BuildingAfloat

[JAZZCNC]

I have followed Jazz's inputs on varied posts and have to say from what I have read I do have faith in his advice, however I was brought up to question everything where you have doubts, so I wont follow anyone blindly :-)

Good upbringing because I wouldn't want anyone blindly following my advice and I only offer it to help the person come to the best design for there needs and hopefully steer them clear of any issues I know thru experience will come from what I see or comment on.!

I have read that this idea can cause problems, yet one of my favourite machines out there is the Heiz from CNC-step, This was the inspiration for this feature being included in my build. They can't be that bad (well at least I hope they aren't) as their sales are in the 1000's now!

Ermm I wouldn't be so sure and they are certainly massively over priced IMO.!

Advantages I see are:

1) Open bed design, this is important for me as I will want to get awkward shaped engine components in the machine for engraving.
2) More grunt for moving the heavy gantry.
3) Even loading of gantry to prevent, or at minimum reduce, racking.
4) Reduced component count
and 5) Possibly better accuracy when compared to a single central motor & belt system?

1) preference really but open bed is generally less accurate and more time consuming to set-up accurately.
2) Yes
3) yes
4) Erm not really when you take account of electrical side, wiring etc.
5) Absolutely NOT and the reality in use is that they can possibly be less accurate due to any missed steps in one or both motors slipping by un-noticed until the error shows it's self in the work, which is far too late for me.!!

Disadvantages I see are:

1) Increased cost, but this should be a one-off.
2) Synchronisation/Alignment of the screws at the assembly stage, again this should be a one-off.
3) Machine ties itself in knots if one motor looses steps
or 3.5/4) Worst case scenario machine goes completely to peices should one motor stall or stop all together.

1) The cost difference isn't so much after buying belts and pulleys.
2) Big disadvantage and you'll be doing it all the time (every time you use the machine if you want to be sure of accuracy) either by butting up to adjusted hard stops or using home switch's to sync.
3,3.5/4) Massive potential for serious damage when it happens and unless the slaved motors are run well within there limits then it will happen for sure and it will scare the living day lights out of you at best.!! . . . Best case it will tie it''s self in knots wasting a few hours setting and adjusting backup.!!. . . . Worst case with high probability if it happens at high feed rates damage will occur leaving you crying and shacking in the corner. .

Slaved motors work fine if run within very safe tolerances regards tuning. They are very very intolerant of poor design causing any binding or miss alignment and will cause problems with stalling one of the motors while other continues on it's merry way causing chaos.!!

Belts completely remove this problem with very very good accuracy and are basicly fit and forget.!
In over 3yrs hard use my machine hasn't lost position regards screw sync more than few 10th mill and that was just in first few weeks due to pulley slippage and settling down.
In normal cutting use it has never missed a single step or lost positional accuracy. Again unless I cock up with programming and embed the cutter in something hard or try to run the gantry of the end it never stalls motor.!!. . . and if It does then no big deal just re-home the machine and I'm back on track with no damage to machine or hours straightening the machine out.!

The only down side to belts IMO is the look and the extra work designing into machine.? both more than worth the sacrifice or effort IME.