K2 machine. I'm reluctant to use water-cooled as don't want the faff of pumps and water near my dried woods - after VFD control I'm also running out of capacity on the basic parallel port breakout board. I'm a bit worried about the noise - I use handheld routers a lot - I hope that an air-cooled spindle will be a lot more quiet - does anyone have any experience with one?
- For weight, I rely mainly on extrusions, using plates only where necessary. All plates are 15mm thickness. Machine size is kept as small as possible.

Air cooled spindles are generally very noisy. Not sure why you think the water cooled ones are going to put water all over the place as they are fed with 6mm tubing and the pump and water container can be anywhere off the machine. They are also quiet .

Re the plates I would use 20mm and if you don't want to machine it use cast as that will be flatter.

Have you checked out if any of the bolts clash with each other ie on the bearing blocks for Z and Y

[bluesking]

Air cooled spindles are generally very noisy. Not sure why you think the water cooled ones are going to put water all over the place as they are fed with 6mm tubing and the pump and water container can be anywhere off the machine. They are also quiet .

Re the plates I would use 20mm and if you don't want to machine it use cast as that will be flatter.

Have you checked out if any of the bolts clash with each other ie on the bearing blocks for Z and Y

Thanks Clive,

Point taken re the air-cooled spindle. Water cooling seemed like one extra thing to worry about but perhaps the noise issue will make it worth it. I spent some time with a local CNC machine today which was using the Kress 1050 spindle - air cooled. Whilst not particularly loud (certainly compared to a router) it could certainly have been quieter. I don't see many people using 3kw water-cooled spindles, nor that many places to buy - I wonder why?

Re the plates, what if I used 20mm just on the gantry sides? That seems to be the critical point - surely the z-axis won't matter too much (if anything, the thicker plates will move the spindle further away, creating more torque on the gantry?). Another idea I had was just to bolt some extrusion vertically to the 15mm gantry sides to stiffen them up a bit.

I was going to buy my plates from here: https://www.aluminiumwarehouse.co.uk/aluminium-plate-cut-to-order
I can't see cast here - is there somewhere I can go to specifically buy cast aluminium?

Also I see 2 alloys - 5083 & 6082T6 - but I don't know the difference and which is best for machining. Biggest machining job I really want to take on is drilling holes on my drill press and tapping them.

[Voicecoil]

If I were you I'd stick with 15mm (or even 12mm) on the gantry sides and add some reinforcement ribs (say 40mm tall) all the way up along the edges (40x15mm flat bar for instance) - if you do the sums it works out much stronger than thicker flat plate. Aluminium Warehouse are not bad for plate, even if not the cheapest and having had a slightly checkered history with some of us on here, at the moment they are giving good service, cutting plate VERY square and generally 1...2mm oversize: to select the cast stuff click on "grade" and select the bottom item from the drop down box.
If it were me I'd also be adding some plates top and bottom of your bed frame members to form like a "sandwich" structure and tie it all together in X and Y - though I can see that might have some weight problems for you.

[bluesking]

If I were you I'd stick with 15mm (or even 12mm) on the gantry sides and add some reinforcement ribs (say 40mm tall) all the way up along the edges (40x15mm flat bar for instance) - if you do the sums it works out much stronger than thicker flat plate.


That was my feeling too - If I can spread the cross sectional area of those gantry sides that would be better than basically just adding more mass. I was just going to bolt some 45x45 extrusions to the outside of the plates. Easy to align and not a lot of extra weight.



Aluminium Warehouse are not bad for plate, even if not the cheapest and having had a slightly checkered history with some of us on here, at the moment they are giving good service, cutting plate VERY square and generally 1...2mm oversize: to select the cast stuff click on "grade" and select the bottom item from the drop down box.


Very useful information - I didn't expect the cuts to be oversize - hell, when I have bought pre-cut sheet wood/mdf I expect much better than that! May not prove to be that critical though if I can at least drill all the holes accurately relative to each other. Even if the measurements are out, maybe they will be consistently so, such that two pieces of the same spec are the same size, even if its not the right size!

I do have a table saw and maybe if I buy the right blade I may have to take the plate cutting into my own hands - but I'm a little concerned about cutting it square enough - its not a precision table saw by any means! I'm scared enough of the table saw when cutting hardwood - don't know what to expect with aluminium!



If it were me I'd also be adding some plates top and bottom of your bed frame members to form like a "sandwich" structure and tie it all together in X and Y - though I can see that might have some weight problems for you.

Yes, I may just plonk a single plate on top. I was going to use a couple of layers of 18mm MDF here but might make the lower one of them aluminium. Putting one below the frame will mean some redesign and yet more gantry height plus hinder what little access I have to the drive mechanism - I'm already worried about how I'm going to retension the pulley belt under there.

[bluesking]

I don't see many people using 3kw water-cooled spindles, nor that many places to buy - I wonder why?

Just to attempt to answer my own question - it seems not many people are using 3kw spindles full stop.

From what I can tell, a 2.2kw ran off the common huanyang VFD is often rated around the 8A level for current draw - this means you can plug it into a normal mains socket without worries (assuming you use and appropriate fuse).

The 3kw spindles I'm looking at, when run from an appropriate VFD will likely draw in the region of 18A. You're not going to find a mains socket fuse for this type of current. Still, the ring circuit from your consumer unit will probably allow currents up to 30A, so providing you can get beyond the mains plug you might be fine. One thing worth noting is that 13A fuses may not actually be designed to blow until 20A (go figure....) so it may be possible to get away with it (that's what I read here https://www.pat-testing-training.net/articles/fuse-operation-characteristics.php).

[Voicecoil]

I do have a table saw and maybe if I buy the right blade I may have to take the plate cutting into my own hands - but I'm a little concerned about cutting it square enough - its not a precision table saw by any means! I'm scared enough of the table saw when cutting hardwood - don't know what to expect with aluminium!

Cast plate cuts quite nicely with the appropriate blade if you keep it lubricated (WD40 works OK) - just take it steady. Provided your saw is rigid enough you can do quite good work if you spend the time to get it set up square.

[A_Camera]

I spent some time with a local CNC machine today which was using the Kress 1050 spindle - air cooled. Whilst not particularly loud (certainly compared to a router) it could certainly have been quieter.
Don't worry about the noise generated by air cooled spindles. It only makes a difference if you will be cutting air. ...and you'll be surprised how quiet an air cooled brushless spindle is compared to the Kress or a router...

I have been using air cooled spindle for some years now, though it is only 1.5kW, but it is that noisy before cutting starts. If it must be replaced I'll buy another air cooled spindle, that's for sure.

[bluesking]

Cast plate cuts quite nicely with the appropriate blade if you keep it lubricated (WD40 works OK) - just take it steady. Provided your saw is rigid enough you can do quite good work if you spend the time to get it set up square.

