Page 1 of 3 123 LastLast
Results 1 to 10 of 22

Thread: Interesting ShopBot Blog Post (12/07/18)

  1. #1
    Join Date
    Mar 2013
    Location
    Memphis TN
    Posts
    696

    Default Interesting ShopBot Blog Post (12/07/18)

    I just read this interesting blog post from ShopBot. It has a number of points that contradict the opinions of experts that post on this forum.

    Anyone want to "fact check" this post?


    Why We Build Our CNC Tools the Way We Build ‘em
    ShopBot Details:
    PRS Alpha 96x60x12
    4hp Spindle
    12" indexer
    Aspire
    Rhino

  2. #2
    Join Date
    Apr 2007
    Location
    Marquette, MI
    Posts
    3,375

    Default

    So.... John,
    Because the written word, without tonal inflection can be easily misinterpreted, I need to ask: Since there appears to be differing opinions, which side would you believe to be more true? The link you posted or the opinions of those you refer to as "experts"? Personally, I have seen a good number of knowledgeable guys here, but none would consider themselves an expert. That said, most of them work in the real world using these machines and for the most part would disagree with the majority in that article.

    Myself, I would relish the opportunity to publicly debate Mr. Hall on these exact points. As I did when I worked for the company based on the first time he published that same spin: http://www.shopbottools.com/mProducts/ShopBotdesign.htm As you can see, this is simply regurgitated marketing hype with a few more modern "buzz words" and "catch phrases" added for effect. That first conversation ended in a draw with an agreement to disagree. Since that time, and especially not being an employee of the company, I believe that most every position in the original publication, or published specs here: http://www.shopbottools.com/mProduct...cs_compare.htm can be disproven using a combination of manufacturers data, engineering calculations and some real world testing combined with common sense. Did I mention that to ensure truth and fairness, I would require a panel of 3 impartial engineers to fact check both sides?

    For example the rated maximum speed. Advertised at 30"/sec or 1800"/min. Having owned 2 PRSa machines I can tell you that you can set them that high, but unless you crank the current much higher than the factory recommended settings, they will never achieve that velocity. Even then, on an 8' table there is a very short period of time spent at max velocity as most of the real estate is chewed up during accel and decel. And then there is Oriental Motors max rpm for the AS and AR98AA7.2 motors of 250 RPM. With a 30T pinion that has a pitch diameter of 1.5", a pitch circumference of 4.712" 250 RPM yields 1178.09 "/min or 19.6"/sec. The "published machine specs" show numbers more than 50% higher than the mfgr of the motors say they should be run. What are they set at when they leave the factory? My guess is even lower than the 19.6"/min rated max.

    And while we are at it, for those with a PC router and a ShopBot standard, lets see a show of hands who can cut 600"/min in anything other than air? It isn't very likely to be done 1/4" deep in box store insulation foam. The list goes on and on, but I can't.

    I'm over it. I'm sad. Just the fact that this regurgitated spin has been brought back to life after 6 or 7 years with improved graphics and even more catchy phrases is proof that things in Durham are not well. Desperate times call for desperate words, I guess.
    Gary Campbell
    GCnC Control
    GCnC411(at)gmail(dot)com
    ShopBot Controller Upgrades
    http://www.youtube.com/user/Islaww1


    "We can not solve our problems with the same level of thinking that created them"
    Albert Einstein


  3. #3
    Join Date
    May 2014
    Location
    Tucson, AZ
    Posts
    85

    Default

    I don’t consider myself an expert, but I do have two engineering degrees (one of them being mechanical engineering) and 35 successful years in the aerospace industry. With that as my pertinent qualifications, I’ll challenge a simple one of the claims to start.

    The blog post states “We avoid welded joints that can become distorted with time......”. That simply isn’t true. Welded joints that are properly designed and manufactured don’t change over time or they weren’t designed using industry standards and/or weren’t manufactured with proper techniques and materials. There’s a reason that the frame in my Ford truck is fully welded and not bolted together. It is rigidity and strength.

    Jim
    Jim

    96 x 60 PRSalpha, 5HP Colombo spindle, Custom indexer, Custom vacuum table, Custom Fire Extinguishing System

  4. #4
    Join Date
    Nov 2016
    Location
    New Mexico
    Posts
    67

    Default

    30 to 75"/min is our speed range here. (Desktop with router cutting maple ply)
    Dave B
    New Mexico
    Our most important shop tool is the pencil sharpener!

  5. #5
    Join Date
    Dec 2008
    Location
    Diamond Lake, WA
    Posts
    1,608

    Default

    After 10 years of using my PRSAlpha and going thru every tuning tip I can find, I can say that there is STILL a lot of inherent flex in the PRSAlpha. Other experts on this forum have shown me ways to develop cutting strategies that help compensate for this flex. They do significantly increase cutting time, thus loosing me money, but the cuts are very clean. When you watch a machine change directions and the whole machine shakes, you know it's NOT very rigid.

