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    Default What did I buy? Old machine, new tech, take a look.

    Hi all, I'm the new guy I guess. Hoping someone with some experience can give me info about this design. I'd like to find other discussions or documentation about it, if anyone can point me in the right direction. Would be cool to know the origins of the design or possibly the person who built the machine.

    I am going to read up on the controller, but it looks like its using a parallel port interface. My assuption is I need a windows 32 bit computer to run it?

    It's an older, used, diy machine. It seems to be of reasonable quality for the price. The machine hasn't ran in awhile and will need a bit of set up. Any advise you would like to give me is much appreciated.

    Machine Specs (mostly unkown)
    3" extrusion table, cutting area: 53" x 110"
    Gear rack: unknown
    Pinion tensioner: unkown
    Z-axis screw, rails and carriage: unkown
    Router: Porter Cable 7518
    Main Board: Practical CNC Rev 2.13
    Controller: PMDX - 126
    Drivers: unkown
    Motors: Z-AXIS: P22NRXB-LDF-NS-00 M Series POWERMAX II Hybrid Step Motor manufactured by Pacific Scientific 214 oz in
    X-AXIS and Y-AXIS*: M22NRXB-LDN-NS-00 M Series POWERMAX II Hybrid Step Motor manufactured by Pacific Scientific 253 oz in
    *Y-AXIS is ran with a single motor and long drive shaft.
    Sensors: none
    E-Stop: none

    I paid $2000 usd. Does that seem like a reasonable deal? I'm after a reliable machine that can cut wood panels for prototype furniture. I know its won’t be the fastest machine in the world, but hoping for decent productivity. Are there any obvious weaknesses or upgrades this machine needs?

    For reference I owned an xcarve and did a bit of playing around with the machine, but it caught fire and was a total loss before I was able to do much with it. Thanks to everyone or anyone who can help me get a better understanding of all this.

    Similar Threads:
    Attached Thumbnails Attached Thumbnails What did I buy? Old machine, new tech, take a look.-bdf9545b-335a-4c72-aca6-3a844397fb30-jpg   What did I buy? Old machine, new tech, take a look.-1e6a1f51-ee0f-4445-81e5-8ba3780ef5ad-jpg   What did I buy? Old machine, new tech, take a look.-6430c2c3-b6ef-46d0-9879-e5eda5982606-jpg   What did I buy? Old machine, new tech, take a look.-f097ee7e-f27a-4b9a-8bc3-592cbdf20be3-jpg  

    What did I buy? Old machine, new tech, take a look.-86ed06e7-c6e1-47ae-b94d-060124bb21b4-jpg   What did I buy? Old machine, new tech, take a look.-1d700153-4dcf-4609-be2c-ce5a234f1eb7-jpg   What did I buy? Old machine, new tech, take a look.-fc66a8a5-a48b-4400-aa4d-8461d089e9b7-jpg   What did I buy? Old machine, new tech, take a look.-eaec22e7-4f62-4800-8791-979a6c0dcba9-jpg  

    Last edited by Nicedesigns; 09-02-2020 at 07:45 PM.


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    Default Re: What did I buy? Old machine, new tech, take a look.

    That may have been parallel port interfaced originally but it has been upgraded with a Ethernet
    Smoothstepper (the piggy-back board on top of he PMDX-126) so AFAIK it should work with modern
    64 bit Windows



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    Default Re: What did I buy? Old machine, new tech, take a look.

    What control software does the machine run and do you have a post processor that will work with it?From a mechanical point of view it has a diagonal brace across the end,is there an equivalent along the sides?When you describe the single motor on the Y axis,which is the Y axis?If I were looking for a weakness it would be that the machine seems to use bearings without much separation that run on rectangular steel rails.
    It could be a very useful machine but really needs sensors for home position and an E-stop might be the thing that allows you to stop it before this machine catches fire.



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    Default Re: What did I buy? Old machine, new tech, take a look.

    Awesome! Thanks for your feedback.

    I'll try to plug it into my desktop. AND TRY NOT TO CATCH IT ON FIRE. I don't need another one of those... Definitely plan to add the homing sensors, limit switches and an e-stop or two.

    The controller works with Mach4, which I need to buy a license for. I can model okay in fusion 360 and have played a little bit with posting from it.