I've gone through the design with a fine tooth comb and it seems there is only one plate where the dimensions are critical. If any of the other plates are cut a mil or two oversize it won't make any difference.

Also, costings show that I would pay more for uncut plate of adequate size than I would pay getting aluminium warehouse to cut everything for me.

I'll probably just go with the precut cast plate.

I've given up on a plate for the tabletop - aside from the weight - it'll cost rather a lot. A piece of well attached MDF will suffice I think.

[bluesking]

1

[bluesking]

Don't worry about the noise generated by air cooled spindles. It only makes a difference if you will be cutting air. ...and you'll be surprised how quiet an air cooled brushless spindle is compared to the Kress or a router...

I have been using air cooled spindle for some years now, though it is only 1.5kW, but it is that noisy before cutting starts. If it must be replaced I'll buy another air cooled spindle, that's for sure.

Thanks, it would certainly make things easier to go with air-cooled. I have a small room set aside for the CNC to go in anyway, so that will probably be the best way to deal with overall noise.

You mention that you have a brushless spindle? The one I'm looking at has brushes as far as I know:
https://www.aliexpress.com/store/pro...56c041d6TtIpdJ

I can't find brushless spindles above 1kw. Where did you get yours?

[A_Camera]

Thanks, it would certainly make things easier to go with air-cooled. I have a small room set aside for the CNC to go in anyway, so that will probably be the best way to deal with overall noise.

You mention that you have a brushless spindle? The one I'm looking at has brushes as far as I know:
https://www.aliexpress.com/store/pro...56c041d6TtIpdJ

I can't find brushless spindles above 1kw. Where did you get yours?
The link is not working.
Anyway, all three phase spindles are brushless, for example this one:

https://www.ebay.com/itm/From-EU-3-Phase-3KW-ER20-Air-Cooled-Spindle-Motor-Wood-Cutting-CNC-Engraving/273783298597?hash=item3fbec19a25:g:~P8AAOSwBydbh17 8

Note that this is just one I picked from ebay, though I bought mine from a different seller. Anyway, the only thing I'd do differently today is that I'd probably by a spindle with square housing today, and if possible, I'd buy one with active cooling fan, which is driven with a separate 24V, so the fan has a constant speed. I think those are better than the round ones with the fan mounted on the motor axis.

[A_Camera]

I do have a table saw and maybe if I buy the right blade I may have to take the plate cutting into my own hands - but I'm a little concerned about cutting it square enough - its not a precision table saw by any means! I'm scared enough of the table saw when cutting hardwood - don't know what to expect with aluminium!


Cutting aluminium on a table saw is no big deal. I have a Bosch GTS 10 J (https://youtu.be/CidyfnsmS2Y) and with the Bosch blade made for cutting aluminium, it cuts aluminium like butter. Squaring the saw took some effort, but now it is square enough for this type of work. It is though messy to cut aluminium, so a shop vac is a must.

[bluesking]

The link is not working.


Here is a link to an eBay listing of the spindle I'm looking at:
https://www.ebay.co.uk/itm/EU-3KW-Air-Cooled-CNC-Spindle-Motor-ER20-220V-18000rpm-for-Wood-Cutting-Milling/254196400436

I quite like the mounting plates on these square ones - seems easier to relocate the spindle up and down. Obviously still not as easy as a round spindle!



Note that this is just one I picked from ebay, though I bought mine from a different seller. Anyway, the only thing I'd do differently today is that I'd probably by a spindle with square housing today, and if possible, I'd buy one with active cooling fan, which is driven with a separate 24V, so the fan has a constant speed. I think those are better than the round ones with the fan mounted on the motor axis.

I have read that a constant speed fan is quieter as you suggest, but I don't think I have actually seen that mentioned on any of the listings I've seen on eBay/Aliexpress. I haven't planned a 24V supply either, so maybe it will be easiest if the fan is spindle driven, but I'm obviously still concerned about the noise.

[cropwell]

you'll be surprised how quiet an air cooled brushless spindle is compared to the Kress or a router....


I wouldn't. I've got a Kress, they are just as noisy as any other brushed motor router.

[bluesking]

Made a few minor updates based on the useful comments to date:

Upped the side plates from 15mm to 20mm (I've changed my mind about using reinforcement ribs here - seems like these might increase the risk of snagging on something or someone whilst the CNC is doing its thing)

Changed the front and back from extrusions to solid 20mm plates. Added 3 foot-like features to these so the base of the machine is basically a tripod to prevent it wobbling on the workbench.

25720

Added some heavy duty steel brackets to the centre of the bed - I can't afford the cost or weight of a solid aluminium bed so this is my compromise. It'll all be connected to an MDF sheet lying on top of the bed structure with a 2nd MDF sheet on top of that as a spoil board.

25721

Most everything else will be achieved using long screws into the extrusion cores, attaching them to the various plates.

Won't be able to machine my big plates on any CNC I can get access to but I am hoping to get access to a Bridgeport mill so I can at least drill all of the holes in precise locations (assuming I can figure out how to use a Bridgeport!)

[cropwell]

Hi Bluesking,

I don't know if you are aware of Nottingham Hackspace, but there is a Bridgeport there. I am a member, but haven't been there for a long time as they were located principally up stairs and I can't negotiate stairs and carry anything. They were in the process of opening up a downstairs workshop for the heavy machines.

https://hms.nottinghack.org.uk

Cheers,

Rob-T

[Voicecoil]

Won't be able to machine my big plates on any CNC I can get access to but I am hoping to get access to a Bridgeport mill so I can at least drill all of the holes in precise locations (assuming I can figure out how to use a Bridgeport!)
If you can't get access don't worry. You'd be suprised at how accurately you can place holes "the old fashioned way" using a surface plate, height gauge and optical centre punch.

[A_Camera]

I wouldn't. I've got a Kress, they are just as noisy as any other brushed motor router.

The Kress is MUCH noisier than any brushless motor of the same (or even higher) power. My 1.5kW brushless spindle is definitely much quieter than the 1kW Kress. Perhaps you misunderstood my post... ;)

[cropwell]

The Kress is MUCH noisier than any brushless motor of the same (or even higher) power. My 1.5kW brushless spindle is definitely much quieter than the 1kW Kress. Perhaps you misunderstood my post... ;)

My point was that a Kress spindle is just a BRUSHED motor and it is noisy. As noisy as any other BRUSHED hand held routers that I have in my workshop. Kress call it a spindle as it has better front bearings than a hand held router, giving it less run-out and more suitability for long switch-on periods as in CNC routing.

