First Project - Aluminium

[cchaos]

Hi everyone,

After a lot of reading on this forum and designing (nearly a year by now) maybe its time to show my project to you guys, and ask a lot of questions in the process.

Some of the goals I defined for my project where :
1) Working space at least 180cm x 60cm x 25cm (approx. 70” x 23” x 10”)
2) Build out of aluminium (except for the MDF working surface)
3) One long side must be placed against a wall of my workshop and can not be accessible
4) The Machine must be capable of handling MDF and occasionally aluminium.

The tools that are available for the construction are :
1) Drill
2) Standard that can hold a drill to make a simple drill press
3) Table saw with blade for aluminium
4) Router with aluminium bit

I will start by posting a single picture to give a general idea of what I have in mind. Please feel free to let me know if you see potential problems in this design or ask questions where the design is not clear.

And I already have some specific questions :

1) Stepper voltage and Power Supply voltage :

I have bought 4 steppers (RHT34-740) and 4 drivers (Gecko G203V) from HomeShopCNC.
After reading
stepper power supply?
and some other sources the voltage for the steppers is either :
Simple formula : 2.0V * 10 = 20V
More complex formula : 32 * SQR(2.7mH) = 52.58 V
But on YouTube I find this impressive Clip from HAYDN812
"http://www.youtube.com/watch?v=3_qdZB9iGhU&feature=channel_page&fmt=18"]YouTube - CNC Stepper Motor Demonstration
in which he uses the same steppers at 60V according to his comments.

I could order the KL-6520 Power supply from Keling :
http://www.kelinginc.net/SwitchingPowerSupply.html
I already use 4 steppers for 3 axes and maybe will add a 5th stepper for the 4th axis in the future, so the 20 amps would cover that.
However, will the 65V (61.3V at 5A) from the KL-6520 be to much for my steppers ?

2) Sawing aluminium with a table saw :

I have already used my table saw (Festool CS50 with blade for aluminium) to saw Alu profiles without any problem. However, in my construction the sides of the base and the sides of the gantry are made out of aluminium that is 15mm (approx 5/8” inch).
Does anyone know if this will present problems for the tablesaw ?

cchaos

btw English is not my native language so please forgive me any accidental abuse of your language

[ger21]

Cut the aluminum 3mm per pass.

[cchaos]

Gerry,

Tanks for the reply. Cutting in several passed will be the solution.

BTW, is my thread in the right forum, or should it better be in the parent forum (DIY-CNC Router Table Machines), since I am not yet actually building ?
If so, can you tell me how to move the thread ?

Cchaos

[cchaos]

Some more pictures of the design.

The machine will be build out of extruded aluminum :
100mm x 40mm x 4mm for the gantry (approx 4" x 1.5" x 1/8")
180mm x 50mm x 4mm for the base (approx 7" x 2" x 1/8")
The sides of the base, the sides of the gantry and the Z-Axis will be build out of masive Aluminum of 200mm x 15mm (approx 8" x 5/8")
(what is the correct English word for "masive aluminum" ?)

Ball screws on the X-Axis and Y-Axis will have a 10mm pitch.
Ball screw on the Z-axis either a 10mm or a 5mm pitch.

I've designed the machine so that the ball screws are Direct driven (because this seems the easiest way and I am a Newby) but it should be fairly easy to convert the machine so that the ball screws are driven through pulleys. (see 3th pic) This would make the machine smaller which is good as I also will have to build a cover for it. Using pulleys would also make it possible to change the ratio between the steppers and the ball screws if that is needed.

In some of the pictures I removed the MDF surface and the side of the gantry to give a better view on the construction.

Do you guys think that the unusual orientation (gantry over the long side instead of over the short side) will create some issues ?

Cchaos

[cchaos]

Rick, from HomeShopCNC, solved my question about the Max Voltage for the RHT34-740 steppers. It seems that 65V will be no problem. Hurray !
Well, in fact his answer was far more elaborated and better explained , but the conclusion is that 65V will be fine.

Now, I still have to decide on a breakout board. Any Sugestions ?

[cchaos]

In the meantime some more hardware for the control box has arrived from Keling :
- Powersupply KL-6515
- Breakout board C11G

Sadly, after testing it seemed that the 12V output of the power supply does not work. The 65V and 5V outputs are fine.

