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View Full Version : NEW MEMBER: Hi from a (very) hot Spain



gerrymoore
03-08-2009, 05:10 PM
Hi all...... yet another newbie with lots of questions. Just in process of building my first CNC machine.....will post on appropriate forum(s) soon :-))

gerrymoore
03-08-2009, 06:52 PM
OK....after a good few weeks trying to get as much info as possible and watching lots of Utube videos.........

I've got my machine...roughly 450mm x 400mm working area..... up and running. Got nema type 23 motors and controller off EBAY (from China) and linear bearings, rails etc from motion control in Bournmouth ...living here in Spain it's very difficult to source anything at all (except the steel) and made even worse by my poor Spanish...but I've only lived here 8 years :-))

Actually dragged it (the machine) ....with the help of my long-suffering wife.......up from my underbuild (very small workshop really) last week and plugged it into the PC.

Using Mach 3 I stuck a pencil on the Z axis where the router will eventually go and asked it to draw my name - lazycam conversion of the word GERRY done in illustrator.

Eureka...it actually worked but wrote it backwards and mirrored :-(( After much head scratching I eventually sussed out I had the x and y axis reversed...in the end it wrote GERRY and, sad as it may seem, I was over the moon!!

Now 1st question - this has proably been asked before many times but it's just too hot here to search!!

For economy reasons, I'm using ordinary threaded rod with ordinary nuts..I know all about backlash but I'm broke!! This means that everything runs a bit slow as it takes approx 17 turns for a 25mm movement.

I have measured it at 'rapid' feed rate to be around 20 inches per minute - not too bad....... but of course when it's 'cutting' (drawing) it's much slower.....also, if I try to speed up the steppers they just seem to stall - don't know why - hope someone can explain......

Is there anything in the Gcode that I can change to speed the cutting up a bit....remember 3 months ago I'd never heard of Gcode!!

I have a plasma cutter and would like to make a machine for that but the present one, although slow, would be OK for a wood router, but much too slow for my plasma.

Anything simple I'm doing wrong??

HiltonSteve
03-08-2009, 07:11 PM
Ok, when your motors stall it means from my experience that you are trying to run them too fast. If I take mine over 700rpm then I get the same problem. One solution for this (but not tried it) is more voltage, what voltage power supply are you using??

As for your feed rates, you should be able to run as fast as your rapid rate. So you say 20 inch's a min (why are you not working in mm??) is your rapid rate so if you put a feed rate in ie G01 X100 Y100 F500 (this is mm min) then this should give you feed rates similar to your rapid speeds.

If you want more speed then you could either drive the screw through a step down pulley system which will reduce your torque but increase your speed or put a larger pitch screw in.

Hope this helps...

irving2008
03-08-2009, 07:12 PM
...
For economy reasons, I'm using ordinary threaded rod with ordinary nuts..I know all about backlash but I'm broke!! This means that everything runs a bit slow as it takes approx 17 turns for a 25mm movement.

I have measured it at 'rapid' feed rate to be around 20 inches per minute - not too bad....... but of course when it's 'cutting' (drawing) it's much slower.....also, if I try to speed up the steppers they just seem to stall - don't know why - hope someone can explain......

Is there anything in the Gcode that I can change to speed the cutting up a bit....remember 3 months ago I'd never heard of Gcode!!
...

Anything simple I'm doing wrong??
Well done on getting something working...!

OK 17turns for 25mm = 1.5mm pitch threaded rod (M10?)

20ipm = 8.5mm/sec @1.5mm pitch = 5.7revs/sec which assuming 200step motors = 1133steps/sec. which shouldnt max the motor out but depends on drivers. You dont say what controller software but you should be able to increase it there.

The threaded rod/nut combo very high friction so most of your motor torque going into turning the rod not moving the load.

You may find that a brass or Delrin nut will give improvements.

A higher supply voltage (if the drivers can stand it) may give improvement.

What motors, and drivers and power supply voltage?

gerrymoore
04-08-2009, 08:56 AM
Thanks for the replies guys!!

First...I'm 58 and keep switching between metric and imperial - I tend to look at the tape measure and take the nearest one!! sorry :-((

Ok......... I'm using Nema 23 type motors from China - supposed to be 1.7nm models.

I'm using a generic driver board with 3 Toshiba TA8435 chips mounted on a large heatsink with two fans cooling it......I'm running in 1/8th step mode...could this be the problem?

Power supply is 27volt 13 amp switch mode type (Chinese).

Mach3 software. I have tried adjusting each motor axis but as soon as I try to get it a bit faster the motors stall....my knowledge of Mach3 is severely lacking:-((

I would like to use my old Toshiba laptop (normal printer port) so I don't have to drag the machine up three flights of stairs in this 100 degree heat but Mach3 doesn't support laptops - anyone out there using a laptop?? if so what (simple) software is available??

Oh...the threaded rod is not too bad friction wise but my 'precision' engineering is a bit rough so I don't think everything is perfectly aligned just yet...but I'm trying!!

The machine is currently in bits as my x axis was too 'wobbly' (technical word) as I tried to cheat and only use one pair of linear bearings....I am redesigning it now for two sets :-0

If this works there may be a picture.........nope thought not!

Anyone tell me how to upload an image??

I'll get back to work on it and advise any progress.....many years ago I built a mini excavator in my garage so I keep telling myself this CNC business should be easier!!!

thanks again............

Swarfing
04-08-2009, 09:19 AM
Gerry its not so much that Mach does not support laptops its just the ability to turn off all the power saving that come with laptops. I have EMC2 on a laptop and during my testing of my 5 axis Chinese board did not see anything you are experiencing. look at the bios on the lappy and see if you can switch it all off? or download the Ubuntu distro that EMC2 is wrapped up in and give that a try (remember for the motor setup look at the pictures that come with your board instructions for clues for set up rather than the verbal useless info in the text.

Swarfing
04-08-2009, 09:20 AM
As a thought it could be power saving on your PC that may be interrupting this?

gerrymoore
04-08-2009, 10:17 AM
cheers Poz??

I've not heard of EMC2 but I'll certainly have a look in the laptop bios and also switch off all I can on the PC ..........

Swarfing
04-08-2009, 10:24 AM
The nice thing about EMC2 is you can boot off the CD and try it to make sure the distro works on your machine first before flattening it. Not everything works in this mode. Hers the link and look on the left side for the distro download which you burn to CD.....http://www.linuxcnc.org/

gerrymoore
04-08-2009, 11:42 AM
cheers for the link....need to get my head around it though..Ubunto ?? wot the heck is that!!...I was hoping things would get easier :-))

irving2008
04-08-2009, 01:58 PM
cheers for the link....need to get my head around it though..Ubunto ?? wot the heck is that!!...I was hoping things would get easier :-))
Ubuntu... its the Zulu word for Karma or some such...

Its really easy to install, just boot from the CD (assuming you have enough RAM) and have a play... if you like it, install it - you can even install it dual-boot so your PC can be Windows when you want it to be and Linux for CNC'ing and you can share data between them. This means you can use Windows apps for creating drawings and Linux apps for processing the output files and cutting...

Like all things, do some reading first...