PM-833 Maximum Z Travel with Limit Switches

[ahazi]

The stops must be set to handle conflicting requirements. With a powered Z-axis using the fast traverse, you must allow extra space for the knee to stop before hitting the physical end stops. This means it must stop the motor well before the end is reached. Both the spring in the switch housing and the stop spring are fully compressed when the end of travel is reached.

If you then use the power feed at slow speed then you will lose quite a bit of feed length because the motor will stop much more quickly when the stop switch is pressed.

I have mine set for safe fast traverse feeding and use the handle if I need the last little bit of travel. I seldom do.

David,

Thank you for the heads up on the reason for the springs in the stops. You are saying that the springs are there to protect from the momentum of the head mass moving fast up or down. Interesting. I will take a look to see how long it takes to stop in either direction from fast traverse.

 

[ahazi]

You might consider using Item-northamerica.com Profile 10 50x20 E, T-slot aluminum extrusion with 50x20 grey end caps for limit-switch end-stops.

View attachment 319993

David, where do you get these extrusions? Are they stocked in the US or imported? They seem like a variation on 80/20 part but much larger size and slot for the nut.

 

[parshal]

After you pointed out what the "extra" part was for I mounted it. I raised my Z stop by 2.5" and it will go all the way to the top now. I could have gone 2" and it would have been perfect stopping at exactly the highest point. The lowest point it will go from the end of the spindle is .5-1" below the top of the jaws in my vise. If I were to need to go lower I can remove the lower stop but I can't imagine ever needing to go lower than that.

 

[davidpbest]

David, where do you get these extrusions? Are they stocked in the US or imported? They seem like a variation on 80/20 part but much larger size and slot for the nut.

The item.com components are made in Germany, but they are well stocked here in the USA. They are considerably higher quality than any of the 80/20 derivatives. https://us.item24.com/en/about-us/local-representative/us/item-west/

I suggest you download and decipher their catalog, then you ask for a quote and then call their office in Utah to place the order. (844) 828 9378 It's a bit more steps than buying from a parts supplier, but worth the effort. If you need help figuring out their coding system, let me know.

 

[ahazi]

The item.com components are made in Germany, but they are well stocked here in the USA. They are considerably higher quality than any of the 80/20 derivatives. https://us.item24.com/en/about-us/local-representative/us/item-west/

I suggest you download and decipher their catalog, then you ask for a quote and then call their office in Utah to place the order. (844) 828 9378 It's a bit more steps than buying from a parts supplier, but worth the effort. If you need help figuring out their coding system, let me know.

This is exactly what I did, even received a quote. Seems reasonable but weird... waiting for shipping and delivery info.

McMaster sells 45 mm 80/20 profile that can serve the same purpose. Much easier process to order. See below. What do you think?

 

[davidpbest]

This is exactly what I did, even received a quote. Seems reasonable but weird... waiting for shipping and delivery info.

McMaster sells 45 mm 80/20 profile that can serve the same purpose. Much easier process to order. See below. What do you think?

View attachment 320115

View attachment 320116

If you like spec houses, you'll probably be happy with the 80/20 from McMaster. I have purchased extrusions from McMaster at times and it's all low end commodity stuff. Item is in another league - exudes quality. Look a little deeper:

Link 1
Link 2
Link 3

 

[Buffalo21]

When I put power feeds on my 3 mills, I found the limit stop stop track to be rather flimsy, so I made a bracket for it out of a piece of aluminum angle, the pop riveted the track to it. The aluminum angle bolts solidly to the side if the mill, I did this on the Y and Z feeds.

 

[mksj]

I used the 80/20 profile 1534, simple and easy. The stock rail is bulky and looks cheesy. If I recall you may need to slightly profile the T nut. One would probably question the need for a lower stop on a bench mill, on my knee I have both mounted but only use the lower stop when I lower the knee.

1534-Lite

1.50” X .75” Lite T-Slotted Profile - Single Open T-Slot

8020.net