[bluesking]

Hi Bluesking,

I don't know if you are aware of Nottingham Hackspace, but there is a Bridgeport there. I am a member, but haven't been there for a long time as they were located principally up stairs and I can't negotiate stairs and carry anything. They were in the process of opening up a downstairs workshop for the heavy machines.

https://hms.nottinghack.org.uk

Cheers,

Rob-T

Thanks Rob,
Yes, that is the very Bridgeport I'm referring to. Still waiting for an induction on it - I've never used a mill before!

I was there a few days ago and the metalworking stuff is still upstairs. Theres lots of setup work going on in the downstairs area but its far from complete by the looks.

[bluesking]

If you can't get access don't worry. You'd be suprised at how accurately you can place holes "the old fashioned way" using a surface plate, height gauge and optical centre punch.

Interesting, I don't understand what method you are referring to - can you describe a little more or point to a vid? What are the surface plate and height gauge used for?

If I can't use the mill I was just going to print some templates - stick them on the stock - punch the hole centres - and drill them out on my drill press. This is basically the same as what I do for making guitar templates - a job I thoroughly hate, mainly because I can only print A4 and have to tile my printouts.

[bluesking]

So a short update on my build. Things are going slower than I would like. I have gathered almost all of the components I need but am still waiting on a few key things.

Last few days I have been working on the various end plates and spacers for the machine.

I produced a technical drawing containing all the plates from my fusion 360 model. Using the fine-line-style setting when exporting to PDF was important to produce the most accurate output. All fits on a single sheet of A0, cost about £3 to print at a local printing shop:
25787

Cut everything out and used spray contact adhesive to glue to the plates. Every time I use this stuff with paper I regret it. Horrible to clean up and unnecessarily strong.

The design of the my CNC means the actual plate dimensions are not critical. You can see all my plates are cut about 2mm too big from the supplier but this doesn't matter - the key thing is that all the holes are precisely located relative to each other. There are only 2 critical plate dimensions - and these only on one edge, corresponding to the 2 butt joints in the design. Paying attention and gluing the corresponding templates right up to the butting edge should be good enough.

Heres all the plates with their templates applied:
25788

Thanks to reading Voicecoil's posts, I bought myself an optical centre punch and had a bit of fun using it. Its fun playing with the scope, pretending you're a CNC sniper, hahaha.
25789

Silliness aside, the end results look well worth it - best punching accuracy I've ever had, should have got one ages ago:
25790

[Ger21]

- Relies on low-risk mature technologies (parallel port, Mach3)


Mach3 is obsolete, and imo should never even be considered for a new machines. And trying to use parallel ports on PC's these days is far more problematic than it was when Mach3 was created.

Consider UCCNC, which is very similar to Mach3, but far superior in most ways. For the same cost as a Mach3 license, you can get a UCCNC license plus an AXBB motion controller. This will be far superior to Mach3 and a parallel port, with superior performance, and much greater reliability.

[bluesking]

Mach3 is obsolete, and imo should never even be considered for a new machines. And trying to use parallel ports on PC's these days is far more problematic than it was when Mach3 was created.

Consider UCCNC, which is very similar to Mach3, but far superior in most ways. For the same cost as a Mach3 license, you can get a UCCNC license plus an AXBB motion controller. This will be far superior to Mach3 and a parallel port, with superior performance, and much greater reliability.

Thanks Gerry. Clive also pointed this out. When I started planning things out in more details I quickly realised you guys were right.

Since then I've got a UC400ETH. Didn't know about the AXBB at that time but I already have a parallel BoB that brings the VFD and charge pump features so I think it'll work out functionally similar.

I intend to use UCCNC.

[bluesking]

Following on from my plate design work, yesterday I drilled the various holes:

25791

Everything seemed to go well. I have a mixture of M5, M6 and M12 bolts to accommodate. Many of the holes don't need tapping so I created mostly 5.5, 6.5 & 13mm holes to accommodate the screws.

I also have a bunch of M5 holes that needed tapping. Here I made a bit of a mistake. Really didn't think it would make a difference so I just used a 4mm drill bit I had laying around. Drilling went well, but as soon as I started to tap this happened:

25792

My lack of metalworking experience takes it's first casualty! Today I re-drilled all the offending holes and I think I got away with it overall.

Here's what I have learned:
1) If you want to use a M5 tap, you need a 4.2mm hole. No getting around this. Maybe 4.5mm would also work, but I didn't even try this as 4.2 worked perfectly.
2) If you break a tap in a hole there really isn't any way to recover. You try to drill it out, but because aluminium is so much softer than hardened steel, the drill bit wanders around the tap creating a bit of a disaster.
3) Cutting oil is a mixed blessing. Makes all the work super messy but I think improves results. If doing again I'd drill all the holes dry and use cutting oil just to do the tapping work.

The one hole I messed up was meant to attach to one of my z-axis HIWIN carriages. I'm hoping I can get away with using only 3 out of the 4 holes to mount this. I think this will be fine so I'm not going to bother buying/making a whole new plate for now.

[Doddy]

Here's what I have learned:


Been there. I think most of us have.

[AndyGuid]

I bought myself an optical centre punch and had a bit of fun using it.25789

If you bought it online, please could I have the link?

[bluesking]

If you bought it online, please could I have the link?

I got mine from Axminster:
https://www.axminster.co.uk/axminster-optical-centre-punch-100244

On mine, the crosshair optic is out of alignment :( but the circle/dot optic is perfect :)

[mekanik]

Hi Bluesking
Broken drills/taps in non ferous materials can be dissolved using Alum solution.
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=2ahUKEwiljrr4kqfiAhWIRBUIHY6vDzYQFjABegQIDBAK&url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DJC ADI0YSt8M&usg=AOvVaw2IYhTYr99aX0rtzdbxJhZP
Also when tapping go with the recommended size from your Zeus book ie 4.2mm but use a solid(no flute's) spiral tap.
Regards
Mike

[Clive S]

I also used Alum see this post #11 http://www.mycncuk.com/threads/8903-Tap-removal?highlight=alum I am not sure if there are different strengths of Alum

[bluesking]

Hi Bluesking
Broken drills/taps in non ferous materials can be dissolved using Alum solution.
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=2ahUKEwiljrr4kqfiAhWIRBUIHY6vDzYQFjABegQIDBAK&url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DJC ADI0YSt8M&usg=AOvVaw2IYhTYr99aX0rtzdbxJhZP
Also when tapping go with the recommended size from your Zeus book ie 4.2mm but use a solid(no flute's) spiral tap.
Regards
Mike

Nifty solution, thank you.

I used a 3 flute straight M5 tap with some cutting oil. Did about 50 holes with no problems at all (once I’d drilled everything to 4.2). What would be the advantage of solid spiral tap?

