EXAMENSARBETE INOM MASKINTEKNIK, Robotik och mekatronik, högskoleingenjör 15 hp SÖDERTÄLJE, SVERIGE 2017

Improving CNC machine utilization using robotic machine tending

Abraham Mwebesa

SKOLAN FÖR INDUSTRIELL TEKNIK OCH MANAGEMENT INSTITUTIONEN FÖR TILLÄMPAD MASKINTEKNIK

Improving CNC machine utilization using robotic machine tending

by

Abraham Mwebesa

Examensarbete TMT-545 2017:52 KTH Industriell teknik och management

Tillämpad maskinteknik Mariekällgatan 3, 151 81 Södertälje

Bachelor of Science Thesis TMT-545 2017:52

Improving CNC machine utilization by Robotic machine tending

Abraham Mwebesa

Approved

2017-08-09 Examiner KTH

Lars Johansson Supervisor KTH

Lars Johansson Commissioner

Robotdalen Contact person at company

Ingemar Reiyer

Abstract The purpose of this thesis is to verify, if it is possible to implement a mobile automation system for CNC tending at VMI AB, which could be moved from one CNC to another. Thereafter, evaluate how it can be done, and if it will be economically feasible. VMI AB’s aim is to improve their CNC machine resource utilization. Through a company visit and interviews with the companies CEO, information was collected and used as base of the study. Analysis of the information gave further understanding of why VMI AB wanted to automate and what kind of robot they desired. The company wanted a mobile and collaborative robot that could machine tend at least 80% of the products. Two mobile and collaborative robot systems were then suggested by experts at Robotdalen, to be evaluated. The two robot systems were the Opiflex and Universal robots. The robots would be evaluated on their weight capacity, reach, and overall usability. A simulation of a concept robot cell was made, using Creo-parametrics and Robotstudio. The simulation was used to test the robots reach and supporting the reasoning regarding the robots usability. The simulation showed that, the longer the reach, the better the robot could pick things up objects. The long reach allowed the robot to have the robot to pick up object with better mechanical stability since the robot didn’t stretch to its limit to pick up objects. Thereafter an investment calculation was carried out to evaluate if the alternatives would be profitable or not over time. In conclusion the study found the Universal robots system to have the lowest price but of the lesser use to the company, since it had a low lifting capacity. The Opiflex system was found to be the more expensive but of greater use to the company, since it has a high lifting capacity and a much longer reach. Key-words Machine tending, CNC operator, Robotstudio, Creo-parametrics, break even, usability

Examensarbete TMT-545 2017:52

Förbättrat utnyttjande av CNC-maskiner med hjälp av robotiserad maskinbetjäning

Abraham Mwebesa

Godkänt

2017-08-09

Examinator KTH

Lars Johansson

Handledare KTH

Lars Johansson Uppdragsgivare

Robotdalen Företagskontakt/handledare

Ingemar Reiyer

Sammanfattning

Målen med detta examensarbete är att verifiera om det är möjligt att implementera ett mobilt robotsystem för att betjäna CNC-maskiner hos VMI AB, att föreslå hur automatiseringen skall genomföras, och att göra beräkningar för att undersöka om den är ekonomiskt genomförbar. Från VMI AB:s sida är syftet att utnyttja maskinresurserna bättre.

Genom ett företagsbesök och intervjuer med VD insamlades information till studien, och när informationen bearbetats stod det klart vad för slags robot som företaget behövde. De ville ha en mobil och kollaborativ robot som skulle kunna bistå vid bearbetning av minst 80% av produkterna. Två robotsystem föreslogs för utvärdering av experter på Robotdalen. Robotsystemen var Opiflex och Universal robots. Robotarna utvärderades med avseende på viktkapacitet, räckvidd och användbarhet.

Robotarna testades med en simulering av en koncept-robotcell som skapats med Creo-parametrics och Robotstudio. Simuleringen användes till att testa robotarnas räckvidd och stödja resonemang kring frågorna om robotarnas användbarhet. Simuleringen visade att en robot med en lång räckvidd kunde plocka upp objekt med bättre mekanisk stabilitet än en robot med en kortare räckvidd. En robots mekaniska stabilitet blir bättre om den behöver inte sträcka sig till maximal räckvidd för att plocka upp något. Slutligen gjordes en investeringskalkyl för att utvärdera om alternativen kan bli lönsamma i framtiden.

Universal robot hade det lägsta priset, men studien fann att den skulle bli mindre användbar för företaget då dess lyftkapacitet är låg. Opiflex-systemet var dyrare, men mer användbart eftersom dess lyftkapacitet är högre och räckvidden längre.

Nyckelord Maskinbetjäning, CNC-operatör, Robotstudio, Creo-parametrics, break even, usability

Improving CNC machine utilization using

Robotic machine tending

Abraham Mwebesa

Preface This bachelor’s thesis was authored by a student from KTH Södertälje in the mechanical

engineering program. Knowledge from the mechanical engineering program, experience

doing projects and expert help in the branch was used to base all the project decisions.

Programming knowledge in Robotstudio, Creo-parametrics and basic economics were

crucial for the project’s success.

