I Have Used Thk Rails For 10 Years On Ind Machs, Works Good.
I Am Working On My First Cnc Router. Here Is Wip Of First Design.
Design Is In Rhino 3d.any Help

Hay Can't Upload Pic. Of My Design. What Do I Have To Do? I Don't Know Heeeelp

Click Go Advanced > Manage Attachments, select the file using browse and upload it. Wait until the upload is finished and then close the attachments window.
Click Submit Reply.

Jason

Thanks Jason

looks to me like you headed in the right direction, are you planning on having screws on both sides of the x axis?

Yes But Am Still Trying To Size Them Correctly. Any Help

Yes But Am Still Trying To Size Them Correctly. Any Help? Iam Only Going To Be Cutting Wood.

well the size of the screws is goint to depend on how long they are and how fast your going to turn them, the longer the thicker, and the faster the thicker... what you will be fighting is that the spinning screw will reach a point were it will begin to deform, ie "whip" while spinning, and going thicker is the fix... the down side is that thicker is more $$$$$ how you mount them will also play an important part, a simple bearing on each end will not be as good as a pair of bearings on each end...

Joez, Welcome to the Zone.

I went with dual leadscrews on the X of my last machine. It really helped with gantry racking (the left to right twisting). It worked very well for me. I used two motors, but many have a belt between the two with a single motor in the center.

As far as keeping a leadscrew from whipping, a few things I have learned. Keep the pitch low. If you move a farther distance with each revolution, you can keep the rpms down and it won’t whip as much. Conversely you will gain speed with a given rpm, and I keep repeating to people that speed is fun and also needed for routing certain types of media. A fat leadscrew won’t help that much. 1/2" is plenty. A larger diameter will be harder to spin and you will reduce torque. Much better to spend time on mounting the screw to the machine. Use a double bearing on the motor side and a single on the free side. The double bearings should be clamped together against a thrust plate. The free end should be tightened to keep the screw in tension. This will keep the screw taught, reducing whip and backlash, while saving the bushings in your motors.

Look at commercial machines with ballscrews. Their lead pitch is low, their diameter is small(er), and they are correctly mounted.

What kind of linear bearings did you draw? Are those of your own design?

Steve

linear bearings are THK (HSR15)