[Voicecoil]

The best taps I've found for through holes in ali are the blue ring spiral point types like this:
25793
They're made specially for aluninium, the interrupted thread higher up seems to help with binding. Typically I've found you can tap a hole in 12mm plate in 3...4 seconds with one of these in a cordless drill with some cutting fluid. For blind holes as Mekanik said you need to use a spiral flute tap (to get the chips out), again I've found the blue ring types are marginally the best.

[mekanik]

This might be of interest
http://www.europatool.co.uk/threading/application-taps
Regards
Mike

[m_c]

In a nut shell for taps-
Spiral Point - Only good for through holes, as they push the swarf forward through the hole.
Spiral Flute - good for blind holes, as the swarf comes up around the shank, but are more prone to binding if the swarf doesn't clear.

My preference is always spiral point, as they're the stronger option.
If you're only going through relatively thin section, I'd avoid the interrupted flute ones Voicecoil posted a pic off, as a bit inadvertent sideways pressure with only two or three support flutes engaged can quickly jam the tap and snap the tap/rip the threads out the hole.
As always, lubrication is key. For tapping aluminium, a drop of good quality cutting oil is essential to stop things sticking.

There are also threadforming / roll forming taps which can give a stronger thread in aluminium, but drill hole size is very critical, so I would advise against them unless you can control the hole size well. Undersize and the tap will quickly jam, oversize and you won't have much of a thread.

[Kitwn]

I got mine from Axminster:
https://www.axminster.co.uk/axminster-optical-centre-punch-100244

On mine, the crosshair optic is out of alignment :( but the circle/dot optic is perfect :)

Here's an alternative manufacturer's product being demonstrated...
https://www.youtube.com/watch?v=9zBl9yLacWs

[MikeyC38]

Hi Bluesking

Just seen your post here. Well done for joining the forum, doing a design and taking advice!. I wish I had seen this earlier because I would have told you to get the parts water-jet cut which also would have done some of the bigger holes for you and spotted the rest. This is the approach I took on my build and saved me a lot of grief (see build here http://www.mycncuk.com/threads/8206-Ar-last%21%21%21-Started-my-Gantry-3-Axis-CNC-Build post #10 ) All I had to do was counterbore and thread the extrusions using a spiral tap. I then used a finishing tap to clean the threads or a plug tap where the hole is stopped.

Regards
Michael

[bluesking]

Hi guys,
Have not been on for a while as have been busy sorting out my new workspace and stocking up on parts. Thanks for everyone's various messages - don't have time at the mo to answer everyone individually.

Its all go on the CNC front now my space is sorted and I have all my parts, so I wanted to post an update.

Today I built a table for the CNC. 18mm MDF & C16 CLS timber from B&Q. About £30 worth of materials:

1 Cutting to size
25845

2 Table top is 900mm x 1220mm; Supported by a timber frame:
25846

3 700mm legs screwed on to table top:
25847

4 timber base frame for support and shelf:
25849

5 MDF shelf for base frame, and a few corner supports for increased rigidity (may need more of these in the short-dimension in future)
Table finished, ready to start assembling the machine itself:
25850

[Doddy]

Looking good. Just a thought - is MDF the best, most appropriate worktop for something that could end up working with water (if only a failure-case for the spindle coolant, for example). My point - I have a sacrificial MDF layer on my "electronics" bench - and that's suffered some small water damage from an ultrasonic bath - and the surface is now perpetually feathering and impossible to flatten. My personal preference atm is ply, but most of the shops are stocking cheap eastern boards with large filled voids. The bench I've used for the mill is steel framed with ply top, sheathed in 1.2mm steel sheet (I had a bit lying around) - that's tough as boots.

I'm assuming that the bench is entirely separate from the machine? (it doesn't form part of the machine build?)

[bluesking]

Looking good. Just a thought - is MDF the best, most appropriate worktop for something that could end up working with water (if only a failure-case for the spindle coolant, for example). My point - I have a sacrificial MDF layer on my "electronics" bench - and that's suffered some small water damage from an ultrasonic bath - and the surface is now perpetually feathering and impossible to flatten. My personal preference atm is ply, but most of the shops are stocking cheap eastern boards with large filled voids. The bench I've used for the mill is steel framed with ply top, sheathed in 1.2mm steel sheet (I had a bit lying around) - that's tough as boots.

I'm assuming that the bench is entirely separate from the machine? (it doesn't form part of the machine build?)

Yes it is a separate bench - not connected to the machine - though I will probably mount the X cable chain directly to it. I will mount the electronics to the lower shelf for now and see if this causes any problems.

I'm using an aircooled spindle so hopefully no issues with moisture.

[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:
25859

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
25860

2 Leave for 1-2 mins to let it soak in and peel the paper off; dead easy
25861

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:
25862

[Lee Roberts]

Nice!

What table saw have you got?

I use blades by OX TOOLS (https://www.ffx.co.uk/tools/product/Ox-Tools-Tcta-2163080-5060359912299-Aluminium-Plastic-Wood-Saw-Blade-216Mm-X-30-X-80T), check out FFX (https://www.ffx.co.uk/tools/product/Ox-Tools-Tcta-2163080-5060359912299-Aluminium-Plastic-Wood-Saw-Blade-216Mm-X-30-X-80T) 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 (https://www.toolstation.com/ox-tct-circular-saw-blade/p27484)

[bluesking]

Nice!

What table saw have you got?

I use blades by OX TOOLS (https://www.ffx.co.uk/tools/product/Ox-Tools-Tcta-2163080-5060359912299-Aluminium-Plastic-Wood-Saw-Blade-216Mm-X-30-X-80T), check out FFX (https://www.ffx.co.uk/tools/product/Ox-Tools-Tcta-2163080-5060359912299-Aluminium-Plastic-Wood-Saw-Blade-216Mm-X-30-X-80T) 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 (https://www.toolstation.com/ox-tct-circular-saw-blade/p27484)

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/Product/Workcentre%20Systems/Workcentre%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
25869

2 Y axis ballscrew
25870

3 X axis assembly beginning
25871

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 (http://www.mycncuk.com/threads/8206-Ar-last%21%21%21-Started-my-Gantry-3-Axis-CNC-Build)) 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 (http://www.mycncuk.com/threads/8206-Ar-last%21%21%21-Started-my-Gantry-3-Axis-CNC-Build)) 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!

[Voicecoil]

I'll agree 100% about the HGR20's being a little sticky, but I'd rather they were that way and had no play, than "free and easy" and wobbling all over the place. If you can turn the ball screw end shafts smoothly between finger and thumb then I guess it should be OK - after all, a decent stepper should be giving a good few hundred Ncm torque.

[bluesking]

I'll agree 100% about the HGR20's being a little sticky, but I'd rather they were that way and had no play, than "free and easy" and wobbling all over the place. If you can turn the ball screw end shafts smoothly between finger and thumb then I guess it should be OK - after all, a decent stepper should be giving a good few hundred Ncm torque.