Well, 12V is only needed for the fan(s) in the control box and for the moment I can power them using the 12V from an ATX Power Supply that I made a couple of days ago.

Next step will be to make that control box...

CChaos

[CarveOne]

I have a very similar setup and chose to buy a couple of 3" 120vac fans that will operate off of the standard ac line voltage we have here instead of using dc fans. The Keling power supply I have does not have the 12vdc output, just two 72vdc 20 amp outputs.

It should not be difficult to repair it, or get it repaired locally. Just be very careful of the large capacitors. They can dump a lot of amps if shorted when still charged up.

CarveOne

[cchaos]

For the control box I used the case of an old and broken PC.

First I removed everithing inside (motherboard, disk, power supply, ...)

The case itself exists of :
- An outer steel case = Bottom and Sides only
- An inner steel case = Bottom and Front and Back only
- Steel cover = Top only

I removed the inner steel case and replaced it with a new one made from MDF.
I choose MDF because at this stage I assume I will will make several mistakes, or have so called better idea's that will result in a lot of adjustments. These adjustments will be a lot easier in MDF than in Al.
Once I am happy with the result, I can replace the MDF with Al.

In the long run, MDF may be not a good idea to hold components that will become hot and an Al or plexi front would look nicer too.

CChaos

[cchaos]

CarveOne,

Thanks for the reply, I'm always very impressed with the things you show and describe in your threads.

About the broken 12V output :
I informed John at Keling about the problem, and will first wait for his responce.

Maybe it is easy to fix, but I have no experiance with electronics so I would need a good "How to" to perform the repair myself.

The AC fans are a good idea, however, if I can get my hands on some free fans from discarded PC's I would prefere that. I have no idea what a 220Vac fan would cost.

The capacitors are powerfull indeed. I could see on my multi meter (how is that thing called in English ?) that it took more than 10sec before they where drained after I turned of the main power.

CChaos

[cchaos]

Next step was making a heat sink for the Gecko drivers.

For the moment I have 4 of them, but I want to have space for a 5th one for if I decide to install a 4th axis later on. (The Y axis will be driven on both sides of the table, so 4 Geckos for 3 axis at the moment)

For the heat sink I used a piece of Al profile that I had laying around.

I cut off the bottom, and then cut a lot of fins using my table saw.

Looks good, although the Al is somewhat thin (1.5mm ~ 1/16").
I hope it has enough cooling capacity for the drivers.
I suppose this will depend mostly on the airflow in the case.

The last picture shows how I intend to fit everithing in the case. Still a lot of room at the moment, but I like this because it makes it easier to manage the wires, and it makes it possible to add stuff (2nd BOB ?) if I want to.

Next step will be to fix everything inside and start connecting stuff.

Cchaos

[CarveOne]

CarveOne,

Thanks for the reply, I'm always very impressed with the things you show and describe in your threads.

About the broken 12V output :
I informed John at Keling about the problem, and will first wait for his responce.

Maybe it is easy to fix, but I have no experiance with electronics so I would need a good "How to" to perform the repair myself.

The AC fans are a good idea, however, if I can get my hands on some free fans from discarded PC's I would prefere that. I have no idea what a 220Vac fan would cost.

The capacitors are powerfull indeed. I could see on my multi meter (how is that thing called in English ?) that it took more than 10sec before they where drained after I turned of the main power.

CChaos

Standard line voltage here is 120vac 60 Hz single phase for most lights and appliances. Homes have 220vac single phase for electric ovens, dryers, and airconditioners. I don't recall seeing any 220vac small fans, but have never looked for one.

We call them "multimeter" whether they are analog or digital type.


CarveOne

[cchaos]

Today I completed the heatsink for the Gecko's

Marked the positions for the holes.

Drilled and tabbed the holes.
This was the first time I used a tab, and it went reasonably well. Thanks to the thin Al (1.5mm ~1/16") and the small diameter (3mm ~ 1/8") I suppose.

Then I fitted the drivers to check if everything fits together. It did
I used no thermal compound yet as I first want to check if the all the drivers are working as expected.

CChaos