Ball screw advice

[333-CNC]

Good evening all.
I introduced myself to the forum few weeks ago and gave a brief description of build so far (http://www.mycncuk.com/threads/14348-New-Member-Build). I am now after some advice on ball screws, after researching the forum I believe I have purchased the wrong ball screws for the size of the machine (1605). And after more reading, I have seen some members mention problems with whip on long screws.
My machine needs a minimum of 1365mm ball screws on the X axis and 1500 on the Y axis and will need to shift a heavy 80160 gantry. I currently have 3Nm steppers and ideally will use pulleys on the Y & X axis as the steppers can be placed neatly. I am in a position to order the new ball screws but would like to be sure I order the correct size, I have read that some members have used 1610 and also 2020, there is a huge price difference from BST on aliexpress so hoping someone can advise on this prior to ordering.

Thanks for reading.

[JAZZCNC]

Either of those will work, but for the long screws, if using 16mm, I would use fixed end BK12 bearings on both ends, just to tell Fred at BST you want machining for BK at both ends.
It helps greatly with screw support and helps with Whip.

[333-CNC]

Hi Jazzcnc.

Thanks for the reply, in regards to 2020 ball screws, I have just been searching on Aliexpress on BST site and found 2020 screws approx £30 extra each. So is it worth getting 2020 over 1610's? I'm using Nema 23 3Nm and hoping these will be adequate to move a gantry weighing 32kg and the Z axis is approx 18kg not including the spindle. I'm happy to pay the extra for 2020's if they will be the safer option.

Thanks

Rob

[JAZZCNC]

Hi Jazzcnc.

Thanks for the reply, in regards to 2020 ball screws, I have just been searching on Aliexpress on BST site and found 2020 screws approx £30 extra each. So is it worth getting 2020 over 1610's? I'm using Nema 23 3Nm and hoping these will be adequate to move a gantry weighing 32kg and the Z axis is approx 18kg not including the spindle. I'm happy to pay the extra for 2020's if they will be the safer option.

Thanks

Rob

Personally, I would pay the extra for 2020 because it gives you more scope to gear the motors and lower the screw speed which lowers the chance of whip.

[333-CNC]

Thanks fro the advice, I have been in contact with Fred from BST and the quote provided for the 2020 with both ends machined to accept bk15 seems reasonable, so I shall be ordering soon as possible.

Thanks again.