Thanks for confirming my thoughts about the HGR20s. I think I've got the rails sorted, its the ballscrew causing issues I think. I have got it to a much improved state, but I can't quite "turn the ball screw end shafts smoothly between finger and thumb". Whilst the resistance along the entire travel is now pretty much uniform, there is a little patchiness to the motion - there are occasional slight sticking points which require a bit more force than just two fingers can apply. I mainly test it using the belt to move the ball screw and it all operates ok in motion though from a standing start it can be a little "sticky".

It may well be fine with the reasonably overpowered servos I will be using. I'm going to leave it as is and proceed with the other axes so I can compare the motions between each axis.

If its still a problem I can think of only 2 ways forward:
- widen some of the mounting holes so the major extrusions have a little more "wiggle room" so I have broader alignment range
- buy a new ballscrew - I worry I may have subtly bent this one during my initial tests and now it will bind whatever I do...

[Voicecoil]

there is a little patchiness to the motion - there are occasional slight sticking points which require a bit more force than just two fingers can apply
BTW, did you check the ballscrew for smoothness throughout its' length before mounting it?? As I mentioned in my thread here: http://www.mycncuk.com/threads/12524-gritty-ballscrews , although Fred tries hard to please, his engineers don't always seem to adhere to the old saying "cleanliness is Godliness" when it comes to machining ballscrews. Even the replacement parts he sent me needed a clean, strip down, flush through and re-grease before they were acceptably smooth. Try running (twisting) the sticky portions through a piece of clean tissue and then examine under magnification to see if there's any small flakes of swarf.

[bluesking]

BTW, did you check the ballscrew for smoothness throughout its' length before mounting it?? As I mentioned in my thread here: http://www.mycncuk.com/threads/12524-gritty-ballscrews , although Fred tries hard to please, his engineers don't always seem to adhere to the old saying "cleanliness is Godliness" when it comes to machining ballscrews. Even the replacement parts he sent me needed a clean, strip down, flush through and re-grease before they were acceptably smooth. Try running (twisting) the sticky portions through a piece of clean tissue and then examine under magnification to see if there's any small flakes of swarf.

I think you may be right. I need to dismantle much of my machine anyway so best get to cleaning the ballscrews!

In my hurry I didn't attach the nipples to my HIWIN carriages so this is probably a good opportunity to do that as well. I see you have made a post about these nipples: Do you know if the following are a good way to go for greasing the carriages? Are they also suitable for greasing ballscrews/nuts?

https://www.toolstation.com/laser-grease-gun/p29224
https://www.toolstation.com/lithium-grease/p89691

[AndyUK]

I think you may be right. I need to dismantle much of my machine anyway so best get to cleaning the ballscrews!

In my hurry I didn't attach the nipples to my HIWIN carriages so this is probably a good opportunity to do that as well. I see you have made a post about these nipples: Do you know if the following are a good way to go for greasing the carriages? Are they also suitable for greasing ballscrews/nuts?

https://www.toolstation.com/laser-grease-gun/p29224
https://www.toolstation.com/lithium-grease/p89691

Thats what I use, and it works on the ballnuts that Fred has sent me. I think the nipples for the HGR20s are the same, but I haven't gotten that far yet. Highly recommend the flexible extension for the gun, and don't try loading the grease gun for the first time in toolstation's car park when you're inside the car. Not a clean experience. Worth watching a youtube video or two on loading, attaching, and de-attaching grease guns if you've never had the pleasure to using them before, there are a couple of nuances.

This is the flexible bit I'm talking about:
https://www.toolstation.com/laser-grease-gun-hose-connector/p33147

[bluesking]

Thats what I use, and it works on the ballnuts that Fred has sent me. I think the nipples for the HGR20s are the same, but I haven't gotten that far yet. Highly recommend the flexible extension for the gun, and don't try loading the grease gun for the first time in toolstation's car park when you're inside the car. Not a clean experience. Worth watching a youtube video or two on loading, attaching, and de-attaching grease guns if you've never had the pleasure to using them before, there are a couple of nuances.

This is the flexible bit I'm talking about:
https://www.toolstation.com/laser-grease-gun-hose-connector/p33147

Thanks Andy,
Just got back from toolstation with the gun, but didn't get the flexible hose, looks like I'll be going back!

One question, how do you grease your ballscrews? There is no nipple I can see...

[AndyUK]

One question, how do you grease your ballscrews? There is no nipple I can see...

There isn't a nipple on the screw itself. The bits that move are the bearings and the ballnut - the rest just needs a slight surface coating to protect the metal. The bearings are sealed, so its just the ballnut that needs the gun.

I over-greased the ballnut and then ran it up and down the screw to smeer the grease all around. The other way would be to smeer some grease with a finger all the way along, then run the ballnut up and down a few times.

[Lee Roberts]

Make a new video so we can see and hear whats happening now you've tweaked it some more!

I was about to say the same as Voicecoil re making sure everything is clean, I always suggest people do that with the nut's because I don't think I've seen one yet that didn't have crap inside from the factory.

It can be tricky and the balls will fall out if you remove the nut from the screw, that's OK because your going to flush it all out and clean everything anyway but it can be a little time consuming reloading all the balls back in, to do this pack the nut with some grease first, enough to hold them in place not literally "packed".

The trick is getting the nut back on the screw without dislodging any of the balls, its very doable but equally easy to try and go to fast and knock the balls back out when your trying to thread the nut back on.

While/if your there, count how many balls you've got out altogether, its common for some to be missing from the 17 per track on a 1605 ball nut (even from BST).

Have another read of this thread re nipples and so on, you can include the ball nut: http://www.mycncuk.com/threads/12835

Also (for everyone), if you read the document from Hiwin on the their Linear Guideways it has quite allot of info, Page 27 (2-1-7 Lubrication), shows you info on the grease nipple and ALSO the additional mounting locations built into the blocks so you can move the nipple if you want to: https://www.hiwin.com/pdf/linear_guideways.pdf

[Lee Roberts]

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 mean I can move my whole Z axis from the left to the right of the X axis (gantry) really easily, I can push it with my finger and the ball screw on the X axis just spin's like its nothing, its actually amazing that I got it so perfect pre dial indicator to check anything. I think I just got well lucky but it wasn't first time fitting, i went back and forth (literally) for hours loosening the rails and the ball nut and screw fixings until everything just moved perfectly by hand, I used the same method I gave above to do this and at some point you have to say OK that's as good as it gets and start tightening things up as permanent.

