School me on the best machine for big hardwood

**bluesking** · 17-04-2019

Originally Posted by Washout

Hi bluesking

I also machine guitars on my CNC machine (check my signature for my channel). I normally machine around the 3000mm/min mark using 4 to 10mm cutters dependant on operation and strategy (e.g. larger multi-flute cutters are great for adaptive/trochoidal clearing when roughing bodies and body pockets).

Personally I would go for option 1. as you will know what you are getting and can design out some of the compromises in the other options. £3K is not unreasonable for a decent aluminium framed machine (mine was about £2K-£2.5K including software).

Option 2 looks OK, but I'd like to see how that X axis (long axis) is being driven and the electronics might be a bit of a lottery (i.e. stepper type/voltage, driver type, controller board etc.).

Option 3 a. not familiar, but if there are valid criticisms from JAZZCNC or the other regulars here then I would heed them.
Option 3 b. not familiar so can't give an opinion
Option 3 c. I would not go for any machine with leadscrews and probably not without linear guides/bearing (square supported rails) given the choice these days.
Option 3d. You will likely find that many machines will start to get close or pass the 200Kg mark, once you get it fully loaded - generally provided the motors are sized correctly (and some other factors), heavier is better

Hope that helps.

Washout, that really does help, thank you very much!

Option 1 certainly is attractive but I am somewhat concerned about disappearing down the rabbit hole into a long build. I'm prone to this anyway, and I can see myself getting carried away! At least if it turns out heavy I know I can easily dismantle it for transportation which solves that problem.

Option 2: X axis is driven by a single, central 2005 ball screw. As for electronics, they seem OK on paper. For my own build I was thinking about using this (https://www.cnc4you.co.uk/CNC-Kits/P...3-Axis-Nema-23). The Omio seems similar to what I would have used in my build, I think the drivers will be about the same, the PSU will run a little lower at 40V rather than 48V, and the steppers seem like they are 3Nm rather 4Nm (can't really tell, only info on the steppers is they are rated 4.2A - no idea what torque this corresponds to). Not really sure how different the BOBs would be. I don't know whether this all would really impact what I'm doing as my own design was based on what can easily be bought in at low risk (given they are packaged as a kit I was relying on compatibility), rather than on any real engineering design factors. Perhaps this kit would be overkill for what I need and perhaps the Omio would be just fine - or perhaps not?!?! Overall, at 95kg and with an easily removable gantry I would feel comfortable knowing I can also move it around.

The biggest differences I can see between the omio and my own design are:

a) Omio uses 5mm lead pitch with direct coupling between steppers and leadscrews - I was going to design belt-gearing to get a bit of extra speed. Either should be able to run at over 3000mm/min so perhaps this is irrelevant, given what speeds you have found work best. I'm hoping to use more standard router cutters than milling bits, 1/2" flat bits for clearing, 1" ballnose for contours and top carves - not really sure if these expectations are overambitious or just plain crazy - not seeing anyone else doing this - wonder why? Those are the bits I'd use when hand routing and I can't say the forces involved seem dramatic at all - some of my handbuilt guits have made use of these bits supported by pretty rudimentary MDF sleds and jigs - sure there is often around 0.5mm of flex - never caused any problems after sanding and finishing! Hell, I'm currently using an angle grinder for most of my top-carves - not fun, not accurate, but gets a great result in the end.

b) I would have used significantly larger extrusions - its hard to tell what size extrusions the omio utilises - but then the omio makes more use of more aluminium plate - have no idea what rigidity to expect from either option!

c) Omio will hopefully be much easier and quicker to get going on. Also, the bellows seem a nice touch, I have the feeling that the omio will be more protected from sawdust than anything I will ever end up designing.

I have just had a very reasonable price from Omio for supplying the X8 without the electronics or steppers. So a hybrid approach may be best (and even cheapest). With this I'd probably end up combining the omio mechanics with the cnc4you electronics kit and.... hoping.... that Robert really is your father's brother?!?!

I had a look at your youtube channel and realised I have already seen all of your Andy Summers tele build
during my research. I think I've seen every guitar CNC video on youtube by now haha. Really enjoyed your work, particularly nice and sharp sunburst you got on that one!

Cheers!

**Clive S** · 17-04-2019

First welcome to the forum bluesking.

