Shopbot users - what have you learned?

[Forhire]

Originally Posted by DonRotolo

Randy, are you saying you cut at 0.40" depth at 108 IPM with your shopbot?

Yes. We found we had better chip evacuation with a through material cut, full depth. Slotting can be problematic for sure. Endmills are designed to cut on the flutes as well as the ends. It's a lot easier to push a full length chip out of slot than a small chip from the bottom. The long chip is your friend in this case, it carries the heat and is less likely to load up. The 1.5xdiameter was pushing our luck for sure but all I had with me was some 1/4" endmills. We made 4 of these side plates... we didn't start crazy fast from the go... but by the fourth we had the recipe perfected. Our Shopbot is a PRSAlpha Buddy with the 18k rpm 2.2HP spindle.

It's possible that some of the rest of the post may be a bit off topic but the OP wanted to know what we've learned having run a shopbot. Here you go.

Understand that despite the Shopbot performing so well we had terrible difficulties with the software crashing. Little jobs that should have taken 15 minutes stretched into an hour due to lockup/pausing problems. Multiple parts and or multi-operation jobs were delayed due to lockups between parts. During the build season isn't the time to diagnose issues... we just needed it to work. We lived with it. The student that ran this machine would get so frustrated he'd leave. Near the end of the season we discovered that if we closed the RPM pane the machine wouldn't lock up as much. A little too late. This is an on top of it being a terrible user interface and using OpenSBP. Claiming to support g-code but really only handing the basic linear and arc commands. No canned drilling ops. No spindle speed control from within g-code. The list went on and on.

After the season we converted the Shopbot to use a Dynamotion Kflop motion controller with KmotionCNC. We only ran it for a few weeks before the end of the school year but it was 100% worth the upgrade. No crashes and the interface is more similar to the Centroid and Fanuc based cnc machines the students also run in the shop. Being that the students have to know some basic g-code for the other machines... standardizing makes it much easier. The shopbot was an odd duck in the shop. Here's some more information:
http://www.cnczone.com/forums/dynomo...-software.html

The adapter board that plugs in where the Shopbot control plugged in. It was designed in Eagle and sent out have the PCB made. This allowed the machine to be changed over without any permanent modifications. It includes a TTL_RS485 module that allows spindle control via Modbus directly from the Kflop. Once it came back the adapter was installed along with the Kflop. Programming is done in C so between a mentor and some students it was running in a few days. Now we can change spindle speed while running. And when we pause the work... it pauses instantly. And if there is something we don't like... we can readily change it.

Here's some photos:





Here's some UHMW being done for the first time after converting:
https://www.youtube.com/watch?v=hTLwlvJWWCk