Lure Duplicator...looking for some help

[JasonB14]

So for now I have scrapped the idea of going CNC to make the lure I’m wanting to make and have decided to build a lure duplicator utilizing a 4” angle grinder with a saw blade. I have a pretty good idea of the frame and using linear bearings for the grinder to ride on and using a 50-60 rpm motor for the turning of the wood and master but where I get lost is the carriage. The rpm of the motor vs thread of the lead screw to ensure that I get about 1” per minute movement on the carriage.  
Is there anyone here that’s built one that would be willing to give me some insight and I’m sure save me some time and money? I’d be willing to pay for good advice and help in this project. 
 I’d like to have it setup where grinder is on top and master is on bottom just for space saving but that’s not set in stone. I have linear rails and bearings already from where I was going to build a pantograph type duplicator but I think the grinder deal is a much better option for 3D and the lure I want to make. I would like to make one similar to the one pictured but my electronic and engineering skills are lacking. I do have a full machine shop and wood working shop in my basement so no lack of tools. 
 

thanks In advance 

[Vodkaman]

Good choice of cutter, you seem to have a good understanding.

The solution is gearing. The travel threaded spindle rotates at half the speed of the master and woodblock spindles. You can see in the image that the master and woodblock spindles are driven by the motor. What you don't see is the bicycle chain gearing to the motor carrying spindle geared at a ratio of 2:1

Dave

[JasonB14]

I’ve got some stuff in my cart now for a prototype but having a hard time finding a decent sized leadscrew with threaded collars. I’ve got a 12v dc 60rpm motor in cart for block and master and a 10rpm for Carriage that I plan to wire through a potentiometer to dial carriage speed in. 
 

would 3/4” -16p threaded rod hold up ? Was looking for acme rod but having a hard time finding the rod and nuts at a reasonable price

[Vodkaman]

OK, now you are  getting down to the real BONES of duplicator problems; the drive screw. The two major drive screw problems are deflection and slop. In my first duplicator build I basically ignored these two issues.

Deflection - sling a threaded bar between two bearings and hang a 2Kg weight on the thread and there IS going to be deflection of the bar. The deflection depends on the diameter of the bar, the distance between the support bearings, the mechanical properties of the bar and the weight of the carrier.

Slop - Basically the tolerance of the thread and the fixed nuts in the carrier. If you are using precision drive screw then the tolerances will be tight and the problem eliminated with $$$s. If you are using standard issue threaded rod (as I did) then you are in for a world of problems with repeatability. Slop and deflection will give you an end product that is significantly different to your master.

For me, an expensive machined drive screw was not an option, but in terms of cost and availability. I had no choice but to go with standard threaded rod. Even though I did not deal with deflection and slop, I was happy with my results, but the differences between the master and the product were a concern, but the results were consistent.

However, before I could build the design that tackled the problems of deflection and slop, I was evicted from my house and lost everything that I had done, my workshop, templates, machines and tools were all gone.

I did build a second machine before I lost the workshop. It addressed the deflection issue, but it was not a good solution.

If I were to build a third prototype, I would still use 12mm dia standard threaded rod with a 1mm thread pitch, I would support the weight of the cutter machine on separate rails, thus leaving the threaded rod to push and pull the carriage with no bending loads.

The slop can be taken care of with some thoughtful, creative design. I found solutions by Google.

Dave

[JasonB14]

Yessir the bulk of my weight will be supported by linear rods and bearings. Doing some math the 16tpi threaded rod would only move the carriage .630 in a minute with the 10rpm motor if I go 8tpi then I get 1.250 in a minute and I can dial that down with the potentiometer correct? I may look at an 8tpi precision drive screw and see how much I’m looking at 

[Vodkaman]

I am not going to advise you on your choices because I do not have practical experience of those choices, all I can do is pass on experience gained from the choices that I made.

There is simple math to help you with deflection questions. You can Google deflection calculations. You can then decide whether it is a good solution for you to support your cutter carriage on the threaded drive. Decide in your head what is an acceptable deflection, say 0.5mm. This would give a cutting error of 1mm (twice the deflection error). Then collect all the required information and do the calculation.

Other problems to be considered in your design are spindle alignments. You have three major spindles spanning the machine; the woodblock spindle, the master spindle and the cutter carriage spindle, and ALL must be in perfect alignment. If the side plates are cut by CNC or a skilled machinist then the alignment problems will be minimal, but if you are cutting yourself then you had better build in some adjustment, and figure out some procedure for performing those adjustments.

I am not trying to discourage you, merely identifying the problems that you will face.

Best advice is to build the first prototype with the understanding that a 2nd prototype WILL be necessary to solve the problems identified in the first build. My first two builds never got as far as mounting motors, they were both hand cranked. Proto3 was slated to use a 12v car wiper motor.

Dave

[JasonB14]

19 minutes ago, Vodkaman said:

I am not going to advise you on your choices because I do not have practical experience of those choices, all I can do is pass on experience gained from the choices that I made.

There is simple math to help you with deflection questions. You can Google deflection calculations. You can then decide whether it is a good solution for you to support your cutter carriage on the threaded drive. Decide in your head what is an acceptable deflection, say 0.5mm. This would give a cutting error of 1mm (twice the deflection error). Then collect all the required information and do the calculation.

Other problems to be considered in your design are spindle alignments. You have three major spindles spanning the machine; the woodblock spindle, the master spindle and the cutter carriage spindle, and ALL must be in perfect alignment. If the side plates are cut by CNC or a skilled machinist then the alignment problems will be minimal, but if you are cutting yourself then you had better build in some adjustment, and figure out some procedure for performing those adjustments.

I am not trying to discourage you, merely identifying the problems that you will face.

Best advice is to build the first prototype with the understanding that a 2nd prototype WILL be necessary to solve the problems identified in the first build. My first two builds never got as far as mounting motors, they were both hand cranked. Proto3 was slated to use a 12v car wiper motor.

Dave

Thank you Dave for all your help so far, as I said in previous post I think deflection will be minimal as it will be riding on linear shafts with linear bearings and the carriage will just do the push/pull process without any real weight unless I’m missing something. On a side note I just found a 12mm ballscrew with bearing supports, nut and coupler for 45$ shipped...probably not the best but I’d say better than threaded rod if the pitch will work out. As far as alignment goes with my experience in machining and cabinet building I think I’ll be able to work that out. 

[Vodkaman]

You seem to be on top of the project. The ballscrew looks like a good solution, it should eliminate the slop. You have eliminated the bending, and good machining practices will eliminate the adjustments.

Dave

[Vodkaman]

Motor power and speed control is an issue that deserves some research. For small low power motors a potentiometer will work, but for more powerful motors requiring more current, you may have to find another solution.

I chose a wiper motor because they were the correct speed for my project, easily available 2nd hand and easily enough power for the job.

Dave

[JasonB14]

18 minutes ago, Vodkaman said:

Motor power and speed control is an issue that deserves some research. For small low power motors a potentiometer will work, but for more powerful motors requiring more current, you may have to find another solution.

I chose a wiper motor because they were the correct speed for my project, easily available 2nd hand and easily enough power for the job.

Dave

Dave the motors I’ve chose are high torque 12v dc motors with gear boxes very similar to wiper motors and only 12$ a piece. If for some reason they don’t work I’m not out much. On another side note that ball screw has a 4mm pitch, so with my 10rpm motor I could just dial it back to around 6rpm and get the 1” of travel per minute ....right? I think I read here or somewhere that was the optimal speed with round tooth blade for best finish...?. Or did I dream that?

[Vodkaman]

The speed I found was limited by the bounce of the follower on the master and/or the cutter on the woodblock. I found that around 60rpm was the limit. If you can solve the stylus bounce issue then you can get more speed.

If you can automate the run with an auto-off micro switch then speed is not really of great concern. What is of most concern is the finish or step distance between cuts. The finish is not going to be smooth, but how much rough can you live with. Finish is down to cutter step distance. I liked 0.5mm on my machine. It still required a 30s touch up with a flap wheel.

