Messages

7461

General Mach Discussion / Re: How to calibrate unit - i.e. ensure that x0 and y0 are always the same

« on: August 10, 2010, 01:13:06 PM »

I don't use sensors on my CNC but I think that the fully enclosed, short distance type would be better ( similar to this http://cgi.ebay.co.uk/CONTRINEX-DW-AD-703-M8-3MM-INDUCTIVE-PROX-SENSOR-NEW-/260465431469?cmd=ViewItem&pt=UK_BOI_Industrial_Automation_Control_ET&hash=item3ca4f313ad )
There are many manufacturers of this type and you should be able to find a couple at a good price.

If it were me I would investigate your problem with skipped steps and resolve that issue as a priority. My machine (although small in comparison) regularly runs GCode programs in excess of 340,000 lines for 8 hours at a time with no lost steps or loss of position and I think this is true for all regular Mach users. The machine size is not really relevant as long as the axis are free without binding or tight spots etc.

Tweakie.

7462

General Mach Discussion / Re: How to calibrate unit - i.e. ensure that x0 and y0 are always the same

« on: August 10, 2010, 11:54:57 AM »

I was thinking of purposely sending the unit past 0,0 something like -1, -1 (the machine will skip a little) and then reset the x,y DRO to 0,0.

I don't think this is to be recommended unless the current to your steppers is small enough to ensure that no damage could be caused by hitting the buffers (so to speak).
Surely a better way would be to fit home switches / sensors and use the built in Mach routines for homing.

I suppose I have to ask the question - Why are your axis losing position in the first place ?.

Tweakie.

7463

FAQs / Re: plug and play with old machine?

« on: August 10, 2010, 02:33:34 AM »

Hi Tom,

why do you think there are only 4 inputs? There are six pins connected to the circuit board is that not 6 inputs?

The standard PC parallel port consists of inputs and outputs (1-9, 14, 16 & 17 are all output pins 10-13 &15 are all input pins and 18-25 are ground).
So by my reckoning you have pins 1,14,16,17 to control the steppers and pin 11 as a feedback / interlock / etsop / whatever - pin 25 is ground.

The active high / low relates to the circuit design of the driver board and can be found by trial and error if it is not previously known.

Here is a link to a typical driver PCB with some setting up instructions which you might find useful. http://www.cooperman.talktalk.net/MDfly.zip

Tweakie.

7464

FAQs / Re: plug and play with old machine?

« on: August 09, 2010, 02:05:44 AM »

If what is says on the edge of your driver card "3 x 2A 36V" is correct then your existing PSU etc. should be just fine.

As mentioned earlier mach requires two outputs for each axis and your driver seems to only have 4 inputs for all 3 axis (not sure how this works, unless it only moves any one axis at a time).

Tweakie.

7465

Show"N"Tell ( Your Machines) / Re: Dixie Duke - A machine in the making.

« on: August 09, 2010, 01:58:15 AM »

Great work Sam - at this rate it will be making chips in two weeks   

Tweakie.

7466

FAQs / Re: plug and play with old machine?

« on: August 07, 2010, 12:37:29 PM »

Hi Tom,

I have done a bit of searching on this but no luck. HME Technology are very cagey with their information but it appears to be a Rishton CNC designed machine. There is more than a good chance that your control board is for Serial operation using the (2) setup of pins 14,16, 17 and a computer installed driver.

If you are unable to get the necessary info from HME (bearing in mind that all suppliers to schools and the educational market are very guarded with their info and software) then the best bet would be to remove the board and fit another cheap 3 axis driver such as this one http://cgi.ebay.co.uk/3-AXIS-TB6560-CNC-DRIVER-BOARD-4-STEPPER-MOTOR-ROUTER-/110570269975?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item19be806d17
There are plenty of these type of boards available on ebay and, in my opinion, they represent an economic solution.

Hope this helps,

Tweakie.

7467

FAQs / Re: plug and play with old machine?

« on: August 07, 2010, 11:32:48 AM »

Tom,

From that information I would think this is not designed to connect to the computers parallel port at all but to a, perhaps PCI, driver card fitted in the controlling PC.

Tweakie.

7468

FAQs / Re: plug and play with old machine?

« on: August 07, 2010, 08:47:35 AM »

Tom,

Just one point that is very important - do not disconnect any of the motors whilst the board is powered up.

Tweakie.

7469

FAQs / Re: plug and play with old machine?

« on: August 07, 2010, 08:11:38 AM »

OK Tom, excellent photos. This looks like it will be an easy one, well at least not very complicated.

A common convention (but there is no defined standard) is;
LPT Port Pin      2   X Step
                       3   X Direction
                       4   Y Step
                       5   Y Direction
                       6   Z Step
                       7   Z Direction

With pins 18-25 as GND or 0 Volts.

This is the very basic and initial connections required to move the motors but there may be an enable signal (e-stop) to be found also.
If it was me, I would connect the cable to your computers printer port and try configuring Mach with the above pin allocations (2 to 7) as trial and error and see what happens. Once you get axis movement then you need to set the steps per and velocity / acceleration etc. for each axis and get the directions right. (the Mach manual and videos will give you more details of this).

The next step is to find the limit / homing switch, e-stop and spindle control pins (2-9, 1[seldom used], 14, 16 & 17 are all output pins driving the machine functions) (10-13 &15 are all input pins connected to e-stop, limits, safety interlocks etc.) (18-25 are ground)

Good luck with the experiments.

Tweakie.

7470

FAQs / Re: plug and play with old machine?

« on: August 07, 2010, 06:19:14 AM »

Tom,

I have never seen one of these machines before and their website doesn't give much away either but if the machine is operated by 'step and direction' signals generated by the PC then there is a good chance that it can be used with Mach without too much hassle.

If,on the other hand, the stepper motor pulses are generated by the machines internal controller then there may be quite a lot of work to do.

A photo of the machines internal electronics might help.

Tweakie.