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View Full Version : z-zero plate and dust shoe problems on PRT



MaxFrenzy
05-19-2015, 12:03 AM
Hi guys,

I have a benchtop PRT as some of you know and have run into a couple issues the past few days.

1st: My zero plate stopped working. I'm not exactly sure what happened as I didn't change anything and had zeroed a bit previously. I wanted to surface some MDF and input 1 wouldn't light up. The way I have it wired is the setup for using a shopbot 3d probe and z plate on input 1. So on the controller side, I have a red wire going into the 5v input, a black wire into input 1 and a white wire going into ground. That leads to a wago clip where I have connected the 3 wires and then also connected in my zero plate and ground wire into the wago clip, doubling up on the black and white cables. From there, the black wire leads to my zero plate and the white wire leads to an alligator clip for grounding. The only thing I can tell you is that when I touch my white grounded cable to the zero plate, input 1 lights up. Some how that is completing the circuit? I will admit that my setup is rather ghetto. My zero plate is this paper thin piece of copper that I glued to a piece of a acrylic (I didn't want something that conducts electricity in case I use the probe). Any ideas?

2nd: The dust shoe that I bought from shopbot sucks...but not in the good way. I'm not sure what other machines have to use this shoe, maybe the buddies? But, for over $200 the design leaves a lot to be desired thus far. The design has the 4" hose feeding in from the rear instead of coming down from the top like a Kent shoe for example. The problem is that in order to make it fit, the hose is smooshed down and then wedged in the back of the shoe giving it a very narrow opening. I was surfacing MDF and had the hose yank out of the dust shoe mid job...WHAT A MESS on an already extremely messy operation. Now granted, that was my fault for not giving it enough slack. However, the placement of the hose is quite a ways back from where the bit is spinning. My 4" dust collection unit has a ton of suction and is dedicated to the CNC. When I use it for vacuuming up the dust that the shoe isn't collecting, it's awesome. When I was shopping for a solution I talked to Kent CNC about using a hose reducer to fit through the top opening of the benchtop prt (something like a 4" to a 2.5-3" back a 4"), he thought that would lead to poor performance. The benchtop doesn't have a ton of space between the router and the frame of the machine (x-axis rail). Well, I fail to see the difference between that and crushing a hose down to a practically inch wide opening and setting it way back from the bit. My 70 gallon dust collection bag has some chips at the bottom, but my floor and shop vac from me cleaning non-stop during the job has a hell of a lot more. The whole reason I bought a 4" DC unit was for power, health, noise reduction, optimum dust collection etc. Does anyone have any suggestions for how to make this work any better? I'd love for a simple solution and I'll gladly eat that crow. I'm not sure what the return policy is like, but I may have to find out cause right now it feels like a piece of plastic that just gets in the way of bit changes.

Thank you for the help. Sorry if I sound frustrated :)

adrianm
05-19-2015, 05:06 AM
Could you mount the extraction hose with a Kent shoe on the opposite side of the spindle? That's what I did on my PRS as the Kent shoe is not long enough to allow the hose to go into the standard position.

jerry_stanek
05-19-2015, 09:29 AM
I really like the way I have my dust shoe works. I made it myself and mounted it so that it is stationary instead of moving up and down with the spindle. To change bits I just do a z3 or 4 and that brings the spindle up and the bit clears the shoe change the bit and off I go. I made a slotted bracket that I can move the dust shoe up or down depending on the thickness of my stock.

Joe Porter
05-19-2015, 10:37 AM
I'm not sure if I fully understand, but my original ShopBot dust shoe came with a short piece of 3" hose coming out of the shoe that would twist into the 4" hose from the dust collector. This was a good transition. The only reason I changed to the Kent shoe was for easy bit changes and it looked neater. Maybe they didn't send the entire kit...joe

MaxFrenzy
05-19-2015, 12:19 PM
Could you mount the extraction hose with a Kent shoe on the opposite side of the spindle? That's what I did on my PRS as the Kent shoe is not long enough to allow the hose to go into the standard position.

This little benchtop is 32x24. When looking down from above (birds eye), the Z car has its stepper motor coming off its ass end and the router sticking out in front. The combination only leaves around 3 inches from the router and the x axis rail it moves along. I'd have to measure in back but the stepper motor takes up a similar amount of room.

