Upgrading questions...

[steve_g]

I have an older 1:1 Alpha... I know that the ASM911 swap to the ASM98AA-T7.2 is the standard upgrade path... I'm wondering what other options are out there. For example:
1) My 12" Z and A axis came with ASM98AA-T10 steppers, as is my B axis. If I went with them on the X and Y also... all my motors and drivers would be the same... one backup in reserve would serve any axis. I know that I would lose some top jogging speed but would not care if everything else was happy.

2) Are there still no off the shelf gearboxes available that fit the ASM911 Stepper? Belt drive reduction looks simple enough... just more than I want to construct by myself right now. Is anyone happy with their belt reduction units?

3) There are some ASD16AC / ASM98AC T7.2 motor & drive combos available on EBay reasonably. These are 220V units. The input says N---220. Will the residential version of 220 (-110 --- +110) work?

Thanks!

SG

[Brady Watson]

It is highly unlikely that you would have a motor failure with these drive systems. So the idea of interchangability shouldn't even factor in the decision process. Going 1/2 way around the world to save a few bucks on a motor of unknown quantity makes no sense to me...Not when list is $399 for the motor retail.

Belt reduction is the path of least resistance. You would have more torque than a 7.2 gearbox variant, and a tad more resolution.

-B

[steve_g]

I guess that's the final word then... I had hoped for a little more input.
Brady, thanks for yours. Your two statements... "It is highly unlikely that you would have a motor failure with these drive systems" And "a motor of unknown quantity" seem self contradictory.

I guess the desire for interchangeability is brought on by a "tick...tick,tick...tick" sound in my z axis during long jogs up or down, like when Z zeroing after a bit change.

$399.00 isn't so bad... but multiplied times 3 and add 3 drivers at $600.00 - $900.00 (new) each, makes for a fair investment and the used market attractive! All this for a machine that really is working well. I am just wanting a little better resolution when doing some of the logos and personalization I do... a very small part of my business. Speaking of business... As I slide ungracefully into retirement, my bot is going from workhorse to pet! This is why I had hoped to keep the upgrade price under $1000.00. I can do this with used equipment or likely with some belt drive cobbling...

SG

[richards]

I had the original 1:1 motors on my PRT-Alpha and then built a series of 3:1 belt-drives. Chatter was reduced significantly. Later on, I bought the 7.2 motors/drives that were offered in an upgrade kit. There was no noticeable improvement in cut quality over the 3:1 belt-drive.

I would suggest that you try a belt-drive system on the X and Y axes.

[Brady Watson]

"It is highly unlikely that you would have a motor failure with these drive systems" ...And a motor of unknown quantity" seem self contradictory.

It does sound that way, until you factor in the part about them being from 1/2 way around the world...Is the pigtail connector cut from the motor? Is the shaft all galled up? Does the motor look like it was laying at the bottom of a lake? There are other attributes to a motor than it's electrical ones...

The tick-tick is normal backlash in the gearbox - unless your Z rack gear lash is not set correctly.

Early on, some PRs came with belt reduction boxes on them standard from ShopBot. Mike was the first to put them on an Alpha and report his findings to the group. It seems like the best solution - and it should cost you no more than $600 to do all 3 axes, maybe 4.

-B

[bruce_taylor]

Anybody making the parts for the gear reduction? When I have some down time I would like to make some for my bot.

[steve_g]

Bruce


parts for the gear reduction? Did you mean belt reduction?

SG

[steve_g]

Brady

Thank you for pointing out what should have been obvious to me! Free shipping from Korea isn't free if the product has been abused. It's the proverbial "pig-in-a-poke". I've had nothing but success buying from other botters here on the forum... Ebay-ers in Korea may not have the same standards!

I'm investigating belt-drive methods.

SG

[CNYDWW]

Not to interject but i found these some time ago and have bought some products off the guy. Fast shipping and reliable as far as my experience goes.
He's got gear boxes for motors here...

http://www.kelinginc.net/CNCGEARBOX.html

Just food for thought.

