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c.n.c .

using mach 3 & cut 2d

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CNC milling with MACH3  - Part 5

CNC milling with MACH3 - Part 5

Profile milling using curves

Dennis05/10/2010 12:15:31
12 forum posts
1 photos
hi . Just converted a small bench mill to c.n.c. arc euro trade step motors every thing is up and running but having a problem with cutting a wheel spokes ,when i run the program i  think am losing steps in the z movement when the program moves from one spoke to the next by about two m/m.The motors are 36nm 1amp.The calibration and the setting up of step per unit of the z movement of mach 3 works ok.
John Stevenson05/10/2010 12:49:28
5068 forum posts
3 photos
Could be that the motors are not powerful enough for the Z axis with the weight of the head.
Tell us more about your machine.
John S.
David Armstrong05/10/2010 17:38:18
4 forum posts
it does sound as John rightly suggests that it could be the z axis motor not being powerful enough for the job , give us details of the stepper motors used , and the machine you have converted , or even a photo will help , and no doubt we will be able to help further and solve your problem.
also does this 2mm multiply each time ? i.e it becomes additive to the measurment before , or is it consistant on each movement of only 2mm , if so this would indicate
more of a backlash or axis screw / nut movement
also give details of your power supply ? , it could be you are just not supplying enough voltage or current specificaly to the z axis motor , as this is usualy the most demanding axis , having to lift the weight of the head etc .
Dennis05/10/2010 19:00:57
12 forum posts
1 photos
Hi, john, Dave,    The machine is one i built from a old emco lathe that was given to me by a frend,with the machine is bolted to base in a up right positsion using the head stock as the milling head.The  2m/m movement is lost each time,there is very little back lash in the screw.  The power supply is 24 volt 3.75 amp .may you are right about the motor ,can i suppy more amps to it its a 36nm spec 1amp .                                                                                                  
Andrew Johnston05/10/2010 19:15:54
4936 forum posts
560 photos
Errrr, I think the specification might be 36 Ncm, not 36 nm; quite a difference. Two orders of magnitude in fact. For reference the stepper motor that drives the Z-axis on my CNC mill is  1200 oz-in, about 850 Ncm.
Does the z-axis lose motion in one direction only or in both directions? For example if you ask the head to move down in successive 5mm steps, does it work correctly? Conversely, if you ask the head to move up in successive 5mm steps, does it work correctly? If it misses steps in both directions it may be due to friction, or stiction, in the works. If it works correctly in the down direction, but not the plus, then I would agree with John S that the stepper motor may not have enough ooomph to lift the head.

Edited By Andrew Johnston on 05/10/2010 19:16:35

Edited By Andrew Johnston on 05/10/2010 19:17:05

Dennis05/10/2010 19:48:44
12 forum posts
1 photos
hi   Andrew the head works correctly up 40m/m and down 40m/m i have not tried anti clockwise direction.  The machine cuts fine up to .5m/m of soft metal can be removed at a pass.                                                                                                                                                   Thanks all for yor help.                                                                                                                       Dennis
Dennis10/11/2010 10:24:44
12 forum posts
1 photos
hi   All just a word to tell you i found out what my problem was it was command in the G code,in my 2cut cam programe .G01 Z .5 F 18.0 the feed is too slow for my motor,and feed screw.

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