# PM-833 Maximum Z Travel with Limit Switches



## ahazi (Apr 7, 2020)

I finished installing the X and Z power feeders. They both work very well. The Z axis is a little tricky and the instructions can benefit from a rewrite...

I did not finish the limit switch installation on the Z axis as I realized that as recommended it actually reduces the travel range to 15.5" vs the 17.5" that the mill is capable of and spec'ed at. I might replace the fency stops with the springs (see pictures) with something smaller without a spring that does not consume so much vertical space, not sure why a spring is needed, the limit switches have springs inside and the X axis is not using such stops.










Am I the only one experiencing this or this was observed and corrected by others?

Ariel


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## davidpbest (Apr 7, 2020)

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.


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## parshal (Apr 7, 2020)

The way I mounted the accordion chip shield the head stops when it's flush with the top of the column.  I'd used it before I installed the shield and ran the head higher than that point.  How high can the head go and still retain rigidity?

I ask the above because the Z stop on mine stops the head as soon as it's flush with the column.


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## ahazi (Apr 7, 2020)

parshal said:


> The way I mounted the accordion chip shield the head stops when it's flush with the top of the column.  I'd used it before I installed the shield and ran the head higher than that point.  How high can the head go and still retain rigidity?
> 
> I ask the above because the Z stop on mine stops the head as soon as it's flush with the column.



The total (possible) movement of the Z axis is 17" which is exactly the spec from PM.
The head protrudes over the column by about 2.6" to achieve the full range.
The (vertical) size of the head that moves on the column is 9.5" so you still have a 7" engagement even when you go to the end of the travel. I would like to preserve the full travel range for the cases where I need to use the machine as a drill and in particular for large wood pieces so the rigidity is not really an issue.


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## parshal (Apr 7, 2020)

Where did you mount the top of the chip shield on yours?  Mine was not connected.

I would think we could simply get a longer bracket and run the stop above the column.


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## davidcarmichael (Apr 7, 2020)

ahazi said:


> I finished installing the X and Z power feeders. They both work very well. The Z axis is a little tricky and the instructions can benefit from a rewrite...
> 
> I did not finish the limit switch installation on the Z axis as I realized that as recommended it actually reduces the travel range to 15.5" vs the 17.5" that the mill is capable of and spec'ed at. I might replace the fency stops with the springs (see pictures) with something smaller without a spring that does not consume so much vertical space, not sure why a spring is needed, the limit switches have springs inside and the X axis is not using such stops.
> 
> ...


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.


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## aliva (Apr 7, 2020)

That's some clean mill


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## RJSakowski (Apr 7, 2020)

The stop is easily removed for those cases where you need the extra travel.  You can make a witness mark for ease of repositioning when putting the stop back in place.


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## ahazi (Apr 7, 2020)

parshal said:


> Where did you mount the top of the chip shield on yours?  Mine was not connected.
> 
> I would think we could simply get a longer bracket and run the stop above the column.


Brian,

There was a metal bracket that came inside the blue toolbox that was removed during transportation. See pictures below:









Ariel


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## parshal (Apr 7, 2020)

That's what that's for!  LOL


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## ahazi (Apr 7, 2020)

davidcarmichael said:


> 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.


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## ahazi (Apr 7, 2020)

davidpbest said:


> 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.


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## parshal (Apr 7, 2020)

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.


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## davidpbest (Apr 8, 2020)

ahazi said:


> 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.


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## ahazi (Apr 8, 2020)

davidpbest said:


> 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?


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## davidpbest (Apr 8, 2020)

ahazi said:


> 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?
> 
> ...


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


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## Buffalo21 (Apr 11, 2020)

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.


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## mksj (Apr 12, 2020)

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


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