Flood Coolant Set Up Questions

[TomS]

That looks great. I guess this is hand coded

Today I tapped 135 1/4-20 holes in about 22 minutes. Hand coding this would have taken way too long and tested my patience. I use CamBam for generating gcode. With the help of another CamBam user I used a custom script he provided. I tweaked it a bit to suit my mill characteristics then generated the gcode file.

Here'a screen shot of a test piece I created and the script. I removed the dwell before the M4 command and changed the feedrate to suit my spindle RPM and thread pitch.

 

[Boswell]

Here'a screen shot of a test piece I created and the script.

I used CamBam originally but eventually moved to BobCad. The sub-routine that you show above is what I was thinking would have to be custom. Looks very simple.

I can't imagine tapping 135 1/4-20 holes by hand or even with a hand drill.

Thanks for sharing this.

 

[spumco]

Sweet.

I rigid tap, so I don't have a floating holder. Was just thinking you could put a little bit of stiff clay in the bottom of a few holes and then tap them. Check hole top to the top of the clay and that'll give you a ballpark on the over-run before the spindle reverses. I'm betting you could get pretty close to the bottom of a blind hole once you tested a few with some clay.

 

[TomS]

Sweet.

I rigid tap, so I don't have a floating holder. Was just thinking you could put a little bit of stiff clay in the bottom of a few holes and then tap them. Check hole top to the top of the clay and that'll give you a ballpark on the over-run before the spindle reverses. I'm betting you could get pretty close to the bottom of a blind hole once you tested a few with some clay.

Thanks for the tip. Hadn't thought about blind hole tapping yet.

 

[MontanaAardvark]

Finally had some time in the shop today. The lag at Z retract was due to the CCW Spindle Spin Up setting in Mach3. Changed it from 1 second to zero and no lag now. Here is a link to my media gallery showing the floating tap holder tapping six 1/4-20 holes in aluminum. http://www.hobby-machinist.com/gallery/albums/users/toms.24891/. I still need to fine tune the feedrate to reduce the amount of tension on the retract cycle but overall I'm pleased with the results.

I missed that this had morphed from a conversation on the flood coolant and breakout board problems into CNC tapping. I just tapped four 10-32 holes in my tooling plate and while I did more than you did in that video, each hole took longer than the six holes in that video.

How much do those tapping heads go for? I'm still working on changing to a spindle motor I can control from Mach3 (or whatever) - at least in concept. Adding tapping capability would be extremely cool.

 

[TomS]

Yeah, this thread went off in a couple of directions. Sorry about that. Started out as a BoB relay wiring issue, then moved into a M3/M4 problem that raised it's ugly head when I tried to use my floating tap holder. Fixed that problem then after going through all of this I was finally able to test out my tap holder.

OK. Now to answer your question. My floating tap holder is a ER20 sold by Shars and bought on eBay. As I recall I paid $111 delivered to my door. It's actually a nice piece of tooling; ground on all surfaces and the tension/compression action is silky smooth. It takes a little adjusting to get the feedrate and spindle RPM to match up. In the video I had the feedrate set at 95% of the calculated feedrate per Tormach's recommendation. As you can see the tap was being pulled out of the hole. Not a big deal but it does distort the thread lead in somewhat. When I tapped the 136 holes I set the feedrate at 20 IPM, which is the calculated feedrate. I had minimal tap pull out and the thread was not distorted.

BTW - I'm using a PMDX BoB and spindle control card and a ethernet smoothstepper to control my spindle. Got this idea from jbolt.

 

[MontanaAardvark]

Having the reversible spindle has to be a big part of it. I noticed the spring action on the tap holder, but didn't know it wasn't intended.

Replacing the spindle motor is on my ToDo list for this year. Haven't spent the time looking for a BLDC motor, but I'd like to do something around 1-1/2 HP. 1 HP would be adequate. I'm pretty sure I'll need to replace my breakout board - I have a simple CNC4PC board and I don't believe it has any capabilities for motor control.

 

[spumco]

I'm pretty sure I'll need to replace my breakout board - I have a simple CNC4PC board and I don't believe it has any capabilities for motor control.

I have an unused C23 board from CNC4PC that has on-board spindle control. It's NIB - just didn't use it as I needed different input voltage capabilities for my spindle encoder so I went with a different BOB. PM me if you want to upgrade your BOB.

I also have a "3HP" BLDC motor available much like the 'kits' sold through Automation Technologies. You'd need to find a driver for it but it was working fine when I upgraded to an induction motor. The reason I pulled it was the driver - which I still have - was junk, and the BLDC drivers that are available now weren't really proven a few years ago.

It's 5k RPM, and it's probably about 2 or 2.5HP once you discount the marketing lies.

 

[TomS]

Having the reversible spindle has to be a big part of it. I noticed the spring action on the tap holder, but didn't know it wasn't intended.

Replacing the spindle motor is on my ToDo list for this year. Haven't spent the time looking for a BLDC motor, but I'd like to do something around 1-1/2 HP. 1 HP would be adequate. I'm pretty sure I'll need to replace my breakout board - I have a simple CNC4PC board and I don't believe it has any capabilities for motor control.

The spring action is intentional. It's purpose is to compensate for differences in spindle RPM vs. feedrate. If the difference is too great you get what shows in the video. It's not the ideal tapping method. I have to believe rigid tapping is the ideal method but the floating tap holder with a little finessing is a satisfactory alternative.

 

[spumco]

I have to believe rigid tapping is the ideal method but the floating tap holder with a little finessing is a satisfactory alternative.

I don't know this from personal experience, but I believe the ideal method is to use rigid tapping with a tension-only holder. This permits peck-tapping as the thread starts at the same point every time, but also permits a slight amount of variation between the thread lead and spindle synchronization on retract. No over-run on entry so you can tap to within a few 'thou of a blind hole every time in all materials.

It's reported in a few places online that this method creates more accurate threads and the taps last longer.

If someone wants to send me a tension holder I'd be willing to give it a go...