Backlash on machines

AOMT

Back LashLecturer – D.Evans

Aims of Session

To analyse and evaluate the materials used for most manual machinery axial movement (lead-screws and nut)

To identify and describe what backlash is in a machine tool lead-screw context.

Acme Thread Profile

Hardened and ground Steel

(14 ½ degrees)

Acme Lead-screw ……..

Provides themovement in three axes as well asthe screw cutting drive on most lathes.

What do the three shafts do?

Early model – Later model

Materials used…………… and why?

Half/Split Nuts

Provides the axialmovement in allthree directionson milling machines

£125 for Z axis and £125 for y axis lead-screw and nut£150 for X axis lead-screw and nutAvailable from a well known internetbased auction site

Efficiency?

http://www.youtube.com/watch?v=5dGtmUhKzg0&feature=related – mc rebuild

Strengths and weaknesses of Acme

Backlash pic next slide

Backlash (wear)

Backlash

Just past zero doh!!

CW

Positioning with backlash

https://www.youtube.com/watch?v=NqF_ETWvBCA&feature=player_detailpage - backlash

How do we work with Backlash ?

Recap

• Hardened and ground steel shaft with powerful driving thread - cost• Brass/Bronze nut – reason and cost• Strength/Weakness• Product = Backlash

With all rotating shafts !!

Any Questions ?

Aims of Session Met?

To analyse and evaluate the materials used for most manual machinery axial movement (lead-screws and nut)?

To identify and describe what backlash is in a machine tool lead-screw context?

AOMT

Thank-youLecturer – D.Evans