    The claim to make things backward compatible is a half truth. Years ago, Shopbot and Thermwood worked together to develop an interface program between Thermwoods eCabinets software and Shopbot CNC's. It was and still is the backbone to my cabinet business. However, I am stuck at the 3.6 versions of SB Control software because upgrading to the 3.8 versions would break the SBLink compatibility, thus putting me out of business. Another problem I had with control software over the years was that when released it was never ready for production use. It went thru several bug fixes to get it close to production ready. I'm sorry, I'm not a beta tester. The software should be 100% bullet proof when it's released.

    The one thing I didn't see mentioned in the blog article was the VERY weak link of using USB communication technology between the control computer and the CNC controller. This has been and will continue to be a VERY weak link in a Shopbot solution. Something needs to be done to eliminate the constant "lost communication" problem. Sorry Shopbot, but most of us don't work in a clean room. We work in dusty, staticy environments. That's a fact of production shops. Shopbot has still done nothing to address this problem. Having an electrical engineering degree so you can develop a good grounding system for your PC, CNC Controller, CNC machine and dust collection system should not be a prerequisite of owning a CNC machine in a wood shop. I was lucky in that my background was 23 years in electronics in the Coast Guard where I learned all about good grounding systems and how to implement them. I would surmise that most folks on this forum don't have this kind of background so the lost communications error problem is incredibly frustrating. After 10 years owning my CNC there is still NOT a solution to this problem. Shopbot FIX THIS DAMN PROBLEM!!!!
    Don
    Diamond Lake Custom Woodworks, LLC
    www.dlwoodworks.com
    ***********************************
    Life is not a journey to the grave with the intention of arriving safely in one pretty and well preserved piece; But to skid in broadside, thoroughly used up, worn out, bank accounts empty, credit cards maxed out, defiantly shouting "Geronimo"!

    If you make something idiot proof, all they do is create a better idiot.

  6. #6
    Join Date
    Mar 2013
    Location
    Memphis TN
    Posts
    696

    Default

    I find my PRSa to be an excellent and reliable machine FOR MY PURPOSES. That said, I noticed a curious thing the other day. I was aligning the X axis for use with the indexer and had a wrench balanced on my zero block (a 2x4 about 10" long) on the indexed bench. I was moving the X axis in .01" increments and the tool started wobbling back and forth considerably. Granted, I had been moving the tool a number of times and a harmonic had set in but still, moving the X axis .01" caused the entire machine to vibrate noticeably. Curious.
    ShopBot Details:
    PRS Alpha 96x60x12
    4hp Spindle
    12" indexer
    Aspire
    Rhino

  7. #7
    Join Date
    Apr 2007
    Location
    Marquette, MI
    Posts
    3,375

    Default

    John...
    Is this a recurring issue or a one off anomaly? If recurring, do you have a video or a set of actions to recreate? This does not seem to be something other than rare and has my curiosity up. There has been some oddities in the keypad operation since the modifications were made for the desktop, but yours is a new one.
    Gary Campbell
    GCnC Control
    GCnC411(at)gmail(dot)com
    ShopBot Controller Upgrades
    http://www.youtube.com/user/Islaww1


    "We can not solve our problems with the same level of thinking that created them"
    Albert Einstein


  8. #8
    Join Date
    Dec 2000
    Location
    Thorp, WI
    Posts
    2,675

    Default

    Yeah, if you're doing a fixed keypad nudge with the right settings for the fixed amount and get a good button press rhythm going, you can get a strong jiggle going. Especially in the X axis.
    Scott

    If guns kill people, I guess pencils misspell words, cars drive drunk and spoons make people fat.

    "Those who hammer their guns into plows, will plow for those who do not" - Thomas Jefferson




  9. #9
    Join Date
    Apr 2007
    Location
    Marquette, MI
    Posts
    3,375

    Default

    Quote Originally Posted by srwtlc View Post
    Yeah, if you're doing a fixed keypad nudge with the right settings for the fixed amount and get a good button press rhythm going, you can get a strong jiggle going. Especially in the X axis.
    Really??? With a bit of a tuneup even a PRS standard will fly: https://youtu.be/33gLcfC59pA
    Gary Campbell
    GCnC Control
    GCnC411(at)gmail(dot)com
    ShopBot Controller Upgrades
    http://www.youtube.com/user/Islaww1


    "We can not solve our problems with the same level of thinking that created them"
    Albert Einstein


  10. #10
    Join Date
    Jan 2004
    Location
    iBILD Solutions - Southern NJ
    Posts
    7,940

    Default

    Quote Originally Posted by Gary Campbell View Post
    With a bit of a tuneup even a PRS standard will fly: https://youtu.be/33gLcfC59pA
    That thing totally rips for a Standard. I've never seen a ShopBot running SB electronics (including an Alpha) move like that. I always wished they would though. Pretty impressive considering that controller is less than $300, including cables and power supply.

    Better. Cheaper. Faster. American. What's not to like? ShopBot should just use these and quit fooling with outdated ideas and tech. It's just better in every way. The wireless MPG is pretty sweet.
    High Definition 3D Laser Scanning Services - Advanced ShopBot CNC Training and Consultation - Vectric Custom Video Training IBILD.com

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •