Guitar builders CNC

[Eyestone]

My recent guitar project got me stuck on a routing problem I realized I could only solve with a CNC router. So I'm building one. 1200*800*500mm rails has been ordered and 3*nema 23's with 3Nm steppers, dm556 and mach3 usb board. I intend to use two lead screws to lift the gantry, driven by a belt and drive the Y with a stepper that has a steel rod with two pulleys running belts. Z is regular belt driven. The gantry I intend to make with four 40mm square tubes and plywood, putting a 2.2kw spindle in the middle, so it'll be pretty heavy, but rigid.

Since I've never had a CNC machine before, my knowledge is limited. I wonder if anyone could give me a clue to what type of belts and lead screws I should use. Would a 15mm GT2 be strong enough for this? And would 10mm lead screws with 8mm pitch work? I'm considering counterweights, though that would put more weight into it, so if I don't need it, maybe not.

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[peteeng]

Hi Eye - Don't use a 2.2kW spindle for this project. Its too heavy for the structure you are talking about (plus you are driving it with belts that will be springy and its mass will take a long time to stop vibrating) Use an 800W or 1500W water cooled spindle. If 1500W use a Er16 collet. That will take 10mm bits which for guitar work is a very good size... My first machine used 16mm AT belts and these proved to be very good. Made many necks and guitar bits for people using a 500W DC spindle. But I strongly recommend you do not use a belt for the Z axis. Too springy, which I found out on my first machine. When plunging you need a very stiff Z axis. Use a 4mm or 5mm pitch ballscrew for the Z axis.
Leadscrews are an unfortunate choice due to backlash and keeping them synchronised will be difficult, especially on the lifting Z axis. I recommend ballscrews.
15mm belts are strong enough but are springy, I'd go 25mm minimum after using 16mm belts on two machines. But go ballscrews, by the time you sort idlers, custom brackets and tensioners you are at same cost as ballscrews without the hassles and much much better performance.

Think through the lifting gantry a bit more. If your Z is 500mm ? It may not function as you thought it may. A long stiff Z is probably better then a lifting gantry. Plus make the machine a high rail design its much stiffer and keeps the dust out of the mechanics. See images attached.

Attached are photos of a mainly plywood machine I have just sold it goes to a surfboard shaper to make fibreglass fins. It cuts timber, plastic and aluminium very easily and it uses an 800W water cooled spindle. A bigger spindle does not mean you can cut any faster or deeper if the structure is not up to it. A 2.2kW spindle is a big heavy beast that requires a really big solid gantry to get the best out of it.

An 80x80mm gantry is not up to it, try for at least 100x100mm in steel and 120x120mm or a bit bigger in ply. A solid plywood gantry is stiffer and damper then a thin steel one and usually lighter. I'm making a 3m long plywood gantry at the moment for a 8x4 long ways machine. I'd flick Mach3 and look at Knighthawk (KN)/Commander. You can use the KH board with the drivers you have bought. The KH can use your mobile phone as a pendant which is really good. Its also wireless and by the time you buy a motion controller and machine controller your $$$ are more than the KH.

You won't need counterweights if designed well. Time to get busy on CAD and get a design together. Peter

Oh DM556 drivers - use the max voltage they can take ie 48V. The higher the voltage the smother and faster the motion.

- - - Updated - - -

Hi Eye - Don't use a 2.2kW spindle for this project. Its too heavy for the structure you are talking about (plus you are driving it with belts that will be springy and its mass will take a long time to stop vibrating) Use an 800W or 1500W water cooled spindle. If 1500W use a Er16 collet. That will take 10mm bits which for guitar work is a very good size... My first machine used 16mm AT belts and these proved to be very good. Made many necks and guitar bits for people using a 500W DC spindle. But I strongly recommend you do not use a belt for the Z axis. Too springy, which I found out on my first machine. When plunging you need a very stiff Z axis. Use a 4mm or 5mm pitch ballscrew for the Z axis.
Leadscrews are an unfortunate choice due to backlash and keeping them synchronised will be difficult, especially on the lifting Z axis. I recommend ballscrews.
15mm belts are strong enough but are springy, I'd go 25mm minimum after using 16mm belts on two machines. But go ballscrews, by the time you sort idlers, custom brackets and tensioners you are at same cost as ballscrews without the hassles and much much better performance.

