Hi,
I joined the Openbuilds community exactly a year ago and bought myself a 1500x 1000mm OX kit, TinyG and a Kress 800w spindle. Since then I have honestly just had problem after problem, some of which was my fault in testing limitations (3x TinyG’s later) but many, just through the billion variables required to work out in the DIY CNC world… hindsight I should have spent $5-10k on a pre-fab CNC as I will be using this for prototyping ideas for my next business.
What I am looking for is someone on the Central Coast or around Sydney to spend a few hours with me working out why I am having such trouble with accuracy, setting up the machine, G code and outputting it from Fusion 360 or SW17 and also the tricks to Chilipeppr… Before everyone says have you read the Wiki on the TinyG- It’s like searching for the answer before knowing the question sometimes and I am happy to pay someone experienced to help a brother out for money and I don’t mean $20 (I am willing to pay up to $500 for 4-8h)… on the other side I don’t want someone that’s just got one working without knowing that much to look at it (unless that’s all I can find near by).
I have the bigger OX as I want to be making some large detailed panels so unfortunately I can’t just move on to a Stepcraft2-840 directly (too small) or invest in some other unit right just yet
Cam software was a massive headache too but Fusion 360 and exporting a STEP file from Solid works might have resolved that unless I am advised of an even better way…
Please ask around- I have no one I know that can help at all locally (only used commercial CNCs and no clue on DIY)
Cheers
Mitch Taylor
So, what are the issues
To improve accuracy check for square on all axis, tram the z axis, change from belt drive to lead screw, change drivers from what you have to industrial Geckos. I prototype with my open builds machine and I have industrial grade drives IM483 I have belt drives that I have to constantly tighten and recalibrate. If you desire extreme accuracy then you will need to spend about $50000 US
There are so many small nigely ones, some include;
- Motor 1 and Motor 3 are my Y axis and sometimes (especially when doing backoff- limit one of the motor looks to be engaged but not the other or it’s delayed so the Y axis isn’t straight. This happens randomly sometimes jogging the machine too, Both motors are set identically and most of the time ok but it should be 100%
- Using Chilipeppr and JSON server makes my PC go spaz sometimes and I can’t close the server/ restart the PC… It’s a dedicated Intel NUC i3 with WIN10 64bit. Could possibly be something else but just adds more paid.
- In Gcode and jogging the Z axis is fine but when doing the Touch plate widget in Chilipeppr it always goes the wrong way first time but then I reset it and it goes the right way… I made the Z 150+ and the same in minus which someone recommended but still same result.
- I finally got the unit cutting and moving properly after finding Fusion 360’s CAMing software which is fantastic but trying to cut a 5mm/10mm keyhole in MDF and HDPE for mounting with a 3mm flat end mill ( tried 2 different type bits) it just cut horrible so inaccurate cuts. I slowed it down to 400mm/pm and even did 1.5mm passes but still was so bad. There’s no flex in the 3D printed mount so if it’s that it must just be the stock OX…
- Possibly related to above, I cut out a rectangle in the 16mm MDF and 12mm HDPE which was supposed to be 294x 224mm which ended up being 287x220mm so I changed the revoultions from 60 to 58 and got 303x 233mm so I thought I would try doing a quick check and calibrate it by doing a quick drill operation, send it 100mm x drill then 100m y and drill… and it was spot on the money to the 0.10mm.
Checked the Gcode and it was no different to the last cut which was so off… Just soooo frustrated!!!
Everytime I use it I am finding more small annoying things or spiratic behaviour from the machine when jogging or using Chilipeppr. Just hoping someone can physically show me what the tricks are to actually having some consistency with this thing.
Cheers
@Tracy_Ranson Thanks for the advice, I bought this machine before I knew much about CNC and yes if it was a quick change I would make all axis on thick lead screws! belts are just a waste of time IMO, too much fiddling and the lead screws are much more accurate with zero give when tightened properly… lots of work to change now. The Y axis is as still as it can be with reinforcement every 350mm or so.
