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Thread: Repair, upgrade or replace?

  1. #1
    Join Date
    May 2010
    Location
    Qualicum Beach, B.C.
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    145

    Default Repair, upgrade or replace?

    We've been running a Colombo spindle equipped PRT Alpha for just over ten years now. A couple of years ago we upgraded to the 7:1 motors and added the PRS gantry, before those changes were made we installed a vacuum hold-down system. We're still not quite getting the results I'd like on some projects and as such I tend to avoid taking in plexiglass jobs as every minor imperfection shows all too well.
    Our rails are definitely getting tired and with the Y-axis being driven by a single motor and rail, jobs featuring long sweeping arcs are not always at their best.
    Pinions have been replaced, springs are adjusted and table assembly is tight.
    I'm wondering if we're simply at the limitations of the machinery? Would we be better off modifying it or replacing it? I love our Shopbot as well as all the support the forum members have provided over the years but I'm giving serious consideration to replacing it with an offshore import. From what I've seen they can be very good value IF you buy well. As always, any and all feedback would be most welcome! - Boyd

  2. #2
    Join Date
    May 2010
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    Qualicum Beach, B.C.
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    Default

    AYE CARUMBA!...just got a quote for new hardened rails from Shopbot. Just under 3300.00 with shipping. Is this normal? Wasn't expecting they'd be anywhere near this expensive.

  3. #3
    Join Date
    Mar 2004
    Location
    Delray Beach, FL
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    3,708

    Default

    Check out Superior Bearing. I have them on mine for years and I like them just fine. I also went to larger wheels and track on x. Had to make some adjustments but it came out fine.
    Note that I added the hardened rails to my Y first when still using the original PRT Gantry. When I changed the x's I also changed from the angled rail to a Bosch Rexroth extrusion topped with a solid aluminum pillow block on which the rails were attached. Concurrently I changed the gantry altogether for a PRS that I got some parts from SB and others independantly. Total parts cost in the neighborhood of 5-6K. Still was running standard motors and Gecko controller. Jog actually went down from around 10 to 8 due to the greater mass of the gantry but max cut speed on our standard cabinet parts doubled. Latest was going Alpha power. Cut speed doubled again and Jog went to 16 (although I can go higher that's enough for me. Rarely in our cut files does it have to jog across the whole table and ramping distances increase as jog speed goes up.)
    Just noticed we had this conversation in July! Check out your previous post about it.

  4. #4
    Join Date
    May 2010
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    Qualicum Beach, B.C.
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    Thanks Dave and yes we did speak of it earlier. We ended up investing what little spare cash we had at that time on a new laser cutting system, we're now back in a position to spend a bit on equipment. In the course of educating myself on lasers I crossed paths with a number of CNC types that had purchased either laser or CNC setups that were made offshore and most seemed quite happy. This is what got me thinking about new versus upgrading as it relates to cost. All things being equal I'd much rather stay with Shopbot or at least North American made. FWIW we ended up buying a US made Epilog laser setup.
    You and a couple of others on these boards seem to be the real gurus with regard to upgrading these machines, sure wish you'd all get together and write a book on the topic!

  5. #5
    Join Date
    Mar 2004
    Location
    Delray Beach, FL
    Posts
    3,708

    Default

    A good idea except for one thing. If one shopbotter actually ponied up the buck to buy it they would then post everything in it!
    Actually one of the big plusses in SB world is the way things that go around come around. Back in the old days (feels like the last century) when I bought mine quite a few guys were very helpful in getting me over the humps. I'm glad to help when I can. It's only fair.

  6. #6
    Join Date
    Jun 2011
    Location
    Melbourne, Australia
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    1,010

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    Boyd the Chinese machines appear to be fantastic value and terrific bang for the buck. We are currently helping a guy get one going and trust me its an absolute nightware. There simply is no usefull support and software is all illegal. One not so silly option could be to plonk all your old SB innards on the Chinese job and you could end up with a half decent unit. You really tend to value your Shopbot a lot more once you start battling with no documentation/ support!
    Buddy BT48 with 6' power stick
    2.2 HSD Spindle
    Aspire 9.5
    6" ShopBot Indexer

  7. #7
    Join Date
    May 2010
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    Qualicum Beach, B.C.
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    Thanks Bob, I have to agree with you about support. The user forum was one of the main drivers that convinced me to go with Shopbot ten years ago. Being a neophyte with cnc the forums and Shopbot support were invaluable. I am proceeding with caution and if it's possible to soup-up our present machine at a reasonable price, that's definitely the route I'll take.

  8. #8
    Join Date
    Jan 2004
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    iBILD Solutions - Southern NJ
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    7,986

    Default

    You have to ask yourself how much your machine has made you over the years & then think about what you owe the machine in return. It's kinda like running a good American tractor for years reliably and then buying a Chinese one because it needs new tires.

    Plus, the SBP language is just SO nice to work with...I really wouldn't want to use a G-Code machine every day because I'd really have to think about operations that are 2nd nature in SBP. It's so easy to code.

    The hardened rail option seems expensive until you factor in all of the labor involved in drilling out & bolting up BWC or PB hardened rails. It's work to do it properly. The rail strips by themselves aren't more than $700 to do the whole machine, but the labor is where you get bitten. The SB solution is a bolt on deal. You'd be done in a 1/2 day & you wouldn't believe how smooth the machine becomes after replacement. It's a new machine again...with new rack too.

    A new PRS Alpha is upwards of $20k...Adding hardened rails to your well loved and productive PRT pretty much gets it to new Alpha specs since you already have the 7.2s. Don't throw the baby out with the bathwater...

    -B
    High Definition 3D Laser Scanning Services - Advanced ShopBot CNC Training and Consultation - Vectric Custom Video Training IBILD.com

  9. #9
    Join Date
    May 2010
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    Qualicum Beach, B.C.
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    Thanks Brady, the hardened rails will take care of the years of use and abuse that our SB has taken but that still leaves the Y carriage issue.
    We've already upgraded to the PRS Z setup but the Y axis is still handled by a single motor on our bolt-together gantry. Would love to either have a second Y motor or carriage assembly similar to the PRS machines. Again, the problems that we're noticing are on circular, arc or angle cuts particularly in acrylic. We almost lost a show (Robocop) when we weren't able to deliver satisfactory cuts to a large quantity of acrylic for them. - Boyd

  10. #10
    Join Date
    Jan 2004
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    iBILD Solutions - Southern NJ
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    The price you mentioned sounds to me like it includes the Y rails. I'm still rolling on angle iron rails (non-hardened but NOT soft malleable bent ones like 99% of the PRTs out there) - and I get great edge quality in acrylic. I have dressed them a few times with a file because of roll forging, but other than that they are doing just fine.

    Having owned a couple of PRS tools, I personally prefer the PRT gantry for it's lower center of gravity and stability. The PRS I-beam looks sexy and is more open & accessible than the PRT, but I still prefer the PRT config to the PRS personally...but hey - that's just me.

    -B
    High Definition 3D Laser Scanning Services - Advanced ShopBot CNC Training and Consultation - Vectric Custom Video Training IBILD.com

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