Several people have been instrumental to the projects. Much thanks to: Lars Johansson, my

supervisor and examiner at KTH Södertälje, for helping me with the report writing. Bernt

Henriksen and Ingemar Reyier from Robotdalen, helped with Robotstudio, project

structure and discussions to keep the project on course.

Pontus Säfström, the CEO to Västerdalarnas Mekaniska Industri AB, was always available

on phone and mail to answer my questions. Your input and knowledge has been very

helpful and this project would not have been possible without it.

Table of Contents 1 Introduction....................................................................................................................................................... 1

1.1 Background................................................................................................................................................. 1

1.2 Problem description ................................................................................................................................... 1

1.3 Aim ............................................................................................................................................................. 1

1.4 Objectives ................................................................................................................................................... 1

1.5 Restrictions ................................................................................................................................................. 2

1.6 Methods ..................................................................................................................................................... 2

2 Description of current situation ........................................................................................................................ 3

2.1 Production process ..................................................................................................................................... 3

2.1.1 Factory Layout ..................................................................................................................................... 4

2.1.2 Equipment ........................................................................................................................................... 5

2.1.3 Products .............................................................................................................................................. 6

2.2 Work force and capacity ............................................................................................................................ 6

2.3 Time and disturbances ............................................................................................................................... 6

2.3.1 Waste .................................................................................................................................................. 6

3 Tools and methods ............................................................................................................................................ 7

3.1 Robotstudio ................................................................................................................................................ 7

3.2 Creo- parametric ........................................................................................................................................ 7

3.3 Investment return calculation .................................................................................................................... 7

4 Requirement analysis for the robot .................................................................................................................. 8

4.1 Functional requirements ............................................................................................................................ 8

4.2 Technical requirements .............................................................................................................................. 8

4.3 Other system requirements and non-functional requirements ................................................................. 8

5 Proposals ........................................................................................................................................................... 9

5.1 Opiflex Robot system ................................................................................................................................. 9

5.1.1 Robot for OpiFlex .................................................................................................................................. 12

5.1.1.1 Reach .............................................................................................................................................. 13

5.1.1.2 Weight capacity .............................................................................................................................. 15

5.1.1.3 Overall usability .............................................................................................................................. 15

5.2Universal-robot system ............................................................................................................................. 16

5.2.1 UR10 .................................................................................................................................................. 16

5.3 Material in and product out ..................................................................................................................... 17

5.3.1 Regular euro pallet ............................................................................................................................ 17

5.3.2 Drawer based system ........................................................................................................................ 18

5.3.3 Vision and Lidar ................................................................................................................................. 18

5.4 Deburring station and re-gripping station................................................................................................ 18

5.5 Tool rack ................................................................................................................................................... 19

5.6 programming ............................................................................................................................................ 21

5.7 I/O ............................................................................................................................................................. 21

6 Results and analysis ......................................................................................................................................... 22

6.1 Robot cell .................................................................................................................................................. 22

6.1.1 Materials in and out .......................................................................................................................... 22

6.2 Investment calculation ............................................................................................................................. 23

7 Discussion & Conclusion .................................................................................................................................. 26

7.1 Achieving the goals and objectives .......................................................................................................... 26

7.2 Conclusion ................................................................................................................................................ 26

References .......................................................................................................................................................... 27

Appendix 1 ......................................................................................................................................................... 28

Appendix 2 ......................................................................................................................................................... 29

1

1 Introduction

1.1 Background This degree project was intermediated through Robotdalen where the study was

conducted on behalf of Västerdalarnas Mekaniska Industri AB (VMI AB). Robotdalen is a

non-profit government organisation whose mission is to advance automation technology in

Sweden. Robotdalen is funded by VINNOVA, the European Regional Development Fund and

partners from the industry, academia and public sector in Central Sweden.

VMI AB is a prototype and contract manufacturing company located in Malung Sweden. A

fleet of nine CNC machines is used to machine parts with precision and high quality. In

order to stay competitive, the company aims to utilize the CNC machines more than they do

at the moment. So Robotdalen is tasked with doing a study to find out whether automation

would increase resource utilization and be a profitable investment.

1.2 Problem description With a purchase price of millions for CNC machines, it is essential that they are used as

much as possible to get a profitable return. The factory currently operates during daytime

so the CNC machines are working for just that time only.

The machine tending is currently done manually. So the production completely depends on

the availability of CNC operators. The factory is located in a small town where there aren’t

many people, so they have difficulties finding people to recruit, plus the there isn’t much

enthusiasm to become CNC operators.

To become a CNC operator, it takes about a year of training. The training is carried out in

house and has ended up being an unavoidable expense since it’s hard to find already

educated operators. The company wants to increase production by adding night shifts but

it would be expensive since the operators cost more for night shifts.

1.3 Aim VMI AB aims to have an autonomous robotic system that can manufacture batches of

products on its own and gain 16 hours of production time a week.

The purpose of the study is to evaluate how production would be impacted by automating

the machine tending by the two robotic systems suggested by Robotdalen, that is the

Opiflex system and universal robot system.

1.4 Objectives The expected results for the thesis are as follows:

The study will provide a suggestion to which robotic system to invest in.

The study will provide an investment return calculation that shows the impact of the investment on profitability.

