Centroid Community CNC Support Forum

Hello,

I'd like to start using a 3d touch probe for my vise and fixture setups. Unfortunately at $699 the Centroid KP-3 is out of my budget. So far I've looked at the following budget probes:

https://www.cnc4pc.com/touch-and-tool-p ... shaft.html $135. Not adjustable. No claim for repeatability.

https://drewtronics.org/s5000led $169. Adjustable. They claim .001" repeatability.

http://engravingbit.com/CNC%20probe%20d ... probe.html $249. Adjustable. They claim .0001" Repeatability.

So far I'm leaning towards the engraving bit unit. I'd like to hear from anyone who has tried any of these out though.

Thanks,


Chris

http://www.wildhorse-innovations.com/in ... oductId=80

This is another option...which is really the same as 2 of the others

I'm running a Drewtronics probe. It is usually very accurate and well within the .001" specified. However it will occasionally be off by about .003". As a work around I probe the part and set the WCS. Then I reprobe it to see if it is off. If it repeats (which it almost always does) I go with the first settings.

Maybe get one of the cheaper probes then upgrade to the Centroid one later. If you get a probe you will never want to be without one again. Also look into the Probeapp that Swissi made. It works great.

Buy once cry once.....
My vote is to save for the KP-3

martyscncgarage wrote: ↑Wed Jan 20, 2021 10:44 am Buy once cry once.....
My vote is to save for the KP-3

Usually I'd agree with you but it's just not in the budget for now.

I bought a used Renishaw MP1s from ebay for around £180 / $200. It's an older model but works very nicely indeed, certainly more accurate than my machine will ever be. Originally it had a contactless (inductive) connection but that simply unscrewed to reveal a 5 pin DIN ("audio") socket for a wired connection. You can buy replacement(!) styli from the Far East for about $20 for which there is enough runout adjustment in the probe body to zero them out.

I wouldn't be without a touch probe - it transformed the accuracy of my work setup and made life so much easier. That and an electronic tool setter.

Here is a drawing of the probe I made. In practice it seems to be as accurate as a mechanical edge finder. I followed the probe setup described in the centroid PDF for probes. I also made a tool setter that works with the same input. To use the tool setter, I made a jumper cable that connects the probe tip to the mill table. Then I use the probe assembly as my Z reference tool and touch off on the tool setter. It works well for me. If my description is confusing, I can try to make a poor quality video and post in on youtube.
The biggest problem I have had with this setup is forgetting to connect the wire to the probe. If you do this then the vice bends the probe tip. That's why I made the tip replaceable with a set screw. If I bend a tip, I install another length of 3/8" rod, then turn the tip down while mounted in the mill, then update the tool table with the new tip diameter.
Good luck with your decision.
Mike

That's a good idea. I looked at eBay and there are a few in my price range. They are mostly Cat40/50 shanks. I assume that you can pull them off the shank and turn/modify one to fit.

I don't have any idea how they work though. I'd have to dig into the control electronics before I bought one.

Muzzer wrote: ↑Thu Jan 21, 2021 5:58 am I bought a used Renishaw MP1s from ebay for around £180 / $200.

I've thought about making something like this. It's basically the same circuit as a touch plate. The tool is insulated instead of the plate. I'll keep it in mind.

fusion wrote: ↑Thu Jan 21, 2021 1:05 pm Here is a drawing of the probe I made. In practice it seems to be as accurate as a mechanical edge finder.

ChrisAttebery wrote: ↑Fri Jan 22, 2021 2:18 pm They are mostly Cat40/50 shanks. I assume that you can pull them off the shank and turn/modify one to fit.
I don't have any idea how they work though. I'd have to dig into the control electronics before I bought one.

Yes, the body is held to the toolholder with 3 screws and sits against a ball bearing. This allows you to adjust / zero out the runout. It also allows you to replace the holder with whatever you want. I took an ISO40 holder and turned it down, right back to the first shoulder to minimise the gauge length.
https://www.renishaw.com/media/pdf/en/1 ... 5ed654.pdf

Like most of these probes, it has 3 pairs of ball bearing contacts and a sort of tripod arrangement. The patent has clearly either expired or didn't hold water, as the concept is widely applied.
https://resources.renishaw.com/en/detai ... ks(115030)

The 3 contacts are in series, so they form a normally closed circuit. If any of the contacts are broken, the circuit goes open. You should ideally detect a current threshold but for our purposes, the Acorn pullup resistors work fine.

The probe claims to be capable of around 1um repeatability. My machine claimed to be good for 10um when new and well set up. So I can get accuracy approaching perhaps 20um with care. That's about 0.001" - although it may not be in Youtube Warrior territory, it's good enough for the likes of me.