Please excuse my rudeness. Just so happy to find a group that might be able to help that I got all excited and forgot to introduce myself.
I'm from Oz and I have an interest in watches.
One of the lesser understood areas of watchmaking is the printing of dials.
This is typically done by producing an image into which ink is deposited.
This ink is then picked up by a silicone pad and the pad is moved over to the dial and pressed down upon which the ink is transferred to the dial.
I have made a fully manual prototype machine and I am looking to automate the process.
I haven't actually tried the manual system but expect to do that within a fortnight.
Some images on dials are overprinted many times to build up the texture of the numbers so I'm looking for a fairly high accuracy for repeatability.
The difficulty with this whole project is that I am working with so many grey areas where knowledge is gleaned in small slivers and I'm trying to put together the pieces of the jigsaw.
Actually, the cnc portion is fairly well documented overall but I don't yet have the experience to understand and implement all of the concepts.
Original post
I'm surely going to miss providing some of the required information so just ask and I'll provide (if I can).
The project is to build a pad printing machine.
This is a boring little machine that has an X axis that goes back and forwards about 110mm and a Y axis that goes up and down the same distance.
They effectively alternate in operation.
(As an aside, most commercial machines use pneumatics and I want to use electrics to remove the requirement for a compressor.)
A manual machine is built using Vslot components and I'm looking to see how much work would be involved to convert this to CNC.
As I have the prototype I have measured some forces with a digital scale.
I have picked a travel speed of 500ips (212mm/s) but I don't know how achievable that is. Speed is of the essence otherwise the ink will dry out before it gets deposited on the workpiece.
So X axis 110mm travel Approximations with g=10m/s/s Load 35N =3,5kg ~ 7lb Speed 500IPM 212mm/s
Y Axis 110mm Travel Load 120N = 12kg = ~25lb. This is needed to press the pad onto the stencil. Speed 500IPM 212mm/s
I have sized some steppers but that is a secondary consideration until I understand what drive system will work.
I was thinking of using 6mm GT2 belts but when checking the specs I see
GT2 6mm has a of working tension = 3kg and breaking tension = 56kg I could probably use that for X drive but I think commonality would be good so I would try and use the same drive system for X and Y..
For Y Axis the load (which only occurs at the end of the stroke) appears to be far too high for the 6mm belt.
I was trying to use 2 x NEMA23 with a holding torque 120Ncm (probably something like a 57HD4016-01-A which is just a motor spec I found on fleabay). At this point I have no idea if the model numbers tell anything about the stepper.
I was going to use one of the same motors for the X axis as well as I'm thinking that similarity would be helpful.
My lack of knowledge means that I don't understand how to overcome these items.
1. Belt load on Y axis is much higher than nominal (even with two belts).
If I can get it to fit I would expect I'd need a belt width of about 25mm for GT3. (I have downloaded a Powergrip GT3 Derive design manual but I can't see the working tension).
Or should I consider an Acme thread leadscrew?
If the GT3 is suitable it would appear that I need a 20mm dia pulley so the torque is sufficient.
2. I am not sure how simple it is to put the two steppers in parallel. The motors have 2 phases @ 5.2V and 2 amps each. Do I just buy a whopping power supply and plug them in parallel to one drive socket?
TIA.
BTW if someone wants to know more about the complete project please let me know and I'll be happy to answer what I can.
Regards
Alan