Brass vs Aluminium Vs Steel, questions, questions and questions...

[alexccmeister]

Here are a few pics of the X axis cnc conversion.

[S_J_H]

I think brass will be fine. It's plenty strong in this case. It's just an expensive material to be used for that sort of thing.
Steve

[alexccmeister]

Hi Steve,

Thanks for the info.

Anyway, what luck I had yesterday. Managed to damage a stepper motor by accidentally dropping it on the floor. Broke a bolt hole where I mount the support rod to the stepper so now one of the stepper has only 3 legs support instead of 4. I hope it doesn't any worse than this. Now I have to order a new stepper motor. I wonder if I can switch the head of the damaged motor to the motor that has the broken bolt hole.

[alexccmeister]

Another thing I found, my stock acme leadscrew just has too many threads on it. Although accurate, the movement of the table is real slow.

I think its probably time to change to ballscrew or leadscrew with 5 or 8 tpi.

Anyone know where to get this? Thanks.

[ataxy]

i dont know how slow is slow for you but remember the 10 thread will give you more precision then 8 or 5 also keep in mind that those machine can not be pushed like industrial machine so you may end wishing it would go slower

[rustamd]

Originally Posted by alexccmeister Hi Steve, Thanks for the info. Anyway, what luck I had yesterday. Managed to damage a stepper motor by accidentally dropping it on the floor. Broke a bolt hole where I mount the support rod to the stepper so now one of the stepper has only 3 legs support instead of 4. I hope it doesn't any worse than this. Now I have to order a new stepper motor. I wonder if I can switch the head of the damaged motor to the motor that has the broken bolt hole.

It is not recomended to take stepper motor apart. Almost everytime someone takes it apart it will loose alot of its torque(just what i read)

[alexccmeister]

rustamd, I did the unthinkable. I went ahead and changed the cover, the motor still runs fine after the swap. As for the damaged motor, it now doesn't run. I think the shaft is bent. When I turn it with a plier, it will turn fine and then gets harder at one point. I suspect the shaft hit the ground and was bent to one side causing the motor to stall. So thats $60 down the toilet.

Ataxy, The motor is fine running at 300mm/min. I set to 200mm/min and it stalled as the table gets closer to the end of its run. I would prefer it to go all the way to the end but it stalled at around 50mm from the edge. Still alot alot travel to lose. I think it may be the alignment of the leadscrew and the motor shaft. Will adjust it and see what happens. I think I am comfortable with 200/250mm/min velocity so I may stick with that when churning out parts.

[The Blight]

It stalls because of the ways. They are uneven on these types of machines, and I would reccomend lapping the ways. I spent a couple hours doing this, and I can tighten the gibscrews up to the point where I can't move the table from side to side (twist it) without it binding at any point, and it has just as little slop all the way. I would not use screws with a pitch greater then 4mm as you loose some precision. 2mm would be perfect. I don't like microsteps so with a 2mm pitch, you would get 0.01mm per step (10micro).

One of my motors also has a hard point when I turn it, but it works just perfectly. Does yours not run at all?

[alexccmeister]

Hi The Blight,

I am relatively new to cnc but have learned a lot from this forum. But after saying that I am still short on my vocabulary. What do you mean by the ways? When you say 4mm screw pitch, what do you mean?

The damage motor is the one I am talking about that I can't turn the shaft. Its gone I think as there isn't any signal going to the motor. I checked the driver and it is ok. Thanks.

[tanu1029]

Hi..

If we are choosing between brass and Aluminium ..which one is better conductor of heat? I am cooling something by Thermal contact conductance using either brass or Aluminium but not sure which one to use. Any recommendations..?

Thanks

[Geof]

You can Google 'Thermal Conductivity' and probably find tables ;isting different materials. Just of the top of my head I think brass is better than aluminum but not by much. You also need to take into account the cross-sectional area and may be able to save money by using a larger cross-section of aluminum.

[691175002]

MatWeb - The Online Materials Information Resource
MatWeb - The Online Materials Information Resource

You can find the thermal conductivity of both metals on this site. I would avoid using brass for heatsinks mostly because its thermal conductivity varies greatly by alloy and is generally less than aluminium. It is also expensive and weighs a lot.