A computer simulation of the CNC machine Mazak Integrex 400-IV with the robot

system will be presented as an example of the solution with the help of Robotstudio

and Creo parametric.

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1.5 Restrictions The study is restricted from the following:

The study will revolve around one machine (Mazak Integrex 400-IV) as case study.

The study will not include the implementation of the robot

The study will not include buying of the robot.

The study will only account for the immediate costs relating to the machine tending,

such as construction costs to accommodate the robot.

1.6 Methods In order to achieve the study’s objectives as stated in section 1.3, various methods will be

used. This includes a situation analysis, investment calculation and robot simulation. The

methods and terms will be further more explained in chapter 3.

A current situation analysis will be carried out, where the company’s practices and

methods will be recorded and analysed to understand VMI AB’s organisation. A one day

visit at the company will be undertaken and their Chief executive will be interviewed. In

order to get a better understanding of how VMI AB currently operates, questions will be

asked regarding the reasons for investment, factory’s manufacturing routine, bottlenecks,

lay out, products, expectations and desires. The visits will include a tour of the factory’s

machines, plus choosing one machine to be the focus of the project. The company will

provide several documents depicting the different products that are produced, pictures,

videos of important operations plus a 3D rendering of the machine that is to be focused on.

Out of this information, a robotic simulation will be made using RobotStudio and Creo

parametric. An investment calculation will also be done. This should provide a basis for the

study’s conclusion.

3

2 Description of current situation

2.1 Production process

The production process starts with an order that is sent via mail sent by a client. The order

will contain essential information that includes dimensions in form of a drawing or a 3D

model of the part, how many duplicates to be manufactured and material used in

manufacturing.

Fig 2.1 Part example

A CNC machine, material required and tools are allocated to the order and placed on to a

list. The orders are uploaded to a Google doc spread sheet and arranged by earliest

deadline first so that the parts are manufactured in time. Orders are accessible via the

station computer by CNC operators and technicians.

A CNC operator will pick the material from the warehouse and cut it to size. 80% of the

products are of round form before machining. The part shown in Fig 2.1 started out as a

round piece with Ø160/100 mm dimensions. The pieces can be made of steel, aluminium

and other materials. Depending on what kind of material and what the client wants, the

pieces can be coloured. So they can be blue, white, silver etc.

The pieces are placed in a cart at random. Thereafter, the pieces are transported to a

temporary storage location within the cart. It is at this location the operator responsible for

cutting puts all the cut pieces, and from this temporary storage location another CNC

operator gets the pieces for machining as shown in the factory layout in Fig 2.2 in the area

surrounded by a blue rectangle.

A CNC technician is the one responsible for programming a task into the CNC machine and

choosing tools for the operation. The CNC tools are found at the location named Tools in

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Fig 2.2, and the shelf shown in Fig 2.4 holds the different CNC tools. CNC tools have to be

manually placed into the CNC to be used. Depending on what material and shape the part

will take, different tools need to be used in order to get the best quality. If the factory has

never produced a particular part before, the technician will be responsible for test

manufacturing to check whether the CNC settings and part quality is as desired. This is

done by manufacturing parts till the first good quality part is produced. This also counts as

the first quality check.

The CNC operator takes over the machine tending after the CNC technician obtains the

desired product quality. At this stage, the CNC operator checks the quality of the parts as

they come out plus taking care of the post manufacturing finish that is mainly, deburring.

The deburring process is done by hand using a grinding machine named GRIT GIS 75 to

clean up the edges, and another called GSZ 8-280 PE to deburr the holes.

After machining, some parts need extra work that could include a check on whether two

pieces, that were to fit together, actually fit. Most parts go directly to the warehouse for

transport to the client.

2.1.1 Factory Layout The factory layout was designed so that the production can be as flexible as possible. The

arrows in Fig 2.2 depict the material flow from warehouse to cutting, temporary storage,

the CNC machines, extra work station for the parts that need it, and then on to the

warehouse for transport.

Fig 2.2 Factory layout

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2.1.2 Equipment The factory has a fleet of CNC machines but this study focuses on the Mazak Integrex 400-iv

as shown in Fig 2.3.

Fig 2.3 Mazak Intergrex 400-iv

Depending on what shape a part will take and what material it is made of, CNC tools are

chosen out from the tool shelf. The shelf is marked with yellow tags as in fig 2.4 to show

where they are to be placed. The tools are transported by trolley. The trolley is colour

separated, red for tools that are to go back to the shelf and green for tool to be used for

machining. An example of a trolley is shown in Fig 2.5.

Fig 2.4 Tool shelf

Fig 2.5 Tool trolley

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2.1.3 Products A variety of products are manufactured at the plant. The main characteristics of the

products are that 80 % of the products weigh less than 10 kg before machining and have

cylindrical form at this stage. After machining, a part’s weight can range from 1 kg to 8.5 kg,

and at this stage they can be of any shape but mostly rectangular or circular.

2.2 Work force and capacity The work force consists of two CNC technicians and 4 CNC operators. The factory normally

operates from 6:45 AM till 4:00 PM till on Monday till Thursday and 6:45 AM till 1:00 PM

on Friday.