Edit note: I post in the buddy section of the forum due to the similar operation of the benchtop prt and buddy system. Remember though that the axis are reversed. That is, my moving deck is the y axis instead of your x axis. Thanks

MaxFrenzy
05-19-2015, 12:21 PM
I'm not sure if I fully understand, but my original ShopBot dust shoe came with a short piece of 3" hose coming out of the shoe that would twist into the 4" hose from the dust collector. This was a good transition. The only reason I changed to the Kent shoe was for easy bit changes and it looked neater. Maybe they didn't send the entire kit...joe

Yeah I kind of have that short lead as well that slips into the 4" hose, but on the other side, where your hose meets your dust shoe, is the hose smooshed down to fit the rear of the shoe?

MaxFrenzy
05-19-2015, 12:22 PM
I really like the way I have my dust shoe works. I made it myself and mounted it so that it is stationary instead of moving up and down with the spindle. To change bits I just do a z3 or 4 and that brings the spindle up and the bit clears the shoe change the bit and off I go. I made a slotted bracket that I can move the dust shoe up or down depending on the thickness of my stock.

What model do you have? Could you post some pics potentially?

jerry_stanek
05-19-2015, 01:19 PM
I have a PRS standard here are some pics of what I made. These are old pics as I upgraded the brush on it to be just around the cutter head about 3.5 inch circle. It does a better job around the edges of the table

Brady Watson
05-19-2015, 02:10 PM
Your PRT Benchtop should have 4 holes in the 2x2 Z tower uprights that allow you to adjust the whole Z up or down by 2" either way. By raising it up, you gain some extra Z clearance, AND you pick the motor up high enough to then slide the entire Z assembly either towards or away from the 3x3 angle. From there you can stuff a 4" hose down there no problem. FYI - it's a tight squeeze, but you can get two 3hp spindles in that Z bay...

-B

MaxFrenzy
05-20-2015, 02:13 AM
Your PRT Benchtop should have 4 holes in the 2x2 Z tower uprights that allow you to adjust the whole Z up or down by 2" either way. By raising it up, you gain some extra Z clearance, AND you pick the motor up high enough to then slide the entire Z assembly either towards or away from the 3x3 angle. From there you can stuff a 4" hose down there no problem. FYI - it's a tight squeeze, but you can get two 3hp spindles in that Z bay...

-B

Interesting. I'm going to have to take a close look at that tomorrow to see if I can identify what you are explaining. Am I understanding correctly meaning that the whole z assembly can be both raised up a couple inches and positioned forward of backwards as well? If so, I think they would explain another issue I was having. I've never see any official shopbot info about that possibility. While I've got you, do you know how a pinion replacement happens for the Z stepper? The x and y axis use that spring tension and it seems pretty straight forward for getting those yanked and doing the repair. Unfortunately in the rear of the Z, there doesn't seem to be a plate that the motor is attached for a handy removal. There it seems like if I unscrewed the screws on the back of the stepper I would just be pulling the cover off the motor. There is a little oval cutout that lets you peak in the rear to see a little of what's going on inside with the rack/pinion, but I haven't figure out a smart way to go about it.

Thanks

Brady Watson
05-20-2015, 09:16 AM
There are a few ways to get to it, but here's how I'd do it. You'll need to make yourself a couple of lasso-shaped pieces of copper wire using scrap Romex etc. This is assuming that you have coil springs and not the old leaf springs. Take each looped lasso (should be 10-12" long BTW) and pull the springs off their bottom perch by using the looped end. Leave them on the springs for later.

Locate the stop bolt on the back side of the Z. Remove it.

Remove the lower spring perch bolts and perch. Set it aside.

Lift the entire T-rail with router straight up and out of the v-rollers...slowly.

From there you can clean, inspect and replace/lube the pinion. It's a good time to clean the inner workings of the Z axis from years of build up too. There is usually no need to mess with the motor at all for this process, unless the t-rail is severely worn and you ran out of eccentric adjustment on the roller bearings. If the Z doesn't already have 8 roller bearings, you may want to add them. It extends the life of the Z by a factor of 5 or more. T-rails are unobtanium...

-B

Joe Porter
05-20-2015, 10:28 AM
Yes, my 3" hose was shaped to fit the dust shoe. This came assembled and ready to go. I don't know how they did it, but it fit well...joe