Regards
Randy

[bleeth]

OK-I'm not a complete stepper motor expert but I was just directed to the following supplier for a couple transformers by my machine maintainence guru and the same product I needed was twice as much elsewhere.

They carry a lot of stuff for do-it yourself modification freaks!!

http://www.automationdirect.com/adc/Home/Home

For parts to build your own gearboxes Misumi cannot be beat for great service, quality, and fair pricing.
Steve:

Drop me an e-mail regarding that route.

[mrsoliver]

I have prt alpha with the ASM911's - would like to add gearbox - anyone have a source for buying - not making - thanks Scott

[steve_g]

Scott

The only over the counter gear boxes I know of are the ones Randy D. gave a link to earlier in this thread... Those have a backlash of 6 arc seconds. I don't know what that means in terms of CNC, but I've been told it's 12' over 3000 miles. I'm in the process of installing belt drives I bought from another ShopBotter, this was the best solution for me.

SG

[richards]

There are easy ways to make your CNC router "sing". Some of the eariler Shopbots used stepper drivers that are inferior to the stepper drivers available today. That should not be suprising. Most of "yesterday's" electronics are inferior to today's electronics.

I prefer to use Geckodrive stepper drivers when "upgrading" a stepper motor/stepper driver system. They make reliable products at an affordable price.

I also like to use belt-drives instead of gearboxes. Belt-drives are bulky, but they are simple. It's far easier to replace a $20 or $30 component than it is to replace a $250 - $800 stepper/gearbox. If you have room, investigate using a belt-drive before spending a lot of money on gearboxed motors. I tried both. Although the upgrade motors offered by Shopbot to replace the motors that came with my PRT-Alpha were a bargain, when compared to the cost of buying those same motors directly from Oriental Motor, they cost many times more than it cost to add a belt-drive to the original motors. Cut quality was NOT improved with the gearbox motors when compared to the belt-drive motors.

Sometimes we forget that a CNC router can easily cut DelRin and other "plastics" that are required with belt-drives. Why not improve the cut quality of your machine if you can do it for $150 or so per axis? Belt-drives are not rocket science. Anyone who can cut dovetails can cut the parts for belt-drives. Measure carefully and you'll do just fine.

If you need a little advice, email me at miker@xmission.com. I'm old and I'm feeble, but I try to answer emails in a timely manner.

[steve_g]

I finally got my belt reduction boxes installed... The Y car gave me grief! I finally had to remove the Z axis to get clearance enough to get my hands and tools in there. I think the close quarters was because I have two Z axis' and they are located at the outside edges of the car rather than one in the center.

I've never had transfer rate issues even though I have only had a 42% transfer efficiency rate. After having to triple the unit values I had to clean things up and do it right with a powered hub. Now I'm at 72% and everyone is happy!

I haven't cut anything yet... hopefully tomorrow, after I square up both Z's. It's also time for a new spoil board. It's hard to imagine how different the Bot sounds now! It really sounds quiet and smooth... I think the biggest difference may be that the motors are now essentially isolation mounted and no vibration is transferred from the motors to the frame.

So far mechanically I'm very pleased with this route of upgrading. everything is solid and simple. I'll try cutting tomorrow.

SG

[mrsoliver]

Steve does he make and sell them - would be interested in purchasing a set - thanx- Scott

[steve_g]

To anyone interested...

My source was Mike Richards... He is not in a situation where he can make more drives, but is willing to discuss them If anyone wants to contact him off-line (miker@xmission.com).

Also Dave RosenBleeth has a set of plans he sells.

SG

[richards]

If you already own a Shopbot and if your controller puts out step and direction signals (as opposed to CW/CCW signals) and if your controller can output a pulse stream 3X faster than it does now, you can convert your machine to use belt-drives.

The advantage is 3X to 4X more torque (depending one the pulley ratio that you select). My PRT-Alpha without a gearbox, output a little less than 600 oz*in of torque. That's the same as 37.5 lb*in of torque. The 7.2:1 gearbox Alpha motors are limited to 80 lb*in of torque. That's a significant improvement. Those 600 oz*in motors become 1,800 oz*in motors (50% greater than the 7.2:1 motors). That's even more of an improvement.