    I'm referring to the long side as the y axis, but I guess I don't know how it's wired.

    @routalot in terms of the carriage rolling on bearings riding the extrusions, is this design inherently troublesome, or something that can be made better with a wider bearing spread? How nice of an upgrade would it be to mount up some linear rails and some chunky ball bearing carriages?



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    Default Re: What did I buy? Old machine, new tech, take a look.

    I'd think the best thing would be to get the machine working and see what it-and you-are capable of.The bearings you have will work as far as moving the machine is concerned but the more use they have and the more wear that results,the more play will develop to the detriment of accuracy.If that reaches a level that you find unacceptable then linear rails would be a big improvement or if that seems like too much expense for the machine a 20mm round supported rail with good carriage separation might be an intermediate step.



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    Default Re: What did I buy? Old machine, new tech, take a look.

    Thanks, I've wondered what the realistic difference is between the 20mm round rails and the linear rails.

    You're right, I just need to get it going as it for now.

    I reached out to CandCNC, they're awesome and hopefully I'll use their motor/driver upgrade one day. The rep Tom who replied to me said the mechanical weak spot of the machine is the thin driveshaft used to drive the non-drive side of the long axis.

    I've learned a lot about the controls since my first post. The pwnx-126 is just the breakout board and it has the needed Ethernet Smooth Stepper controller already installed. Those should do fine for my skills and this machine for now. Seems simple enough to connect limit and homing switches and an e-stop. Is there a best place to find switches? I like the idea of using proxity sensors, the avid cnc kit looks great but seems over priced for what it is. Can someone provide a recommendation for a good value option? Thank you!!!

    https://www.cncrouterparts.com/peppe...kit-p-293.html



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    Default Re: What did I buy? Old machine, new tech, take a look.

    There is a thread on proximity switches here: https://www.cnczone.com/forums/diy-c...me-sensor.html .

    They don't have to cost a huge amount and are quite easily found. https://ukcnc.net/index.php?route=pr...&product_id=92



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    Default Re: What did I buy? Old machine, new tech, take a look.

    Quote Originally Posted by routalot View Post
    There is a thread on proximity switches here: https://www.cnczone.com/forums/diy-c...me-sensor.html .

    They don't have to cost a huge amount and are quite easily found. https://ukcnc.net/index.php?route=pr...&product_id=92
    Thanks very much for your replies and dropping the links! It's poor etiquette not to do the search myself, but it's easier to just have you to do it for me What did I buy? Old machine, new tech, take a look. :joke:



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    Default Re: What did I buy? Old machine, new tech, take a look.

    Hi all, so I'm up and cutting but I'm getting some odd results. I did my models and cam in Fusion360. The simulation seems straightforward and correct. But when I cut the 2D adaptive pocket the Z height goes deeper on some of the passes, see pics. Any Idea what's causing this? I know the bit isn't moving in the cutter. I stopped the last attempted when I noticed the bit was cutting too much, but it cut about 3/4" deep when it should have only cut 3/8" deep. I sent the z up to zero, and as you can see from the photos, the cutter is still quite a bit below the model top. So somehow my actual z height on the machine is getting lower as I run the program and the controller doesn't know that. Anyone have a theory on my issue?

    I want to give a big thanks to anyone here and everyone who has contributed to the online consumer CNC discussion. I learned A TON about these machines, the ESS, breakout boards, wiring inputs, controller setup, etc from the forums. To me it's so cool to design and carve stuff I can't even express it in words.

    For posterity: I updated my original post with some more machine info.

    Attached Thumbnails Attached Thumbnails What did I buy? Old machine, new tech, take a look.-20201023_160036-jpg   What did I buy? Old machine, new tech, take a look.-20201023_160142-jpg   What did I buy? Old machine, new tech, take a look.-20201023_162519-jpg  


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    Default Re: What did I buy? Old machine, new tech, take a look.

    I would be looking for something that has either worked loose or flexed and if that can be eliminated,lost steps or electrical cross talk.I have had a bad soldered joint give this kind of outcome and it was an easy fix once I had located it.A little time with a multi-meter on the Z axis connections might eliminate the possibility.I don't know enough about Mach 3 or 4 to recommend acceleration settings but it might be the place to go after investigating mechanical and electrical systems.



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    Default Re: What did I buy? Old machine, new tech, take a look.

