New Machine Build- Advice / help / recommendations

[lostmyed]

Hi all,
After lurking on this forum for a few weeks for inspiration I have finally decided to go ahead and start design for my first router table.

Objectives:
To build a 3 axis router/milling machine to cut wood and its derivatives and also aluminium.

Cutting Area:
X Axis – 2040mm
Y Axis – 1040mm
Z Axis – 150mm

The design at this stage is using the following drive systems:
X Axis – Dia:25x5pitch Rolled Ballscrew, carriage running on Dia:25 open linear bearings.
Y Axis – Dia:20x5pitch Rolled Ballscrew, carriage running on Dia:20 open linear bearings.
Z Axis – Dia:16x5pitch Rolled Ballscrew, carriage running on Dia:16 open linear bearings.

I am currently happy with the Y & Z drive assemblies but still not sure about the X axis. At present I have a single Ballscrew centrally located below the X axis carriage, but I am considering changing this to twin screws, although at present I don’t think I will have an issue with X axis crabbing a twin screw system will ensure this and as the XYZ carriage weight is currently nearly 100kg it should also help here too.
I have yet to get my head around the electrical side of the design as this is by far my weakest area of knowledge but for a twin Ballscrew (twin motor) X axis system would I need a 4 axis controller system or could the second X axis motor be controlled by some sort of slave from the first? Also how would I ensure the motors are perfectly in sync ?

I will attempt to attach some screen shots to give you an idea of where i am at present with the design.

As you can see from the screen shots i have still yet to decide on a spindle, i have spent some hours looking at posts regarding the ebay water cooled options but still i have yet to reach any decision. Has anyone used any of these for milling aluminium ?

BTW this is a couple of around a million questions I have for this project, I am slowly answering many of them myself as I lurk these forums. Any help/advice/recommendations will be appreciated.
Thanks.

Ed.

[CarveOne]

It is possible to run two motors from one drive, but it depends on the driver design. It has been discussed in this forum in the recent past so try using the forum search tool.

It doesn't appear to be commonly done, and I haven't seen any mention of how successful it was. Slaved motors are commonly done with settings in Mach3 or EMC2. I have done it with both software. I have had some skewing (crabbing) problems. It can come from crosstalk in the wiring and/or from missed steps.

CarveOne

[Phife]

Looking good, I would add a center support for the bed, you dont want that sagging in the middle.

As for a spindle I would go for a spindle if you can afford it, or you can do what I did, Get a Porter Cable 890 (892,893 are the same) its a 2.25hp router, fairly cheap ($250) and works well, then you can upgrade to a spindle when you have an extra $1000 and your PC dies. Get the Precision collets for the porter cable from Precisebits.com and its an excellent spindle.

Get your Z mounting plate drilled for the K2 router mounting brackets, that way you can just swap in the 80mm bracket when you need a new spindle.

Slaving the X axis is easy to do in mach3, and if you use servos you can avoid issues with lost steps. I rarely have my dual drive X axis skew, but I do check it once in a while. You can ensure you have a perfectly square and aligned X axis if you use limit switches on both X axii for homing. Its fairly headache free.

You got alot of great people on here willing to help, so ask away!

[lostmyed]

Thanks for the input guys.

I have added 2 jack screws ea. side between the bearing beams and support beam to help with any sagging caused from the carriage. I did not want to fix this in any other mechanical way as the bearing beams are bolt in items what will be machine skimmed for the bearing rails. See attached image.

I have also made a few adjustments to the design so I have enough screw travel to add a second ball nut to each of the axis’s if I find I am getting to much backlash from the ballscrews.

I have now decided to start with one central ballscrew for the X-axis but have again modified the design so I can add a second and reposition the original if or when needed.

For the control side I am being drawn towards the gecko G203V’s and the CNC4PC G11C break out board, although I am still researching and scratching my head with this. Will this set up allow me to add another gecko drive for the second x-axis motor if I need one?

Many thanks again

Ed.

[Phife]

I use servos and the Gecko G320s and the CNC4PC C11G BOB. I am pretty happy with the setup, the c11g will handle 4 axis (I think 6 even) and all your inputs.

The built in chargepump, analog 0-10V, and relays are nice too.

I have no experience with steppers or the G203v, but ive heard good things.

[CarveOne]

Originally Posted by lostmyed -snip- For the control side I am being drawn towards the gecko G203V’s and the CNC4PC G11C break out board, although I am still researching and scratching my head with this. Will this set up allow me to add another gecko drive for the second x-axis motor if I need one? Many thanks again Ed.

Yes, it will. You will need four G203V drives. The C11G breakout board is a special version just for the Gecko drives. You would go into Mach3 Configuration and tell it to slave the A axis to the X axis. That's what many of us are doing. Slaving can be done in EMC2 also but the procedure is not so obvious as it is in Mach3.

CarveOne

[lostmyed]

Back for an update.
I have made some modifications to my design and finished off the majority of the cosmetics too. I have changed a few things around and redesigned to make both the Y & Z axis ball screws fully protected against the ingress of swarf. Bearings are now rail and block type (all size 25), im still only starting off with a single motor & ball screw assembly for the X-Axis but making all the parts to be able to slot a second one in when/if needed.

See attached images.

I have virtually finalised the mechanical side now, the only things (apart from the control panel) I am not sure of as yet are the limit switches. Has anybody had any issues with mechanical limit switches not holding good accuracy for datum’s?

Things are really moving at last, linear rails ordered, screws hopefully ordered by next week and fingers crossed the framework steel by the end of the week.

Massive thanks to Dean (hemsworthlad) for a whole load of help offline.

Cheers mate.