The disadvantage is bulk. Look carefully at the photo that Steve posted. Did you notice how the body of the belt-drive hangs below the rack? That reduces clearance on the Y-Axis. That was not a problem to me, but it may limit the type of work that you can do. Another disadvantage is that YOU have to design and build your own belt-drives. It is not hard, but it may take a try or two before you get it the way that you want it. I designed four different models before I was satisfied.

Send me an email off-line if you have questions. (miker@xmission.com)

[steve_g]

I thought I'd post another image of the reducer actually on the Z axis... The arrow shows my actual loss of Z axis to be less than 1/2". Fortunately I had 12" to start with!

I wrote a little program to air cut a 36" diameter circle increasing the speed until I missed steps. At 7"per Sec I started noticing little hiccups, and serious problems at 8. I figure if I cut at 6ips or less I can keep the resolution selection switch at 1000, however after reading old posts, people have reported no significant degradation in cut quality after setting the resolution to 500. Just a reminder... jog speed is not the same as cutting speeds.

I tried my first cuts on a logo Thursday night with horrible results! an examination of the belt drive installation revealed I had failed to tighten the set screws on the pinions after I aligned them with the rack. I was able to sleep that night knowing I could fix the problem... I woke up early Friday AM with a sore elbow and an arm the size of a watermelon (slight exaggeration). Subsequent doctor visits reveled a torn blood vessel, long story short... I've been banned from the shop and life in general and haven't been able to try my hot rodded bot!

Hopefully today!

SG

[roney c]

Steve, I'm sure some of us are waiting for a report on your arm and Oh yeah, your belt drive results...how's it going?
-RC

[steve_g]

Roney and all...

Sorry to keep ya'll at the edge of your seats! Those of you who know me personally know that I walk with a cane and a limp... My ShopBot crafted canes are nice but the limp has been getting real bad. The issue with my arm turned out to be a fracture suffered from a fall... to make a long story short, I get a new hip Wednesday the 19th.
Understandably my shop time has been limited... However, I'm very pleased with the cut quality I'm getting now. The testing I did earlier by air cutting a three foot diameter circle to determine maximum possible cutting speeds apparently was not a legitimate test. All was fine until I tried V-carving a detailed logo... the bot was not happy. I had to reduce the pulse count from the driver from 1000 to 500 (remember it's an Alpha). My initial results were very exciting but things seemed to slowly deteriorate... Close examination showed that the set screws on several of the pinions had worked loose... New set screws with a locking compound seems to have brought back the initial excitement! Cuts I did today in HDPE are the best I've done in plastic on the bot. The recurring corporate logo that prompted the desire to upgrade has text in it about 1/8" tall... I believe a recent batch I did reached the limits of the substrate rather than the Bots abilities.

In conclusion... I'm not reverting to pre belt-reduction any time soon! Also, if you're designing your own and can get set screws that use something larger than a 5/64" Allen wrench, you'll possibly avoid some issues I've had.

My surgery rehab days include plans to edit an article on "hold down methods" similar to the one I did on "router bit basics" more on that latter in another thread!

SG

[roney c]

Thanks for the updates Steve. Best wishes and a speedy recovery.
-RC

[aschutsky]

Steve - I know it's been a while but thanks for posting your impressions. It seems clear that the belt reduction upgrade is the clear path vs. the motor upgrade alone. Is anyone aware of plans, kits, or assembled boxes for sale for us 911 motor owners? :)

[steve_g]

Andrew…
As far as I know, Talking with Mike Richards or buying Dave Rosenbleeths plans are still the best options…
SG

[Gary Campbell]

I may have another option. Belt reduction units for the PRT similar to those shown in the pics below. Prices as follows:

X1, X2 & Y gearbox on PRT bracket. (requires drilling an additional hole for stability)
For NEMA 23 nongeared motors (3/8 shaft): $275 ea with 350 ozin motor: $400
For NEMA 34 nongeared motors (1/2 Shaft): $300 ea with 600 ozin motor: $450
For AS911 NEMA34 nongeared motors (14mm shaft): $350 each

Z axis (non swivel mount) reduction box for R&P: $300 with motor add as above
Z axis AS911 (non swivel mount) reduction box for R&P: $350

Z axis ballscrew assembly with mount kit: $400 with motor: $550 (standard Z) Extended add $75

Prices assume purchase of 4 units minimum. Single price add $100. Lead time 3-4 weeks, as they are made to order.