Each CNC machine manufactures a number of parts a day, but the number varies

depending on many factors. The Mazak Integrex 400-IV manufactures about 20 parts per

day on average. The entire factory manufactures about 7.5 – 10 thousand details per

month.

2.3 Time and disturbances Every order has a five day guarantee so five days from when the order was made; it will be

manufactured and delivered. Some products need surface treatment so they have to be sent

to another contractor for this, and therefore a delay can occur. Other than that, the only

other reasons for production to slow down are machine breakdown and workers becoming

unavailable.

2.3.1 Waste The CNC machines are only utilized during daytime. A CNC machine investment is an

expensive one and with such a machine, it needs to be utilized as much as possible to get a

profitable return in a short time.

7

3 Tools and methods Several tools are used to help in achieving the study’s objective. The tools are provided by

KTH and are available for any student who is working on a similar project.

3.1 Robotstudio The robot studio program was developed by ABB and is used for simulation and

programming ABB robots.

The program can simulate a real station with all the parts that are desired in the robot cell,

where the program can be tested without needing to upload it to the actual robot. This

provides an opportunity to test everything on the computer before trying it in reality.

Simple 3D models can be designed within the Robotstudio environment, but more

advanced drawings that are usually made in other 3D modelling environment, like Creo

parametric that is described in the next heading.

Fig 3.1 Robotstudio

3.2 Creo- parametric Creo-parametrics is a modelling program where drawings of both two and three

dimensions can be rendered in a computer environment.

The objects are made to the same size that they would have in reality. Such programs are

used in 3D printing, a 3D model is made on the computer and it’s printed out to scale.

3.3 Investment return calculation In order to estimate how the automation investment will affect profitability an investment

calculation needs to be done. An investment may be described as a capital usage with long

term and short term consequences. An example of an investment can be a new machine,

building or anything a company buys (Företagsekonomi 100, upplaga 16, Page. 301). It is

very hard to predict the profitability of an investment, but a calculation that considers how

things could possibly turn out over a period of time before the investment is carried out.

This kind of calculation is known as an investment calculation.

8

4 Requirement analysis for the robot

4.1 Functional requirements The robot has to be able to Carry 10 kg of load if not more. 80% of the pieces weigh

below 10 kg before machining. The robot has to be able to lift the piece, tool changer

and the tool itself altogether.

The robot is preferably a movable robot, meaning it can be moved from one CNC

machine to another.

The robotic solution should be a collaborative system, meaning it will be able to

work with humans present. Normally a robot system is surrounded by a safety cage

where it can operate at top speed and away from people. So this robot system has

to be able to work without the cage but still keep people safe.

The robot should be able to do both machine tending and the extra post machining

procedures, such as deburring.

4.2 Technical requirements The robot has to be able to be connected to the CNC machine so they can

communicate and work together.

The robot must be able to work fully autonomously, meaning the CNC operator

doesn’t have to be present for the robot to carry out a given task.

4.3 Other system requirements and non-functional requirements The robot must not be an obstruction to normal workings of the factory.

9

5 Proposals VMI has suggested an example robot cell with the Mazak Integrex 400-IV be proposed. The

activities that the robot would do at the station are machine-tending and deburring. The

robot cell will need five components: a place for new material, a place for finished products,

a robot system with safety equipment, deburring station, tool rack and a re-gripping

station so the robot can get to the other side of the product and deburr it.

Fig 5.1 Robot cell layout

5.1 Opiflex Robot system The OpiFlex system is a system developed, produced and supplied by OpiFlex Automation

AB. The system is made up of the three sections that are the stand, control module and the

robot.

As shown in Fig 5.2, the orange docking station is at the base of the system. It is attached to

the factory floor and serves as support for the entire system to stand upon. There are four

positions located at the corners where the overhead platform can be mounted upon. This

part of the system is stationary, so if the robot is to be used on several stations, more of

these would be needed.

10

Fig 5.2 OpiFlex stand

The control module is a platform that is placed on top of the stand and serves as a base for

the robot. It carries all the robot control systems plus safety equipment. A Pallet jack can be

used to transport the module with robot on top to different stand stations.

Fig5.3 Control module

The safety system mounted on the control module consists of two laser scanners and they

are placed at the end of the two arms sticking out in Fig 5.3. The arms can be pivoted

upwards on a joint at the point where it connects with the controller module. In an

upwards position, the system can be transported without them getting in the way.

The laser scanner substitutes a safety cage as it would normally be on a robot cell; it

detects objects or people, and then performs pre-programed actions. The detection is

divided into zones as shown in Fig 5.4 where they are represented by colour. The area

surrounding the yellow zone is the warning zone. A flashing light that sits on top of the

control module warns if the robot is active. The yellow Zone is slow down zone, meaning

that if a person or object enters this zone, the robot will slow down to 250 mm/s till the

person or object passes the yellow Zone. The red Zone is the stop zone. For safety reasons,

the robot will come to a complete stop if anyone or any object enters this area and a reset

would be needed to start again. The data from the scanners is processed by the control

module that handles the robot.

11

Fig 5.4 Scanner Zones

The Zones layout in Fig 5.4 was made for a particular company, meaning they can be

customized to the task at hand.

