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Apr 19, 2019, 10:33 AM
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Discussion

Start with a HobbyCNC board?


Time for me to build a foam cutter.

I have a HobbyCNC board I built a few years ago but have never used. I assume I didn't do too bad of a job and think it probably works.

However, the HobbyCNC board seems to be a bit dated and requires six-wire motors. Those seem to be more expensive than unipolar motors.

Am I better off grabbing another controller solution and unipolar motors or is the HobbyCNC board good enough it is worth the more expensive motors?

This board: https://hobbycnc.com/product/hobbycnc-pro-4-axis-kit/
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Apr 19, 2019, 11:17 AM
Father of Fr3aK, DLG Pilot
tom43004's Avatar
I used a HobbyCNC kit for my recent build. Unipolar motors can be had for about $40 on ebay.

Many "hybrid" motors can be rewired to unipolar as well. Make sure your motor current is compatible with the HobbyCNC board. I think it ranges from 1.0 to 3.0A IIRC.

Here is a similar auction. Just make sure you're finding 6 wire motors.
https://www.ebay.com/p/5-X-Stepper-M...2781443&chn=ps
Apr 19, 2019, 07:34 PM
Summit Model Aeronautics
Steve85's Avatar
I've built two HobbyCNC boards and used them for several years now without any problems. You should be aware however that some of their boards have a well-documented issue with their idle current limiting function, which suspends power to stepper motors if they've been idle for a specified time (in order to prevent excessive heat build up). The problem occurs when the motor driver powers up again after being idle, with lost steps being the result. Not all boards have this problem (any board lacking idle current reduction isn't affected) and a straightforward fix requiring minor rewiring of the board is readily available following a Google search.

Steve
Apr 19, 2019, 08:00 PM
Registered User
Thread OP
Thanks for the info. I was thinking I would order some motors todsy, guess I will keep on with the research first.
Apr 20, 2019, 10:04 AM
Summit Model Aeronautics
Steve85's Avatar
Check out this link for the fix:

https://forum.shapeoko.com/viewtopic.php?f=25&t=2691

Steve
Apr 22, 2019, 03:50 PM
Aurora Builder
Now I'm curious what Tom built with his...EDIT: hotwire cnc from his other thread.

They are good boards and can work fine but the Gecko 540 is quieter, enables idle current reduction, is more tunable and generally simpler for not too much more money.

The other option I would look into is the new BlackBox from openbuilds, at $150 in a nice case with easy connectors, I would have a hard time recommending folks spend $105 on a HobbyCNC board with the same functionality but caseless and outdated driver tech: https://openbuildspartstore.com/blac...roduct-reviews

Still, if you have it it will work!
Last edited by samc99us; Apr 22, 2019 at 04:19 PM.
Apr 22, 2019, 07:38 PM
Registered User
Quote:
Originally Posted by rcsoar4fun
....However, the HobbyCNC board seems to be a bit dated and requires six-wire motors. Those seem to be more expensive than uni-polar motors....
6 wire motors are uni-polar motors. They are outdated as are uni-polar drives like the HobbyCNC board. That does not mean they won't work for a foam cutter. If you have both motors and driver already then I would give it a shot. Foam cutting is low speed anyway. If you have yet to buy motors then buying old fashioned uni-polar motors may not be a good investment. Bi-polar motors (4 wires) and drives have a far greater selection.

8 wire motors can be setup as uni-polar or bi-polar (series or parallel).