I'm really close with the Y axis (bed) but I think its just off a little bit still, like you I still have "sticky points" along the travel, if I push my gantry it is much harder to push along then the X axis for sure but dose go with enough force to get the screw spinning. Still building my machine but i'm going over at the weekend to have another play, I'll get my mate to video me pushing mine about so you can see, maybe the others with more experience can then give their thoughts.

From what I understand, anything less than dial indicator prefect just means uneven ware and tare on the parts and that on a hobby machine used 2-3 times a week, this ware would be negligible because it would take forever to accumulate enough to effect anything a hobbyist would be looking to achieve - Somewhat subjective I know.

[bluesking]

Lee, you are a legend, thanks for all the detailed and helpful responses. I will be sure to post a vid showing some of the machine motion once its rebuilt.

Machine is currently in pieces because today I have disassembled all 3 of my ball screws. Cleaned every part with naphtha and relubed with lithium grease (thanks AndyUK - I just smeared about 3cm^3 on the screw and ran the nut over it, repeating until none was left collecting on the rubber seals at the ends of the nut).

Counted the ball bearings - exactly 51 in each ball screw and I managed to get exactly 17 back into each track when reassembling. I reassembled them dry, using the ballscrew itself to guide the balls into their channels. Found this easy and I think its less messy than using grease to stick everything in place. I used the method in this vid to repack the balls https://www.youtube.com/watch?v=GXdt5M8ZeoE

All I have to show for my work is the following vid. Shows all the nasty stuff left floating in the naphtha after cleaning each ballscrew:
https://streamable.com/up3n4

End result certainly feels subjectively smoother - will only know for sure once the machine is rebuilt. One thing I've noticed is that after cleaning the nuts do not spin as easily - though they do spin much more smoothly. I put this down to increased viscosity of the lithium grease compared to what was in there from the factory.

[Lee Roberts]

Lee, you are a legend, thanks for all the detailed and helpful responses. I will be sure to post a vid showing some of the machine motion once its rebuilt.

Machine is currently in pieces because today I have disassembled all 3 of my ball screws. Cleaned every part with naphtha and relubed with lithium grease (thanks AndyUK - I just smeared about 3cm^3 on the screw and ran the nut over it, repeating until none was left collecting on the rubber seals at the ends of the nut).

Counted the ball bearings - exactly 51 in each ball screw and I managed to get exactly 17 back into each track when reassembling. I reassembled them dry, using the ballscrew itself to guide the balls into their channels. Found this easy and I think its less messy than using grease to stick everything in place. I used the method in this vid to repack the balls https://www.youtube.com/watch?v=GXdt5M8ZeoE

All I have to show for my work is the following vid. Shows all the nasty stuff left floating in the naphtha after cleaning each ballscrew:
https://streamable.com/up3n4

End result certainly feels subjectively smoother - will only know for sure once the machine is rebuilt. One thing I've noticed is that after cleaning the nuts do not spin as easily - though they do spin much more smoothly. I put this down to increased viscosity of the lithium grease compared to what was in there from the factory.

No problem, great that's good to know about the ball count if you ever lose any let me know I can send you some the right size.

Yea that's how I started doing them years ago (dry+screw) I've rebuilt quite a few for people now and found it a little obstructive using the screw (length/weight) so I just use a tube of ali to the right OD with a hose spring clip attached to one side, I slide this in just after I've got the first track filled, it depends on the job though as some people ask for the nut to be on the screw when i send it back because they don't want to risk it again. Both ways though I still use a little grease as a "retainer", they used to ship the nuts with the tube and a clip on both ends but they seem to be a plastic tube with cable tie now.

13mm (1/2") Aluminium Alloy Tube

Best served with some of these: Double Wire Spring Clip

[bluesking]

Equipped with my newly cleaned ballscrews I made substantial progress today.

First I reworked all of the Ali plates. I widened a bunch of holes. The M12 bolts had 13mm holes, now 14mm. The M5 bolts had 5.5mm holes, now 6.5mm. The idea is to allow more wiggle room so I have wider alignment range on all the mechanics. This worked a treat: I no longer need to use any shims, careful and methodical alignment allowed me to find good alignment without messing about with coke cans and tin foil!

I then bevelled most of the holes in the Ali Plate. I was worried that the burrs around the holes were messing with precise mating of all the pieces:
25896
25897

Whilst I was at it I bevelled the edges of all the plates at 45deg on my spindle sander. I was getting tired of the sharp edges opening up my skin and getting blood all over the machine!
25898

Rebuilt the Y axis (major axis) and aligned the hiwin rails. Here is a vid of the gantry running on just the rails. About the same as before, maybe a bit better, seems fine to me.

https://streamable.com/22i2r

I then connected and aligned the Y axis ballscrew. Got the resistance completely even along its entire travel, all the way to the extremes. It is a HUGE improvement due to the cleaned ballscrews and the improved alignment. Here is me turning the ballscrew and moving the whole gantry with one finger, it is this way along the whole length!

https://streamable.com/n26nm

I can even push the gantry and the Y ballscrew spins accordingly. Unlike Lee, I simply cannot do this with one finger, need both arms and a sure footing! Still, this was completely impossible before:

https://streamable.com/sbztv

Here are some vids showing the same behaviour on the X axis, once again over the entire length of travel. Even easier to move (I think mainly because it is lighter, rather than due to any better alignment).

https://streamable.com/yzbnr

https://streamable.com/73cc5

In summary, everything is hugely better. I now believe this machine is set up absolutely adequately for my purposes, belts encounter almost no resistance when turning, my servos should be able to throw this beast around no problems. In fact, it is much better than my little desktop CNC that I have been using to cut guitar fretboards.

I do not think I can possibly improve on this setup. I love the idea that Lee can move his Z-axis side to side with one finger, but that seems impossible to me on my machine - even disconnecting the ballscrews and one hiwin rail (i.e. moving on just a single rail) I cannot get this performance with the rails I have!

I'm very impressed and grateful for everyones help.

