New Build 1000x600x200mm (newbie)

**Robin Hewitt** · 05-07-2015

I have never found a pulley separation calculator that got it right. I draw the two PCD's at around the separation I want, add two tangents to connect them as the belt would, trim the circles to those tangents, list the two arcs and one tangent then tally their lengths. Undo until I am back at two circles, tweak the separation and start again until I get it near as makes no difference. If you mount motor and shaft bearing in the same piece of metal you don't actually need any adjustment if your machine is accurate.

Make sure none of the pulley bolts coincide with the belt and if you are really canny you add a fixing for the plastic conduit that protects the motor leads, because that is never in quite the right place if you forget it now

**Noplace** · 05-07-2015

Hey guys, so just encountered an issue which is upsetting but hopefully with your guidance I can fix it. I didn't get a chance to take photos of the machine to show the problem but I'll explain it first now and hopefully post photos later if needed.

so I connected the actual side plates to the X Axis rail and ballscrews:

if you notice bottom 4 M5 screw holes are for connecting to the ballscrew nut bracket, this is the same screw you saw in the video, what happens is there is a mismatch between distance of the (4 M5 and 4 upper M8 holes) in the plate and the screw and rail distance so I have to lift the side plate a bit up to match the 4 M8 threaded holes and the when I screw everything fit the ballscrew is forced to strain upwards and causing me jittery movement if going slow along with noise and stalling at the far end side ( tested with drill just like video ) . it is opposite of result in video , very bad hopefully ill capture it but I don't want to repeat putting the sides haha.

so my question, can you just solve this by machining the side plate to have the same slot solution as we discussed for motor plate?
instead of 4 m5 holes ill have a slot of same radius but gives me little tolerance to adjust the height correctly?

hope this is clear, if not I will post a photo of the real thing but the place I have my stuff in has no Air conditioner so I have to plan a shower after it haha.

**njhussey** · 05-07-2015

You can slot holes so that you can have adjustment there's no problem there, of course it's better if they're spot on but once they're tightened up it won't really matter. I cocked up the dimensions on my Z back plate for the lower bearing plate for the Y axis and they're slightly slotted, it's still fine!!

**Clive S** · 05-07-2015

After you have put in the slots and you get it all true you could then drill another hole through and put some dowels in to hold it in position. ..Clive

**Noplace** · 06-07-2015

one of the local workshops made it for me, will test and cross fingers and hopefully no more stress on ballscrews.

on a separate note, back to the spindle I have tested it and seems to be working well with the relays and mach3, the speed is not being controlled accurately and I suspect the spindle pulley setting in mach3 but still didn't figure it out, ill post a video of this issue soon.

but main thing about spindle is I ordered and received a braking resistor, its 200W 70Ohm as per the spec in the document. I know it's not needed but thought what the hell, I just have to revert the P14 setting the sylveski mentioned earlier and I think all the other default settings are good. if anyone wants to advice on this part please let me know.

thanks!

**Boyan Silyavski** · 08-07-2015

Originally Posted by Robin Hewitt

I have never found a pulley separation calculator that got it right.

This one has it right. Proven a couple of times. Also drawing circles with pulley external dimension / teeth/ as per specs, connecting circles with straight lines at tangential points, deleting unnecessary and using CAD to calculate total length has proven spot on, even for a couple of pulleys where small to none adjustment was necessary.

**Robin Hewitt** · 17-07-2015

Originally Posted by Boyan Silyavski

This one has it right.

I have book marked it and I will give it a try next time I set a pair of pulleys.

It took me a while before I could bring myself to mount pulleys with absolutely no possibility of adjustment, but now I can't imagine why

**Noplace** · 01-08-2015

Quick question gentlemen, on my long axis I have a motor ballscrew setup for each side, what is the best way to align & make parallel both rail blocks/side plates/etc before attaching the gantry pieces and make one of the motors a slave? should I get a long machinist square? I don't have one that would reach all the way to the other side atm but would that suffice anyway?

thanks!