Ratio is 3:1 (standard) for 4:1 add $25 per unit

For more info contact: caseworxmfg (at) gmail (dot) com

PRT swivel reduction units are similar, but not exact to versions shown!! Current version uses bushed 3/8" aluminum in lieu of steel swivel plate.

[Gary Campbell]

I've had a number of inquiries and sales (thanks guys) regarding the belt reduction units for the direct drive PRT Alpha with ASM911 motors. Yes they are available, here are the specs and prices:
Units are $400 USD each in groups of 4. They are constructed from billet 6061 aluminum with pressed in ABEC3 sealed bearings and have all keyed shafts. Reduction ratio is 4:1 (only) using HTD 15mm wide belt. All hardware, pulleys, belts and 24t pinion gears are included. There is also the option to add a second support bolt in a provided slot if your application requires it. All components are cut on my CNC Bridgeport Mill. Z product is available to fit most every version of the PRT Z assembly, including the new style Retro Z. Custom configurations are available.

Torque is 3.3 times that of the original with 20t pinion. Resulting unit value is ~2122 steps per inch.


Units ship will full instructions and an "SBD" file with new unit values installed, ready for a few clicks to import.

For more info email: GCnC411@gmail.com
Here are a few pics:

http://www.talkshopbot.com/forum/attachment.php?attachmentid=27753&stc=1http://www.talkshopbot.com/forum/attachment.php?attachmentid=27754&stc=1http://www.talkshopbot.com/forum/attachment.php?attachmentid=27755&stc=1

[jon]

Those reduction units look great Gary. I am a little confused however concerning the comparison between these 4:1 belt reducers and the 7.2:1 tapered hob gearbox motors from Vexta. Would the resolution not be almost double with the 7.2's compared to the 4:1's?

[Gary Campbell]

Jon...
Simple answer no. Do your homework. Remember that resolution is what you set it at. Also remember those are different motors with different drives with 20 and 30 tooth pinions. Also remember that cut quality is a combination of speed, resolution, torque (the ability to hold position at microstepped levels) and backlash.

Each and every one of those is changed by resolution settings, reduction ratio, pinion size and motor torque. Combinations are developed are always a compromise. Laws of physics, when one spec is increased, most certainly another will decrease.

[jon]

Gary, I'm trying to do my homework here by understanding all of this. I suppose that the reason shopbot used the 30 tooth gears was to give the bot a smoother action on the linear rack. Do you know if it's worth it to put the 20 tooth pinions on the 7.2 motors? If I made a 2:1 reduction belt box and added it to the 7.2 gear head would there be more backlash than resolution gain? Would the communication and software be able to handle that? I have the newest control card in my box.

[Gary Campbell]

Jon...
Your idea of homework and mine are different, I think. So between myself and a couple of friends I have access to uncounted hundreds of hours with motors and racks and pinions, dial indicators, torque meters, even a small hydraulic stepper dyno. That's homework. Finding out what someone else "thinks" in the internet is not.

I assume that the 30 tooth gears returned the best combo of speed, torque and cut quality within the range they were looking for. Actually this is true.

I know for a fact that there will be an inverse gain using 20T pinions on the 7.2TH ASM's.

Adding 2:1 reduction will not improve anything, except in the most rare of cases. You want these motors to stay in their torque range to be able to hold position on angular and radiused cuts.

The backlash, 6 arc minutes or 1/10 of a degree is inherent with those 7.2 gearmotors. 1.5" pinion * pi / 360 /10 is seldom the cause of issues. Pinion wear, wear from use and maladjustment are far more likely to cause issues.

Buy a set of the new AR series motors and drives and throw them on.