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Need advice
« on: February 09, 2007, 11:24:06 PM »
Hello:

Thanks to all that have put this site together and others who contribute to the forum.

I need some advise.

I have a Bridgeport Series I Mill that I bought from a state auction. I looked at the machine after I bought it and I thought man this guy is sick. I weighed the thought of trying to sell the machine on Ebay and other sites. I was able to power the machine up and discovered it was worse than I thought.

Then I discovered MACH3, man what a great product. This got me fired up and began reveiwing all my Home Shop Machinist issues about computers in the shop and discovered that maybe I do have a gem.

The system was an original  Heidenhain TNC 150 but was upgraded in the mid 90's to a Dynapath CNC. The ways all still have the jewelling and the machine feels tight. The table does not show any "student" abuse.

The machine has SEM DC brushed servo model MT30R4 - 58 motors 3.2 NM at 2500 max. rpm @ 145 VDC.  It has Heidenhain shaft mounted encoders (125 line count) with multiplier box (X 5) TTL output. The total resolution is what I figured to be (125 * 4 * 5 = 2500 counts).  The ball screws are 5mm pitch screws and the servos are coupled via cogged 2:1 belt drive. The servos are connected to Bosch legacy Z15 - 1 - 240A drives. The drives unfortunately require 0 - 10 VDC command for step and direction control.

I have also a 2.4 GHz motherboard and all the PC stuff for the controller.

I am wanting to use as much as possible of the original equipment to upgrade the machine and start making some chips (budget). I have read as many post from the MachSupport groups and the Yahoo groups, but need some good sound advise on other hardware
selection(s).

I am undecided on a breakout board selection, I have looked at all the usual selections. They seem to all be good products but what is the best value, has the most features and works the best with Mach3?

I plan on single phasing a small 2 H.P. VFD for spindle control. The machine has a variable speed head but would prefer software to control the spindle. So speed control is a important feature to have.

I would like to use my existing drives if all possible. I have looked at the Pixie product and hope that this will aid me with my existing "dumb" drives.

I would also like to use a MPG and different latched outputs (i.e. coolant, lube pump and VFD control).

What is some products that you guys have used and are fond of? What products do I need to stay away from. I want to make good, smart economical decisions. No do-overs or expensive mistakes.

Thanks in advance from everyones advise and I look forward to conversing with you all.

Todd

Offline Chip

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Re: Need advice
« Reply #1 on: February 10, 2007, 09:14:41 PM »
Hi, Todd

Ive used the Rutex drives on a water-jet cutter, herd good comments on the Pixie boards, just haven't try-ed them yet.

Thy would get you started, and give you time to get up to speed hear.

Off to a slow start on comments today.

Thanks, Chip

Offline poppabear

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Re: Need advice
« Reply #2 on: February 10, 2007, 10:24:46 PM »
Yeah, the Skyco boards are a good choice to convert the step and dir to analog.

If you want to do some "Production" CNC, I would pick the "Accu-Step" board from "CNC Building Blocks". (Ed Gilbert Engineering).
His boards are truely opto isolated and you can run Differential Encouder lines and you can run 5 V on the PC side and up to 24 v on the other side.

The best part is, each of the boards has a Encouder count "Homing function", that is super duper accurate, you can home to 1-2 Tenth's all day!!  You will have to have Encouders that put out a "Z" or Index signal to use it though.

His BB's are about 150 each and well worth the money. There is NO board as well made as his.  Since I also use PLC's in my stuff he makes a Kick-As* 24 bit, very high speed opto board as well, that is great for interfacing to stuff that needs higher voltages.

I think his Website is:  www.cncbuildingblocks.com

Scott
Commercial Mach3 & Mach 4, Design/Build/Retrofit CNC and Industrial machines.
http://www.ss-systems-llc.com/
Re: Need advice
« Reply #3 on: February 11, 2007, 02:41:21 PM »
I have a question to add about homing accuracy. I seem to be having some issues with my machine losing what appears to be position, not steps. on the z. after referencing home to z a few times the head on my machine seems to be about a few hundredths lower then when I started the day. Im using optical limit switches. and bob campbells breakout board. I am running a servo system with 1000 line encoders mounted on the ballscrews. not the motor shaft. what kind of accuracy should I expect to be getting out of this kind of settup as far as homing is concerned.

Offline Chip

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Re: Need advice
« Reply #4 on: February 11, 2007, 03:27:24 PM »
Hi, Todd

If your encoders have Index Puls output there are a couple of cards you can use to be right on every time.

If not then try slowing the "Speed %" down in Config, Homing/Limits, default is 20 % of max speed.

Increasing your "Kernel Speed", Config, Ports and Pins, Port Setup would give Mach more scan time to look at your OPTO Inputs.

Changing kernel speed requires restart of Mach and re-tune of motor tuning, I think.

Just some Thoughts, Chip