[tjbaudio]

I would not use a Varister. They break down over time and you won't know they have failed. How close to the relay contact ratings are you running? DC is worse for contacts than AC. Also a snubber on the contacts is solving a slightly different problem from the diod on the relay coils. I would go for an RC snubber solution if it is really needed. I am not sure one is needed.

[kuroguy]

the varistor or diode (depending) goes across the coil and only prevents back EMF from the coil. The contacts should be fine so long as they are rated for the voltage and current you are switching. You'll notice that contacts are rated for a much higher AC voltage than DC. That's because any spark that crosses the gap during switching will be extinguished during the next zero voltage crossing which is always less than 1/60th of a second away in the USA. In DC, suppression is usually done with a capacitor and resistor to ground, but that is typically used for switching very high voltages. I doubt you need anything for your relay contacts if your contacts are properly sized.

[matth]

the varistor or diode (depending) goes across the coil and only prevents back EMF from the coil. The contacts should be fine so long as they are rated for the voltage and current you are switching. You'll notice that contacts are rated for a much higher AC voltage than DC. That's because any spark that crosses the gap during switching will be extinguished during the next zero voltage crossing which is always less than 1/60th of a second away in the USA. In DC, suppression is usually done with a capacitor and resistor to ground, but that is typically used for switching very high voltages. I doubt you need anything for your relay contacts if your contacts are properly sized.

I'm sorry but that is not true. Varisters can be used on mains rated coils to prevent noise and on contacts to prevent contact welding. This is because if an inductive load is being switched then a massive voltage spike occurs as the contacts open (just like the old coils and points on a car engine), this spike will be many times over the contact rating and needs to be shunted through something else, in this case a Varister or other device.

[kuroguy]

I stand corrected

[kuroguy]

...but on an old car, that spike was shunted through the condenser which was a capacitor, not a varistor.

[mactec54]

Here is some good information for varistor (MOV) use, for Widgit's use he is better off with the RC snubbers


Frank's Training Course

[widgitmaster]

Here is some good information for varistor (MOV) use, for Widgit's use he is better off with the RC snubbers


Frank's Training Course

Thanks again Mac!
That was very informative! I never knew the difference between a surge and a spike, but I do now
Widgit

[widgitmaster]

Today I removed the top box from the Monster, and drove to Grainger for another 12-VDC relay! Now I can mill a hole in the side of the box, and file the corners square so the thermostat fits! Next I drilled the mounting holes in the back of the box, so I could mount the relay's socket. Then I doodled up a schematic of the thermal E-Stop switch, and started my day-long journey through the wires! If I had known there was going to be so many wires and stuff in this box, I would have given it a bigger port-hole!
Eventually, I managed to reconnect all the components! Now The Monster has a thermostat controlled water-cooled spindle! The new relay has a diode installed, and I have an extra diode for the one in the big Hoffman box!
Widgit

[pippin88]

I've run my 1.5kw spindle without water pump running once and not run into problems. Unsure how long.

I think it would be quite different if the spindle wasn't full of water though.

[widgitmaster]

Has anyone used 2" x 6" Toung & Groove pine lumber as a spoil board?

I was thinking of attaching the planking with brass screws, so the screw heads were recessed. Then i could surface the entire top area, and glue an MDF spoil board on top of that!
Widgit

[CNCMAN172]

Widget, the issue with using a softwood or hardwood planking is wood moves as the humidity changes over time. This will cause your flat table top to move as well. This is one of the challenges all woodworkers face when building furniture, you have to design the furniture to handle the wood movement. You might want to consider aluminum extrusion bars and then screw the MDF to those, or possible using some 2" hard foam board. With the MDF on top of that stuff it would remain pretty flat. You would surface the MDF after you get it all screwed down. Some people have glued a couple sheets of cabinet grade plywood together as a base, because plywood contains many layers of wood in alternating directions to address wood movement and is much more stable than solid wood. An expensive option would be phenolic plastic which is extremely strong and stable but pretty expensive especially the size you need. Just a few thoughts.

Russ

[widgitmaster]

Thanks Russ, I'll go with the MDF for now!

Here is a new Video of the Monster in motion!



Now I know it will never cut at 1000 IPM, but that's the rapids when the g-code "G0" is processed!
Widgit

Ps: When my iPhone compressed the video, it made it look like it was 2000 IPM !!

[tahustvedt]

It says the video is private.

[widgitmaster]

[CNCMAN172]

Widget, wow that is smoking fast. LOL Congratulations.

Russ

[tahustvedt]

So fast and smooth. More than twice the speed of my machine.

[widgitmaster]

Thanks guys!

I'm bored waiting for the new spindle & inverter to arrive!
Today I tried to install the XHC Wireless MPG in Mach3, the install was no problem, but the XHC has something wrong with it!
The screen blinks once, and goes blank! So that's another $100 bill in the trash
I hate dealing with Chinese CRAP!
Widgit

[tahustvedt]

You have had more than your share of bad luck. Have you tried contacting the seller? The chinese Ebay sellers are usually very eager to please, in my experience.

[CNCMAN172]

Widget, My son has this exact unit and it works fantastic. I would contact the seller as suggested, you might have just got a defective one. They work nice and smooth.

Russ

[widgitmaster]

Widget, My son has this exact unit and it works fantastic. I would contact the seller as suggested, you might have just got a defective one. They work nice and smooth.

Russ

Only one problem Russ!
I bought this on eBay over 6-months ago! Then I put it on a shelf, with the plan to include it in with the machine when it got up to this point!
So I guess I'm stuck with it!
Widgit