Think through the lifting gantry a bit more. If your Z is 500mm ? It may not function as you thought it may. A long stiff Z is probably better then a lifting gantry. Plus make the machine a high rail design its much stiffer and keeps the dust out of the mechanics. See images attached.

Attached are photos of a mainly plywood machine I have just sold it goes to a surfboard shaper to make fibreglass fins. It cuts timber, plastic and aluminium very easily and it uses an 800W water cooled spindle. A bigger spindle does not mean you can cut any faster or deeper if the structure is not up to it. A 2.2kW spindle is a big heavy beast that requires a really big solid gantry to get the best out of it.

An 80x80mm gantry is not up to it, try for at least 100x100mm in steel and 120x120mm or a bit bigger in ply. A solid plywood gantry is stiffer and damper then a thin steel one and usually lighter. I'm making a 3m long plywood gantry at the moment for a 8x4 long ways machine. I'd flick Mach3 and look at Knighthawk (KN)/Commander. You can use the KH board with the drivers you have bought. The KH can use your mobile phone as a pendant which is really good. Its also wireless and by the time you buy a motion controller and machine controller your $$$ are more than the KH.

You won't need counterweights if designed well. Time to get busy on CAD and get a design together. Peter

Oh DM556 drivers - use the max voltage they can take ie 48V. The higher the voltage the smother and faster the motion.

- - - Updated - - -

Hi Eye - Don't use a 2.2kW spindle for this project. Its too heavy for the structure you are talking about (plus you are driving it with belts that will be springy and its mass will take a long time to stop vibrating) Use an 800W or 1500W water cooled spindle. If 1500W use a Er16 collet. That will take 10mm bits which for guitar work is a very good size... My first machine used 16mm AT belts and these proved to be very good. Made many necks and guitar bits for people using a 500W DC spindle. But I strongly recommend you do not use a belt for the Z axis. Too springy, which I found out on my first machine. When plunging you need a very stiff Z axis. Use a 4mm or 5mm pitch ballscrew for the Z axis.
Leadscrews are an unfortunate choice due to backlash and keeping them synchronised will be difficult, especially on the lifting Z axis. I recommend ballscrews.
15mm belts are strong enough but are springy, I'd go 25mm minimum after using 16mm belts on two machines. But go ballscrews, by the time you sort idlers, custom brackets and tensioners you are at same cost as ballscrews without the hassles and much much better performance.

Think through the lifting gantry a bit more. If your Z is 500mm ? It may not function as you thought it may. A long stiff Z is probably better then a lifting gantry. Plus make the machine a high rail design its much stiffer and keeps the dust out of the mechanics. See images attached.

Attached are photos of a mainly plywood machine I have just sold it goes to a surfboard shaper to make fibreglass fins. It cuts timber, plastic and aluminium very easily and it uses an 800W water cooled spindle. A bigger spindle does not mean you can cut any faster or deeper if the structure is not up to it. A 2.2kW spindle is a big heavy beast that requires a really big solid gantry to get the best out of it.

An 80x80mm gantry is not up to it, try for at least 100x100mm in steel and 120x120mm or a bit bigger in ply. A solid plywood gantry is stiffer and damper then a thin steel one and usually lighter. I'm making a 3m long plywood gantry at the moment for a 8x4 long ways machine. I'd flick Mach3 and look at Knighthawk (KN)/Commander. You can use the KH board with the drivers you have bought. The KH can use your mobile phone as a pendant which is really good. Its also wireless and by the time you buy a motion controller and machine controller your $$$ are more than the KH.

