Member postings for Tony Ray

Hi, Not sure I follow you exactly. I use Draftsight, if you have the latest release please ensure you have it in classic view the toggle is at the top somewhere on the left as I will attempt to explain using the classic view. I think you are asking what the grid setting is ? At the bottom right click on the grid and a window will open showing the setting. You can check it by drawing a line of a known grid spacing with snap on then measuring it with dimension. To draw a straight line turn on Otho at the bottom near the Grid button. Without ortho using the line command the line will be straight but can be at any angle. To draw a line of fixed length just click on the desired start point then enter the length you want. So if Instarted my line at 0,0 with ortho on I start my line going vertical and enter 3 and the line will be that length. Another way is to use relative coordinates With the @ sign so from zero you could enter @ 0,3 and that will give you a length of 3 along the X axis. If this does not help post a dimensioned sketch and I'll draw it from that. Have you downloaded the tips & trick e book ? That s quite helpful

I have a vertical slide on my Stent T&C grinder but it doesn't do that. The Model Engineers Workshop Manual, George Thomas describes retaining gibs (albeit horizontal) from lateral movement with a pin as I recall to improove the action of the slide.

Firstly I nothing about model boiler testing, I do know about autoclaves but let me ask this question

I buy a Polly kit with boiler today, it comes with a boiler number and a test certificate ? I get it fully assembled and working and get all safety checks etc etc done. I take it to an open day and the boiler lets go due to a mufacturing defect and someone gets seriously injured. If what you say aboput Polly's lack of records is true, rather than them just not wanting to hep you, I would not want to be the H&S manager at Polly when the HSE turn up asking to see;

Calibration records for testing equipment

Training records for the person dong the testing

Records of Tests vs boiler numbers & dates for the Boilers they make

FWIW I am always suspicious of anything that has been repainted. If the machine is good a lick of paint won't make a jot of difference imho.

Airlink transformers will custom wind you a toroidal, replied to my query within a day or so

(500va 440v to 1x110v + 1x24v). £92.50 + vat + delivery suprisingly affordable given that an off-the-shelf 550Va laminated with only on secondary is £50 +

they do 42 +42 V of the shelf which is I would suggest near enough,given that the input side will fluctuate in voltage anyhow

**LINK**

Oh I envy you ! Look at Abom79 channel on YouTube he has a K&T he is a full time machinist with a homeworkshop too and has restored his. K&T is serous stuff and makes Bridgeport stuff ( nothing wrong with BP) look weedy. One thought, do you have 3 phase or enough welly to run it off an inverter ? do check that the motor is dual voltage. I think the mill is mostly hydraulically controlled so there should not be several power feed motors to deal with.

David,

Can't answer the reverse question. 83mm on an X2 with a boring head ? I'm not sure I would want to try that on my SX3. A rotary table would be better. I take it that you can't turn it, is that due to lack of facilities or the part ? I have seen folks mount the parts on a mandrel/ arbour rotate tihe part in the mill and mount the tool in the milling vice slowest useable rpm is the key and you are working upside down but a simple flange should not be too difficult.

Keith,

Plenty of suppliers of milling chucks but yet to see anything you could use on your Boxford. You could be up and running with an ER set quite quickly, if you could find a suitable TG one is not going to be cheap, or you could try making one for your TG,s. I see that collet nuts are available and that's possibly the harder part to make. Looks like the gripping range of each ER is wider so fewer collets needed - less to store. What do TG 100 sell for on eg flea bay ? I'll have Seig SX3 R8 coming up for sale soon if that's of any interest, I'm in the South. R8 is a good choice, I don't use my ER set in the mill, too fiddle and require much more holding torque vs R8.

Yes the bed profile is the same on chippie and bantam ( but not a Bantam mk111 which is the same as a Harrison M250)

Trevor,

New reg fitted and I'm a happy man - thank you and as you predicted the IRF3205 is fine. I will see how I can retro fit the protection diode.

I have learned a lot; not to jump straight to suspecting the output device and to check the simple things like voltages first.

I have had a quickl look at current limiting circuits but nothing stands out , any suggestions would be welcome.

Tony

Gents,

I checked the MOSFET and it is OK so pulled the 7812 with the aid of the bit I described earlier

and soldered it to a bit of stripboard for testing. I put a led with resistor across it to pull a bit of current and the out put was around 2.9V so my conclusion is that the reg is fried. Before removal I tried looking for the source of heat, definitely not the 555 probaly the 7812 but the thing was only barely above ambient. I should have the new device in a couple of days & will put on in. I suppose I could power up the 555 with an external supply but its probably not worth the effort and I can change it if I need to. Anyway I'll report back whn I have some news

Murray,

Thanks for the explanation on the track drops I'll keep it in mind for the future.

Tony

Gents

I'll recheck for the source of heat and probably remove the 7812 as its a little easier to access apart from the retaining screw on the heatsink - I had to shorten a 25mm hex bit and use a right angle bit driver when I changed the mosfet.

No great loss if I need to destroy the 555, at 10 for £1.70 they really are cheap as chips (sorry).

