[Eric S]

First off, thank you all for contributing to this sites wealth of knowledge! I have been doing a ton of reading before starting a 5'x10' CNC plasma table build.
Just wondering if anyone here uses candcnc's servo's with planetary 10:1 precision Gearboxes? Was thinking on purchasing their kit but I am a little weary since I don't see many in use?


http://www.candcnc.com/BladeRunner_D...Cut_Servo.html

[plain ol Bill]

If they are offering it I'm sure it has been tested to the max. I would have no qualms about purchasing one. CandCNC stands behind what they sell and knows what customer service means. That's my experience.

[Eric S]

Thanks for the reply. I've read many good things about CandCNC which is really the reason I'm tempted to give these a try instead of using their other kit with 620 oz-in motors and make my own belt drives. I was hoping there might be a couple build threads out there that I missed that used them. I tried the search but it didn't come up with much.

[CNCCajun]

Dynatorch, along with about a 1/2 dozen+ other turn-key tables use gearboxes when using servos.

Besides, if Tom is using them, he has run them harder testing them than you ever will.

Face it, he knows what will make them fail if there is any potential for them to do so.

Visited his shop in Dallas. You can tell from just being there he & his people are very serious about what they do.

Steve

[Torchhead]

The BladeRunner servo with the smaller 23 servos and 10:1 precision gearheads is a relatively new product and most of the sales continue to be the stepper systems. We recommend the servos only when you need the wider torque range they offer. Typically a combo table with router and plasma starts to call for the servo approach or one where you need the added acceleration at all speeds that they offer. We have one setup and running in our shop but most of our day-to-day cutting is on our 620 stepper system. I never try to "upsell" a system to a customer. I try to match what the customer really NEEDS based on what they are cutting. The reason you HAVE to use gearboxes with servos is they are much lower torque but much higher RPM than steppers so you need much higher gear reduction to take advantage of the motors inherent characteristics. We have been making and selling servo systems with bigger motors now for many years and the same EZPLug interface cards with differential driver /receiver and a processor based monitoring circuit. The BladeRunner Servo is not just some servo motors thrown onto a stepper controller box. It is a downsize of our high end big servos systems we have been selling for. a long time. We spent a lot of time testing the motors and electronics because on paper the numbers were frankly really impressive. In testing we found that there were indeed some performance improvements. We took the acceleration up 3X over what we use on the steppers to over 100 IPS/sec.....only problem was that it was so high that on detailed cuts with plasma on thin material it made the HD gantry vibrate from the rapid direction changes. We moved the setup to a table that has a heaver gantry and a router mount and it is better utilized because it can go both types of cutting equally well.

TOMcaudle
www.CandCNC,com

[Eric S]

Thank you for the information Tom. The added acceleration is what I am really interested in. The 5'X10" table that I want to build will mostly be used for plasma cutting (steel 16ga-1/2" or so) but I am trying to make it a high quality unit that can cut corners nicely. I do not want to go though all the effort in the build to be disappointed with the results in the end.
If the budget works I would rather overbuild a bit than cut things close. I may add a router for random job here or there but the main design will be for the gantry to be carrying a Hypertherm Machine torch, plate maker and maybe a pneumatic spot drill.
Mostly I'm a little worried about backlash that might show up through wear of the gearbox. Belts are easy tightened as things wear.

[Torchhead]

The gears are all hardened and precision cut. The problem with belts and servos is that you cannot get a 10:1 ratio in a single step with off-the-shelf belst and pullieys. So you have to use a double belt system. More things to get loose. We have a bigger servo table used in daily production that has belt reduction and we have to stop and tighten setscrews at least once a month. Than you have to figure out where and how to included the double belt drive in the drive train. You cannot simple bolt it on the motor and go. We felt like the servo model needed to be interchangeable with a given table so you could use the 23 frame 620 motors with the 3/8" shaft or bolt on the servo's in the same bolt pattern and same output shaft size. On the bigger Precision Plasma gantry (MD and HD series) they come with belt reduction but you can get them to change the ratio to something like 1:5:1 or 2:1 and the match to the servo and gearhead will amp up the torque even more. The travel speeds of a servo with gearheads and 2:1 belt to a 1" pinion will offer you about 600 IPM top speed and some really impressive torque across the entire speed range. One of the principle advantages of servos are their relatively flat torque range at all RPM that means you can accelerate and decelerate at 300 IPM just as good as at 50. Steppers have a lot more low end torque but lose it as you go up the RPM curve and eventually just run out and start losing steps (Stalling). A properly designed stepper system can have good performance but in a more narrow range of speeds. The ratios we suggest for gearing on a stepper are for plasma cutting up to about 250 IPM. You will see statements the "servos are BETTER than steepens" or vice versa but it all depends on the application and it is NEVER as simple as that. It drifts into the emotional part of the spectrum like which is better: Gasoline or Diesel Engines. Servos improperly controlled or poorly implemented with the wrong gearing can be a nightmare. A poorly designed stepper table is just as bad.