Here is a current snapshot of the machine, ready for assembly of the Z axis:
25901

[MikeyC38]

Hi blueskin
Looks a treat and a nice build. It is worth investing in specialised shim stock, because it allows you to shim precisely. see here (https://www.ebay.co.uk/itm/STEEL-SHIM-ASSORTED-PACK-10-PIECES-002-003-004-005-006-008-010-012-015-020/254037717058?hash=item3b25d3f042&enc=AQADAAAC8FjVrDbVsZ8oH%2F8PNHtt9VX4%2Fw7FZcmMuq sX8uaFEduV6CaQQAljVA8WkbuZuBn3c1m5zglD5Rek9Aus8Yz1 EaXU8Vnip1WJP4goismYL5nAZ%2FB27w2BQ8YPqBoNwftgxjpv 4tbHTbsIVw2yXTrm7RMpTYoH%2FU%2Frq7Q3idjB3JswCcLJ1i 0bzKjvLG0f9kEBWyrQMdCaA%2F9VNSNoPg9Y5zTTU9n00Kb9z8 G07Lv1evQp68OyTK5hf6SvaGakh4zySZqgnr%2BQHnesXY2vyg iw00P%2Bkw4NBQEcPUbCTdgpwXLxNWWyiocDBQv5vjG2%2BuT5 6JY%2ByEQQoK9%2BWpsAijTLwSvF7of6a0DuP3xn4%2Br8bV8K br23tEb0%2BBXEEOEtsAc6Je6pSYwrzo1hcszcrV9l97DyA%2F xS%2BOQX2AUa%2BHbb8cWm2SLnAL0qfd%2FT5L9HKVjsVrm%2F %2Fm4kJcnBFfAmRnWaW6PSRxZ2Ner538a9XAXeBF9RPnn8iZek 0djYJsbeqvsqFzydE5QxLPvFA1kYESH%2FFWFs%2FRrJF1e14O MSs8%2FiwK7JbwWIQHb1%2F5MoH5aWJtJ6aScafVpiXGo%2BsR kFczjXBJUrysYohuPjc%2BNYXRwtDmGwSMzCZb%2B5%2B7wbWs 4WsNUsJUnzU5jzpn7dk%2FB7EBuF2twvxVx2Tv%2Bv1XN%2Fce MnoS7ZalAS7SDWEKRtjdZc%2FOKHYtvHZz%2Fjs8mdSikAqmp3 5uAyNeWhrAmY1%2FrUEGeT%2F43E%2F%2BVGwo4b6%2BeKAsrc 1ag%2FvEz5WhhNKoUBJ24%2F9axBLXQFPcxfIwLKAy1EcdiB5l qgbIk%2ByW77QgTDCFXFh10vWlq1pgqdqr6M%2F7n4ym0oTlz3 6gHcfHQ4coUrhleYmNZKlie2XqlfamUV63K8HdsnD2EPBoPUNe szKj537lR%2BPSW7s3WSX80%2FGpL3BwmpHBOG6EiyeFohV21u Em3qfR%2F%2FHXdUxrA%2Biv8MpV%2BSarCEg4QWZVTE%2FpEq jtrkx2qAOcoZ&checksum=25403771705851e72528a1464fdca17dc8df6bd84 f6c)
Also get you axis nomenclature clear. If you assume that the bottom left corner of your machine (looking top view) is 0,0 then the Y axis is the axis between the gantry sides and the X axis is the longest axis. Z zero is the topmost point of travel on the z axis.

Now start to work out where cable chain will run. This is something I did'nt do until I was at the same stage as yourself. I had to lash something up but luckily the design had space for aluminium channel to be fitted to support the chains

Finally for your spindle mounting, also try and design some means of adjusting for tramming the spindle. It will make your life easier. At the moment I'm using shims and it is tedious!

Keep going!

Michael

[Voicecoil]

Also get you axis nomenclature clear. If you assume that the bottom left corner of your machine (looking top view) is 0,0 then the Y axis is the axis between the gantry sides and the X axis is the longest axis. Z zero is the topmost point of travel on the z axis.l

Surely if you're standing at the front of the machine looking down, (i.e. 0,0 is front LH corner) then this is the opposite to how you'd have X and Y on a normal graph?? I'm with Bluesking on this one :-) Not that it really matters, he's made it perfectly clear what he's doing.

[cropwell]

Most 2D/2.5D drawing packages use the normal mathematical convention that the X axis is L -> R as you look at the paper, the Y axis is at right angles to it. How you orient your paper or machine is irrelevant. My machine is in portrait mode and it just makes it easier to visualise if it is the same as the drawing. My Z zero is at the top of the workpiece, but my Z homes to the top of travel. X and Y homes to Left and Nearest me respectively. I just find it less confusing this way and therefore mistakes are less easily made.

[MikeyC38]

Hi Guys

Sorry everyone, this is what I meant - standard landscape graph mode.But I of course it does'nt matter which way you do it providing you know what to expect...

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[bluesking]

Wow, what a controversial issue my axis labelling has turned out to be! I'm happy with my system, long axis Y, short axis X, corresponding to a portrait graph as you guys call it.

[bluesking]

Z axis build today.

aligned the hiwin carriages first of all as I can't get to them after anything else is assmebled
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then finalised the fit of the hiwin rails
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then ballscrew aligned and attached the spindle once I was happy there was no binding
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entire travel moves smoothly, it is easily pushed down by hand, not so much up for obvious reasons. My biggest concern here was that the Z axis would fall under its own weight. Well, I got lucky, there is just enough friction to keep the axis from falling down so I won't need to bother with a brake. Here is a video of how it behaves as it is - this is without the belts/servo connected, so after connection there will be even less chance of it falling after powering down:


https://streamable.com/z05b9

bolted on the reinforcement struts to the base to improve rigidity - seems to make a noticeable improvement
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quick measure up of the drag chain - I'll cut some Ali Plate to support this - one end will be attached to the gantry, the other directly to the table - not pretty but I think it'll work just fine - I liked Wal's build that he had his chain under the table, but I have my reinforcement struts there and prefer rigidity over neatness!
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finally, a quick test fit of the servos to see if there is enough pulley adjustment range (broadly planned that there should be throughout the build!) and to check whether the belts I have are of suitable length. I need to buy a slightly longer Z axis belt, you can see that the servo doesn't quite mount properly as is - I had to shorten the support extrusion for it during the build as I couldn't be arsed to cut an indent to go around the ballscrew bolts.
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[Lee Roberts]

I can even push the gantry and the Y ball screw spins accordingly. Unlike Lee, I simply cannot do this with one finger, need both arms and a sure footing!

I love the idea that Lee can move his Z-axis side to side with one finger, but that seems impossible to me on my machine - even disconnecting the ball screws and one hi-win rail (i.e. moving on just a single rail) I cannot get this performance with the rails I have!]

Just to clarify mate, I can only push my Z axis across the X (gantry) left to right with hardly any resistance, watching your video of you moving the gantry up and down the Y axis (bed), I would say we are very close in terms of effort required to make it move and the screw to spin.

You should note I'm using supported round rail, I thought I mentioned that in my other post, if I didn't sorry about that. Your rails are far superior to the ones I've used on this machine, overall I think your now on to a winner and agree you should move onto the next parts.

What pitch screws have you used on your longer axis's ? I've used 1610 ball screws on both X and Y, I think that may also be why its a bit easier for me to make things move. The rails on this machine will be making the most difference.

Well done, keep going looking forward to seeing you push the Start button :thumsup:

[bluesking]

What pitch screws have you used on your longer axis's ? I've used 1610 ball screws on both X and Y, I think that may also be why its a bit easier for me to make things move. The rails on this machine will be making the most difference.

