Originally Posted by LongRat  Personally I would go with the 0.2" pitch screws (I have these myself). You will then be revving the steppers less to get decent rapid speeds, which will reduce the chance of you losing steps. Operating in the lower rev range for a given traverse speed will place you in the higher torque regime of the steppers. The difference in resolution will most likely make no odds after you factor in all the other factors that come into play, especially on a hobby machine. If you ever lose any steps this will almost certainly be far more harmful to your results than any effect of reduced resolution of motion. |
Thanks LongRat,
The reason I am/was considering using the 2.5mm pitch ballscrew is because the other day I temporally fitted and wired up a 3Nm stepper motor to my X axis I was using the stock screw of 1.5mm pitch. The reason I did this is because I wanted a temporary power feed to help me find out what the machine was capable of where feeds and depths of cut where concerned. Also because I am very new to milling metal I wanted to use the machine manually for a while so I would have a better idea when it came to using it CNC’d.
Anyway getting to the point; with the set up I can get over 1000mm/min with lots of torque (unable to stop the table with my body weight) and up to 2100mm/min rapids. So it did not seem logical to go to such a high pitch ballscrew. The problem I have is because I am new to working with metals in general I have very little idea to what feed speeds I will be needing for general hobby use. I see things this way if I don’t need the speeds a 5mm pitch screw gave me then I would be better off going for extra cutting force which a 2.5mm screw would give me. If you or anybody else can advise me as to what would be the max feed speeds I would need I will be in a better position to calculate screw pitch, stepper motor rating and the like.
John
EDIT: Also the extra resolution would not hurt.