On top of the control module an arm robot is attached, that has been supplied by the ABB

Group. Different kinds of ABB arm robots can be supported by the system, and they are

chosen based on what the task the robot is to do. Arm robots imitate a human arm, and

possess six axes of mobility.

Fig 5.5 IRB 4600 on the OpiFlex platform

12

5.1.1 Robot for OpiFlex The OpiFlex presents an opportunity, to choose a specified robot size without needing to

change platform since they are simply mounted on top. The robot suggested will be chosen

based on three characteristics: reach, weight capacity and overall usability. The two robots

that were Opiflex suitable and possible candidates for the tasks were IRB2600 and

IRB 4600 40/2.55.

Fig 5.6 IRB4600 40/2.55, Downloaded 10/05/17 from

http://new.abb.com/products/robotics/sv/industrirobotar/irb-4600

Fig 5.7 IRB2600 20/1.65, Downloaded 10/05/17 from

http://new.abb.com/products/robotics/sv/industrirobotar/irb-2600

13

5.1.1.1 Reach A robots reach is how far the arm can reach. Just like a human arm, it is considerably more

difficult to lift something with a strait arm compared to when the arm is bent and it

provides a better mechanical stability.

The IRB2600 is the smaller of the two, even if it does not look so in Fig 5.7, and it has a

reach of 1.65m. Mounted on to the OpiFlex platform with a euro pallet beside, it needs to

almost stretch out to its limit in order to reach the end as shown in Fig 5.8.

Fig 5.8 IRB2600 reaching to the end of the euro pallet

While the robot can make it to the end of the euro pallet on its left, it cannot reach the

entire euro pallet placed on the right as shown in Fig 5.9. The IRB2600 would actually

crash into the control module if it tried to stretch itself out as shown in Fig 5.10.

Fig 5.9 IRB2600 reach to the right

14

Fig 5.10 IRB2600 crash

The IRB 4600 40/2.55 is bigger and has a reach of 2.55m. With the larger reach, the robot

is able to reach around itself better than IRB2600 as shown in Fig 5.11and 5.12. The arm

robot reaches just as well on both the left and the right side.

Fig 5.11 IRB4600 reach to the left

15

Fig 5.12 IRB4600 reach to the right

5.1.1.2 Weight capacity The robot has to be able to lift the object, tool charger and the robot tool as described in

section 4.1. Out of the 80% products manufactured, the heaviest product after machining

weigh 8.5 kg, so it is safe to assume that it weighs more than 8.5 kg before machining. The

robot tool and tool changer’s weight depend on the weight capacity needed for the task. So

it could weigh as much as 2-3 kg, so the robot must lift more than that to be safe.

The IRB2600 comes in two different weight capacity classes, which are 12 kg and 20 kg. In

order to be safe, the 12 kg capacity robot would be too close to the maximum weight to be

lifted, so the 20 kg would be better. The 20 kg robot leaves room for future applications

that may need a greater lifting capacity.

The IRB4600 comes in 4 weight capacities that are 20 kg, 40 kg, 45 kg and 60 kg. The 20 kg

weight capacity robot would be the obvious choice, but the 40 kg weight capacities would

be better since it has a 5 cm reach advantage, which would be better for future usage.

5.1.1.3 Overall usability The IRB4600 40kg/2.55m offers the most flexibility to the factory. With such a wide reach,

the robot gets a large operating radius without losing mechanical stability. Since the robot

comes mounted on a mobile platform, many other uses might be found so a high lifting

capacity would be an advantage.

16

5.2Universal-robot system The Universal robot system is developed by universal robots, a Danish industrial robot

arms manufacturer based in Odense. They produce six axis robots that come in three sizes.

The smallest one is called UR3, the medium one is UR5 and the largest is UR10. Other than

the size, the other differences are lifting capacity and reach. The lifting capacity of each

robot is stated in the name and measured in kilograms.

Fig 5.13 UR10, Downloaded 10/05/17 from https://www.universal-

robots.com/products/ur10-robot/

Just like the OpiFlex system, the universal robot system comes with easily moveable

controller and safety systems. The UR10 controller is 17 kg and has dimensions of

475 mm x 423 mm x 268 mm so it is relatively small. The controller comes separate, in

contrast to the Opiflex, but it is small enough to be easily transported plus it can be

mounted on the robot stand. On-board the arm robot, multiple force sensors detect if the

robot is getting any push back as it would get if person was to be in its way. The robot

moves at a constant low speed so it can stop in time before it does any harm. (read

information 10/05/2017 from https://www.universal-robots.com/products/ur10-robot/)

To deploy the robot, a stand or any stable rigid surface like the factory floor that provides

good mechanical stability is needed. The base of the robot can be bolted to such surface and

the robot is ready to be programmed and used. Robot stands come in different designs, and

a stand can be designed to be mobile on wheels.

5.2.1 UR10 Just like the robot for the OpiFlex system, the universal robot suggested will be chosen on

three characteristics that are reach, weight capacity and overall usability. With only three

choices, UR3 and UR5 can be instantly eliminated because their weight capacity is to low,

so the focus is on UR10.

