Wobblycogs CNC Mk2

[EddyCurrent]

Eddy Is that to stop the electric from falling out.

No that's what insulation is for also when I first read it was an 'inverter' I mounted it upside down

[Wobblycogs]

Cheers Eddy. Once the case is finished it will be dust tight (I think your case is the same design). I figure anyone inside the case should have a pretty damn good idea of what they are doing or they shouldn't be in there! The cover over the power supply is stop stupid accidents, it wouldn't stop a concerted effort to electrocute yourself.

I don't remember seeing any spec's for space around the rectifier although I'm guessing there will have been some. There's a good bit of space around it though and the aluminium it's bolted too will act as a great heat sink. I'll keep an eye on it but I don't envisage a problem. I don't like the way the bleed resistors are connected at the moment, it feels like a bodge although it works fine. I was asking about the power supply over on another forum and someone pointed me in the direction of active rectifiers, apparently they dissipate almost no power - I bet they cost a fortune though.

Something else I meant to ask, how are you connecting the various bits inside your cabinet to the various bits on the outside e.g. steppers, e-stop / limits etc. I'd like to be able to just unplug everything and take the case away but I'm concerned plugs and sockets will introduce noise.

[EddyCurrent]

I figure anyone inside the case should have a pretty damn good idea of what they are doing or they shouldn't be in there!

You can't use that as an excuse though.

I don't remember seeing any spec's for space around the rectifier although I'm guessing there will have been some.

I meant the VFD, sorry I never usually call them VFD's

Something else I meant to ask, how are you connecting the various bits inside your cabinet to the various bits on the outside e.g. steppers, e-stop / limits etc. I'd like to be able to just unplug everything and take the case away but I'm concerned plugs and sockets will introduce noise.

I'm going straight into terminals via compression glands in the bottom gland-plate, I can't see me wanting to move it much but I'm prepared to disconnect if I do. From my experience, albeit on much larger VFD's, the plugs & sockets did not like the high frequencies coupled with the current, although they were sized for the job the insulation used to break down over time.

[Washout]

That's a very nice box setup/layout.

Can I ask where you get your Din rail and connectors etc. from - I may have to look at something similar for my control box and also I have a 1970's horror of a lighting circuit junction box in my loft that needs replacing with something more elegant.

Regarding the VFD, the mounting orientation advice in the manual is likely because of the cooling fan, so its not blowing hot air over something else that might be susceptible to over heating (the number of times front to back and side to side cooling for servers and networking kit has been overlooked when buying kit for some data centres I have had to look into is scary).

[Wobblycogs]

Almost all the DIN mounted stuff comes from Chalon Components. Their prices are about as good as I found anywhere. The enclosure is particularly nice. I think the only major item I didn't get from them was the main door locking switch.

Now that I realise Eddy meant the VFD I can see why he's mentioned it. There's not 70mm below but there's not much air restriction. There will be a hole above to let hot air out and it's at the top of the case specifically so it doesn't heat anything else.

[Wobblycogs]

I've been working on the control case on and off for the last couple of months, I got a good few hours in today so I thought I'd share an update and a couple of pictures.

I got the soft start parts ordered, built and fitted. I'm really pleased with the out come. There's certainly no more tripping breakers / blowing fuses. I don't know if it's psychological but it actually sounds quieter when the main power is engaged. I've set the timer to two seconds to give the capacitors a chance to fully charge while the system is still being current limited. I also re-jigged the bleed resistors so that they dissipate a lot less power.

After that I set about making the top and bottom panel. My plan was to have all the connections coming out the bottom of the control case with just a couple of vents at the top. The whole case can then be mounted on a wall somewhere up out of the way. I spent an inordinate amount of time researching connectors and eventually settled on some from ebay (and AliExpress). I have to admit they weren't the cheapest connectors but they are a pleasure to work with and well over spec'ed.

As I (currently) have the VFD in the case I've gone for a 16A connection. I'm sure the total draw could be met by a 13A connector but the 16A stuff is just better suited to this sort of situation.

With all my focusing on the main connectors I completely forgot to leave space for the parallel port. Fortunately there was just enough space up the right hand side next to the fan. I actually think I would probably have put the connector there if I had planned it so all in all that's worked out well. The only slight bodge is that it's actually glued into place. The PMDX manual states that the metal outer case for the socket shouldn't be connected to the case (earth loop issues). I didn't have space for a plastic mounting plate so it was hot melt glue to the rescue.

[GEOFFREY]

That looks really neat and professional. Well done. G.

[Wobblycogs]

Thanks Geoffrey.

In answer to your question on Neils thread yes it was Lincoln with an l (I found the missing l on the floor). I was surprised how much I liked the place actually and I agree everyone was very friendly. We were up at the top of the hill just by the castle, the walk up and down the hill each day to get into town certainly helped burn off any excess calories!

[GEOFFREY]

Glad you liked Lincoln, there are some great places in the UK, but I am off to sunny Tenerife for a week tomorrow (won't be burning off any calories though. I bet that there will be a week of wall to wall sunshine here and that it will probably end on the 24th when we return!!! G.

[Wobblycogs]

Hello again . Seems a bit quite around these parts, where's everyone gone?

Anyway, it's been a while (cough, 10 years) but I've finally got around to starting to build this CNC. I started by building a sturdy bench for it to sit on. I was on safe ground here. The cross members are 2x9's and it's covered with a sheet of 18mm ply.



I made my first mistake while making one of the support brackets for the x-axis box section. I was rushing and I managed to break a drill bit. In the replacement hole I then managed to break a tap.


Moving swiftly on... Here's a shot of all the parts I've put together so far carefully arranged to make it look like I've done more than I have. I was going to mount the linear rail to the box section when it occurred to me that might not be a good idea. Obviously, I've got to get the x-axis exactly perpendicular to the y-axis. I feels like I should build the y-axis and mount it before drilling the mounting holes for the x-axis. Does that sound about right or should I mount the x-axis rails now and then try to adjust them square to the y-axis later? To adjustment them I'll have a tiny bit of play in the rail mounting screws or I can get more by opening up the holes that mount the x-axis rail assembly to the frame. It feels like I'll only get one shot at this so I don't want to screw it up.