Nice one Lee,
I'm using 1605 throughout and various gear ratios. As I'm using servos my main goal is to slow everything down enough rather than to speed it up like most stepper guys are doing.

Between that and the round rails you are using I'm feeling confident that I've managed to squeeze out all the performance I'm likely to get from my machine. Thanks again, you've given me really helpful advice about what I am aiming for and now I can move on with confidence, its a good feeling!

I'll mainly be focusing on the electronics and software from now on.

[Scustom]

Hi bluesking
Any progress lately?
What gear ratios did you use for x,y and z axis?I assume 2:1 on x,y and 3:1 on z?
Thanks

[bluesking]

Hi bluesking
Any progress lately?
What gear ratios did you use for x,y and z axis?I assume 2:1 on x,y and 3:1 on z?
Thanks

Hi,
I've almost finished the machine. Just about to post a progress update. Gearing is 2:1 on XY and 4:1 on Z.

[bluesking]

Been a little while since I last posted but progress has been made. Almost finished and very pleased - things all worked pretty much to plan, even the electronics and software.

1) Made a simple 400x400mm MDF enclosure for the control box. 3D printed some connection panels so I can change the interface in future if necessary. Bit of spare clear acrylic for the top.
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2) Spent about 50 hours of bench time to wire the control box. Surprised at how long this took - thought it would be simpler but I was testing individual functions as I went to make sure it all integrated OK.
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3) A lot of the bench time was spent preparing cables and connectors. Here's all of the prepared cable ready to go into the workshop:
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4) Back in the workshop, attaching the drag chain to some 3d printed mounts:
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5) Attaching various homing and limit switches, once again on 3d printed mounts. Laying cable in the drag chain.
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6) Here is the basically complete machine!
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Heres a quick vid of the machine doing some initial rapids. Spindle yet to go on, but I'm getting 9000mm/min on the X & Y axes before servos stall. Thats setup for a theoretical precision of around 1/1000th of a mm with the encoders I have and running the UC400ETH at 200kHz. Obviously that precision is pretty goofy, I was just erring on the side of caution - still there is plenty reason to think I can squeeze a bit more speed and torque from this setup after a bit of experimentation and tuning.

https://streamable.com/orect

There is still spindle mounting and some tuning to do for precise axis scaling and servo PID controller tuning. After that I'll be moving on to spoil board, jigs and dust extraction.

[Kitwn]

I love the control box! It's so much easier to fix everything to MDF than mild steel or aluminium and makes future changes a lot easier. It also allows you to concentrate the funds where they make a difference rather than just spending money on something that looks good. I've never quite seen the point of making one-off home constructed machines mimic professional, mass produced factory built versions. The priorities are completely different.
The only possible problem is electrical noise, a discussion going on elsewhere on the forum. This is something you can address with additional screening and appropriately placed capacitors if and when it shows up during testing.

Kit

[bluesking]

I love the control box! It's so much easier to fix everything to MDF than mild steel or aluminium and makes future changes a lot easier. It also allows you to concentrate the funds where they make a difference rather than just spending money on something that looks good. I've never quite seen the point of making one-off home constructed machines mimic professional, mass produced factory built versions. The priorities are completely different.
The only possible problem is electrical noise, a discussion going on elsewhere on the forum. This is something you can address with additional screening and appropriately placed capacitors if and when it shows up during testing.

Kit

Thanks Kit. I couldn't care less what it looks like, as long as it functions well!

Everything seems to be ok so far - no interference yet, but it is very early days. I have implemented a single point star ground and shielded cable throughout, even on the limit switches - I am more worried about interference on all that cable than I am into the control box. Also, almost every EMI noise source in the room is actually sitting in that box already, so I'm not really convinced a metal enclosure will help anything for me! We shall see!

Also, I've been meticulous in avoiding ground loops. Despite this, I did knowingly introduce one ground loop into the system - this loop goes between the control box and the VFD, and back through the mains circuit. I wanted to avoid this, but I also wanted to have a Z probe which worked without a crocodile clip. There were a few options I could see:

1) lift the mains earth in the VFD - this would probably be the best way but the VFD is very high power and I was worried that earthing it through the signal cable shield could potentially dump a huge amount of current into the control box if the VFD failed. Then I would have to replace not only the VFD, but also debug and fix the whole control box!

2) rely on a common earth between the control box and VFD - earth both to the mains, and assume that is adequate to close the loop on my Z probe. This would certainly have worked in my workshop - because I plug both devices into the same mains circuit so they share a common earth. However, if I ever moved the machine somewhere else and the two devices no longer shared a common earth, my Z probe would fail! This seemed like a really unpleasant easter-egg for future me (or another owner) to have to deal with!

3) Knowingly introduce a ground loop. This may or may not cause an interference issue - but is safest option. No issues noted so far!

[cropwell]

I also wanted to have a Z probe which worked without a crocodile clip.


My tool tip has earth continuity, so this type of touch plate works for me.
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Even though your spindle body may be earthed, that may not continue to the tool if you have ceramic bearings, so a switch type would have to be used.

Have you metered the resistance between collet and spindle body ?

[Kitwn]

As I've just mentione elswhere, an RCD in your mains supply offers no protection against shocks from the output of your VFD. Don't take risks with the safety earthing of your spindle.

[bluesking]

My tool tip has earth continuity, so this type of touch plate works for me.
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Have you metered the resistance between collet and spindle body ?

I've metered between collet all the way to the BOB, thats what made me think it would work. I then tested the z probe (same idea as the one in your pic), thats how I know it works!

Weirdly my spindle is quoted as having ceramic bearings though so not quite sure why it does work. But I'm happy so far.

[bluesking]

Don't take risks with the safety earthing of your spindle.

I haven't taken any risks: the spindle is earthed. Thats the reason why I had to introduce a ground loop to make my z probe work how I wanted and still be safe - at the cost of some potential interference...

It's a basic catch 22 - and the reason why many valve amps have a ground lift switch. Always seems a bit dangerous to me to leave it in the hands of the guitarist to decide what is safe! But it's there when you use multiple amps and you know they are all on the same mains circuit yet the ground loop is causing noise to get in the system.

[Kitwn]

We should probaly start a new thread to start talking about multiple amps, Brian May, whether Russian ECC83s are better than the Chinese, using CNC machines to build guitars.....................

Kit

[bluesking]

We should probaly start a new thread to start talking about multiple amps, Brian May, whether Russian ECC83s are better than the Chinese, using CNC machines to build guitars.....................

Kit

For sure. And by the way, the best ECC83s are dutch: amperex bugle boys. They might not be as well known as mullards but they are cracking. You can find them for under £10 each - if you know where to look :)