UR10 has a 1.3m reach and it stands on a small platform that is the same diameter as its

base so it is very flexible. This means that the robot has no problem reaching around itself,

picking up objects and delivering them where they have to be. In section 5.1.1.1 it was

17

observed that the IRB2600 couldn’t reach the entire euro pallet because it was standing on

a large base, so even though it has more reach than the UR10, the UR10 still has the

advantage.

With a 10 kg lifting capacity, the UR10 has a reduced lifting capacity when it is equipped

with a tool, tool changer and tool plate. The tool, tool changer and tool plate are explained

in section 5.5.

With the average tool weighing 3 kg, 7 kg material or products would be its maximum

lifting capacity. This means that the robot won’t be able to handle all the products Listed in

Appendix 1, but it will be able to lift most of them.

5.3 Material in and product out There are many ways that material can be introduced into the robot cell, as well as

removed from the cell. Currently there is no system to arrange the cut materials as

discussed in section 2.1. The pieces are put in a cart at random. This hasn’t been a problem

for the CNC operators but with a robot, there has to be a sorting system incorporated

because a robot is better at picking and placing objects at a predetermined location than at

random.

5.3.1 Regular euro pallet With a regular euro pallet, objects can be placed on a piece of plywood, cardboard or any

material that can provide a flat surface. In this way objects can be placed in an arranged

manner as shown on Fig 5.14. Interest points can be drawn on the cardboard piece, and

afterwards the robot can be programmed to find the piece there.

Fig 5.14 regular euro pallet

18

If the batch comprises more than 20 products, as shown in Fig 5.14, a piece of cardboard

could be placed in between the materials and thus stacking them as shown in Fig 5.15.

Fig 5.15 Cardboard spacer

5.3.2 Drawer based system A drawer basset system would be similar to the regular euro pallet solution but the

cardboard pieces are replaced by trays that can slide in and out of a drawer. This solution

is heavily used in machine tending solutions and is used for robots with bigger batches to

manufacture. The robot would simply pick from a tray, and switch to the next tray after

having finished the previous one.

5.3.3 Vision and Lidar Vision systems are mostly used in situations where the position or orientation of the object

isn’t predetermined, and a camera is used to locate the object with a pre-recorded image of

what it is to look for. Lidar functions in a similar manner, but a laser scanner is used to scan

for the object instead.

This system can work for randomly placed objects, but there is no guarantee that the

products will be seen every time since the technology is still in development and relatively

expensive.

5.4 Deburring station and re-gripping station The deburring station would simply be a tool to clamp an object still, so that the robot can

deburr it when using a deburring tool similar to GSZ 8-280 PE. For surface grinding with

GRIT GIS 75, the robot can hold the object and gently grind it as a person would as shown

in Fig 5.16.

Fig 5.16 Two clamps clamping a product still for deburring

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A re-gripping station doesn’t need to be more than a flat surface. The robot can reorient a

square objects to another side, and a “V” shaped holder, as shown in Fig 5.17, can be used

for circle shaped objects.

Fig 5.17 Re-gripping station

5.5 Tool rack A robot must be equipped with tools to carry out the tasks given to it. For machine tending,

one can use a gripper tool with three claws to pick up both material and products similar to

the one shown in Fig 2.1. Since most of the products are cylindrical in shape, a three

fingered tool would be able to pick them up. A suction cup tool to lift flat objects would be

needed for the Cardboard spacer shown in Fig 5.14. For deburring, there are tools that

resemble the hole deburring tool currently used today, but made for robots. When it comes

to using machines like GRIT GIS 75 to deburr the edges, the robot can use the gripper tool

and work the product along the spinning deburr to smooth the edges.

In order to be able to change tools, a special tool changer needs to be mounted onto the

robot, as shown in Fig 5.18. What it does is clamp onto a tool when it is to be used. It is an

easy and automatic solution to the task. The tool changer goes hand in hand with a special

plate that is mounted onto the tool, so that the tool changer can grab hold of the tool. The

plate is shown in Fig 5.19 and 5.20.

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Fig 5.18 Tool changer mounted onto a robot in Robotstudio

Fig 5.19 Tool plate, the side that connects to the tool

Fig 5.20 Tool plate, the side that connects to the tool changer

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5.6 programming Both Opiflex and universal robot system are designed to be easily programmed.

Programming can be done on both computer and on a tablet. A robot programmer called a

flexpendant is shown in Fig 5.21. The programmer can use the joystick on the pendant to

move the robot to desired positions, save the positions and use them to a make a robot

program. Both systems offer the possibility to simulate using programs like Robotstudio

for Opiflex and Polyscope for universal robots. Programs can be made and saved to be used

at a later time or reused over and over again. The Robots come with inbuilt logic that

performs on the spot calculations, which make sure that the robot is correctly positioned.

So when moving the robot, it will move based on the joystick setting.

Fig 5.21 Flexpendant

The Opiflex supplier programs the base structure of the task the robot will be doing. The

base structure could include the location of the tools and other important positions. With

this base structure, programming for a specific action, becomes as a series of choosing

options on the flexpendant. The supplier also offers programming lessons and from

experience, it hasn’t been a problem for the other factories that have acquired the system.