    It sounds like your Z axis might be losing steps on the upstroke. When it tries to raise the head but fails, there's nothing to tell it it hasn't achieved the commanded position, so it assumes it's arrived there. But in fact it's lower than it should be, so when it goes down again, it ends up lower than the DRO shows. You can check this afterwards by commanding a move to Z zero. If that's lower than when it was set originally, then you've either lost steps or the mechanism is failing.

    The first thing to do is to check for mechanical problems in the Z axis, like couplers that are slipping, lubrication failure, or some obstruction that's interfering with its motion. If that's all okay, try reducing acceleration; cut the number in half and retest. If there's no improvement, you might need to provide a counterforce to balance the weight of the Z assembly. I've found gas springs work pretty well for this.

    Andrew Werby
    https://computersculpture.com/


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    Default Re: What did I buy? Old machine, new tech, take a look.

    Thank you, that sums up the issue very well. The z height in the dro does confirm it's loosing steps on the z up dirention. Hopefully it's just a loose set screw!



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    Default Re: What did I buy? Old machine, new tech, take a look.

    Well I went over the whole machine and it seems like everything was tight. However, as I tried to clean and re-lubricate the sliding parts I found the z movement to get much rougher. The ball screw feels course in my hands and the movement is quite jittery. I inspected the x-y movement a little closer and it also has a lack of smoothness. I'm not sure what is causing the binding there. Anyway I'd like to buy a complete z assembly instead of making one as I have some projects I want to cut asap. The CNC router parts assembly looks pretty good, but also expensive for an extrusion vs solid plate based chassis. Is there a go to resource for good quality z assemblies? I plan to upgrade to linear rails, better rack and pinion and a stiffer gantry/bed, maybe a spindle and vacuum chuck next year, so I'd like to get an appropriately good quality z assembly now to match it later. Does something like this look decent? https://www.ebay.com/itm/Sliding-Tab....c100752.m1982



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    Default Re: What did I buy? Old machine, new tech, take a look.

    here are a couple screen grabs for posterity

    Attached Thumbnails Attached Thumbnails What did I buy? Old machine, new tech, take a look.-ebay-snip-jpg   What did I buy? Old machine, new tech, take a look.-ebay-snip-2-jpg  


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    Default Re: What did I buy? Old machine, new tech, take a look.

    This one looks pretty slick!

    https://www.ebay.com/itm/LINEAR-STAG...wAAOxyQqBRGhW1

    Attached Thumbnails Attached Thumbnails What did I buy? Old machine, new tech, take a look.-ebay-snip-3-jpg  


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    Default Re: What did I buy? Old machine, new tech, take a look.

    only down side to this one is the acme screw. they transmit power well but the efficiency is not as good as a ball screws so you need more power to drive them as a result. then you get into the question of how much backlash is in the nut? it could have a double nut to take the lash out but i did not see anything in that listing that talked about it. the low height would be a big plus but my hang up would be the acme nut.



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    Default Re: What did I buy? Old machine, new tech, take a look.

    If it's a Kerk lead screw it will have some form of anti-backlash. You could ask the seller the screw/nut model # as Kerk has several.
    My preference would be a ball screw over acme.

    Anyone who says "It only goes together one way" has no imagination.


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    Default Re: What did I buy? Old machine, new tech, take a look.

    Hold out for an automation actuator with profile rails and a ball screw. They make great Z axes, and often can be bought cheaply if used or NOS. You can always substitute your own motor for the one that came with it, if you can't figure out how to drive it.

    Andrew Werby
    https://computersculpture.com/


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    Default Re: What did I buy? Old machine, new tech, take a look.

    Interesting, thank you! I asked the seller of the low profile assembly for more info on the Kirk lead screw.

    The first listing I posted is for a much cheaper chinese assembly. It says it uses a ball screw. Are there any other obviously disadvantages or concerns about that assembly?



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    Default Re: What did I buy? Old machine, new tech, take a look.

    Quote Originally Posted by awerby View Post
    Hold out for an automation actuator with profile rails and a ball screw. They make great Z axes, and often can be bought cheaply if used or NOS. You can always substitute your own motor for the one that came with it, if you can't figure out how to drive it.
    Would that be something like this? https://www.ebay.com/itm/320839352439




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