Dave

[JasonB14]

I can deal with a little sanding on balsa.

im now to the point of holding the wood blank I was thinking a wood lathe drive spur in the middle that will ride in pillow bearings and on the other end a drive spur that will also ride in a pillow bearing but will have some sort of acme screw to clamp wood between centers.....problem I’m having is finding drive spurs that are not Morse tapered, so I see me machining those, unless you have a better idea....do you have any pictures of yours?

[Vodkaman]

I invented my own wood block holder. Basically spiked plates that did the same job. Not brilliant or time efficient, but got the job done.

Dave

[JasonB14]

38 minutes ago, Vodkaman said:

I invented my own wood block holder. Basically spiked plates that did the same job. Not brilliant or time efficient, but got the job done.

Dave

Thanks again for the help, I ended up ordering a contraption that I’ll make work...got just about all the parts ordered now, just need to go to the steel yard and get some tubing to make the frame and carriage. Should be able to have mocked up by the weekend. Here’s the tail stock I ordered to press wood into the spur...I’ll probably cut the point off the live center and make some teeth in it. 

[Nathan]

If you go to YouTube and search “Redg8r” He started this site and was working on a lure copier years ago.The video maybe of some help..Nate

[Vodkaman]

32 minutes ago, Nathan said:

If you go to YouTube and search “Redg8r” He started this site and was working on a lure copier years ago.The video maybe of some help..Nate

That was the machine that inspired me.

Dave

[JasonB14]

I mocked up my machine on wood base and it appears everything is gonna work out just fine, so now im  in the fabrication stage. Im gonna need help with with wiring a couple of limit switched and a switch to reverse the motors. Is there anyone  that can draw a diagram to show me how to do that? Ive googled it and that just further confused me lol. Im not by any means an engineer or an electrician so reading electrical diagrams is like reading a foreign language. Its probably more simple than it seems looking at the internet. I have attached a sketch of my plan if some one could look at it and give me some guidance....not an artist either.

Basically i need to wire the power supply to both motors, both through a potentiometer, limit switches on number 2, and forward/reverse switch on at least number 2.

Edited February 1, 2021 by JasonB14

[Vodkaman]

Yes, as you hinted, only motor-2 needs to be reversible.

There are two main types of motor speed control:

1 – PWM. Pulse Width Modulation. This circuit supplies the motor at full voltage and current but in a series of on/off pulses. The wider the pulse then the faster the motor turns. Basically you are switching the motor on and off very rapidly to control the speed.

2 – Voltage control. This is what you have in mind in your description, varying the supply voltage through a variable resistor. This is the method that I will discuss further.

You cannot use a simple potentiometer (pot) because the pot has to be capable of carrying the current drawn by the motor. A large pot might be capable of carrying say 100mA, but the motors for this project are likely in the range of 5W – 10W power rating. This means a current draw of 0.5A to 1A or even higher depending on the spec of the motor and the load that it is turning.

You have to use a low power pot to control a mosfet which in turn controls the motor voltage.

I am very reluctant to get involved with electronic advice with an electronics novice and seeing that I have never done any motor speed control or used mosfets before. But, this looks like the simplest way to go. But, components have to be chosen that can handle the power rating of the motor. You must provide as much information as possible. I will try to assist you but I will NOT be taking blame.

Reading the motor label, what information is provided; voltage, current, power etc.

What type of motor is it; A/C, DC, induction, stepper etc.

Have you tested to see if the motor reverses when the power cables are reversed?

What is the speed (rpm) of the motor?

Dave

[JasonB14]

These are the items I already have...the motor and speed controller...where I get fuzzy is running that through a reversing switch and a limit switch 

[Vodkaman]

OK, good information. PWM unit is a good choice, you don't have to build anything which was my nightmare.

Your information states that the motor is reversible simply by reversing the supply, this is good.

So, all you need now is a limit stop and reverse circuit. I will have a think on the micro switches and a simple reversing circuit and get back to you.

Dave

[Vodkaman]

The reversing switch is done with a DPDT (Double Pole Double Throw) switch.

These come in various forms; rocker, toggle, push on/off etc. They all have 6 connectors. Here is a rocker DPDT switch.

The PWM outputs (+/-) are connected to p3 and p4.