The Universal Robots can be programmed just like the Opiflex system, but can also be

programmed through lead through programming. Lead through programming is when a

robot can be manually moved to desired positions using hands, as one would do using a

joystick. Then the recorded movements can be used to program the robot.

5.7 I/O Both systems can communicate with other machines, like the Mazak Intergrex 400-iv, using

input and output signals. Therefore the robots can carry out programmed processes on

their own.

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6 Results and analysis

6.1 Robot cell The robot would be working at a factory that specialises in prototype and contract

manufacturing. The products manufactured vary from contractor to contractor. As shown

in the Appendix 1, the products are of different sizes and the batches are of different

amounts. This means that the potential products that the robot and VMI AB will

manufacture are expected to change often.

A robot with the capacity to lift all the products specified in Appendix 1 was the VMI AB’s

request. The robot will need a lifting capacity that is over 8.47 kg, since the heaviest object

is 8.47 kg. As discussed in chapter 5, a robots capacity decreases once the weight of the tool

and tool charger are added in. This means that a robot of a 10 kg capacity, such as UR10,

will only be able to lift 12 out of the 17 products mentioned in Appendix 1, which is 70% of

them.

In order to be able to list all the products, a robot with a higher capacity is needed. The

Opiflex system offers two robots that have sufficient capacity and superior reach. The

IRB4600-20kg/2.0m and IRB4600-40kg/2.55m would offer flexibility.

The IRB4600-20kg/2.0m would be sufficient for all the products listed in Appendix 1, but

it is only 15 000kr less than the IRB4600-40kg/2.55m. With 15 000kr more, the

capabilities would be improved to 40 kg lifting capacity and a 2.55m reach. The robot will

be able to lift all the products listed in Appendix 1, plus the 20% that weighs above 10 kg

and most products that are to be manufactured in the future.

6.1.1 Materials in and out The ways materials come into and leave the system dictate how long the robot can be left

unattended. The robot can theoretically run constantly, as long as there is material to

handle. Since the robot system will need to be flexible, the way material comes into the

manufacturing system need to be flexible as well. The euro pallet with cardboard spacers in

between stacked material would be the cheapest and most flexible. More advanced systems

such as lidar, vision and conveyor belt would be better for big batches but they are not

flexible and suitable for moving around. With just euro pallets, the current way of

transporting material wouldn’t have to change much, since euro pallets are currently used

on site.

Mathematical calculations or observational methods can be used to determine the best way

to arrange the pieces on the euro pallet to achieve the best use of space. Fig 6.1 shows an

example of a calculation made using a website that helps determine how many cylinders

can fit on a euro pallet with a given diameter and enough distance apart so the robot can

pick them up. The space in between depends on the size of the tool, a clawed tool would

need to pick up a piece without disturbing the others.

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Fig 6.1 eleven cylinders on a euro pall

with a 250mm diameter and 30 mm distance in between them. Downloaded 26/05/17

from http://www.engineeringtoolbox.com/circles-within-rectangle-d_1905.html

From there on, the material or products can be stacked. The products start out in simple

forms so they can be easily arranged in a pattern that can be programmed into the robot

for picking and placing. The amounts of stacks that can be made are only limited by the

robots reach and other factors such as the stacks being too high to be transported safely.

The products in Appendix 1 are manufactured in batches small enough to not even tower

the control module on the Opiflex system. Appendix 2 depicts how many stacks are needed

for the different products mentioned in Appendix 1.

6.2 Investment calculation A more in depth investment calculation has to be carried out to deduce the effects of the

investment on the company’s production and economy. The calculations in the following

investment calculation are just theoretical and need to be complemented later on. The

calculations also assume that there is no disturbance to the production from the start till

end of the year.

The calculation will focus on how much money the company can save by using a robot for

machine tending. Since the machine tending is carried out by the CNC operator, the cost per

hour would be the hourly cost of the operator, which is 200kr. The factory is operational 52

weeks of the year but counts 47 weeks of operational weeks after subtracting 5 weeks of

holiday. According to VMI, they earn 350kr/hour minus the operation costs and other

additional costs and we also know that, the hourly cost of a CNC operator is 200kr. Since

the robot doesn’t take hourly salary, the company would save the 200kr/hour with a robot.

This means the hourly income becomes 550kr/hour.

In order to get a more realistic calculation of how the Opiflex system would fair

economically, two scenarios will be presented. In the first scenario, the robot works 46

hours a week on just one station. The 46 hours consist of 30 hours manufacturing during

the day and 16 hours manufacturing during the night. In the second scenario, the robot

works 53 hours a week on two stations. And here as well the 53 hours are separated by

night and day.

Scenario one’s total hours per year becomes 2162 hours. This equals to the annual income

of 1,189,100kr per year. The robot solution will need investment. According to the CEO of

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Opiflex AB, the Opiflex platform with a IRB4600-40kg/2.55m robot, tool changer, tools, and

installation costs will about 1,700,000kr.

The time it would take for the company to break even is calculated using the formula in

equation 6.1. The numerator values are fixed costs and the denominator are time

dependant costs so they vary from time to time depending on the situation. Break even can

also be seen as the time it will take for the investment to be profitable. The maintenance

cost of a robot is too difficult to assume since a robot can go for years with no problem so it

will be neglected in the actual calculation.