What are geckos? individual motor controllers? I honestly don’t want to edit the machine much more than I already have now as it’s more sturdy than it ever was when I first built it and really don’t need it to be crazy accurate just get resonable 5x10mm keyholes and 2mm drill holes down pat so I can start to rely on it.
@Mitch_Taylor have you tuned the current on your stepper driver potentiometers? Sounds like you are either experiencing missed steps or backlash… Also engaging the motors at all times while operating will help with the racking you are experiencing along the Y axis. It’s a setting in the firmware
Also I do know there were some issues with circular interpolation (G2/G3 movements) in some versions of the firm ware I had to switch my post processor for my cam to interpret arc moves as G1 line segments to get better accuracy of larger holes made with smaller endmills
@Alex_Krause All motors are engaged when in motion so it should be holding, it’s the newest TinyG so the firmware would be the latest or close enough to. From what I have read that is rather old firmware that doesn’t support circular motion. Tuning these isn’t as simple as focusing a camera lens… It moves and doesn’t jitter unless the computer is slowing down so how am I to know if it’s right or not?
“engaged when in motion” can be the issue if that’s really what you mean. That means they’re only engaged when they’re moving so they’re free when they’re supposed to be holding while another stepper is moving. Make sure it’s set to “enabled in cycle” which means it’s powered when it’s moving or not. I learned that difference after my Z didn’t lock and I buried it into the bed while homing.
Mitch I have a Large Ox also and have had similar commissioning problems. I am a complete noob at cnc also but I did notice one thing that may be your problem that I have overcome, your spindle mount.
I had a Dremel tool as a spindle at first but have recently put a small Bosch router on a nice solid mount and just tonight I have finished replacing the Exreme wheels with stainless steel ones (bought 30 through aliexpress for $80Au)
@Mick_Hatton the spindle mount on my Z has zero play thankfully. It was 3D printed from another user and is cable tied and bolt tightened on. I’ve played with it and found the only give is in the Z axis but really isn’t that bad for the results in getting…
@Mick_Hatton comparably to the Z axis give in the rollers they had way less. The 3D printed mount is made to fit around the spindle and cable tie mount is just to secure the top. The bottom is clamped with 2 bolts. I’ve tried wiggling it and it’s not the issue
I had a major improvement in accuracy after installing the 4th pair of wheels and proper spindle mount, also do you have your X axis 60mm extrusions glued/joined together ? I used 4 pairs of these to join mine for extra torsoinal rigidity.
@Mick_Hatton x axis is screwed together. This machine is so much more re enforced thwn the standard OX wich many have little to no issue with so I very much doubt it’s the physical set up but thank you for the tips
Personally I would recommend added a 4th wheel on the Z (even reducing the size of the Z), getting a proper spindle mount, do the double belt mod, I would move the controller off the gantry and make sure everything is square and your spindle is tramed
@J_K11 , yes my thoughts exactly and having put stainless wheels on my Ox just recently I saw a further increase in rigidity.
The spindle doesn’t move in it’s mount. The whole neck of the Kress is in contact with the mount and has two bolts compressing it in. The 3D printed mount is solid and was designed to perfectly wrap and hold the top of the spindle. Cable tie isn’t lose at any contact point. When you try and move the spindle on the z axis the movement is in the wheels and mounts that connect it to the gentry. I could mod it and add dif wheels and extra wheels and more belts or even change it to direct drive threaded rod on all axis but as my thread originally pointed out… I’m pretty done with the whole thing. Keyholes shouldn’t be a problem to cut out with a completely standard Ox build but it’s not on my machine. I’ve seen peoples builds that are considerably less rigid than mine produce much accurate cuts. The main reason I posted was to find someone to visit and advise in person as there are too many variables to go over here…
I’m currently looking at just building a CNCROUTERPARTS Pro 4x4 foot system complete so there is no DIY angle or problems. Wish I did it to start!
@Mick_Hatton At be careful with those wheels. I can see them possibly wearing down the rails (just a thought not for sure).
@Mitch_Taylor You correct a standard OX can do that should fairly easily with good results. These are just possible solutions to you problems. To me you weak point is the Z axis (same with pretty much any ox). Personally I would solve your issues with your own OX before moving to another machines as the OX can do amazing things.