You won't need counterweights if designed well. Time to get busy on CAD and get a design together. Peter

Oh DM556 drivers - use the max voltage they can take ie 48V. The higher the voltage the smother and faster the motion.

[Eyestone]

Thanks for the response! About the gantry; my plan was to use 4 40mm square steel tubes, spaced 40mm apart, fill them with epoxy. Then they will have a plywood box around them, with rails on top and bottom of the steel tubes, 4 in total. The spindle will be sliding in between, fixed with two clamps.

Wouldn't ball screws for z let it drop, when you power off the machine?

I'll look into this knighthawk thing and keep thinking. I've been looking back and forth at BS, LS, belts and chains the last few days. I'll look more. Again, thanks for the reply!

[peteeng]

Hi Eye - There's lots of details to work through. Buy a motor with a brake for the Z axis. If the power is off the brake is on. You can also buy a brake separate if you have a two axle motor... Its wasting money going the epoxy route, may as well buy a bigger steel tube. Dual gantries are tricky, as one becomes dominant when the gantry deflects so at any point of time only one is resisting the deflection. So the dual gantry is inefficient, better to use one large member. May as well use a solid plywood section, will be damper and stiffer then the multipart steel thingy. Peter

[Eyestone]

Hi Eye - There's lots of details to work through. Buy a motor with a brake for the Z axis. If the power is off the brake is on. You can also buy a brake separate if you have a two axle motor... Its wasting money going the epoxy route, may as well buy a bigger steel tube. Dual gantries are tricky, as one becomes dominant when the gantry deflects so at any point of time only one is resisting the deflection. So the dual gantry is inefficient, better to use one large member. May as well use a solid plywood section, will be damper and stiffer then the multipart steel thingy. Peter

The steel squares and the plywood is basically because I already got them, trying to use what I got to keep the price down. I also have an enormous aluminum H beam, but I guess it's not the best profile for the twisting motions that might occur, even though it's massive. Or I could stiffen it with bracing I guess. Hmmm.. I'll look into the break. Good tip. The reason for the tall z is, I'm thinking, you loose 12-16cm because of the height of the spindle brackets. Then you need to be able to switch bits, I need at least 15cm for my acoustic guitars and I might want a 4th axis later. I'm guessing 40cm would do, but.. I guess I'll make a cad project to see how it looks, my drawings are too 2-dimensional. Thanks for the reply!

[peteeng]

Hi Eye - I have lots of scrap paper at home but I wouldn't make a machine from it. A 500mm Z axis is very ambitious. My machines have 350mm standard and it took at least 5 machines to get that right. Initially a CAD model is free so don't compromise a design by cost. You have already compromised the design by buying bits before you have resolved the design. You need to be clear about the machine requirements before you start, then design a machine that meets the requirements, then decide how to reduce cost. Keep at it. Peter

[Eyestone]

Hi Eye - I have lots of scrap paper at home but I wouldn't make a machine from it. A 500mm Z axis is very ambitious. My machines have 350mm standard and it took at least 5 machines to get that right. Initially a CAD model is free so don't compromise a design by cost. You have already compromised the design by buying bits before you have resolved the design. You need to be clear about the machine requirements before you start, then design a machine that meets the requirements, then decide how to reduce cost. Keep at it. Peter

Scrap paper and lots of glue can make a sturdy material. But yeah, I might be a bit hasty, more obsessed with the guitar build than the CNC. I'll take some time to figure out my design in CAD.
Assuming the gantry will be 20kg, what type of belts would I need for a machine like this?

[peteeng]

Hi Eye - Well bond paper is MDF just thin... If your going belts I'd go AT-25mm. But cost out ballscrews they maybe cheaper. Or go rack and pinion this would suit a lifting gantry quite well... The gantry plus the spindle, z axis etc will be more than 20kg....Better get busy in CAD....Peter