Break even =

Equations 6.1 “Break even”

As shown in equation 6.2 break even becomes 1.4 years if the robot is operated 46 hours a

week, for 47 weeks of VMI’s working year.

Break even =

Equations 6.2” Break even”

Each new station is estimated to cost 700,000kr. A new Station means another docking

station motioned in section 5.1. The 700,000kr include the installation price of the

platform and tools. Therefore the investment cost becomes 2,400,000kr. Scenario two’s

total hours per year becomes 2491 hours. This equals to the annual income of 1,370,050kr

per year.

As shown in equation 6.3 the break even value becomes 1.7 years if the robot is operated

53 hours a week, for 47 weeks of VMI’s working year and two stations.

Break even =

Equations 6.3” Break even”

The Universal robot is cheaper compared to the Opiflex’s. The arm robot costs 299,000kr

and its stand costs about 100 000kr. The tools and tool holder can be estimated to cost

70,010kr combined. Equation 6.4 estimates the break even for UR10 to be at about 0.3

years when the robot is operated 46 hours a week, for 47 weeks of VMI’s working year.

Break even =

Equations 6.4” Break even”

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The break even estimate for a Universal Robot system is much lower than that of the

Opiflex system. However, the result is far from reality. The UR10 only has a lifting capacity

of 10kg. With a 10 kg lifting capacity, it shrinks to 7 kg when the robot has to carry a tool

changer and tool. This means it cannot be able to be used as much as the Opiflex, and is

therefore not being able to have a 0.3 break even.

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7 Discussion & Conclusion

7.1 Achieving the goals and objectives The aim of the study was to evaluate how production would be affected at VMI AB, if part of

the production was to be automated and suggest a robot for the task. The study was to

focus on 80% of the products which weighed less than 10 kg and further focus on the

ultimate goal that was to improving CNC machine utilization resource. An analysis of the

company’s requirements and several products was carried out, and from this information,

two robot systems were suggested by Robotdalen. With much experience in the field,

Robotdalen suggested the Opiflex and Universal robot systems for the task.

A robot cell was modelled in the Robotstudio simulating program, with the help of a 3D

modelling program called Creo-parametrics. Models of the CNC machine, products, tools

and other items to be in the robot cell were modelled and a simulation was made. Within

the Robotstudio environment, several arm robots were tested in order to determine which

robot would suit the task best. The effects of the investment were assessed in an

investment calculation and a time calculation that showed how many extra hours the CNC

would be active.

Due to lack knowledge in the universal robots simulation environment and time, the

universal robot could not be simulated but since it is an arm robot, it has similar functional

properties to those of the ABB arm robots. Therefore, the conclusions regarding the UR10

were based on the Opiflex simulation.

Analysis of the robot cell showed that the amount of time the robot can operate

autonomously depends on how much material that is available to the robot. The amount of

time it takes to finish manufacturing the material on an in pallet is the time the robot can

operate autonomously. With the current batch sizes, analysis showed that they could all be

stacked on a euro pallet with spacing in between the pieces as discussed furthermore in

6.1.1. The solution will be easy to implement since the factory already uses euro pallets to

transport material and the stacks wouldn’t be tall enough to be difficult transporting.

7.2 Conclusion Even though the investment calculations are based on assumptions, the calculations still

count as valid insight into how that investment will fair over time. The Universal robot

system is limited to about 70% of the products in appendix 1 but it is less expensive. On the

other hand, the Opiflex system is more expensive but has a much greater lifting capacity,

longer reach and a batter overall usability.

The UR10 robot will only be able to lift about 7 kg materials and it has a 1.3 m reach so the

robot cell will have to be small. The Opiflex system with the IRB4600 40kg/2.55m robot

will have a much higher lifting capacity and reach.

The UR10 robot is advantaged by price but limited by usability and poor future prospects

while the Opiflex system with the IRB4600 40kg/2.55m is disadvantaged by price but

advantaged by usability and positive future prospects.

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References Universal Robot.2017.UR10 https://www.universal-robots.com/products/ur10-robot/

(read information 10/05/2017)

ABB.2017. IRB4600 40/2.55,

http://new.abb.com/products/robotics/sv/industrirobotar/irb-46008 (Downloaded

10/05/17)

ABB.2017. IRB2600 20/1.65

http://new.abb.com/products/robotics/sv/industrirobotar/irb-2600 (Downloaded

10/05/17 from)

Engineeringtoolbox.2017.http://www.engineeringtoolbox.com/circles-within-rectangle-

d_1905.html (Downloaded 26/05/17)

Skärvad,P., & Olsson,J. (2014). Företagsekonomi 100. upplaga 16. Stockholm: Liber.

CEO. OpiFlex Automation AB. (Johan Frisk, pers.comm., 2017)

CEO. ARHO AB. Universal robots.( Andreas Rask, pers.comm.,2017)

ARHO AB. Universal robots.( Jörgen Mossberg, pers.comm.,2017)

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Appendix 1 80% of the product manufactured at VMI, they weigh less than 10 kg before and after

manufacturing.

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Appendix 2 Material relation with the Opiflex platform