We have been building and selling stepper and servo controls for years and there are pro's and cons on both. We use both here in our shop and we do not have to compromise because of cost.

[Eric S]

Thanks for all the information, it has been quite useful. I do believe I will be giving the your BladeRunner Dragon Cut geared servo system a go. Quite excited to get going but the devil is into details so back to the CAD system to get everything sorted properly...I hope

[fabricator909]

The gears are all hardened and precision cut. The problem with belts and servos is that you cannot get a 10:1 ratio in a single step with off-the-shelf belst and pullieys. So you have to use a double belt system. More things to get loose. We have a bigger servo table used in daily production that has belt reduction and we have to stop and tighten setscrews at least once a month. Than you have to figure out where and how to included the double belt drive in the drive train. You cannot simple bolt it on the motor and go. We felt like the servo model needed to be interchangeable with a given table so you could use the 23 frame 620 motors with the 3/8" shaft or bolt on the servo's in the same bolt pattern and same output shaft size. On the bigger Precision Plasma gantry (MD and HD series) they come with belt reduction but you can get them to change the ratio to something like 1:5:1 or 2:1 and the match to the servo and gearhead will amp up the torque even more. The travel speeds of a servo with gearheads and 2:1 belt to a 1" pinion will offer you about 600 IPM top speed and some really impressive torque across the entire speed range. One of the principle advantages of servos are their relatively flat torque range at all RPM that means you can accelerate and decelerate at 300 IPM just as good as at 50. Steppers have a lot more low end torque but lose it as you go up the RPM curve and eventually just run out and start losing steps (Stalling). A properly designed stepper system can have good performance but in a more narrow range of speeds. The ratios we suggest for gearing on a stepper are for plasma cutting up to about 250 IPM. You will see statements the "servos are BETTER than steepens" or vice versa but it all depends on the application and it is NEVER as simple as that. It drifts into the emotional part of the spectrum like which is better: Gasoline or Diesel Engines. Servos improperly controlled or poorly implemented with the wrong gearing can be a nightmare. A poorly designed stepper table is just as bad.

We have been building and selling stepper and servo controls for years and there are pro's and cons on both. We use both here in our shop and we do not have to compromise because of cost.

From reading the literature on you website, it seems there is no need to gear down these servos for a gantry under 120lbs, is that correct? I like the fact we could buy the servos and have a direct drive to the pinion, and not worry about belt reduction. Is there there any downside to using the standard 20 degree pa 20 pitch rack/ 1" pinion with a gantry that will weigh approx 80-100lbs ( on linear rails) with direct servo drive?

[Torchhead]

From reading the literature on you website, it seems there is no need to gear down these servos for a gantry under 120lbs, is that correct? I like the fact we could buy the servos and have a direct drive to the pinion, and not worry about belt reduction. Is there there any downside to using the standard 20 degree pa 20 pitch rack/ 1" pinion with a gantry that will weigh approx 80-100lbs ( on linear rails) with direct servo drive?

I am not sure where you came up with that other than the integrated gearheads (10:1 ) can drive a pinion gear directly for the target weight of 120 lbs. We rate our kits and motors based having good performance on cut speeds up to 250 - 300 IPM (sharp turns and corners) at the target weight. We are conservative with our numbers. You can obtain even higher torque numbers with an added 1.5 to 2.0 belt reduction. For a combo routing and plasma table with a full sized router the added torque is recommended. If you cut lot sof really thin material (i.e. 22ga or thinner) and you need more acceleration at the higher speeds to get sharp (tight toolpath ) cuts.


The direct drive with a 1" dia pinion will provide well over 1000 IPM of travel speeds. For that you give up the added torque/acceleration numbers of the belt reduction.

It factors down to what you want to do with the table and what kinds of things you are cutting and how well you want it to perform.

TOMcaudle
www.CandCNC.com

[Al_The_Man]

First off, thank you all for contributing to this sites wealth of knowledge! I have been doing a ton of reading before starting a 5'x10' CNC plasma table build.
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I have had a lot of luck with Bayside precision planetary, you can often get these for 10¢ on the $ off ebay example 230933305406
Al.