Murray please can you explain how to do this ?

"Or see where the current is flowing using a DVM to follow the track drops."

As one measures current in series ( and can't do that unless one lifts a device leg) do you mean measure the voltage drop various points to referenced to ground ?

Good news on the remaining board - it is also OK again in must have been the C/O switch.

Thanks for the info re RDss.

Tony

Thanks for the suggestions on devices. After losing the first board I fitted an IRF3205 Vdss 55V RDss(on) 8mR this did not fix it. As I understand it this device will generate more heat as the RDss is higher ? Anyway the output of the 7812 is 2.5 V and I can detect some heat coming off the board from somewhere with no motor connected. Does that mean the reg is dead or is something dragging the voltage down ? The PSU is sitting at its usual 22V or so volts. I checked the mosfet for a d-s short and it's ok. I didn't measure the 555 as the reg volts are out. I can put a scope on it if needed; I picked up an analogue 35meg dual trace Hitachi for next to nothing and can measure things even if I don't understand what the trace is telling me. I will try to find board 2 and measure that.

Confession time,

No the 10A fuses have never blown

I checked the Schottky - OK

And there was no short on Q1 D to S

So I checked the output of the 7812 OK at 12.1 V and concluded that with all the other diodes ok unless the 555 was dead there couldn't be much wrong so I bypassed the C/O switch and ... It works The C/O switch is dead.

I definitely blew one up as I shorted the output, but perhaps the second one is ok and the switch fault was intermittent.

The motor is a Parvalux PG4568 rated at 1A continuous 14W, 21W 15 min , 17.5W 1hr. It barely gets warm when powerfeeding

In terms of the basic design I take the point about no over current but I'm using a laptop PSU which itself has in built protection.

Now some questions

If I wanted to fix the dead one what device would you recommend to replace q1 ?

If I did want to change direction whilst power-feeding is it vital to ramp down the PWM before switching through zero?

Is there anything else that one could add easily to further improve it ? To me it does not look that different to the Inchanga design apart from the bipolar drivers.

At this point I'd like to thank you all for getting me back to a working powerfeed.

Trevor, et al

Herewith checked CCT -Thank you, The only change is the 1000uf to the output of the voltage reg. You were right pin 2 & 6 of IC1 are commoned - there must be a track under it that I can't see. I now don't think its a 3 layer board. Theres also a 1N4001 or similar which I think is meant to be for polarity protection but I can't find any track from the anode leading anywhere. I now have a better idea of how its meant to work too. I'll measure the dud boards as suggested and look up my motoers parameters and post them later.

Fleabay PWM controller cicuit diagram and components

Took me a while hopefully its correct sorry if I have broken every diagram convention inthe book ! Component details are in the second image.

Nick, if you look at the steps between 5c collets 1/64" seems the be the norm, with 5C collets you can go undersize with the item to clamp but should never force an oversize item into any collet as it ruins them. I find the clamping range useful on ER collets but object to the amount of clamping force needed, a ball bearing nut is supposed to help but I have yet to try one. Clamping force on 5c is much lower but you are limited in range. I suppose it depends on what you have and what comes your way. The closer or collet chuck has to be of high quality otherwise you won' t get the accuracy, if you buy a used 5c collet or a cheapie and it under performs it will be obvious against other known good collets you have, wheras if the chuck is out....

Gents, thanks for the comments

Trevor,

I have made a start on tracing out the fleabay design, its a little tricky as I think its on a 3 layer PCB but the component count is quite low.

If anyone fancies blowing one up for themselves

**LINK**

The output device is not that common but I did find a datasheet for it eventually

I'll keep working on it and hopefully post in a couple of days.

I'll also dig out the Parvalux info for my drive motor

Tony

Aw its gone awfully quiet, I was enjoying this !

general comments then some questions

General,

Yes do publish electronic from time to time, I find it interesting that this article has elicited so much debate whereas the 'wood butchery' does not.

If a comnon design could be a greed i'd like to see a group buy on PCB's

Questions

Firstly I can build circuits to a good standard but only have a basic knowlege of components & design - I can't be good at or have time for everything.

I have killed two 'bought a PWM speed controller on fleabay for £3.50, Its 555 driven FET with a schottky diod e and what look like a power diode for emf protection and but I'm reversing the polartity to the motor to allow reversing ( It goes through a zero position rotary switch) will that protection diode only work half the time i.e when the polarity is swtiched one way ?

If I buit the Inchanga design am I likley to blow that up too ?

My motor is 24v 1A brushed paravalux running @ 5000 is RPM but greared down and I'm running it at 24V as a powerfedd on my SX3 mill

Any help gratefully received

Tony

John,

I agree, is it because most widgets are now made on CNC machines?

A great halfway house would seem to be the electronic leadscrew - by electonically controlling the speed of the LS relative to the mandrel any pitch can be cut but AFAIK its not commerically available on new machines.

In a similar vein I wonder why the linear scales for DRO's aren't simply incorporated into the slideways rather than leaving the user to have to retro fit them (quite often inelegantly due to space contraints).

Tony