6 wire uni-polar motors can be used with modern bi-polar 4 wire drives by leaving the two center tap wires disconnected. That's not advised due to the very high inductance. Or you can run in half winding mode, leaving one coil disconnected. That puts you into kludgey territory trying to match uni-polar motors to bi-polar drivers. But if you just need a low cost kludge then it might be OK.
Last edited by aerobear; Apr 22, 2019 at 08:08 PM.
Apr 22, 2019, 07:51 PM
Registered User
Quote:
Originally Posted by samc99us
......the Gecko 540 is quieter, enables idle current reduction, is more tunable and generally simpler for not too much more money.......
I hold Gecko products in high regard but I'm not opposed to trying other things. I got some Leadshine DM856 drives to try. $35 each through ebay or 4 for under $150. Substantially higher voltage and amperage rating than the G540. 5.6A vs 3.5A and 80V vs 50V. That's overkill for a foam cutter but it lets you run much stronger motors than the G540 can handle if you have dreams of bigger machines later. The 570oz 3/8" shaft motors from that place in Chicago are a good match. $40 each. The DM 856 can supply the current and voltage to run those at full power. Works out to about $75 per axis for motor and driver. The disadvantage is there is no built in break out board like the G540.
Apr 22, 2019, 08:07 PM
Father of Fr3aK, DLG Pilot
tom43004's Avatar
I loved my G540 but it wasn't strong enough for my last CNC build (Nema34s) so I used 203Vs on that. I chose the HobbyCNC for my foam cutter simply to save money. Foam cutting is low speed, low cost, lower precision, low current. Start with about $100 for the HobbyCNC kit plus about an hour to assemble and test it, then add cheap ebay (unipolar) steppers and I had less than $150 in electronics.

I also bought an Arduino / RAMPs control system but I really wanted to simplify heat control with the GCC2, so I chose this route. I'll use the Arduino and bipolar steppers I bought for that in another project (laser maybe?)
Apr 22, 2019, 08:47 PM
Summit Model Aeronautics
Steve85's Avatar
Yeah, if I were building my first CNC that Openbuilds BlackBox looks pretty sweet. OTOH, HobbyCNC boards are still quite useable (mine cuts kits a couple times a week) and sometimes it's fun to see if you can use what you've got.

DIY CNC has certainly come a long way in the past ten years or so.

Steve
Apr 22, 2019, 08:50 PM
Registered User
Thread OP
Quote:
Originally Posted by Steve85
DIY CNC has certainly come a long way in the past ten years or so.
Indeed it has, hence the problem at hand.
Apr 22, 2019, 09:29 PM
Registered User
Quote:
Originally Posted by Steve85
....DIY CNC has certainly come a long way in the past ten years or so.
No kidding. In the 90's, anything with any kind of power was big bucks. I was poor so I build drives on PCBs I etched myself and drilled by hand. Still only miserable half step drives. When Gecko came along in about 1996 I said "Shut up and take my money". Those drives are still in service. G201 rev A. Quality pays off in the long run. Many more good choices now.

Now even low end servo systems are within the reach of DIY builders. It's a great problem to have.
Apr 22, 2019, 09:37 PM
Summit Model Aeronautics
Steve85's Avatar
Yup, we're plagued with first world workshop problems. . Ten years ago, there were still shops in Kandahar that built AK-47s from scratch by hand...

Steve
Apr 23, 2019, 03:10 AM
Registered User
I know this wont be very popular in The US ..but use some chinese stepper drivers based on tb6600 chips..almost bullet proof and approx 1/3rd the cost of gecko, which if you read threads in this and other forums are prone to over heating.

eg
https://www.aliexpress.com/item/Free...a-47ce6f2dca9e

or 4 of these

https://www.aliexpress.com/item/New-...3-33d5f98dc1e0
Apr 23, 2019, 05:53 AM
Registered User
Quote:
Originally Posted by jregholdsworth
.drivers based on tb6600 chips..
Plenty of these sold in the US. $35 for 5, shipping included! I bought one just to play with. It was advertised as "updated version" but did not actually use the tb6600 chip. Instead they substituted a lower rated Toshiba surface mount chip. Same case and they filled the empty space with a small filler piece of aluminum to make contact with the heat sink. Some of the Chinese sellers are pretty slippery. I'm sure a real tb6600 is more than enough for foam cutting. Just make sure you have a solid money back guarantee in case the seller is playing games.


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