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16th December 2010, 07:59 AM #1Intermediate Member
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Need Advice Sydney / Outer west area
Hi I'm new to the forum and I'm about to start building a router. What I need is someone in the Sydney / Outer west area that is willing for me to come and talk to them about what I'm planning to build. I live at Wallerawang near Lithgow in the Blue Mountains, I can come down any weekend or I could take a "sickie" and come during the week.
Thanks in advance!
Ken
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16th December 2010 07:59 AM # ADSGoogle Adsense Advertisement
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17th December 2010, 12:55 AM #2SENIOR MEMBER
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I'm South West Sydney at Mount Annan, NSW but I'll be busy till after new years, your welcome to come then, I am currently building my 2nd machine here
But If you had any specific questions this forum is more than helpful
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17th December 2010, 01:03 AM #3
first post , welcome to ubeate , im a newbie in cnc as well , collecting bits every week now , starting with my z axis , 1200 long on 20mm rails , 16mm ballscrew ,plan on having a 2.2k water cooled spindle with z axis mounted radiators , still deciding on the size of my 5axis , 1200x1200x600 or a 2400x1200x600 , and what its made from , 200x100 ,10mm steel C section would be nice and heavy , aluminium costs too much , and im good at carbon fibre construction ( easier and cheaper than aluminium (already set up for it )) looks like CF will be the go , im in Darwin so please share info here ,
some things ive found out is watch out for the big steppers , to get the best out of them you will have to use 110v dc or 160v dc and the stepper drivers and power supply's are hard to come by and expensive over 80v
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20th December 2010, 12:24 AM #4Intermediate Member
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Hi Chris,
I appreciate the offer and will arrange to come down in the new year. I've spent all weekend reading the forum and the bug has bitten harder. What are your thoughts on the tron+ cnc router, I've redrawn the plans so it will cut a full sheet of balsa now.
regards,
Ken
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20th December 2010, 01:42 AM #5SENIOR MEMBER
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CNC Frse, Portalfrse, Bauanleitung, DIY Router, Frser, Modellbau Frse, Bauplan, CNC Frsen
The frame looks solid, I'm not sure about gluing the metal together as I have never done it before.
Have you thought about upgrading those linear slides to Ballbearing Supported Linear Rails? and Acme Leadscrew to Ballscrew?
Mostly because both are reasonably priced and easily avaliable out of china these days, they are also an upgrade from the stock linear rails and screws.
Chai on ebay is a popular choice.
http://stores.ebay.com.au/linearmotionbearings
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20th December 2010, 11:09 PM #6Intermediate Member
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I plan to tig the frame together, not to keen on the glue.
I have been looking at the ballscrews and will go that way, just have to change the plans and redesign a couple of bearing mounts.
The Tron uses a stepper motors on both X axis with pulleys and timing belt.Is there any benefits of have the two x axis connected by the belt.
If there isn't any benefits I will do away with the pulleys and belt so I can use a shorter ballscrew.
Ken
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20th December 2010, 11:30 PM #7SENIOR MEMBER
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21st December 2010, 02:38 AM #8
With changing from acme threads to ball-screws , the travel per revolution will be a lot higher , the machine might end up 5x faster with 5x less resolution and 5x less power , look at the pitch difference between the two and do some maths ,
what size are you making , the under side brace with single ball-screw in the centre looks like the go with smaller sizes , saves on one ball screw and the problems running 2 motors on the one stage and having them get out of step from each other ( the belt between the 2 ? )
some more maths
1N.m = 141.612 oz-inch
Max Voltage = sqrt ind x 32
Capacitor size when using switch mode supply's =(80,000 * Amps ) / Volts
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21st December 2010, 03:43 AM #9GOLD MEMBER
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I have run a twin X axis ballscrew machine, 1200 long screws, for two years and have never noticed the X axis out of sync. You do not need to connect the screws with a belt as Mach3 lets you slave the second ballscrew.
You actually want more speed and less torque if you are running steppers. Steppers have max torque at stand still and the torque curve drops of quickly as soon as they rotate. I work on around 300 to 400 RPM as a safety for the stepper stall torque on a big machine so you can see you need to increase the pitch of the screw to achieve speed.
Yes you drop resolution but the difference is negligable and probably still better than your machine can deliver mechanically.
To do some maths on this
Resolution
200 step per rev for a stepper
10 microsteps for say a gecko drive
So 2,000 microsteps per rev.
5mm pitch ballscrew so 2,000 divide by 5 = 400 steps per mm or 0.0025mm resolution.
Double that with a 2 to 1 pulley to get speed and you have a resolution of 0.005.