P1 and P6 are connected together and connected to one side of the motor.
P2 and P5 are connected together and connected to other side of the motor.

I need sleep, it is 6am here, so I will look at micro switches tomorrow. Read the link and my text and make sure you understand what is going on. Different makes of switches may have different pin numbers. Be prepared to test with a meter and adjust design.

Update - I think I have the solution, wiring the micro switches into the DPDT switch. I will draw up a diagram tomorrow.

Dave

Edited February 1, 2021 by Vodkaman

[JasonB14]

1 hour ago, Vodkaman said:

The reversing switch is done with a DPDT (Double Pole Double Throw) switch.

These come in various forms; rocker, toggle, push on/off etc. They all have 6 connectors. Here is a rocker DPDT switch.

The PWM outputs (+/-) are connected to p3 and p4.

P1 and P6 are connected together and connected to one side of the motor.
P2 and P5 are connected together and connected to other side of the motor.

I need sleep, it is 6am here, so I will look at micro switches tomorrow. Read the link and my text and make sure you understand what is going on. Different makes of switches may have different pin numbers. Be prepared to test with a meter and adjust design.

Update - I think I have the solution, wiring the micro switches into the DPDT switch. I will draw up a diagram tomorrow.

Dave

Thank you Dave! 

[Vodkaman]

Before we get into the micro switches, there are some safety issues that need to be addressed and wired into the whole operating system. Here are a few discussion points:

Motor Control Rules

1 – Protection guard MUST be in place before cutter can be switched on (micro switch MS1).

2 – Cutter must be raised before switch on of 12V system (micro switch MS2).

3 – Cutter MUST be running before 12V travel circuits enabled, common power switch.

4 – Cutter direction test isolation (micro switch MS3 and MS4).

5 – Cutter direction (DPDT switch)

6 – Reset travel. Cutter off MS1, cutter raised MS2, set direction, max speed to MS3 or MS4.

7 – Woodblock MUST be turning before travel enabled.

If any of the above rules are broken then a machine catastrophic crash could occur. Make sure you understand the above and the consequences. Each of the above could be controlled manually, but if you make a mistake or miss a step then a crash can occur.

Example 1 - Cutter power is off, cutter in down position and travel screw motor started.
Example 2 - Cutter down when power on.
Example 3 - Woodblock motor stalled while drive screw operating.

And more scenarios. Machine needs to be fool-proof.

Dave

[JasonB14]

15 hours ago, Vodkaman said:

Before we get into the micro switches, there are some safety issues that need to be addressed and wired into the whole operating system. Here are a few discussion points:

Motor Control Rules

 

1 – Protection guard MUST be in place before cutter can be switched on (micro switch MS1).

 

2 – Cutter must be raised before switch on of 12V system (micro switch MS2).

 

3 – Cutter MUST be running before 12V travel circuits enabled, common power switch.

 

4 – Cutter direction test isolation (micro switch MS3 and MS4).

 

5 – Cutter direction (DPDT switch)

 

6 – Reset travel. Cutter off MS1, cutter raised MS2, set direction, max speed to MS3 or MS4.

 

7 – Woodblock MUST be turning before travel enabled.

 

If any of the above rules are broken then a machine catastrophic crash could occur. Make sure you understand the above and the consequences. Each of the above could be controlled manually, but if you make a mistake or miss a step then a crash can occur.

Example 1 - Cutter power is off, cutter in down position and travel screw motor started.
Example 2 - Cutter down when power on.
Example 3 - Woodblock motor stalled while drive screw operating.

And more scenarios. Machine needs to be fool-proof.

Dave

That will be waaaay over my paygrade im sure....that would tying dc to ac also....I just wanted limit switches so that it stops when it gets to the end lol

[Vodkaman]

I agree, I just wanted to point out what would be required should this project be taken commercial. You could not sell this product in USA other than in a kit form. To totally protect the novice user would take electronics. This is why you will never find anyone to publish plans for such a machine, the USA suit mentality makes such help way too risky.

Here is the micro switch configuration for you.

Dave

Edited February 2, 2021 by Vodkaman