Hello There. Planning for UK MechMate Build

[Macwood]

Hello all,

Firstly I should say I have NO cnc experience nor have I build a cnc before, so total newbie in that department.

I design and make furniture for a living in my own workshop near to Guildford UK.
The workshop varies greatly type of furniture it makes from freestanding one off bespoke pieces to fitted furniture to bespoke living spaces.
About 3 years I started looking into having a cnc in the workshop and how it could help with production.
I settled on building a mechmate cnc and have been doing my homework on that ever since.
It will be used for cutting sheet materials and true 3d furniture components. (Ill post some images of the 3d stuff later)

What I have decided so far:
Mechmate cnc build plans purchased
Capacity to cut 2440 x1220 (8x4) Sheets
Z Capacity 150mm
Option to add rotary indexer later
Try to Follow original mechmate plans apart from slightly different table design due to steel I have in stock and electrics.



My biggest weakness is the electrical side of the build. I have no experience with electrics/electronics apart from wiring up a few workshops and building extensions.

My schedule is to complete the planning and material gathering for end of this year. By that time I will have the building ready for where the mechmate will finally live. With the plan to physically start building the 1t of Jan.
I will start a build log on the mechmate site and here as I hope to learn more from this forum that will help my build go smoothly.

Any advice and pointers will be very welcome.

Crikey!! This is long first post, as you have probably guessed I have not done much posting on forums before either ha ha.

[Macwood]

Some of the 3D parts I would like to machine.

[hanermo2]

Dont use the v rails.
Use linear guides ... and bigger is better. Suggest 20-25 mm size import rails for commercial use.

Otherwise, pretty much as mechmates were built.

2.
Use ac brushless step/dir servos of 400W or so.

3.
Use a rigid under-carriage, and use only one motor for the long side.
Drive from center.
Vs using sw slaving of 2 motors.
3. is debatable in many ways.

4.
Don´t worry about mass.

[Ger21]

20mm rails are more than large enough for any DIY router.

If you go with the AC servos, you're going to want to use 10:1 planetary gearboxes, with as little backlash as you can find.

There are several issues with driving a gantry from the center.
1) Racking will be an issue, unless you build a very massive structure.
2) This method requires a table that's suspended at the ends only, which will be less rigid than a fully supported table.
Using two slaved motors is easier, and works fine.

[hanermo2]

Disagree Ger,

1.
Why will racking be an issue ?
A rigid center-driven gantry has perfect balanced push on both sides.

2.
There is zero need for not using a fully supported bed like the mechmate.

3.
There is zero need for not dropping the drive screw 40 cm, under the bed (or even over it).

4.
Ac servos do not need any planetaries - although they might perhaps be used.
Ac servos will work just like steppers, but 20x better acceleration, much better top speed, 10x more accurate.
Importantly, servos stop/fault before making major damage.

The OP looks for a *jobshop* commercial machine.
I recommended stuff for a *commercial* machine.

A mechmate cost == 8000$ to build.
In that context, the servos and 20/25 mm rails cost difference disappear.

20mm rails are more than large enough for any DIY router.

If you go with the AC servos, you're going to want to use 10:1 planetary gearboxes, with as little backlash as you can find.

There are several issues with driving a gantry from the center.
1) Racking will be an issue, unless you build a very massive structure.
2) This method requires a table that's suspended at the ends only, which will be less rigid than a fully supported table.
Using two slaved motors is easier, and works fine.

[Ger21]

You can't have a fully supported bed with a screw under it.
Fully supported must have a different meaning for you.

[Neale]

Why will racking be an issue ?
A rigid center-driven gantry has perfect balanced push on both sides.

Can't see how the geometry of this works. Surely a centre-driven gantry is only balanced if you are cutting a slot up the middle of the bed? Making the gantry stiff enough probably is not a big problem, but the racking loads when cutting at the ends of the gantry are going to put big loads on the guide rails if you want to avoid significant deflection. After all, to be able to cut a 1200mm sheet, you probably want about 1300mm travel, plus width of Z carriage, so the gantry is going to be around 1500mm wide, putting the cutting load point around 700mm from the drive screw. So much easier to drive at both ends, which then allows a better bracing structure for the bed. Slaving two motors really isn't a big deal, after all. If I can do it, anyone can.

[Desertboy]

If it's going to cost $8000 you might as well buy something like this

https://www.sign-in-china.com/produc...CABEgKOHvD_BwE

Looking at freight shipping to felixstowe it'd be £300 which is very reasonable, then you have import tax and cost of transport from felixstowe maybe cost £6k but it looks a very capable 8*4 router.

[Ger21]

If it's going to cost $8000 you might as well buy something like this

But then you have to spend another $3000 and a few months time to get it usable. :)

[charlieuk]

But then you have to spend another $3000 and a few months time to get it usable. :)

and then it will still probably have a twist in the frame and nothing will be trammed so you will have to take it apart and try and figure out how to fix it and that's before starting on redoing the electronics. I battled with some ones china cnc for 6mths over in aus, in the end I gave up trying to fix it and just accepted it for what it was and that you couldn't really do any of any size with any accuracy. I mean when you see holes drilled like this on the spindle mount what can you expect.