Speed difference
Speed at 400RPM on a 5mm pitch screw is 2m/min
Speed at 400 RPM on a 5mm pitch screw with 2 to 1 pulleys is 4m/min.
Mechanically a rolled ballscrew will be lucky to deliver 0.01mm accuracy so even with the pulleys you theoretically have a safety margin of 2. Well worth the percieved loss of resolution for the speed advantage.
The big advantage of twin screw over a single central screw is that you negate racking of the gantry.
I have tried to simplify this as there are other factors that come into play so I hope this helps.Cheers,
Rod
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23rd December 2010, 10:56 PM #10Intermediate Member
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I busy redrawing my table to take Ballbearing Supported Linear Rails and Ballscrews. What would be the best size for the ballsrews, the x axis is 1520mm long.
For the linear rails I'm going for 20mm shaft.
Wishing you all a merry Christmas,
Ken
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24th December 2010, 01:06 AM #11
what do you plan on cutting with your cnc ,
using an engraver to engrave pc boards and cut out balsa wood parts for RC plane's will need a lot less force from the ball screw than sticking a milling bit into solid aluminium and expecting a good feed rate from it , 'at 1520 it will also have to support its weight over that distance , i would say 16mm but since i have not made one yet , take that with a pinch of salt
Im like you just starting to build my first machine , that i want to machine moulds out of solid aluminium ( for my Carbon fibre Violins ) , its for personal use so feed times dont really matter , im looking at the 1200oz/inch "34size" steppers to give it a bit of grunt ,as these motors run at the max voltage of the readily available stepper drivers and noticed the gearhead boxes are quite cheep in that size ( ebay ) most people must have the size 23 or 42's and out bid each other
have you down loaded the software yet , its free to look at , have a good look it and read the guide http://www.machsupport.com/docs/Mach...all_Config.pdf
the wiring up will involve playing with 240v mains power , and using several diffident voltages , do you have a solid understanding of electronics ? or a friend that does ?,
dew to liability issues i think most people wont answer questions once the voltage gets over 50v
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25th December 2010, 09:35 PM #12
finding it had to understand how micro stepping can increase resolution ?reading the documentation of my stepper driver , the micro steps appear to just smooth out a square wave into a sine wave of each step , yes the 1/2 stepping will double resolution ( both coils on at the same time centring the motor at 1/2 way point ,1/2 the holding torque ) but the 16x micro steps looks like it will just smooth out the running of the motor , you cant stop the motor at 9/16th of a micro step ,it will stop at the next full step
is there something im missing ?
then if the pulses are running at full speed that the pc allows , a micro step system will slow it down by 16x ???
so my 16mm ballscrew with 5mm pitch and 200 steps per rev = 0.025 mm per step , 0.0125mm per step with 1/2stepping but at a cost of 1/2 the holding torque , looks like 2:1 gear heads might be the go , upto 5:1
cheers ken
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25th December 2010, 10:42 PM #13GOLD MEMBER
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Hi Ken,
You are understanding correctly - mechanically the best a stepper can hold is a half step. If you have a 1.8 degree stepper you can hold 400 points including the half steps. Of course a 0.9 degree stepper can hold double that.
Where the resolution is improved by microsteps is smoothing out the steps to reduce a jagged edge say like a magnified pixel image. It would also improve the maths havng more decimal places so the rounding off would be more reliable.
Don't get too hung up on resolution unless you really need it. I made a machine with 20mm pitch ballscrews and it produced excellent accuracy. It was capable of around 17m/min on 269oz motors and 24 volt power supply.Cheers,
Rod
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25th December 2010, 10:53 PM #14GOLD MEMBER
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You added to your original post.
A good driver will change to full steps at higher speeds. Gecko call it morphing and only use microsteps at lower speeds.
so my 16mm ballscrew with 5mm pitch and 200 steps per rev = 0.025 mm per step , 0.0125mm per step with 1/2stepping but at a cost of 1/2 the holding torque
Yeah but remember that microstepping is only active at slow speed which is also where a stepper has most torque - see my post above about stepper torque curves.
It evens out the torque and speed issues.
On a machine if you use full steps it jitters and you get effects like resonance mostly evident at lower speeds. You need microsteps for a smooth operating machine.
I suggest you don't get too hung up about it as in preactical operation it is not a huge issue. Play with you driver and stepper and see for yourself the effect of the different settings.Cheers,
Rod
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2nd January 2011, 11:46 PM #15Intermediate Member
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I've finished redrawing the router to take linear rails and ballscrews.
I will need to machine the flange on the Z axis ballnut to fit between the linear bearings (see photo).How much can I machine out of the flange before I would hit the workings of the ballnut. I may have to redraw the linear bearing housings.
regards, Ken
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