I would also go with option one as then you are in control. Have a look at Joe Harris build with a hand held router https://www.youtube.com/watch?v=pZo2...S3i705fuSogBXT

The motor kit is not good as the drives and power supply are not good enough. cnc4you is a good place to buy the motors (or Zapp. https://www.zappautomation.co.uk/ele...er-motors.html)
Wal's machine is currently being modified to make it into a twin screw type. I would advise you to do the same. This can be done with two screws and two motors nema 23 OR two screws and one motor nema 34 with one belt connection both screws and the motor. Both ways are fine personally I prefer two motors. The are pros and cons for both types.

I would go with about 68V power supply and em806 drives or am882 or even https://www.ebay.co.uk/itm/CNC-2DM86...oAAOSwKWJcnaQE.

Ball screws 1610 x and y 1605 on z tried and tested by many.

If you decide to build start a build log to keep all the question in one place. Good Luck

**bluesking** · 17-04-2019

Originally Posted by Clive S

First welcome to the forum bluesking.

I would also go with option one as then you are in control. Have a look at Joe Harris build with a hand held router https://www.youtube.com/watch?v=pZo2...S3i705fuSogBXT

The motor kit is not good as the drives and power supply are not good enough. cnc4you is a good place to buy the motors (or Zapp. https://www.zappautomation.co.uk/ele...er-motors.html)
Wal's machine is currently being modified to make it into a twin screw type. I would advise you to do the same. This can be done with two screws and two motors nema 23 OR two screws and one motor nema 34 with one belt connection both screws and the motor. Both ways are fine personally I prefer two motors. The are pros and cons for both types.

I would go with about 68V power supply and em806 drives or am882 or even https://www.ebay.co.uk/itm/CNC-2DM86...oAAOSwKWJcnaQE.

Ball screws 1610 x and y 1605 on z tried and tested by many.

If you decide to build start a build log to keep all the question in one place. Good Luck

Thanks Clive,

Noted your advice about the drives and power supply - I had a nagging feeling this was a bad area to scrimp on but my choice was driven by ignorance rather than price. I'm sure if I went with your suggestions I'd be able to find someone here who has a wiring diagram for all these exotic options (exotic to me anyway!)

Also noted the need for substantial motoring to move the gantry.

Joe Harris build video is interesting. It looks like a sturdy machine, but what do I know?! It wouldn't work for me - as he rightly points out, making a steel frame structure which is easy to dismantle and reassemble without fubaring its alignment seems like a no go - I am currently moving workshop space and it seems quite likely I will have to move again within the foreseeable future - I can't afford a machine which I can't easily take with me!

I have already started design work in CAD for my build (2 variants actually). Once I have something ready to show I will definitely start a build log and seek comments.

To press on with my design I now really need to commit to either a moving gantry or a fixed gantry. I originally went with a fixed gantry based on what I saw this Maltese luthier doing (https://www.youtube.com/watch?v=6MCyIZIcg48). Its a bit rough and ready looking, but my mechanical intuition is telling me it is a good way forward. Certainly moving 2kg of wood seems like a much easier job than an entire gantry holding a 2.2kw ER20 spindle. Then I saw the thread of Wal's machine and I liked the simplicity and elegance of it - so I went down that route. Now I'm dithering again between the two (can you guess I'm a ditherer yet, hahaha?)

**Clive S** · 17-04-2019

To press on with my design I now really need to commit to either a moving gantry or a fixed gantry. I originally went with a fixed gantry based on what I saw this Maltese luthier doing (https://www.youtube.com/watch?v=6MCyIZIcg48). Its a bit rough and ready looking, but my mechanical intuition is telling me it is a good way forward. Certainly moving 2kg of wood seems like a much easier job than an entire gantry holding a 2.2kw ER20 spindle. Then I saw the thread of Wal's machine and I liked the simplicity and elegance of it - so I went down that route. Now I'm dithering again between the two (can you guess I'm a ditherer yet, hahaha?)

Fixed gantry will take up more floor space and moving gantry. if you are comparing that with the one Wal built then there is no comparison between the two. I pointed you to Joe's machine not for the way it is built but the methods he used with the hand held router. Also he has on his site a very good vid on building the power supply. There are only three components in it.

I forgot but go for 20mm square rails if you can. all this can be got from Fred at BST in China along with the ball screws and bk bf bearings etc.

Also noted the need for substantial motoring to move the gantry.

nemas 23 will be more than enough with the correct drives.

Re the CAD it is always a good idea to do a design first. I don't think Wal's machine is anything like 100Kg