Messages

11

General Mach Discussion / Re: Help with electrical interference

« on: May 20, 2012, 04:20:34 AM »

Thanks Tweakie,
This was something I was also thinking about doing but wanted to hear from others first. So I am clear, we are talking about a normal Ceramic Cap (not electrolytic)??

Appreciate your good advice.

Stuart

OK. Shall give this a try in the morning when I can get a couple of caps.

Thanks.

Stuart
Hi Stuart,

Yes, the miniature ceramic disc caps are OK (don't forget to sleeve the leads, if necessary, so they cannot short to each other)

Tweakie.

12

General Mach Discussion / Re: Help with electrical interference

« on: May 20, 2012, 04:18:21 AM »

Have you got the screen connected at one end only and all screens to the same point
Hood

Hi Hood,
At each Microswitch I have taken the Screen to a lug and connected it to the Aluminium frame of the machine. At the other end of the cables (where they come together at the breakout board) I have joined them all as a common connection and it is connected to the table ground (which is also connected to the supply earth).

Stuart

13

General Mach Discussion / Re: Help with electrical interference

« on: May 20, 2012, 02:45:51 AM »

Thanks Tweakie,
This was something I was also thinking about doing but wanted to hear from others first. So I am clear, we are talking about a normal Ceramic Cap (not electrolytic)??

Appreciate your good advice.

Stuart

14

General Mach Discussion / Re: Help with electrical interference

« on: May 20, 2012, 01:14:26 AM »

E stop wire is some distance away but the limit switch wiring runs in the same cable chain as the wiring from the VFD to the spindle. I had been advised this was OK if I used screened cable all around, but I am starting to think otherwise. Was just looking to see if there were any other possible causes or remedies before ripping the wiring out.

15

General Mach Discussion / Help with electrical interference

« on: May 19, 2012, 11:58:07 PM »

Good evening all,
I have just completed building a 1300mm X 900mm router table with rack and pinion gantry drive design. I am very happy with the operation of the table and have had great success with the accuracy of it but I am now faced with this frustrating problem.

Subsequent to the initial design I have connected 5 limit/ home switches all wired in series and connected to pin 10 on the breakout board. Also a dedicated Emergency stop switch to pin 12 on the breakout board. Both work exactly as expected, however as soon as I start the spindle motor, it triggers a limit switch activation and the machine stops. If I reset it, the machine will run for about another 10 seconds or so before doing the same. On the diagnostic page, all five limit switch LED's illuminate for about half a second each time the interference occurs. The spindle is a Chinese HY brand 1.5 kw unit and it appears to operate without any issues very smoothly. The spindle is totally electrically isolated from the breakout board. I.e. control is only achieved through the operation of the touch panel on the front of the VFD.

This is what I have tried so far to overcome the problem:

All wiring to the stepper motors, limit switches and spindle motor has been replaced with shielded wire and all shielding taken to a common ground.
The spindle carrier frequency has been changed throughout its entire range with no change.
The config debounce has been set to a figure of up to 2000 ms with no change.

Short of pulling what little hair I have left out, I am stumped with how to fix this.

Any help appreciated

Stuart

16

G-Code, CAD, and CAM discussions / Re: Need help adding post file to Mastercam

« on: May 09, 2012, 10:56:18 PM »

Hi Peter,
I am having the same problems as you have had with Mastercam 5 and Mach 3. Could you please let me know where I can download the latest Post processor and whether you found it to be successful or not.

Thanks,

Stuart

17

General Mach Discussion / Re: Steppers are too slow

« on: December 09, 2011, 07:13:50 AM »

Sargon,

Thanks for your explanation. I think I need to do a bit more reading on the matter and refresh my knowledge.

Your post above makes multiple references to measuring power. I have not tried to measure the power in the circuit. It was the current I was trying to measure.

Also your formula is used for calculating the power within a circuit, and to obtain this we multiply the voltage by the current and then multiply it by the Cosine of the phase shift angle. This I understand, but if you are saying my current reading is not accurate, and we don't know the power figure, how can you use this formula? You are missing 2 parts of the equation.

I qualified as an "A" grade electrician in Australia 32 years ago (but have been out of the game for about 20 years) and recall situations where the current wave versus voltage wave were out of phase. We used to come across it if we were fitting a lot of fluorescent lights, where the inductive ballasts in the lights would cause the current wave to lag and we would correct this by fitting capacitors to every 5th light. We referred to the cos(e) part of your equation above as "Power Factor" and had a legal requirement to get this figure above 0.8. (Otherwise the power authorities power meters would not read accurately). The major difference with this situation was however, that we were working with AC circuits on the lights and the output from the PS should be a very stable DC. I was not aware that any of this phase shifting could occur in DC circuits.

Most definitely I can understand your theory if you were trying to measure the power in the motor coils but It's going to take me a bit of getting my grey haired head around the PS side of things.

Thanks again for your explanation.

Guess I'll try to find a good book on the topic and refresh a little on the theory.

Stuart

18

General Mach Discussion / Re: Steppers are too slow

« on: December 08, 2011, 03:06:22 PM »

Gents,

Hope I haven't started a forum war here, but I still have a bit of a problem understanding why a good quality Digital multimeter connected in line with the PS output to the drivers fails to read an accurate current flow compared to a hall effect clamp meter. When i look at the chopwave graph Ian posted at post 44, the current trace has fairly minimal peaks and troughs associated with the switch activity. I read this as the current flow through the coil and not necessarily a waveform of the driver input supply. I would have expected the circuitry within the driver would have provided some smoothing to the input current. Additionally with 4 drivers all connected together I would have expected some further smoothing of this wave form as one goes high and the other goes low.

Is my thinking correct here??

Stuart

19

General Mach Discussion / Re: Steppers are too slow

« on: December 06, 2011, 04:20:11 AM »

Hi Stein,
When you say you had the same problems as I have had, are you referring to the port being U/S or the slow stepper motor issue? (Or both)

Stuart

20

General Mach Discussion / Re: Steppers are too slow

« on: December 05, 2011, 06:23:35 AM »

Thanks Rich,
I can measure that, but I think a few of my other workshop toys give the power meter a bit of a tickle in the ribs more so than this at the moment.

But I'll take your comment on board, thanks.

Stuart